Bioinspired passive radiative cooler with superior transparency and durability for energy-efficient building

Bioinspired passive radiative cooler with superior transparency and durability for energy-efficient building | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Bioinspired passive radiative cooler with superior transparency and durability for energy-efficient building Shichao Niu, Hanliang Ding, Bo Li, Yicong Zhang, Yufan Zhang, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6024085/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Passive radiative cooling (PRC) materials can achieve effective cooling without energy consumption through strong light reflection and spontaneous infrared radiation, which is of great importance in mitigating global warming and energy crises. However, conventional PRC materials lack on-demand light transmission and efficient infrared radiation, making it difficult to meet the demand for high transparency and efficient temperature control in building coverage applications. Herein, inspired by the skin’s thermal management mechanism, a bioinspired passive radiative cooler (BPRC) with wavelength-dependent light modulation and unidirectional heat transfer is developed to achieve temperature control for transparent substrate. Remarkably, BPRC exhibits 89.5% transmittance in the visible band (same with bare glass). Furthermore, BPRC demonstrates a 34% higher UV blocking rate and 38% higher NIR emissivity compared to bare glass. The maximum cooling effect reaches 7.4°C under perpendicular illumination (radiance 653.35 W/m 2 ). In addition, the adhesion between the bioinspired PRC film and the substrate is up to 0.5 MPa, ensuring the durability of BPRC in practical applications. This work offers a general strategy for the mass production of highly transparent PRC materials, with potential applications in energy-efficient buildings and photovoltaic systems. Physical sciences/Materials science/Materials for optics Physical sciences/Materials science/Materials for energy and catalysis/Solar cells Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Induction As global temperature rising, approximately 10% of global electricity is devoted to the air-conditioning of buildings, this continuously growing proportion of energy consumption will intensify the energy crisis 1 – 4 . It is the key point to achieve energy-free cooling for solving the challenges mentioned above 5 – 9 . Passive radiative cooling technology has attracted a lot of attention due to its low or even no energy consumption characteristics 10 – 12 . For the building exterior coverings, many functional materials 4 , 13 – 15 (such as: ultra-white paints) are designed to increase the reflection of visible light (> 90%) and emit heat 16 – 20 through the atmospheric transparency window (8–13 µm) to achieve sub-ambient temperature 9 , 11 , 20 – 22 . However, it is still challenging to create passive radiative cooling methods for transparent materials such as glass curtain walls 23 – 25 . For transparent materials such as glass 26 – 28 , the most effective way to achieve temperature controlling is regulating their infrared radiation and UV shielding performance while ensuring their visible transparency, without adding additional component materials or changing surface structure 29 , 30 . In this way, applying transparent thin films with radiative cooling capability is the most direct approach 31 – 34 . Here involve two issues that thin film products in their application process, the optical and thermal properties of film itself. Firstly, the light wave modulation capability of films above whole light range is a crucial attribution that affects radiative cooling performance. This modulation ability should maintain excellent transparency in the visible light to sustain high imaging capability during utilization. In addition, light in ultraviolet and infrared regions should be shielded as much as possible to prevent the energy from spreading into the interior, or with high emissivity, which can speed up the process of excessing energy to outdoor spaces 16 , 19 , 35 – 37 . Secondly, the unidirectional heat transfer performance of films can effectively prevent external energy from entering indoor environment 2 , 7 , 8 , 22 , 38 . This design originates from the skin’s thermal management mechanism. When the external heat is higher than human body, it is difficult for the external heat to enter the body through the skin. However, when the human body’s heat is higher than external heat, it can easily release heat to the outside world. In addition, the bonding ability 39 between film and substrate is another key point to ensuring its long-term effectiveness 40 – 42 . Although many optical thin film products achieve good optical manipulation ability, it is difficult to meet the actual application environment in regard to their fragile mechanical stability. This study presents the development of a bio-inspired 38 , 43 , 44 passive radiative cooler (BPRC), drawing inspiration from the skin's thermal management mechanisms. The BPRC is notable for its scalability, energy-free operation, and stability under ambient conditions, while maintaining high levels of transparency. Specifically, the superior UV shielding and infrared emission of the skin-inspired hierarchical structures endowed the BPRC with wavelength-dependent light modulation and unidirectional heat transfer for effective temperature control. Accordingly, the BPRC achieved a maximum cooling of 7.4℃ (radiance 653.35 W/m 2 ) and an average cooling of 2.4℃ during the daytime. This bioinspired PRC design created the passive cooling methods for transparent substrates, thereby achieving effective, energy-free temperature control of indoor environments 9 , 45 – 47 . Furthermore, the potential of BPRC extends to the photovoltaic industry, where its application in maintaining solar cells 41 , 42 , 48 at optimal operating temperatures and enhancing their photovoltaic conversion performance is promising. Results and Discussion Inspiration and designing of PRC device. In order to design passive radiative cooling devices for transparent substrates such as glass, a novel inspiration is developed inspired by skin’s thermal management mechanism in this work (Fig. 1 a). The human skin is the largest and most efficient heat dissipation organ, 60% of the heat generated by the body is dissipated through radiative cooling according to research, especially the skin releases excess heat in the form of thermal radiation after being exposed to sunlight conditions (Fig. 1 c). For human skin, the multi-layered structure is connected together tightly (Fig. 1 b), which provides a biomimetic prototype for enhancing the adhesion performance between the PRC film with the substrate. In addition, the skin actively secretes melanin after exposed to sunlight, which can block excessive ultraviolet radiation, ensuring human protected from ultraviolet rays (Fig. 1 d). Based on this inspiration, a triple layer structure (Fig. 1 e) is designed to realize cooling function for transparent substrate. The bio-inspired passive radiative cooling device (PRC device) mainly involves the top layer of PI film, the middle layer of nanostructured ZnO coating and the substrate of glass slide (Fig. 1 f, physical picture is showed in Supplementary Fig. 1). Firstly, the top layer contains a large number of benzene rings, C = O and C-N, ensuring UV absorption capability. Secondly, the C = O functional group have high infrared emission efficiency, which can effectively achieve radiation cooling effect (Fig. 1 g). Thirdly, the nano-structure in middle layer formed by the accumulation of ZnO nanospheres imitates the interlayer structure of skin, enhancing the bonding effect between the film and the substrate. The enhanced bonding performance will be discussed in detail in the following. In addition, PRC device has unidirectional heat transfer capability, which means that it is easier to transfer heat from indoors to outdoors (Fig. 1 g Heat control part). The PRC device can be applied to energy-efficient buildings, as wavelength-dependent light modulation can regulate indoor temperature while ensuring transparency. Especially, PRC device can also be applied to photoelectric system to reduce the solar panels surface temperature and improve conversion efficiency (Fig. 1 h). During the experiment, the internal temperature of the testing equipment covered with PRC device under sunlight conditions (radiance 653.35 W/m 2 ) can be reduced by up to 7.4℃ compared to bare glass (Fig. 1 i). The specific discussion about the cooling performance of PRC device under sunlight illumination will be elaborated in the following section. Fabrication and wave-dependent light modulation capability of PRC device. The fabrication process of PRC device mainly involves two steps. Firstly, the high-temperature decomposition of Zinc acetate to form a wrinkled surface by the accumulation of ZnO nano-spheres. Secondly, the dehydration and molecular cross-linking of polyamide acid (Fig. 2 a and Supplementary Fig. 2). Spatial structure of PRC device is characterized using SEM, especially its connection part from cross section (Fig. 2 b). A triple layer structure can be clearly seen from the side view (elements distribution is showed in Supplementary Fig. 3), with the PI layer thickness is about 6 µm and the ZnO layer thickness is between 100–600 nm (Supplementary Fig. 4). The clear and uniform wrinkled structures can be observed on the surface of the ZnO layer from SEM images (Supplementary Fig. 5). After separating PI layer from PRC device, a large number of ZnO nano-spheres adhered to the lower surface, indicating that the polyamide acid had excellent wettability on the wrinkled surface during the fabrication process (Supplementary Fig. 6). This tightly bonded interlayer style establishes the foundation for its excellent mechanical adhesion performance. In order to determine optical performance of PRC device, which means wave-dependent light modulation capability, the transparency, reflectivity, and emissivity of PRC device is tested from 0.2 µm to 15 µm (including UV, VIS, NIR and MIR). During the optical testing process, four samples are prepared to determine the functionality of each layer. Bare, indicating that no film is fabricated on the glass slide. ZnO, indicating that only ZnO layer is fabricated on the glass slide. PI, indicating that only PI layer is fabricated on the glass slide. As for PRC, it is prepared according to the above fabrication process. According to the results, the total transmittance of PRC device in testing region decreased by 2.68% compared to Bare device (Supplementary Fig. 7a), owing to the transmittance decrease in UV (Fig. 2 c) and NIR (Supplementary Fig. 8c) regions. This capability is exactly expected to be possessed by PRC device. The transmittance of PI device is almost identical to that of PRC device, while the expected performance showing slightly decreased. Under outdoor lighting condition, the UV shielding ability of PRC device and PI device is showed in Supplementary Fig. 7b, c. In terms of emissivity, PRC device can improve by 38% and 1.8% in the NIR and MIR compared to Bare glass (Fig. 2 d). Subsequently, the emissivity of 4 samples is integrated throughout the entire testing band, and the PRC device exhibited the highest emissivity of 76.8%, which is 3% higher than that of bare glass (Supplementary Fig. 9). This performance will ensure radiative cooling performance of PRC device under sun light condition. As for reflectance, the ZnO device is slightly higher in the short-wave region, while the other 3 films are almost the same (Supplementary Fig. 8a). In the medium-wave range, the reflectance of PRC device is lower in some areas (8–13 µm) as showed in Supplementary Fig. 8b. In order to visually observe the optical properties of the 4 samples, integration operation is used to process the transmittance, reflectance, and emissivity in different wavelength ranges, and the specific calculation results are showed in Supplementary Fig. 10. The transmittance in different wavelength regions of 4 samples is further processed, and the results are shown in Fig. 2 e and Fig. 2 f. It can be clearly seen that the selective transmittance of PRC device in Fig. 2 e, with transmittance is almost the same as that of bare glass in 0.4–0.78 µm and 0.78–2.5 µm, however, transmittance decreases by 9% compared to bare glass in 2.5-8 µm. This wave-dependent light modulation capability can prevent more infrared energy from passing through the PRC device and entering the internal space. Afterwards, the transmittance, reflectance, and emissivity were displayed in the form of a percentage bar chart (Fig. 2 f). It can be observed that the emissivity shows an uptrend along with the wavelength increases, while the transmittance shows a downtrend. It can be emphasized that the transparency and emissivity of PRC device perfectly meet the demand for transparent passive radiative cooling materials. Unidirectional heat transfer performance of PRC device. According to traditional understanding, heat transfer performance of substrate will change after a film prepared on the surface. In this work, heat transfer property of PRC device will change compared to bare glass thanks to PRC film (PI layer and ZnO layer). In order to investigate the specific heat transfer performance of PRC film, a simple test is operated (Fig. 3 a) to further clarify the capability of the PRC film in heat transfer process. The heating table is used to provide stable heating condition and an infrared thermometer is applied to obtain surface temperature values. After the temperature stabilizes, the sample is tested in 5 areas. And then, the sample is turned over and tested again. The temperature values of each side are then compared and analyzed. The testing temperature is from 30℃ to 80℃, and raises by 10℃ each time. Figure 3 b shows the infrared images of PRC device and bare glass under the same heating temperature, the left-side images are non-direct heating, while the right-side images are direct heating. From the figures, it can be seen that when the film is placed downwards, the surface temperature difference between the two samples will increase. The comparison results qualitatively indicate that PRC device has the unidirectional heat transfer capability. The temperature of heating table surface and Bare glass surface are recorded in Fig. 3 c, and their temperature difference (△T) is showed in Supplementary Fig. 11. It can be seen from the figure that as the heating temperature gradually increases, the △T also increases gradually. The temperature results of PRC devices under different fabricating parameters are summarized and showed in Fig. 3 d (The raw temperature values are exhibited in Supplementary Fig. 12, fabrication parameters are showed in Supplementary Table 1). For PRC device, it is expected to have the ability to transfer heat easily when the film surface is placed upward, which means the △T between the sample surface and the heating table is smaller. However, when the film surface is placed downward, the heat transfer process should be hindered, resulting in a larger △T between the sample surface and the heating table. With above functional requirement, PRC devices under different processing parameters are selected, the S3 sample best meets the requirement in Fig. 3 d (detail data exhibited in Supplementary Fig. 13). To illustrate the selection process more clearly, the △T between surface and the heating table is showed in Fig. 3 e when the film is placed upward, the △T between surface and heating table is showed in Fig. 3 f when the film is placed downward. According to the above functional requirement, the bottommost curve should be found in Fig. 3 e, and the topmost curve should be found in Fig. 3 f. At this point, it can be found that sample S3 meets the requirements of both. Furthermore, the △T between two states is exhibited in Fig. 3 g. S3 shows the maximum temperature difference. For samples that only fabricate ZnO layer and PI layer, the △T between the two states is not as significant as that of the PRC device (Supplementary Figs. 14 and 15). It can be inferred that the unidirectional heat transfer ability of the PRC device is the result of the combined effect of two layers, and it is impossible to achieve this ability by fabricate any one layer. Mechanical durability of PRC device. After characterizing the optical and thermal properties, another factor to consider is the durability of the PRC device. At present, the reported PRC devices are usually fabricated by integrating the structure and substrate, it is difficult to achieve rapid and large-scale preparation and application with delicate structures. The PRC device designed in this work selects glass as the substrate, which serves as the basis for practical applications. It is worth noting that, the adhesion effect between the film and the substrate is the key point in ensuring its long-term application. If the adhesion effect is deficient in stability, it will lead to performance degradation as time passes. Considering the outdoor environment for application, water flushing test is used to detected the durability of the PRC film. The testing device is showed in Supplementary Fig. 16a. 3 samples are placed on a 3D printed shelf and continuously flushed with water flow for 30 days. Then, optical and mechanical performance are conducted to the samples before and after flushing. Supplementary Fig. 16b-d show the images of ZnO device, PI device, and PRC device before and after flushing. Regarding ZnO device, it can be clearly seen that the coating material decreases after long-term flushing. As for PI device, a large number of bubbles are generated on the surface. While PRC device does not show any difference in appearance. Figure 4 a-c show the transmittance of 3 samples before and after flushing. The thickness of the ZnO device decreases with the reduction of nano-particles, causing increased of transmittance. Due to surface damage, the transmittance of PI device decreases by about 5%. It is worth noting that the transmittance of PRC device is almost unaffected after flushing. Subsequently, mechanical performance is conducted on the samples of PI and PRC devices before and after flushing. Before testing, a small hook with 3M tape is adhered to the sample surface (Fig. 4 d). The sample surface is divided into three regions, containing four corners, four edges, and central area (Supplementary Fig. 17). During the stretching process, there are three types of interface failures that need to be considered: the first type is the interface failure between film and substrate, the second type is the interface failure between film and 3M tape, the third type is the interface failure between 3M tape and hook surface. Any kind of interface failure will result in pulling force decreasing, only when the first type interface failure occurs will the pulling force directly decrease to 0, the other two types of interface failures will both have residual pulling force. Based on the test results, regardless of whether flushing water or not, the displacement of PRC device can reach 1.2–1.8 mm (Fig. 4 e), while the displacement of PI device is only 0.3–0.6 mm (Fig. 4 f). It can be seen that the second and the third types interface failures have occurred to PRC device, which is showed in Fig. 4 g. After the test, the surface of the small hook with M3 tape has already bulged (Fig. 4 h, Supplementary Movie 1). However, as for the PI device, only the first type interface failure occurred (Fig. 4 i), and the test results show that the intact PI layer adheres to the hook surface (Fig. 4 j, Supplementary Movie 2). Before flushing, the adhesion force of the PI device central area can reach 20 N (Fig. 4 k), while after flushing, it is slightly lower than 20 N (Fig. 4 l). The adhesion performance of the other areas is also slightly decrease, basically maintained at 20 N (Supplementary Fig. 18). As for PRC device, the adhesion force of central area before and after flushing both can reach 50 N (Fig. 4 m, n). The adhesion force in other areas also slightly decreased, but remained above 35 N (Supplementary Fig. 19). This excellent mechanical property of PRC device provides an outstanding guarantee for its stability under ambient conditions. Daytime continuous passive radiative cooling measurements of PRC device. Subsequently, the radiative cooling effect of PRC device is tested under outdoor sunlight condition. 4 square boxes sealed with different samples is used as testing devices and their internal temperature are recorded through a temperature sensor within whole day. (Fig. 5 a, Supplementary Fig. 20a). The temperature data of all 4 boxes are recorded in Fig. 5 b (Indoor temperature recorded in Supplementary Fig. SF24). From the overall curve, the square box covered with bare glass reaches the highest temperature (66.2℃), followed by the square box covered with ZnO device (61.9℃). The square boxes covered with PI device (59.9℃) and PRC device (60.1℃) come next (Supplementary Fig. 20b). The 4 curves are all in a continuously rising state before 10 o'clock (Supplementary Fig. 21a, b), and then, they show significant fluctuations and a remarkable increase (Supplementary Fig. 21c). After 14 o'clock, the curves gradually decrease to the same level (Supplementary Fig. 21d-f). The △T between 3 functional devices and bare glass is exhibited in Supplementary Fig. 22, reaching a maximum of 7.4℃ (PRC device). The bar chart in Fig. 5 b shows the irradiance parameter, it is worth noting that, the temperature change trend is consistent with the overall trend of irradiance. The outdoor temperature is recorded every 30 minutes as the black curve in Fig. 5 c. At the same time, the temperatures of 4 boxes are conducted discrete statistics and exhibited in Fig. 5 c. From the figure, it can be seen that the outdoor temperature reaches its highest value around 14:00, rather than 12:54 when the boxes reach their highest value. However, when there is no sunlight, the internal temperature of the boxes gradually drops to ambient temperature. Figure 5 d shows the illumination of the same time as Fig. 5 c, it is consistent with the irradiance. Meanwhile, the light component passing through the PRC device is recorded to evaluate whether it can be applied to cover applications of energy-efficient buildings (Fig. 5 e). Compared with other samples, the ultraviolet region of the light after passing through the PRC device is significantly weakened (Supplementary Fig. 23). The color rendering index Ra and Re of PRC device both exceed 95 (Fig. 5 f), indicating its color rendering performance is very excellent, even suitable for precise optical applications. According to the positions of the four samples on the CIE 1931 (Fig. 5 g), it can be seen that the light passing through the PRC device is close to the white light region, and its performance is similar to that of optical glass, which ensures its applicability to outdoor glass. Application testing of PRC device. Finally, two simple application tests are conducted on PRC device (Fig. 6 a). The first test is to characterize its radiative cooling performance, and the second test focuses on enhancing photoelectric conversion performance of solar panels. For the first test, 40 ml hot water (80℃) is poured in containers covered with PRC device and bare glass (non-full state), and the temperature of containers’ surfaces are recorded. The actual states are captured at 3 and 30 minutes (Fig. 6 b), and the infrared images at the same time are exhibited in Fig. 6 c. At 3 minutes, the thermal images of the two samples are almost identical. However, at 30 minutes, it can be seen that the temperature inside the container covered with PRC device is significantly lower than that of the container covered with glass. From the curves (Fig. 6 d), it can be seen that at the beginning of test, the surface temperature of the container covered with PRC device is slightly higher than the other. After about 4 minutes, the temperatures of two containers reduce to the same level, the temperature of the container covered with PRC device is always lower than the other until the temperature of both containers reaches ambient condition. The △T between the two containers reaches its maximum of 1.7℃ about 9 minutes. The results indicate that PRC device exhibits accelerating heat dissipation performance under non-sunlight conditions. For the second test, the commercial solar panel was packaged with different devices showed in Fig. 6 e, and then placed under simulated light of AM 1.5 (200–1100 nm) to record its internal temperature and output voltage. Figure 6 f shows the infrared images at the test beginning and the end. At the beginning, the temperatures of the two equipment are the same, while it can be seen that the internal temperature of the equipment covered with bare glass is significantly higher than that of the equipment covered with PRC device at the end. Due to the PRC device shielding some ultraviolet light, the total amount of light entering its interior is less than that of the bare glass, so the initial voltage of the equipment covered with bare glass will be slightly higher. From the Fig. 6 g, it can be seen that when the irradiation time reaches 3 minutes, the output voltage of both reaches the same 2.32 v. At this time, the temperature of the bare glass covered equipment is 48.6℃, and the temperature of the equipment covered with PRC device is 47.1℃. Results indicate that when the △T reaches 1.5℃, the photoelectric conversion efficiency of the device covered with PRC device has already exceeded that of the device covered with bare glass. During the continuous lighting period, the temperature of the two devices continued to rise and the output voltage continued to decrease, but the temperature of the equipment covered with PRC device was always lower than the other, and the output voltage was significantly higher. The optimal working temperature for solar panels is 25℃. However, in practical applications, due to prolonged exposure to sunlight, the internal temperature often remains above 60℃, causing severe performance degradation. PRC device can achieve more efficient cooling effects under outdoor sunlight conditions, enabling more conversion of light energy. Conclusion In summary, this work provides a bio-inspired passive radiative cooler with strong ultraviolet light shielding, enhanced infrared emission, and no energy consumption while demonstrating excellent transparency. The PBRC, inspired by the skin’s thermal management mechanism, which integrating dual properties including wave-dependent light modulation capability and unidirectional heat transfer performance, exhibits 89.5% transmittance in the visible band, a 34% higher UV blocking rate and 38% higher NIR emissivity compared to bare glass. During outdoor daytime testing, PBRC achieves maximum cooling of 7.4℃ (radiance 653.35 W/m 2 ) and an average cooling of 2.4℃. This work offers a general strategy for the scalable manufacturing of PRC materials for high transparent substrate, with potential applications in energy-efficient buildings and photovoltaic systems. Methods Zinc acetate solution synthesis. 0.1 mole of zinc acetate dihydrate (≥ 98%) is dissolved in 300 ml of ethylene glycol methyl ether (2-methoxyethanol, ≥ 99.5%(GC)) and add 5 ml of ethanolamine (2-aminoethanol, ≥ 99%) as a stabilizer. Then place the sealed beaker containing the mixed solution in 70℃ water and magnetic stirring for 30 minutes. Take out the beaker and place it in a dark place until the solution cools down before use. ZnO layer fabrication. Silicate glasses with a side length of 4 cm are selected as substrate for ZnO layer fabrication. The glasses are ultrasonic cleaned respectively with alcohol and deionized water, both cleaning times last for 10 minutes. Then glasses are heated in a drying oven to remove surface liquid. The glass sheet is placed horizontally on the spin coater and drip zinc acetate solution to cover the glass surface. The spin speed was set to 3000r/min to fabricate samples. Next, the samples are placed in muffle furnace, set the heating temperature to 370℃, and set the heating time to 30 mins. After the temperature drops to room temperature, ZnO layer is fabricated on the glass surface already. Polyamide acid synthesis. 0.800 g of diamin-odiphenyl ether (ODA) is dissolved in 22 g dimethylacetamide (DMAC). The mixed solution is stirred at 25℃ until the solute is completely dissolved. Then 0.872 g of isophthalic acid dihydrate (PMDA) is added in 4 to 5 portions during stirring process. Stop stirring when the solution becomes transparent. The above prepared solution named PI1 precursor. When DMAC is added first, followed by ODA, the prepared solution is called PI2 precursor. PI layer fabrication. Drip 0.2 g of polyamide acid onto the glass with ZnO layer, and the spin coater is used again to evenly distribute the precursor solution. The spin coating speed is set to 1500 r/min. Then place the sample in vacuum drying oven for moisture removal treatment under 170℃. The drying time is set to 100 minutes. Nanoscale characterization Scanning electron microscopy (SEM) characterization was done by recording on JSM-6700F, JEOL. Optical characterization The measurements of the reflection and transmission properties are carried out using Fourier transform infrared spectrometer (Nicolet iS50, Thermo Fisher) across a wide range of wavelengths (0.2–15 µm). The instrument is equipped with an integrated sphere with a highly reflective inner surface to collect both diffused and direct light. The illuminance and irradiance are test by Spectral illuminance meter (HPC350FR). Thermal characterization Temperature parameters is obtained by using an infrared thermometer (HT-18) in heat transfer part. The outdoor temperature is recorded by a simple temperature meter in Fig. 5 c. The real-time detection of the square box temperature indoors and outdoors is achieved by using a K-type Kepler temperature sensor, which purchased on Taobao. The temperature data is transmitted to the computer through a data acquisition device (Smacq, M2101), processed by the corresponding software (M manager) and recorded. Mechanical characterization The measurement of the adhesion property is carried out using tension meter fixed on the slide rail (MX2-500N), the force and displacement data are transmitted to the computer via data cables and recorded by software (Force Logger Ver2). Declarations Acknowledgements This work is supported by the Foundation for Innovative Research Groups of the National Natural Science Foundation of China (No. 52021003), National Natural Science Foundation of China (Nos. 52222509, 52475300), and supported by “Fundamental Research Funds for the Central Universities”. Author contributions H.D. was associated with conceptualization, investigation, writing—original draft, review & editing, methodology, and resources. Y.Z. and Y.Z. were associated with experiments and characterization. B.L., S.N and Z.H. was associated with conceptualization, funding acquisition, writing—review & editing, resources, and project administration supervision. Competing interests The authors declare no competing interests. Data availability The authors declare that the data supporting findings of this study are available within the article and Supplementary Information. Additional datasets related of this study are available from the corresponding authors upon. Source data are provided in this paper. References Chen Z, Zhu L, Raman A, Fan S (2016) Radiative cooling to deep sub-freezing temperatures through a 24-h day-night cycle. Nat Commun 7:13729 Wang T et al (2021) A structural polymer for highly efficient all-day passive radiative cooling. Nat Commun 12:365 Wu X et al (2024) A dual-selective thermal emitter with enhanced subambient radiative cooling performance. Nat Commun 15:815 Li J et al (2022) A tandem radiative/evaporative cooler for weather-insensitive and high-performance daytime passive cooling. Sci Adv 8:eabq0411 Jaramillo-Fernandez J et al (2022) Highly-scattering cellulose-based films for radiative cooling. Adv Sci 9:2104758 Kou Jlong, Jurado Z, Chen Z, Fan S, Minnich AJ (2017) Daytime radiative cooling using near-black infrared emitters. ACS Photonics 4:626–630 Mandal J et al (2018) Hierarchically porous polymer coatings for highly efficient passive daytime radiative cooling. Science 362:315–319 Li P et al (2022) Thermo-optically designed scalable photonic films with high thermal conductivity for subambient and above-ambient radiative cooling. Adv Funct Mater 32:2109542 Cai C et al (2022) Dynamically tunable all-weather daytime cellulose aerogel radiative supercooler for energy-saving building. Nano Lett 22:4106–4114 Wang S et al (2021) Scalable thermochromic smart windows with passive radiative cooling regulation. Science 374:1501–1504 Liu H, Zhu SN (2021) Hierarchical-morphology metafabric for scalable passive daytime radiative cooling. Kexue Tongbao/Chinese Sci Bull 66:3787–3790 Raman AP, Anoma MA, Zhu L, Rephaeli E, Fan S (2014) Passive radiative cooling below ambient air temperature under direct sunlight. Nature 515:540–544 Xu L, Sun DW, Tian Y, Fan T, Zhu Z (2023) Nanocomposite hydrogel for daytime passive cooling enabled by combined effects of radiative and evaporative cooling. Chem Eng J 457:141231 Li J et al (2022) Protecting ice from melting under sunlight via radiative cooling. Sci Adv 8:eabj9756 Li X, Peoples J, Yao P, Ruan X (2021) Ultrawhite BaSO 4 paints and films for remarkable daytime subambient radiative cooling. ACS Appl Mater Interfaces 13:21733–21739 Cheng N et al (2023) Nanosphere-structured hierarchically porous PVDF-HFP fabric for passive daytime radiative cooling via one-step water vapor-induced phase separation. Chem Eng J 460:141581 Zhu B et al (2021) Subambient daytime radiative cooling textile based on nanoprocessed silk. Nat Nanotechnol 16:1342–1348 Wang X et al (2020) Scalable flexible hybrid membranes with photonic structures for daytime radiative cooling. Adv Funct Mater 30:1907562 Cai L et al (2018) Spectrally selective nanocomposite textile for outdoor personal cooling. Adv Mater 30:1802152 Fan C et al (2023) Dynamically tunable subambient daytime radiative cooling metafabric with janus wettability. Adv Funct Mater 33:2300794 Zhao X et al (2023) A solution-processed radiative cooling glass. Science 382:684–691 Zhong H et al (2021) Hierarchically hollow microfibers as a scalable and effective thermal insulating cooler for buildings. ACS Nano 15:10076–10083 Zhai Y et al (2017) Scalable-manufactured randomized glass-polymer hybrid metamaterial for daytime radiative cooling. Science 355:1062–1066 Lee KW, Yi J, Kim MK, Kim DR (2024) Transparent radiative cooling cover window for flexible and foldable electronic displays. Nat Commun 15:4443 Leroy A et al (2019) High-performance subambient radiative cooling enabled by optically selective and thermally insulating polyethylene aerogel. Sci Adv 5:eaat9480 Fan S, Li W (2022) Photonics and thermodynamics concepts in radiative cooling. Nat Photonics 16:182–190 Liang J et al (2023) Radiative cooling for passive thermal management towards sustainable carbon neutrality. Natl Sci Rev 10:nwac208 Bijarniya JP, Sarkar J, Maiti P (2020) Review on passive daytime radiative cooling: Fundamentals, recent researches, challenges and opportunities. Renew Sustain Energy Rev 133:110263 Bhatia B et al (2018) Passive directional sub-ambient daytime radiative cooling. Nat Commun 9:5001 Yun J et al (2023) Optimally designed multimaterial microparticle-polymer composite paints for passive daytime radiative cooling. ACS Photonics 10:2608–2617 Shan X et al (2022) Aerogel-functionalized thermoplastic polyurethane as waterproof, breathable freestanding films and coatings for passive daytime radiative cooling. Adv Sci 9:2201190 Liu Y et al (2024) Construction of robust silica-hybridized cellulose aerogels integrating passive radiative cooling and thermal insulation for year-round building energy saving. Chem Eng J 481:148780 Galib RH et al (2023) Atmospheric-moisture-induced polyacrylate hydrogels for hybrid passive cooling. Nat Commun 14:6707 Kim S et al (2024) Passive isothermal film with self-switchable radiative cooling-driven water sorption layer for arid climate applications. Nat Commun 15:8000 Xiang B et al (2021) 3D porous polymer film with designed pore architecture and auto-deposited SiO 2 for highly efficient passive radiative cooling. Nano Energy 81:105600 Zhang X et al (2022) A moisture-wicking passive radiative cooling hierarchical metafabric. ACS Nano 16:2188–2197 Liu X et al (2022) Hierarchically superhydrophobic stereo-complex poly (lactic acid) aerogel for daytime radiative cooling. Adv Funct Mater 32:2207414 Lin K et al (2023) Hierarchically structured passive radiative cooling ceramic with high solar reflectivity. Science 382:691–697 Wang H et al (2024) Bioinspired directional structures for inhibiting wetting on super-melt-philic surfaces above 1200°C. Int J Extrem Manuf 6:045503 Song J et al (2022) Durable radiative cooling against environmental aging. Nat Commun 13:4805 Xiong L et al (2023) Thin lamellar films with enhanced mechanical properties for durable radiative cooling. Nat Commun 14:6129 Kim S, Park JH, Lee JW, Kim Y, Kang YT (2023) Self-recovering passive cooling utilizing endothermic reaction of NH 4 NO 3 /H 2 O driven by water sorption for photovoltaic cell. Nat Commun 14:2374 Zhang H et al (2020) Biologically inspired flexible photonic films for efficient passive radiative cooling. Proc. Natl. Acad. Sci. U. S. A. 117, 14657–14666 Shi NN et al (2015) Keeping cool: Enhanced optical reflection and radiative heat dissipation in Saharan silver ants. Science 349:298–301 Tang K et al (2021) Temperature-adaptive radiative coating for all-season household thermal regulation. Science 374:1504–1509 Yang M et al (2023) Phase change material enhanced radiative cooler for temperature-adaptive thermal regulation. ACS Nano 17:1693–1700 Shi M et al (2023) Dual-mode porous polymeric films with coral-like hierarchical structure for all-day radiative cooling and heating. ACS Nano 17:2029–2038 Gerhard M et al (2019) Microscopic insight into non-radiative decay in perovskite semiconductors from temperature-dependent luminescence blinking. Nat Commun 10:1698 Additional Declarations There is NO Competing Interest. Supplementary Files supportinginformation.docx supporting information SupplementaryMovie1.mp4 Supplementary Movie 1 SupplementaryMovie2.mp4 Supplementary Movie 2 Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6024085","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":500787196,"identity":"73be3da2-2997-4584-912f-0f8ed5ee68d2","order_by":0,"name":"Shichao Niu","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA4UlEQVRIie3RMQrCMBSA4UihLkHXSkGv8KSgCNKzJHStUhBcFQq6eIC66BUqXqAi2KXqmrEuzkJWBxNdnNKMgvl58CDkmx5CJtMvZskBRMTKoJQvmT6xCRAt8lGS4DesJv069ngU+ePmcvWI6AK1G4zUeKQggxj33ASCiVOcUxDEazFiuYmCwBH3LAwZnbPRm9CUEdvCauJxSbYsLCWZ6RBwJUlZiCQhUE3sqSAB3RUnAHJxuuviFrtKcj3uOX76dJPHd3hMh51GHhy4inxnA0KO2LW5JhAnLbW/mkwm01/1Ai5ISr2DcPiIAAAAAElFTkSuQmCC","orcid":"https://orcid.org/0000-0003-0208-9996","institution":"Jilin University","correspondingAuthor":true,"prefix":"","firstName":"Shichao","middleName":"","lastName":"Niu","suffix":""},{"id":500787197,"identity":"2c26e6e2-4760-457d-96e5-9e0c10ff08af","order_by":1,"name":"Hanliang Ding","email":"","orcid":"","institution":"Jilin University","correspondingAuthor":false,"prefix":"","firstName":"Hanliang","middleName":"","lastName":"Ding","suffix":""},{"id":500787198,"identity":"e3df452c-f4e3-4a52-a175-7c2f1ddee363","order_by":2,"name":"Bo Li","email":"","orcid":"https://orcid.org/0000-0002-4839-3224","institution":"Jilin University","correspondingAuthor":false,"prefix":"","firstName":"Bo","middleName":"","lastName":"Li","suffix":""},{"id":500787199,"identity":"25d8a288-279e-4ec4-8d29-6f23037d2039","order_by":3,"name":"Yicong Zhang","email":"","orcid":"","institution":"Jilin University","correspondingAuthor":false,"prefix":"","firstName":"Yicong","middleName":"","lastName":"Zhang","suffix":""},{"id":500787200,"identity":"6f9fd906-2c9f-4863-9869-b3189bcc75d5","order_by":4,"name":"Yufan Zhang","email":"","orcid":"","institution":"Jilin University","correspondingAuthor":false,"prefix":"","firstName":"Yufan","middleName":"","lastName":"Zhang","suffix":""},{"id":500787201,"identity":"190175ae-c402-4833-ab92-4652eb7cebf8","order_by":5,"name":"Zhiwu Han","email":"","orcid":"","institution":"Jilin University","correspondingAuthor":false,"prefix":"","firstName":"Zhiwu","middleName":"","lastName":"Han","suffix":""},{"id":500787202,"identity":"d6f600c9-ff87-407d-ad25-f9911a311ca5","order_by":6,"name":"Luquan Ren","email":"","orcid":"","institution":"Jilin University","correspondingAuthor":false,"prefix":"","firstName":"Luquan","middleName":"","lastName":"Ren","suffix":""}],"badges":[],"createdAt":"2025-02-13 14:45:44","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6024085/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6024085/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":89281180,"identity":"7461e0a5-937d-4606-817e-31accc32e1ba","added_by":"auto","created_at":"2025-08-18 10:37:59","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1152208,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eInspiration for bioinspired passive radiative cooling device (PRC device).\u003c/strong\u003e \u003cstrong\u003ea\u003c/strong\u003e Model of human hand. \u003cstrong\u003eb\u003c/strong\u003e Hierarchical structure model of human skin. \u003cstrong\u003ec\u003c/strong\u003e The radiative cooling efficiency of human skin accounts for 60% of the total heat dissipation. \u003cstrong\u003ed\u003c/strong\u003e The melanin in the subcutaneous tissue of the human skin has the ability to shield ultraviolet light. \u003cstrong\u003ee, f\u003c/strong\u003e Triple layer structure design of PRC device. \u003cstrong\u003eg\u003c/strong\u003e The abundant functional groups in PRC device can shield ultraviolet light and infrared light, the absorbed heat can be dissipated by infrared waves. In addition, the film has a unidirectional heat transfer capability, making it easier for heat to dissipate to the outside world. \u003cstrong\u003eh\u003c/strong\u003eThe PRC device can be applied to the glass cover applications of energy-efficient buildings and photovoltaic systems to reduce indoor temperature and improve photoelectric conversion efficiency. \u003cstrong\u003ei\u003c/strong\u003e During the outdoor test, the temperature of the sample covered with PRC device is lower than that of the sample without film, and the maximum temperature difference is 7.4℃.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-6024085/v1/076741c4921dddef0744abc0.png"},{"id":89281206,"identity":"a0d06bcc-0605-458f-892a-a1eb4b216c04","added_by":"auto","created_at":"2025-08-18 10:38:05","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1324962,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFabrication, Characterization and Optical performance of PRC device.\u003c/strong\u003e \u003cstrong\u003ea\u003c/strong\u003e The fabrication process of PRC device involves two steps, first, the zinc acetate is decomposed at high temperatures to form a wrinkled surface structure of stacked nano-sphere as middle layer, second, the polyamide acid is dehydrated in vacuum to prepare PI film as top layer. \u003cstrong\u003eb\u003c/strong\u003e Physical image and microstructure cross-section characterization of PRC device. \u003cstrong\u003ec\u003c/strong\u003e Transmittance of 4 samples in UV, Vis and NIR. PRC device exhibits excellent UV shielding performance, and its transmittance in visible region is almost the same as that of bare glass. \u003cstrong\u003ed\u003c/strong\u003e Infrared emissivity of 4 samples in the testing band (0.2-15 μm). The emissivity of PRC device is significantly improved in the near infrared region. \u003cstrong\u003ee\u003c/strong\u003eTransmittance comparison of 4 samples in various wavelength ranges. \u003cstrong\u003ef\u003c/strong\u003e The proportion of emissivity, reflectivity, and transmittance of 4 samples in different wavelength ranges.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-6024085/v1/cbb21dbb1b95e68a71f59117.png"},{"id":89281181,"identity":"72baf8e2-f686-435a-b2f3-d111c97278a6","added_by":"auto","created_at":"2025-08-18 10:37:59","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":798981,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eUnidirectional heat transfer capability and fabrication parameters selection of PRC device.\u003c/strong\u003e \u003cstrong\u003ea\u003c/strong\u003e Schematic diagram of the testing device, division of the testing area, and two states during the testing process. \u003cstrong\u003eb\u003c/strong\u003e Infrared images of PRC film non-direct heating and direct heating, respectively, captured by changing the direction of the samples. \u003cstrong\u003ec\u003c/strong\u003eTemperature of bare glass surface and heating table surface. \u003cstrong\u003ed\u003c/strong\u003e The temperature values of 6 samples under different heating temperature conditions. \u003cstrong\u003ee\u003c/strong\u003e Temperature difference between PRC device and heat table when film is placed upward. \u003cstrong\u003ef\u003c/strong\u003e Temperature difference between PRC device and heat table when film is placed downward. \u003cstrong\u003eg\u003c/strong\u003e Temperature difference between two testing states.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-6024085/v1/155db17489ae15f25f250f1f.png"},{"id":89282583,"identity":"5d512ffe-85cb-45c1-b45e-aa47845b6e76","added_by":"auto","created_at":"2025-08-18 10:45:59","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":859950,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eMechanical stability of PRC device.\u003c/strong\u003e \u003cstrong\u003ea, b, c\u003c/strong\u003e Transmittance of 3 samples before and after flushing. \u003cstrong\u003ed\u003c/strong\u003e Schematic of the contact interface during adhesion test. \u003cstrong\u003ee\u003c/strong\u003e Schematic interface failure of PRC device during process. The displacement during the process of PRC film is between 1.2-1.8 mm, represented by h1 in the figure. \u003cstrong\u003ef\u003c/strong\u003e Schematic interface failure of PI film during process. The displacement during the process of PI film is between 0.3-0.6 mm, represented by h2 in the figure.\u003cstrong\u003e g\u003c/strong\u003e The images of PRC device during the testing process. \u003cstrong\u003eh\u003c/strong\u003e The surface condition of hook (PRC device) after the test. \u003cstrong\u003el \u003c/strong\u003eThe images of PI device during the testing process. \u003cstrong\u003ej\u003c/strong\u003eThe surface condition of hook (PI device) after the test. \u003cstrong\u003ek-n\u003c/strong\u003e Stress-displacement curves of the central area of PI device (k, l) and PRC device (m, n) before and after flushing.\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-6024085/v1/a069753b7cc70b8b37a4653b.png"},{"id":89281183,"identity":"abaf9363-6c86-4ebf-a3c3-ef895001a4b0","added_by":"auto","created_at":"2025-08-18 10:37:59","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":1098541,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eOutdoor cooling performance of PRC device.\u003c/strong\u003e \u003cstrong\u003ea\u003c/strong\u003e The lighting conditions that can be received from different angles outdoors. Physical image of the testing device, insulated with insulation layer, with temperature sensor attached inside. \u003cstrong\u003eb\u003c/strong\u003e Real time temperature curves of 4 testing devices throughout the daytime, the bar chart inside the diagram represents the current solar irradiance. \u003cstrong\u003ec\u003c/strong\u003e The ambient temperature recorded every thirty minutes, as well as the temperature of 4 devices at the same time. \u003cstrong\u003ed\u003c/strong\u003e Illuminance at the same time as showed in the c. \u003cstrong\u003ee\u003c/strong\u003e The solar spectrum passing through the PRC device at 12:00. Peak wave is 555.5 nm, solar spectrum\u003cstrong\u003e \u003c/strong\u003ereaches 1071 mW/m\u003csup\u003e2\u003c/sup\u003e/nm, central wave is 596 nm, halfwidth is 325 nm.\u003cstrong\u003e f\u003c/strong\u003e 15 general color rendering indices of PRC film. \u003cstrong\u003eg\u003c/strong\u003e The position of light passing through 4 samples on the CIE diagram.\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-6024085/v1/11bb240df91d3609eae6632a.png"},{"id":89281189,"identity":"d8902605-07e5-4711-8d9c-e5aef5b205ce","added_by":"auto","created_at":"2025-08-18 10:37:59","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":1289961,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ePassive cooling capability and optoelectronic conversion performance PRC device.\u003c/strong\u003e \u003cstrong\u003ea\u003c/strong\u003e The sketch map of PRC device, including increased heat dissipation performance and enhanced photoelectric conversion efficiency. \u003cstrong\u003eb\u003c/strong\u003e The actual state of the cooling devices at 3 min and 30 min. \u003cstrong\u003ec\u003c/strong\u003e Infrared thermal images of the cooling devices at the same time. \u003cstrong\u003ed\u003c/strong\u003e The temperature of the cooling devices and the temperature difference between two devices. \u003cstrong\u003ee\u003c/strong\u003e Packaged solar panel with different sample covered is used to test their surface temperature and output voltage under simulated lighting condition. \u003cstrong\u003ef\u003c/strong\u003eInfrared thermal images of two samples at the beginning and end.\u003cstrong\u003e g\u003c/strong\u003e Surface temperature and output voltage of solar panels covered by different samples.\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-6024085/v1/ccf30d8096f41d5ace73fdbf.png"},{"id":89283583,"identity":"fbe3afde-ec84-473b-abb2-1a8ac3c7f05a","added_by":"auto","created_at":"2025-08-18 10:54:01","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":7399632,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6024085/v1/5a3f8ae3-67a4-4387-b793-2b4075a382c5.pdf"},{"id":89281184,"identity":"6e55c64e-7560-446f-8487-c47e217f8404","added_by":"auto","created_at":"2025-08-18 10:37:59","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":15969015,"visible":true,"origin":"","legend":"supporting information","description":"","filename":"supportinginformation.docx","url":"https://assets-eu.researchsquare.com/files/rs-6024085/v1/6cbc971a595443ebf74df4a1.docx"},{"id":89281191,"identity":"25bb0c8a-d9ff-485c-ae5f-ceaccca11df7","added_by":"auto","created_at":"2025-08-18 10:37:59","extension":"mp4","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":19514262,"visible":true,"origin":"","legend":"Supplementary Movie 1","description":"","filename":"SupplementaryMovie1.mp4","url":"https://assets-eu.researchsquare.com/files/rs-6024085/v1/f48b625e2f362bbbe5a1a669.mp4"},{"id":89282585,"identity":"c1ffda69-8d51-4a13-bbb4-7c4679d68b20","added_by":"auto","created_at":"2025-08-18 10:45:59","extension":"mp4","order_by":3,"title":"","display":"","copyAsset":false,"role":"supplement","size":16662527,"visible":true,"origin":"","legend":"Supplementary Movie 2","description":"","filename":"SupplementaryMovie2.mp4","url":"https://assets-eu.researchsquare.com/files/rs-6024085/v1/4a57405bb1680a96f56697ea.mp4"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Bioinspired passive radiative cooler with superior transparency and durability for energy-efficient building","fulltext":[{"header":"Induction","content":"\u003cp\u003eAs global temperature rising, approximately 10% of global electricity is devoted to the air-conditioning of buildings, this continuously growing proportion of energy consumption will intensify the energy crisis\u003csup\u003e\u003cspan additionalcitationids=\"CR2 CR3\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e. It is the key point to achieve energy-free cooling for solving the challenges mentioned above\u003csup\u003e\u003cspan additionalcitationids=\"CR6 CR7 CR8\" citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e. Passive radiative cooling technology has attracted a lot of attention due to its low or even no energy consumption characteristics\u003csup\u003e\u003cspan additionalcitationids=\"CR11\" citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e. For the building exterior coverings, many functional materials\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e,\u003cspan additionalcitationids=\"CR14\" citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e (such as: ultra-white paints) are designed to increase the reflection of visible light (\u0026gt;\u0026thinsp;90%) and emit heat\u003csup\u003e\u003cspan additionalcitationids=\"CR17 CR18 CR19\" citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e through the atmospheric transparency window (8\u0026ndash;13 \u0026micro;m) to achieve sub-ambient temperature\u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e,\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e,\u003cspan additionalcitationids=\"CR21\" citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e. However, it is still challenging to create passive radiative cooling methods for transparent materials such as glass curtain walls\u003csup\u003e\u003cspan additionalcitationids=\"CR24\" citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eFor transparent materials such as glass\u003csup\u003e\u003cspan additionalcitationids=\"CR27\" citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u003c/sup\u003e, the most effective way to achieve temperature controlling is regulating their infrared radiation and UV shielding performance while ensuring their visible transparency, without adding additional component materials or changing surface structure\u003csup\u003e\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e,\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e. In this way, applying transparent thin films with radiative cooling capability is the most direct approach\u003csup\u003e\u003cspan additionalcitationids=\"CR32 CR33\" citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e. Here involve two issues that thin film products in their application process, the optical and thermal properties of film itself. Firstly, the light wave modulation capability of films above whole light range is a crucial attribution that affects radiative cooling performance. This modulation ability should maintain excellent transparency in the visible light to sustain high imaging capability during utilization. In addition, light in ultraviolet and infrared regions should be shielded as much as possible to prevent the energy from spreading into the interior, or with high emissivity, which can speed up the process of excessing energy to outdoor spaces\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e,\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e,\u003cspan additionalcitationids=\"CR36\" citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e\u003c/sup\u003e. Secondly, the unidirectional heat transfer performance of films can effectively prevent external energy from entering indoor environment\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e,\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e,\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e,\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e\u003c/sup\u003e. This design originates from the skin\u0026rsquo;s thermal management mechanism. When the external heat is higher than human body, it is difficult for the external heat to enter the body through the skin. However, when the human body\u0026rsquo;s heat is higher than external heat, it can easily release heat to the outside world.\u003c/p\u003e\u003cp\u003eIn addition, the bonding ability\u003csup\u003e\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e\u003c/sup\u003e between film and substrate is another key point to ensuring its long-term effectiveness\u003csup\u003e\u003cspan additionalcitationids=\"CR41\" citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e\u003c/sup\u003e. Although many optical thin film products achieve good optical manipulation ability, it is difficult to meet the actual application environment in regard to their fragile mechanical stability.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThis study presents the development of a bio-inspired\u003csup\u003e\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e,\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e,\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e\u003c/sup\u003e passive radiative cooler (BPRC), drawing inspiration from the skin's thermal management mechanisms. The BPRC is notable for its scalability, energy-free operation, and stability under ambient conditions, while maintaining high levels of transparency. Specifically, the superior UV shielding and infrared emission of the skin-inspired hierarchical structures endowed the BPRC with wavelength-dependent light modulation and unidirectional heat transfer for effective temperature control. Accordingly, the BPRC achieved a maximum cooling of 7.4℃ (radiance 653.35 W/m\u003csup\u003e2\u003c/sup\u003e) and an average cooling of 2.4℃ during the daytime. This bioinspired PRC design created the passive cooling methods for transparent substrates, thereby achieving effective, energy-free temperature control of indoor environments\u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e,\u003cspan additionalcitationids=\"CR46\" citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e\u003c/sup\u003e. Furthermore, the potential of BPRC extends to the photovoltaic industry, where its application in maintaining solar cells\u003csup\u003e\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e,\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e,\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e\u003c/sup\u003e at optimal operating temperatures and enhancing their photovoltaic conversion performance is promising.\u003c/p\u003e"},{"header":"Results and Discussion","content":"\u003cp\u003e\u003cb\u003eInspiration and designing of PRC device.\u003c/b\u003e In order to design passive radiative cooling devices for transparent substrates such as glass, a novel inspiration is developed inspired by skin\u0026rsquo;s thermal management mechanism in this work (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea). The human skin is the largest and most efficient heat dissipation organ, 60% of the heat generated by the body is dissipated through radiative cooling according to research, especially the skin releases excess heat in the form of thermal radiation after being exposed to sunlight conditions (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec). For human skin, the multi-layered structure is connected together tightly (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb), which provides a biomimetic prototype for enhancing the adhesion performance between the PRC film with the substrate. In addition, the skin actively secretes melanin after exposed to sunlight, which can block excessive ultraviolet radiation, ensuring human protected from ultraviolet rays (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed). Based on this inspiration, a triple layer structure (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ee) is designed to realize cooling function for transparent substrate. The bio-inspired passive radiative cooling device (PRC device) mainly involves the top layer of PI film, the middle layer of nanostructured ZnO coating and the substrate of glass slide (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ef, physical picture is showed in Supplementary Fig.\u0026nbsp;1). Firstly, the top layer contains a large number of benzene rings, C\u0026thinsp;=\u0026thinsp;O and C-N, ensuring UV absorption capability. Secondly, the C\u0026thinsp;=\u0026thinsp;O functional group have high infrared emission efficiency, which can effectively achieve radiation cooling effect (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eg). Thirdly, the nano-structure in middle layer formed by the accumulation of ZnO nanospheres imitates the interlayer structure of skin, enhancing the bonding effect between the film and the substrate. The enhanced bonding performance will be discussed in detail in the following. In addition, PRC device has unidirectional heat transfer capability, which means that it is easier to transfer heat from indoors to outdoors (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eg Heat control part).\u003c/p\u003e\u003cp\u003eThe PRC device can be applied to energy-efficient buildings, as wavelength-dependent light modulation can regulate indoor temperature while ensuring transparency. Especially, PRC device can also be applied to photoelectric system to reduce the solar panels surface temperature and improve conversion efficiency (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eh). During the experiment, the internal temperature of the testing equipment covered with PRC device under sunlight conditions (radiance 653.35 W/m\u003csup\u003e2\u003c/sup\u003e) can be reduced by up to 7.4℃ compared to bare glass (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ei). The specific discussion about the cooling performance of PRC device under sunlight illumination will be elaborated in the following section.\u003c/p\u003e\u003cp\u003e\u003cb\u003eFabrication and wave-dependent light modulation capability of PRC device.\u003c/b\u003e The fabrication process of PRC device mainly involves two steps. Firstly, the high-temperature decomposition of Zinc acetate to form a wrinkled surface by the accumulation of ZnO nano-spheres. Secondly, the dehydration and molecular cross-linking of polyamide acid (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea and Supplementary Fig.\u0026nbsp;2). Spatial structure of PRC device is characterized using SEM, especially its connection part from cross section (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb). A triple layer structure can be clearly seen from the side view (elements distribution is showed in Supplementary Fig.\u0026nbsp;3), with the PI layer thickness is about 6 \u0026micro;m and the ZnO layer thickness is between 100\u0026ndash;600 nm (Supplementary Fig.\u0026nbsp;4). The clear and uniform wrinkled structures can be observed on the surface of the ZnO layer from SEM images (Supplementary Fig.\u0026nbsp;5). After separating PI layer from PRC device, a large number of ZnO nano-spheres adhered to the lower surface, indicating that the polyamide acid had excellent wettability on the wrinkled surface during the fabrication process (Supplementary Fig.\u0026nbsp;6). This tightly bonded interlayer style establishes the foundation for its excellent mechanical adhesion performance.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eIn order to determine optical performance of PRC device, which means wave-dependent light modulation capability, the transparency, reflectivity, and emissivity of PRC device is tested from 0.2 \u0026micro;m to 15 \u0026micro;m (including UV, VIS, NIR and MIR). During the optical testing process, four samples are prepared to determine the functionality of each layer. Bare, indicating that no film is fabricated on the glass slide. ZnO, indicating that only ZnO layer is fabricated on the glass slide. PI, indicating that only PI layer is fabricated on the glass slide. As for PRC, it is prepared according to the above fabrication process.\u003c/p\u003e\u003cp\u003eAccording to the results, the total transmittance of PRC device in testing region decreased by 2.68% compared to Bare device (Supplementary Fig.\u0026nbsp;7a), owing to the transmittance decrease in UV (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec) and NIR (Supplementary Fig.\u0026nbsp;8c) regions. This capability is exactly expected to be possessed by PRC device. The transmittance of PI device is almost identical to that of PRC device, while the expected performance showing slightly decreased. Under outdoor lighting condition, the UV shielding ability of PRC device and PI device is showed in Supplementary Fig.\u0026nbsp;7b, c. In terms of emissivity, PRC device can improve by 38% and 1.8% in the NIR and MIR compared to Bare glass (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed). Subsequently, the emissivity of 4 samples is integrated throughout the entire testing band, and the PRC device exhibited the highest emissivity of 76.8%, which is 3% higher than that of bare glass (Supplementary Fig.\u0026nbsp;9). This performance will ensure radiative cooling performance of PRC device under sun light condition. As for reflectance, the ZnO device is slightly higher in the short-wave region, while the other 3 films are almost the same (Supplementary Fig.\u0026nbsp;8a). In the medium-wave range, the reflectance of PRC device is lower in some areas (8\u0026ndash;13 \u0026micro;m) as showed in Supplementary Fig.\u0026nbsp;8b.\u003c/p\u003e\u003cp\u003eIn order to visually observe the optical properties of the 4 samples, integration operation is used to process the transmittance, reflectance, and emissivity in different wavelength ranges, and the specific calculation results are showed in Supplementary Fig.\u0026nbsp;10. The transmittance in different wavelength regions of 4 samples is further processed, and the results are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ee and Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ef. It can be clearly seen that the selective transmittance of PRC device in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ee, with transmittance is almost the same as that of bare glass in 0.4\u0026ndash;0.78 \u0026micro;m and 0.78\u0026ndash;2.5 \u0026micro;m, however, transmittance decreases by 9% compared to bare glass in 2.5-8 \u0026micro;m. This wave-dependent light modulation capability can prevent more infrared energy from passing through the PRC device and entering the internal space. Afterwards, the transmittance, reflectance, and emissivity were displayed in the form of a percentage bar chart (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ef). It can be observed that the emissivity shows an uptrend along with the wavelength increases, while the transmittance shows a downtrend. It can be emphasized that the transparency and emissivity of PRC device perfectly meet the demand for transparent passive radiative cooling materials.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eUnidirectional heat transfer performance of PRC device.\u003c/b\u003e According to traditional understanding, heat transfer performance of substrate will change after a film prepared on the surface. In this work, heat transfer property of PRC device will change compared to bare glass thanks to PRC film (PI layer and ZnO layer). In order to investigate the specific heat transfer performance of PRC film, a simple test is operated (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea) to further clarify the capability of the PRC film in heat transfer process. The heating table is used to provide stable heating condition and an infrared thermometer is applied to obtain surface temperature values. After the temperature stabilizes, the sample is tested in 5 areas. And then, the sample is turned over and tested again. The temperature values of each side are then compared and analyzed. The testing temperature is from 30℃ to 80℃, and raises by 10℃ each time. Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb shows the infrared images of PRC device and bare glass under the same heating temperature, the left-side images are non-direct heating, while the right-side images are direct heating. From the figures, it can be seen that when the film is placed downwards, the surface temperature difference between the two samples will increase. The comparison results qualitatively indicate that PRC device has the unidirectional heat transfer capability.\u003c/p\u003e\u003cp\u003eThe temperature of heating table surface and Bare glass surface are recorded in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec, and their temperature difference (△T) is showed in Supplementary Fig.\u0026nbsp;11. It can be seen from the figure that as the heating temperature gradually increases, the △T also increases gradually. The temperature results of PRC devices under different fabricating parameters are summarized and showed in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed (The raw temperature values are exhibited in Supplementary Fig.\u0026nbsp;12, fabrication parameters are showed in Supplementary Table\u0026nbsp;1). For PRC device, it is expected to have the ability to transfer heat easily when the film surface is placed upward, which means the △T between the sample surface and the heating table is smaller. However, when the film surface is placed downward, the heat transfer process should be hindered, resulting in a larger △T between the sample surface and the heating table. With above functional requirement, PRC devices under different processing parameters are selected, the S3 sample best meets the requirement in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed (detail data exhibited in Supplementary Fig.\u0026nbsp;13). To illustrate the selection process more clearly, the △T between surface and the heating table is showed in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ee when the film is placed upward, the △T between surface and heating table is showed in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ef when the film is placed downward. According to the above functional requirement, the bottommost curve should be found in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ee, and the topmost curve should be found in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ef. At this point, it can be found that sample S3 meets the requirements of both. Furthermore, the △T between two states is exhibited in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eg. S3 shows the maximum temperature difference. For samples that only fabricate ZnO layer and PI layer, the △T between the two states is not as significant as that of the PRC device (Supplementary Figs.\u0026nbsp;14 and 15). It can be inferred that the unidirectional heat transfer ability of the PRC device is the result of the combined effect of two layers, and it is impossible to achieve this ability by fabricate any one layer.\u003c/p\u003e\u003cp\u003e\u003cb\u003eMechanical durability of PRC device.\u003c/b\u003e After characterizing the optical and thermal properties, another factor to consider is the durability of the PRC device. At present, the reported PRC devices are usually fabricated by integrating the structure and substrate, it is difficult to achieve rapid and large-scale preparation and application with delicate structures. The PRC device designed in this work selects glass as the substrate, which serves as the basis for practical applications. It is worth noting that, the adhesion effect between the film and the substrate is the key point in ensuring its long-term application. If the adhesion effect is deficient in stability, it will lead to performance degradation as time passes. Considering the outdoor environment for application, water flushing test is used to detected the durability of the PRC film. The testing device is showed in Supplementary Fig.\u0026nbsp;16a. 3 samples are placed on a 3D printed shelf and continuously flushed with water flow for 30 days. Then, optical and mechanical performance are conducted to the samples before and after flushing.\u003c/p\u003e\u003cp\u003eSupplementary Fig.\u0026nbsp;16b-d show the images of ZnO device, PI device, and PRC device before and after flushing. Regarding ZnO device, it can be clearly seen that the coating material decreases after long-term flushing. As for PI device, a large number of bubbles are generated on the surface. While PRC device does not show any difference in appearance. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea-c show the transmittance of 3 samples before and after flushing. The thickness of the ZnO device decreases with the reduction of nano-particles, causing increased of transmittance. Due to surface damage, the transmittance of PI device decreases by about 5%. It is worth noting that the transmittance of PRC device is almost unaffected after flushing.\u003c/p\u003e\u003cp\u003eSubsequently, mechanical performance is conducted on the samples of PI and PRC devices before and after flushing. Before testing, a small hook with 3M tape is adhered to the sample surface (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ed). The sample surface is divided into three regions, containing four corners, four edges, and central area (Supplementary Fig.\u0026nbsp;17). During the stretching process, there are three types of interface failures that need to be considered: the first type is the interface failure between film and substrate, the second type is the interface failure between film and 3M tape, the third type is the interface failure between 3M tape and hook surface. Any kind of interface failure will result in pulling force decreasing, only when the first type interface failure occurs will the pulling force directly decrease to 0, the other two types of interface failures will both have residual pulling force.\u003c/p\u003e\u003cp\u003eBased on the test results, regardless of whether flushing water or not, the displacement of PRC device can reach 1.2\u0026ndash;1.8 mm (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ee), while the displacement of PI device is only 0.3\u0026ndash;0.6 mm (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ef). It can be seen that the second and the third types interface failures have occurred to PRC device, which is showed in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eg. After the test, the surface of the small hook with M3 tape has already bulged (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eh, Supplementary Movie 1). However, as for the PI device, only the first type interface failure occurred (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ei), and the test results show that the intact PI layer adheres to the hook surface (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ej, Supplementary Movie 2). Before flushing, the adhesion force of the PI device central area can reach 20 N (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ek), while after flushing, it is slightly lower than 20 N (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003el). The adhesion performance of the other areas is also slightly decrease, basically maintained at 20 N (Supplementary Fig.\u0026nbsp;18). As for PRC device, the adhesion force of central area before and after flushing both can reach 50 N (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003em, n). The adhesion force in other areas also slightly decreased, but remained above 35 N (Supplementary Fig.\u0026nbsp;19). This excellent mechanical property of PRC device provides an outstanding guarantee for its stability under ambient conditions.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eDaytime continuous passive radiative cooling measurements of PRC device.\u003c/b\u003e Subsequently, the radiative cooling effect of PRC device is tested under outdoor sunlight condition. 4 square boxes sealed with different samples is used as testing devices and their internal temperature are recorded through a temperature sensor within whole day. (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea, Supplementary Fig.\u0026nbsp;20a). The temperature data of all 4 boxes are recorded in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb (Indoor temperature recorded in Supplementary Fig. SF24). From the overall curve, the square box covered with bare glass reaches the highest temperature (66.2℃), followed by the square box covered with ZnO device (61.9℃). The square boxes covered with PI device (59.9℃) and PRC device (60.1℃) come next (Supplementary Fig.\u0026nbsp;20b). The 4 curves are all in a continuously rising state before 10 o'clock (Supplementary Fig.\u0026nbsp;21a, b), and then, they show significant fluctuations and a remarkable increase (Supplementary Fig.\u0026nbsp;21c). After 14 o'clock, the curves gradually decrease to the same level (Supplementary Fig.\u0026nbsp;21d-f). The △T between 3 functional devices and bare glass is exhibited in Supplementary Fig.\u0026nbsp;22, reaching a maximum of 7.4℃ (PRC device). The bar chart in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb shows the irradiance parameter, it is worth noting that, the temperature change trend is consistent with the overall trend of irradiance.\u003c/p\u003e\u003cp\u003eThe outdoor temperature is recorded every 30 minutes as the black curve in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec. At the same time, the temperatures of 4 boxes are conducted discrete statistics and exhibited in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec. From the figure, it can be seen that the outdoor temperature reaches its highest value around 14:00, rather than 12:54 when the boxes reach their highest value. However, when there is no sunlight, the internal temperature of the boxes gradually drops to ambient temperature. Figure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ed shows the illumination of the same time as Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec, it is consistent with the irradiance.\u003c/p\u003e\u003cp\u003eMeanwhile, the light component passing through the PRC device is recorded to evaluate whether it can be applied to cover applications of energy-efficient buildings (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ee). Compared with other samples, the ultraviolet region of the light after passing through the PRC device is significantly weakened (Supplementary Fig.\u0026nbsp;23). The color rendering index Ra and Re of PRC device both exceed 95 (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ef), indicating its color rendering performance is very excellent, even suitable for precise optical applications. According to the positions of the four samples on the CIE 1931 (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eg), it can be seen that the light passing through the PRC device is close to the white light region, and its performance is similar to that of optical glass, which ensures its applicability to outdoor glass.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eApplication testing of PRC device.\u003c/b\u003e Finally, two simple application tests are conducted on PRC device (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ea). The first test is to characterize its radiative cooling performance, and the second test focuses on enhancing photoelectric conversion performance of solar panels. For the first test, 40 ml hot water (80℃) is poured in containers covered with PRC device and bare glass (non-full state), and the temperature of containers\u0026rsquo; surfaces are recorded. The actual states are captured at 3 and 30 minutes (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eb), and the infrared images at the same time are exhibited in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ec. At 3 minutes, the thermal images of the two samples are almost identical. However, at 30 minutes, it can be seen that the temperature inside the container covered with PRC device is significantly lower than that of the container covered with glass. From the curves (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ed), it can be seen that at the beginning of test, the surface temperature of the container covered with PRC device is slightly higher than the other. After about 4 minutes, the temperatures of two containers reduce to the same level, the temperature of the container covered with PRC device is always lower than the other until the temperature of both containers reaches ambient condition. The △T between the two containers reaches its maximum of 1.7℃ about 9 minutes. The results indicate that PRC device exhibits accelerating heat dissipation performance under non-sunlight conditions.\u003c/p\u003e\u003cp\u003eFor the second test, the commercial solar panel was packaged with different devices showed in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ee, and then placed under simulated light of AM 1.5 (200\u0026ndash;1100 nm) to record its internal temperature and output voltage. Figure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ef shows the infrared images at the test beginning and the end. At the beginning, the temperatures of the two equipment are the same, while it can be seen that the internal temperature of the equipment covered with bare glass is significantly higher than that of the equipment covered with PRC device at the end. Due to the PRC device shielding some ultraviolet light, the total amount of light entering its interior is less than that of the bare glass, so the initial voltage of the equipment covered with bare glass will be slightly higher. From the Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eg, it can be seen that when the irradiation time reaches 3 minutes, the output voltage of both reaches the same 2.32 v. At this time, the temperature of the bare glass covered equipment is 48.6℃, and the temperature of the equipment covered with PRC device is 47.1℃.\u003c/p\u003e\u003cp\u003eResults indicate that when the △T reaches 1.5℃, the photoelectric conversion efficiency of the device covered with PRC device has already exceeded that of the device covered with bare glass. During the continuous lighting period, the temperature of the two devices continued to rise and the output voltage continued to decrease, but the temperature of the equipment covered with PRC device was always lower than the other, and the output voltage was significantly higher. The optimal working temperature for solar panels is 25℃. However, in practical applications, due to prolonged exposure to sunlight, the internal temperature often remains above 60℃, causing severe performance degradation. PRC device can achieve more efficient cooling effects under outdoor sunlight conditions, enabling more conversion of light energy.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eIn summary, this work provides a bio-inspired passive radiative cooler with strong ultraviolet light shielding, enhanced infrared emission, and no energy consumption while demonstrating excellent transparency. The PBRC, inspired by the skin\u0026rsquo;s thermal management mechanism, which integrating dual properties including wave-dependent light modulation capability and unidirectional heat transfer performance, exhibits 89.5% transmittance in the visible band, a 34% higher UV blocking rate and 38% higher NIR emissivity compared to bare glass. During outdoor daytime testing, PBRC achieves maximum cooling of 7.4℃ (radiance 653.35 W/m\u003csup\u003e2\u003c/sup\u003e) and an average cooling of 2.4℃. This work offers a general strategy for the scalable manufacturing of PRC materials for high transparent substrate, with potential applications in energy-efficient buildings and photovoltaic systems.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003e\u003cb\u003eZinc acetate solution synthesis.\u003c/b\u003e 0.1 mole of zinc acetate dihydrate (\u0026ge;\u0026thinsp;98%) is dissolved in 300 ml of ethylene glycol methyl ether (2-methoxyethanol, \u0026ge;\u0026thinsp;99.5%(GC)) and add 5 ml of ethanolamine (2-aminoethanol, \u0026ge;\u0026thinsp;99%) as a stabilizer. Then place the sealed beaker containing the mixed solution in 70℃ water and magnetic stirring for 30 minutes. Take out the beaker and place it in a dark place until the solution cools down before use.\u003c/p\u003e\u003cp\u003e\u003cb\u003eZnO layer fabrication.\u003c/b\u003e Silicate glasses with a side length of 4 cm are selected as substrate for ZnO layer fabrication. The glasses are ultrasonic cleaned respectively with alcohol and deionized water, both cleaning times last for 10 minutes. Then glasses are heated in a drying oven to remove surface liquid. The glass sheet is placed horizontally on the spin coater and drip zinc acetate solution to cover the glass surface. The spin speed was set to 3000r/min to fabricate samples. Next, the samples are placed in muffle furnace, set the heating temperature to 370℃, and set the heating time to 30 mins. After the temperature drops to room temperature, ZnO layer is fabricated on the glass surface already.\u003c/p\u003e\u003cp\u003e\u003cb\u003ePolyamide acid synthesis.\u003c/b\u003e 0.800 g of diamin-odiphenyl ether (ODA) is dissolved in 22 g dimethylacetamide (DMAC). The mixed solution is stirred at 25℃ until the solute is completely dissolved. Then 0.872 g of isophthalic acid dihydrate (PMDA) is added in 4 to 5 portions during stirring process. Stop stirring when the solution becomes transparent. The above prepared solution named PI1 precursor. When DMAC is added first, followed by ODA, the prepared solution is called PI2 precursor.\u003c/p\u003e\u003cp\u003e\u003cb\u003ePI layer fabrication.\u003c/b\u003e Drip 0.2 g of polyamide acid onto the glass with ZnO layer, and the spin coater is used again to evenly distribute the precursor solution. The spin coating speed is set to 1500 r/min. Then place the sample in vacuum drying oven for moisture removal treatment under 170℃. The drying time is set to 100 minutes.\u003c/p\u003e\n\u003ch3\u003eNanoscale characterization\u003c/h3\u003e\n\u003cp\u003eScanning electron microscopy (SEM) characterization was done by recording on JSM-6700F, JEOL.\u003c/p\u003e\n\u003ch3\u003eOptical characterization\u003c/h3\u003e\n\u003cp\u003eThe measurements of the reflection and transmission properties are carried out using Fourier transform infrared spectrometer (Nicolet iS50, Thermo Fisher) across a wide range of wavelengths (0.2\u0026ndash;15 \u0026micro;m). The instrument is equipped with an integrated sphere with a highly reflective inner surface to collect both diffused and direct light. The illuminance and irradiance are test by Spectral illuminance meter (HPC350FR).\u003c/p\u003e\n\u003ch3\u003eThermal characterization\u003c/h3\u003e\n\u003cp\u003eTemperature parameters is obtained by using an infrared thermometer (HT-18) in heat transfer part. The outdoor temperature is recorded by a simple temperature meter in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec. The real-time detection of the square box temperature indoors and outdoors is achieved by using a K-type Kepler temperature sensor, which purchased on Taobao. The temperature data is transmitted to the computer through a data acquisition device (Smacq, M2101), processed by the corresponding software (M manager) and recorded.\u003c/p\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003eMechanical characterization\u003c/h2\u003e\u003cp\u003eThe measurement of the adhesion property is carried out using tension meter fixed on the slide rail (MX2-500N), the force and displacement data are transmitted to the computer via data cables and recorded by software (Force Logger Ver2).\u003c/p\u003e\u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work is supported by the Foundation for Innovative Research Groups of the National Natural Science Foundation of China (No. 52021003), National Natural Science Foundation of China (Nos. 52222509, 52475300), and supported by \u0026ldquo;Fundamental Research Funds for the Central Universities\u0026rdquo;.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eH.D. was associated with conceptualization, investigation, writing\u0026mdash;original draft, review \u0026amp; editing, methodology, and resources. Y.Z. and Y.Z. were associated with experiments and characterization. B.L., S.N and Z.H. was associated with conceptualization, funding acquisition, writing\u0026mdash;review \u0026amp; editing, resources, and project administration supervision.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that the data supporting findings of this study are available within the article and Supplementary Information. Additional datasets related of this study are available from the corresponding authors upon. Source data are provided in this paper.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eChen Z, Zhu L, Raman A, Fan S (2016) Radiative cooling to deep sub-freezing temperatures through a 24-h day-night cycle. Nat Commun 7:13729\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWang T et al (2021) A structural polymer for highly efficient all-day passive radiative cooling. Nat Commun 12:365\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWu X et al (2024) A dual-selective thermal emitter with enhanced subambient radiative cooling performance. Nat Commun 15:815\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLi J et al (2022) A tandem radiative/evaporative cooler for weather-insensitive and high-performance daytime passive cooling. Sci Adv 8:eabq0411\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eJaramillo-Fernandez J et al (2022) Highly-scattering cellulose-based films for radiative cooling. Adv Sci 9:2104758\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eKou Jlong, Jurado Z, Chen Z, Fan S, Minnich AJ (2017) Daytime radiative cooling using near-black infrared emitters. ACS Photonics 4:626\u0026ndash;630\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMandal J et al (2018) Hierarchically porous polymer coatings for highly efficient passive daytime radiative cooling. Science 362:315\u0026ndash;319\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLi P et al (2022) Thermo-optically designed scalable photonic films with high thermal conductivity for subambient and above-ambient radiative cooling. Adv Funct Mater 32:2109542\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eCai C et al (2022) Dynamically tunable all-weather daytime cellulose aerogel radiative supercooler for energy-saving building. Nano Lett 22:4106\u0026ndash;4114\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWang S et al (2021) Scalable thermochromic smart windows with passive radiative cooling regulation. Science 374:1501\u0026ndash;1504\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLiu H, Zhu SN (2021) Hierarchical-morphology metafabric for scalable passive daytime radiative cooling. Kexue Tongbao/Chinese Sci Bull 66:3787\u0026ndash;3790\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eRaman AP, Anoma MA, Zhu L, Rephaeli E, Fan S (2014) Passive radiative cooling below ambient air temperature under direct sunlight. Nature 515:540\u0026ndash;544\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eXu L, Sun DW, Tian Y, Fan T, Zhu Z (2023) Nanocomposite hydrogel for daytime passive cooling enabled by combined effects of radiative and evaporative cooling. Chem Eng J 457:141231\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLi J et al (2022) Protecting ice from melting under sunlight via radiative cooling. Sci Adv 8:eabj9756\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLi X, Peoples J, Yao P, Ruan X (2021) Ultrawhite BaSO\u003csub\u003e4\u003c/sub\u003e paints and films for remarkable daytime subambient radiative cooling. ACS Appl Mater Interfaces 13:21733\u0026ndash;21739\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eCheng N et al (2023) Nanosphere-structured hierarchically porous PVDF-HFP fabric for passive daytime radiative cooling via one-step water vapor-induced phase separation. Chem Eng J 460:141581\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eZhu B et al (2021) Subambient daytime radiative cooling textile based on nanoprocessed silk. Nat Nanotechnol 16:1342\u0026ndash;1348\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWang X et al (2020) Scalable flexible hybrid membranes with photonic structures for daytime radiative cooling. Adv Funct Mater 30:1907562\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eCai L et al (2018) Spectrally selective nanocomposite textile for outdoor personal cooling. Adv Mater 30:1802152\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eFan C et al (2023) Dynamically tunable subambient daytime radiative cooling metafabric with janus wettability. Adv Funct Mater 33:2300794\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eZhao X et al (2023) A solution-processed radiative cooling glass. Science 382:684\u0026ndash;691\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eZhong H et al (2021) Hierarchically hollow microfibers as a scalable and effective thermal insulating cooler for buildings. ACS Nano 15:10076\u0026ndash;10083\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eZhai Y et al (2017) Scalable-manufactured randomized glass-polymer hybrid metamaterial for daytime radiative cooling. Science 355:1062\u0026ndash;1066\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLee KW, Yi J, Kim MK, Kim DR (2024) Transparent radiative cooling cover window for flexible and foldable electronic displays. Nat Commun 15:4443\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLeroy A et al (2019) High-performance subambient radiative cooling enabled by optically selective and thermally insulating polyethylene aerogel. Sci Adv 5:eaat9480\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eFan S, Li W (2022) Photonics and thermodynamics concepts in radiative cooling. Nat Photonics 16:182\u0026ndash;190\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLiang J et al (2023) Radiative cooling for passive thermal management towards sustainable carbon neutrality. Natl Sci Rev 10:nwac208\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBijarniya JP, Sarkar J, Maiti P (2020) Review on passive daytime radiative cooling: Fundamentals, recent researches, challenges and opportunities. Renew Sustain Energy Rev 133:110263\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBhatia B et al (2018) Passive directional sub-ambient daytime radiative cooling. Nat Commun 9:5001\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eYun J et al (2023) Optimally designed multimaterial microparticle-polymer composite paints for passive daytime radiative cooling. ACS Photonics 10:2608\u0026ndash;2617\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eShan X et al (2022) Aerogel-functionalized thermoplastic polyurethane as waterproof, breathable freestanding films and coatings for passive daytime radiative cooling. Adv Sci 9:2201190\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLiu Y et al (2024) Construction of robust silica-hybridized cellulose aerogels integrating passive radiative cooling and thermal insulation for year-round building energy saving. Chem Eng J 481:148780\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eGalib RH et al (2023) Atmospheric-moisture-induced polyacrylate hydrogels for hybrid passive cooling. Nat Commun 14:6707\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eKim S et al (2024) Passive isothermal film with self-switchable radiative cooling-driven water sorption layer for arid climate applications. Nat Commun 15:8000\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eXiang B et al (2021) 3D porous polymer film with designed pore architecture and auto-deposited SiO\u003csub\u003e2\u003c/sub\u003e for highly efficient passive radiative cooling. Nano Energy 81:105600\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eZhang X et al (2022) A moisture-wicking passive radiative cooling hierarchical metafabric. ACS Nano 16:2188\u0026ndash;2197\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLiu X et al (2022) Hierarchically superhydrophobic stereo-complex poly (lactic acid) aerogel for daytime radiative cooling. Adv Funct Mater 32:2207414\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLin K et al (2023) Hierarchically structured passive radiative cooling ceramic with high solar reflectivity. Science 382:691\u0026ndash;697\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWang H et al (2024) Bioinspired directional structures for inhibiting wetting on super-melt-philic surfaces above 1200\u0026deg;C. Int J Extrem Manuf 6:045503\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSong J et al (2022) Durable radiative cooling against environmental aging. Nat Commun 13:4805\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eXiong L et al (2023) Thin lamellar films with enhanced mechanical properties for durable radiative cooling. Nat Commun 14:6129\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eKim S, Park JH, Lee JW, Kim Y, Kang YT (2023) Self-recovering passive cooling utilizing endothermic reaction of NH\u003csub\u003e4\u003c/sub\u003eNO\u003csub\u003e3\u003c/sub\u003e/H\u003csub\u003e2\u003c/sub\u003eO driven by water sorption for photovoltaic cell. Nat Commun 14:2374\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eZhang H et al (2020) Biologically inspired flexible photonic films for efficient passive radiative cooling. \u003cem\u003eProc. Natl. Acad. Sci. U. S. A.\u003c/em\u003e 117, 14657\u0026ndash;14666\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eShi NN et al (2015) Keeping cool: Enhanced optical reflection and radiative heat dissipation in Saharan silver ants. Science 349:298\u0026ndash;301\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eTang K et al (2021) Temperature-adaptive radiative coating for all-season household thermal regulation. Science 374:1504\u0026ndash;1509\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eYang M et al (2023) Phase change material enhanced radiative cooler for temperature-adaptive thermal regulation. ACS Nano 17:1693\u0026ndash;1700\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eShi M et al (2023) Dual-mode porous polymeric films with coral-like hierarchical structure for all-day radiative cooling and heating. ACS Nano 17:2029\u0026ndash;2038\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eGerhard M et al (2019) Microscopic insight into non-radiative decay in perovskite semiconductors from temperature-dependent luminescence blinking. Nat Commun 10:1698\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-6024085/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6024085/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003ePassive radiative cooling (PRC) materials can achieve effective cooling without energy consumption through strong light reflection and spontaneous infrared radiation, which is of great importance in mitigating global warming and energy crises. However, conventional PRC materials lack on-demand light transmission and efficient infrared radiation, making it difficult to meet the demand for high transparency and efficient temperature control in building coverage applications. Herein, inspired by the skin\u0026rsquo;s thermal management mechanism, a bioinspired passive radiative cooler (BPRC) with wavelength-dependent light modulation and unidirectional heat transfer is developed to achieve temperature control for transparent substrate. Remarkably, BPRC exhibits 89.5% transmittance in the visible band (same with bare glass). Furthermore, BPRC demonstrates a 34% higher UV blocking rate and 38% higher NIR emissivity compared to bare glass. The maximum cooling effect reaches 7.4\u0026deg;C under perpendicular illumination (radiance 653.35 W/m\u003csup\u003e2\u003c/sup\u003e). In addition, the adhesion between the bioinspired PRC film and the substrate is up to 0.5 MPa, ensuring the durability of BPRC in practical applications. This work offers a general strategy for the mass production of highly transparent PRC materials, with potential applications in energy-efficient buildings and photovoltaic systems.\u003c/p\u003e","manuscriptTitle":"Bioinspired passive radiative cooler with superior transparency and durability for energy-efficient building","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-18 10:37:54","doi":"10.21203/rs.3.rs-6024085/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"a7cc9ece-09e9-4cf3-8669-5e000280dfed","owner":[],"postedDate":"August 18th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":53201697,"name":"Physical sciences/Materials science/Materials for optics"},{"id":53201698,"name":"Physical sciences/Materials science/Materials for energy and catalysis/Solar cells"}],"tags":[],"updatedAt":"2025-08-18T10:37:54+00:00","versionOfRecord":[],"versionCreatedAt":"2025-08-18 10:37:54","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6024085","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6024085","identity":"rs-6024085","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}