Self-Powered Liquid Metal Interfaces Enable Autonomous Electrochemical Sensing of Pipeline Microleaks in Extreme Environments

Self-Powered Liquid Metal Interfaces Enable Autonomous Electrochemical Sensing of Pipeline Microleaks in Extreme Environments | 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 Self-Powered Liquid Metal Interfaces Enable Autonomous Electrochemical Sensing of Pipeline Microleaks in Extreme Environments Nailiang Yang, Xueke Wang, Guomin Ye, Xinyang Zhang, Yi Chen, and 6 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6472763/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted You are reading this latest preprint version Abstract The timely detection of pipeline micro-leakages in extreme environments such as deep-sea and extraterrestrial habitats remain a critical challenge due to the limitations of conventional delayed-response detection systems. Herein, we present an intelligent liquid metal bubble generator (LMBG) chamber capable of converting mechanical leakage signals into real-time electrical feedback through a self-powered transduction mechanism. The proposed system exploits the intrinsic electric potential difference of liquid metal (LM) and its oxide. The rupture of LM bubbles at leakage site activates a built-in galvanic cell between the metallic core and its oxide shell, achieving direct mechanoelectrical energy conversion without external power input. Notably, the system demonstrates ultrahigh sensitivity with linear voltage-volume (319.9 V·cm -3 ) and frequency-flow velocity (0.25 Hz·cm -1 ·s) correlations, rapid response characteristics (0.33 s latency). Meanwhile, the exceptional detection resolution for micro-leakages as small as 1.0×10 -3 cm 3 . This achievement in active sensing technology establishes a new route for intelligent infrastructure monitoring, particularly addressing the critical need for robust leakage detection systems in next-generation deep-sea exploration and space habitat applications. Physical sciences/Materials science/Nanoscale materials Physical sciences/Chemistry/Electrochemistry Physical sciences/Engineering/Electrical and electronic engineering Physical sciences/Nanoscience and technology/Nanoscale devices liquid metal triboelectric self-powered galvanic cell visualization rupture detection Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction The global network of energy pipelines – spanning deep-sea trenches, urban undergrounds, and permafrost regions – forms the circulatory system of modern industrial civilization, yet suffers annual economic losses exceeding $ 10 billion due to undetected leaks. 1–5 Conventional detection technologies, relying on pressure differentials or acoustic signatures, face inherent limitations in micro-leakage resolution, response latency, and environmental interference resistance. 6, 7 These shortcomings become critically pronounced in extreme environments. Bubble formation is the typical physical signature of pipeline leakage, presenting significant potential for mechano-electrical energy conversion in extreme environments. 8–11 Bubble-driven nanogenerators based on liquid-solid triboelectric mechanisms have been studied for leakage sensing, but their practical deployment still faces fundamental limitations such as the interfacial adhesion and the essential energy supply. 12–15 In contrast, liquid metals (LMs) offer transformative advantages through their intrinsic fluidic adaptability and self-healing oxide interfaces, enabling seamless integration with complex substrates while maintaining electrochemical activity in extreme environments. 16–20 This unique combination addresses the longstanding trade-off between interfacial compliance and sensing reliability in conventional systems. More importantly, the intrinsic reduction potential differences between LM and its oxide can form a built-in electric field. When the LM coating broken, an electrochemical cell is established between the bubble-exposed core metal and the oxidized layer on the intact coating. An electrical signal may be generated from the mechanical energy of the breakage. Here in this work, we designed a novel liquid metal chamber on the pipeline for the autonomous leakage detection. When the pipeline ruptures, the bubble bursts and leads to the destruction of the thin oxide layer on the liquid metal surface. The oxidation layer and the exposed LM formed a galvanic cell at the instant of bubble burst, and the current signal can be detected (Fig. 1 ). The systemic studies indicate the liquid metal bubble (LMB) can distinguish the size and the form of leakage point with a superhigh sensitivity. The voltage-volume sensitivity has been enhanced by one order, and the minimum threshold volume is better than the triboelectric ones commonly used nowadays, and is even comparable to the best sensing level of capacitive sensors. This new technician based on the self-powered galvanic cell shows great potential for bubble-related monitoring, especially for the equipment safety in the extreme environment. Results and Discussions Preparation of LM coating The surface of the original liquid metal material has a silvery-white appearance with metallic luster and smooth topography, while the surface is quickly to form an obvious thin layer of oxides after contacting of air (Fig. 2 a, the insert diagram shows an optical microscope image of the original liquid metal surface and an obvious oxide layer). 21, 22 SEM images clearly show a large number of folds of the oxide layer (Supplementary Fig. S1 ), which is also evident from the low contrast appearance and pronounced stacking from the TEM images (Fig. 2 b). In addition, the elemental composition and distribution were investigated employing EDS spatial maps, indicating the formation of Ga 2 O 3 thin layers. Ga and O were discovered to be uniformly distributed throughout the film. Selected area electron diffraction pattern indicates that the oxide layer has a low degree of crystallinity, which is consistent with the reported oxide surface on liquid metal surfaces. 23, 24 AFM image shows that the thickness of the oxide layer is about 4.8 nm, which satisfies the typical thickness characteristics of 2D nanosheets (Supplementary Fig. S2). 24 To detect and infer these two different core and layer materials at the interface, XRD analysis was adopted (Fig. 2 c). The XRD results also proved the low crystallinity of both the liquid metal and its oxide. 25, 26 Raman spectra showed that the characteristic peak positions of Ga 2 O 3 were 88.1, 121.2, 151.1, 208.6, and 248.3 cm − 1 , whereas core metal surfaces are mainly interactions between metal atoms and show no characteristic peaks (Fig. 2 d). 27–29 High resolution XPS spectra of the split Ga 2p orbitals show that the surface composition of the oxide layer and core metal samples was mainly Ga and Ga 2 O 3 due to the relatively high Ga ratio in the liquid metal. In the 2p orbital, a clear spin-orbit splitting (SS) is observed, where the peak at 1145.1 eV points to elemental Ga 2 O 3 2p3/2 and the peak at 1118.3 eV points to Ga 2 O 3 2p3/2 (Fig. 2 e-f). 30, 31 In addition, the XPS results comprehensively show that the proportion of oxides on the oxide layer is considerably increased compared to the core metal. Typically, we spread the liquid metal on the widely used substrates as glass fiber and HDPE (Fig. 2 g). The contact angle of liquid metal on them were 85.0 o and 94.2 o , respectively (Fig. 2 h). However, after we spread the liquid metal on the glass fiber and steel plate by scraping, the contact angle decreased to 7.1 o and 10.3 o significantly (Fig. 2 h). Notably, the coating will not rebound or shrink, which is attributed to the oxidation of gallium in the liquid metal in air, forming a stable oxide layer that secures the internal liquid metal and prevents shrink. Meanwhile, when we change the tilt angles of substrates from 15 o to 150 o , the LM coating shows the excellent adhesion stability (Fig. 2 i). With the protection of the oxide layer, the core metal did not rupture and flow out or slip off. When we further applied different speeds of flowing water to the liquid metal coating, it also shows a good stability. The LM coating can even tolerate a flow velocity of 30 cm·s -1 with a tilt angle smaller than 60 o . The liquid metal coating maintains excellent stability under scouring at different flow velocities with a small shear angle (Fig. 2 j-l). Generation and dynamics of LMB When a leakage appeared in the pipe, bubble will nucleate and grow up at the interface between the pipeline and LM core (Fig. 3 a). LMB is thermodynamically unstable that are extremely prone to burst. 32, 33 High-speed imaging results show that the duration of a single LMB from generation to burst is extremely short (~ 300 ms, Supplementary Fig. S3 and Supplementary Movie S1). Further, we captured finite element simulation images of individual bubble generation to burst in order to better investigate the bubble development and morphology inside the liquid metal (Supplementary Fig. S4). The results show that the volume of LMB increases with the increase of the broken area under the same gas flow velocity (Fig. 3 b-c, Supplementary Movie S2). While the volume and morphology of LMBs unchanged for different flow velocities under the same pipe diameter conditions, indicating it is independent of the flow velocity (Fig. 3 d, Supplementary Fig. S5 and Supplementary Movie S3). It is worth noting that the transient pattern of LMB generation is consistent across different gas source areas and air velocity conditions. When a LMB burst, not only does the oxide layer at the top of the bubble rupture, exposing the core metal, but it also causes the core metal inside the LMB to surge upward, forming a “core metal column” as shown in Fig. 3 e. The volume and frequency of bubbles generation at different flow velocity were counted in the experiment, where the volume of bubbles was obtained by multiplying the duration of bubble generation until burst and the gas flow velocity, and the frequency was the number of bubbles produced per unit time (Fig. 3 f-i). The simulation group shows a relationship where the bubble volume increases with the increase in gas flow velocity for bubble volumes generated by various gas flow velocity (Fig. 3 h). The relationship between bubble frequency and gas flow velocity in Fig. 3 i shows the same linear correlation for both experimental and simulation groups, meaning that the frequency rises as gas flow velocity increases. When the internal pressure reaches its limit, the bubble starts to burst with an instantaneous energy release at the gas-liquid interface. 34, 35 The gas-liquid interface generates a high-intensity shear force that shears the bulk liquid metal into many tiny droplets covering the liquid metal surface, resulting in a gas-liquid metal droplet-liquid mixture on the liquid metal surface (Fig. 3 j, Supplementary Fig. S6 shows the entire process of liquid metal breaking by bubble shear stress). Further, it was found that the surface tension also has a great influence on the path and morphology of bubble generation (Fig. 3 k). The bubble generation follows the three processes of: lateral escape of bubbles due to the large surface of the liquid metal in the initial state; intermediate arching of bubbles when the surface tension is reduced to about half of the initial one; and normal ellipsoidal LMB that can be generated smoothly when the surface tension is reduced by a factor of about 10 (Fig. 3 k, Movie S4). The presence of surface oxides leads to significant decrease in the surface tension of liquid metals (Fig. 3 l), which will decrease the energy barrier of bubble generation. 36–39 Electrical and bubble sensing performance of LMBG [EMIM]CL ionic liquids with a volume concentration of 40% are chosen as electrolytes because of its relatively high conductivity (Fig. 4 a). Figure 4 b-c present the output voltage and current performance curves for different flow velocities with a tube diameter of 510 \(\:\mu\:\) m. As the flow velocity increases, the frequency of the output open-circuit voltage and current signals increases significantly, while the amplitude of the corresponding electrical signals little changed (Supplementary Fig. S7). Subsequently, we changed the diameters of the pipelines and found the factor of pipe diameter is strong related to the voltage amplitude, while the current amplitude remains constant (Fig. 4 d-f, Supplementary Movie S5). We further map the relationship between dynamical behavior of bubbles and electrical signals, and found the flow velocity shows a good linear correlation with the frequency of the electrical signal and little correlation with the change in amplitude (Fig. 4 g-h). On the contrary, the bubble diameter does not correlate well with the frequency variation of the electrical signal, while it shows a good linear correlation with the amplitude. Above all, we can make a conclusion that the voltage’s amplitude is mainly related to the volume size of the LMBs, while the pulse frequency of voltage and the current intensity is mainly related to the frequency of the bubble generation, which is also verified by the kinetic process of bubble generation. The output electrical performance is affected by the volume of LMBs, electrolyte, etc. in addition to the upper limit of the redox potential of core metal. 36, 40 The rupture of the surface oxide layer of LMBs triggers the activation of a localized galvanic cell reaction, realizing the conversion of mechanical energy to electrical energy, which in turn can be used as bubble sensor to realize the detection of bubble motion patterns and morphology. The response time was short as 0.33 s. While the response time was longer than 20 s can be attributed to the gradual convergence of the asymmetric potential difference to symmetry caused by re-oxidation of the core metal (Fig. 4 i, Supplementary Fig. S8a-c). Then we defined the voltage-volume dependent sensitivity as S1 and the frequency-flow velocity dependent sensitivity as S2 to study the sensitivity of the bubble sensor (Fig. 4 j). The device exhibits a superb high sensitivity of 319.9 V·cm 3 to the small bubble below 1.1×10 − 2 cm 3 , which is one order better than the best reported work based on our knowledge (Fig. 4 j-k, Supplementary Table S1 ). 14, 41–50 And the minimum threshold volume for bubbles leakage detecting is only 1×10 − 3 cm 3 , which matches the resolution of the best reported work (Fig. 4 j-k, Table S1 ). 14, 41–50 It also shows a good linear relationship between volume of bubble and voltage for different volume ranges of bubbles, with linear relationships of 0.9738 and 0.9955, respectively. Meanwhile, the frequency-flow velocity correlation with a sensitivity of 0.25 Hz·cm -1 ·s and a good linear relationship between signal frequency and flow velocity with a linearity of 0.9997 (Supplementary Fig. S9). In addition to intuitively reflecting the macroscopic LMB volume and frequency of generation through electrical signals, more microscopic detection of bubble motion patterns can be realized. Scenarios involving a single bubble, two consecutive bubbles, and two bubbles fusion in LM are further explored (Fig. 4 l). As shown in Fig. 4 m, a single bubble produced a signal sharp peak, while the fast bubble generation will also shorten the time interval of the series of peaks. In addition, when two bubbles are closely generated, they will merge together and present two consecutive peak’s signal. Interestingly, since the spacer in chamber divided the cell into a cathode and an anode, the voltage direction can reflect the position of bubble (Fig. 4 n-o). For instance, if the bubble generation on left chamber is specified to be negative, then the corresponding right-one will output positive. When we sequentially blew bubbles in the left and right chamber, an alternating voltage can be detected with a good stability (Fig. 4 o). LMBG for pipeline rupture leak detection Beneath urban soils and oceans, the complex networks of pipelines serve as the lifeline of human beings, transporting fluids such as liquids and gases, and the severity of the pipeline leakage can be visually indicated by different colored warnings (Fig. 5 a). 50 In order to verify the effectiveness of this system for application in real scenarios, a pipe pre-buried through the bottom of the left and right chambers was designed (Fig. 5 b). Based on the monitoring device, the circuit and equipment for collecting data will transmit the data to the computer visualization display interface for real-time monitoring, and the monitoring interface will alarm and alert when an inconspicuous gas leakage occurs, and the manager staff will carry out post-processing according to this information (Fig. 5 b iii). When the gas is intermittently blown in, a series of sharp electrical signals can be detected immediately as expected (Fig. 5 c). Because of the establish of the connection between three parameters, including the electrical signal, the leakage of pipeline, and the flow of gas, we can prospect this technician can be expended to the gas pipeline in the deep sea, under the ground, or other extreme environments (Fig. 5 d). Besides, gases originate from multiple sources in daily life, including air exhaled by the human body, the exhaust from machinery and appliances, and gases leaking from conveyor pipelines, etc. This provides possible future application scenarios for LMBG and bubble detection. Methods Materials: The liquid metal, Galinstan (Ga 61.5 In 25 Sn 13.5 ) alloy was purchased from Dongguan Dingguan Metal Technology Co. Ltd, China. Ionic liquid ([EMIM]BF 4 : 1-Ethyl-3-methylimidazolium tetrafluoroborate, 98%; [EMIM]DCA: 1-Ethyl-3-methylimidazolium Dicyanamide, 98%; [EMIM]CL: 1-Ethyl-3-methylimidazolium Chloride, 98%) used were of reagent grade obtained from Aladdin. Ionic liquid solutions of different concentrations are prepared by mixing the original ionic liquid and DI-water in different volume ratios. Unless stated otherwise all chemicals and reagents were used as received. Characterization and measurements of oxide layer and core metal of liquid metal: Optical micrographs of liquid metal surfaces obtained with an Olympus optical microscope. The TEM image, energy-dispersive X-ray spectroscopy (EDS) elemental mapping image, selected area electron diffraction (SAED) pattern image, high-resolution TEM (HRTEM) image of oxide layer was characterized by field emission transmission electron microscope (JEM-F200, Japan Electronics Co., Ltd.). The thickness of oxide layer is obtained by atomic force microscopy (NX10, Park, Korea). The SEM microscopic morphology of the oxide layer on the liquid metal surface was obtained by the Phenom Pro X, and its crystal structure composition and bonding fraction was obtained by X-ray diffraction (XRD, K-Alpha+, Thermo Fisher Scientific) and Raman spectroscopy (Raman, XperRam200VN, Nanobase, Korea). X-ray photoelectron spectroscopy (XPS) was adopted to analyze the composition of oxidation of the liquid metal surface before and after bubble generation. Full spectrum and narrow spectrum of gallium, indium, and oxygen were measured. Adhesion and stability testing of liquid metal coatings on piping materials: Mechanical scraping was used to verify the spreading of the liquid metal coating on the pipe material. The stability of the coating is verified by observing the liquid metal liquid at different angles to see if there is any slippage and cracking out of the liquid. Liquid metal coatings were flushed with water at different angles and flow velocities to simulate the actual fluid flow environment they may be subjected to. Liquid metal bubble generation and bursting: Liquid metals were injected into a 3D-printed container (HALOT-SKY, Shenzhen Creality 3D Technology Co., LTD) with left and right chambers, the bottoms of which are pre-punched with microscopic holes for connecting thin silicone tubes for aeration. The ionic liquid was poured into the container and fully covered the surfaces of liquid metals. The syringe pump (TL-F6, TONGLi Tech Co., LTD, Shenzhen) was used for air intake into the liquid metal, and the gas path is connected between the syringe pump and the bottom of the liquid metal by a silicone tube. The characteristics of the bubbles, including size, duration, and burst time, were then analyzed based on the photographs acquired by high-speed camera. The experiment was conducted at room temperature. Finite element simulation: For simplicity, a two-dimensional simulation model was built, whose dimensional proportions between its parts were kept consistent with the actual experimental setup, to investigate the generation of bubbles inside a liquid metal. The “laminar two-phase. flow-phase field” model of fluid flow affiliation was selected to investigate the bubble generation and the “laminar three-phase. flow-phase field” model was selected to explore the shear effect of gas on liquid metal. The corresponding bubble generation can be obtained by varying different air flow velocities and surface tension of liquid metal. Surface tension and contact angle measurement: The surface tension of the liquid metal as is and after oxidation of the LMB burst was carried out on a contact angle tester (SDC-350KS) by the hanging drop method and the angle measurement method was fitted to the Young-Laplace equation. A contact angle analyzer (FCA2000A, AFES) was used to determine the contact angle of liquid metal with four pipe materials. Electrical measurements of LMBG: The copper wire is inserted into the liquid metal, in direct contact with the liquid metal core, and the entire process of generating bubbles is insulated from the ionic liquid electrolyte. A digital multimeter (2400, Keithley) was used to record the voltage or current between the liquid metals in the two chambers through tinned copper wires. The conductivity data of ionic liquids was obtained by a conductivity meter (SANXIN SX813, Shanghai Sanxin Co. Ltd, China). The syringe pump is fed with different flow velocities of gas to produce bubbles of different volumes and frequencies so that voltage and current signals of different amplitudes and frequencies can be obtained. Cyclic performance testing was completed by continuous aeration with a syringe pump for some time with continuous bubble production. Electrochemical characterization: An electrochemical workstation (CHI-660e, Shanghai Chenhua Co. Ltd, China) was adopted to test the electrochemical impedance and cyclic voltammetric curves of the oxide layer on the liquid metal surface between the left and right chambers within a frequency range from 0.01 to 100000 Hz and scan rate range from 0.01 V/s to 0.5 V/s. Conclusion In this work, we establish a new approach for autonomous leakage detection through the electrochemical regulation of liquid metal interface. The developed liquid metal bubble generator exploits the symbiotic relationship between LM’s intrinsic fluidity and the self-limiting oxide layer’s fracture-reconstruction behavior, creating a self-sustaining electrochemical transducer that operates without external energy input. Our device presents an ultra-high selectivity and performs excellent to the small leakage. Furthermore, a mathematical relationship between breakage size-flow velocity-electrical signals is established, and a multi-dimensional mapping between physical parameters and electrical signals is realized. In this case, our work opens a new class of intelligent flow electronics with transformative applications ranging from industrial microleakage prevention to biomechanical sensing. This fundamental advancement in material-enabled transduction physics opens avenues for developing self-powered monitoring networks in next-generation energy and space exploration infrastructure. Declarations Competing interests The authors declare no competing interests. Author contributions X. Wang carried out the experiment, analyzed the data, and wrote the manuscript. G. Ye managed the validation, methodology, and data curation. X. Zhang embellished the visual processing of the figure. Y. Chen, Y. Hu, Q. Wu, Y. Yang, H. Luo were involved in device fabrications and material testing and characterization analysis. N. Yang, P. Yang, Y. Wan. supervised this research and revised the manuscript. Acknowledgments This work was financially supported by the National Natural Science Foundation of China (No. 12264053, 52271241 and 92163209), the Scientific Research and Innovation Project of Postgraduate Students in the Academic Degree of Yunnan University (No. KC-23234366) and Beijing Natural Science Foundation (JQ22004). The authors thank the Advanced Analysis and Measurement Centre of Yunnan University for the sample testing service and Advanced Computing Centre of Yunnan University. The authors thank the software support from Prof. Yingtang Zhou from Zhejiang Ocean University. Data availability The authors declare that the main data supporting the findings of this study are contained within the paper and its associated Supplementary Information. 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Bioinspired Ultrasensitive Flexible Strain Sensors for Real-Time Wireless Detection of Liquid Leakage. Nano-Micro Lett. 17 , 68 (2024). Additional Declarations There is NO Competing Interest. Supplementary Files SupplementaryInformation.docx Supplementary Information - Figures and Table MovieS1.mp4 Supplementary Information - Movie S1 MovieS2.mp4 Supplementary Information - Movie S2 MovieS3.mp4 Supplementary Information - Movie S3 MovieS4.mp4 Supplementary Information - Movie S4 MovieS5.mp4 Supplementary Information - Movie S5 Cite Share Download PDF Status: Under Review 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. 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Yang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAvUlEQVRIiWNgGAWjYDACdjBpw0OCFmYwmUa6lsMk6DBn5jH8XPDrvIw5ewPjhx8MdnkEtVg28xhLz+y7zWPZc4BZsochuZigFoPDPAbSvD23eQxuJDBIMzAcSGwgQovxb96eczwG9x8w/yZWi5k0z48DQFsY2Ii1ha3MmrchGeiXxDbLHoNkIrQcb958m+ePnb05++HDN35U2BHWwsDAYcDA2AbUy8DYACKJAewPGBj+EKt4FIyCUTAKRiQAADzHNsC61uoxAAAAAElFTkSuQmCC","orcid":"https://orcid.org/0000-0002-5708-8379","institution":"Institute of Process Engineering, Chinese Academy of Sciences","correspondingAuthor":true,"prefix":"","firstName":"Nailiang","middleName":"","lastName":"Yang","suffix":""},{"id":476864828,"identity":"b4db7a0c-d267-4e35-9bfb-0d19d72513b8","order_by":1,"name":"Xueke Wang","email":"","orcid":"","institution":"School of Materials and Energy, Yunnan University","correspondingAuthor":false,"prefix":"","firstName":"Xueke","middleName":"","lastName":"Wang","suffix":""},{"id":476864829,"identity":"808f236e-cede-4528-a606-ca97755e489b","order_by":2,"name":"Guomin Ye","email":"","orcid":"","institution":"School of Materials and Energy, Yunnan University","correspondingAuthor":false,"prefix":"","firstName":"Guomin","middleName":"","lastName":"Ye","suffix":""},{"id":476864830,"identity":"31a4e085-98c4-40c1-830a-9ab27d7e7a2d","order_by":3,"name":"Xinyang Zhang","email":"","orcid":"","institution":"School of Materials and Energy, Yunnan University","correspondingAuthor":false,"prefix":"","firstName":"Xinyang","middleName":"","lastName":"Zhang","suffix":""},{"id":476864831,"identity":"5388bc07-a191-43a2-939f-a7fcb8bc3fc1","order_by":4,"name":"Yi Chen","email":"","orcid":"","institution":"School of Materials and Energy, Yunnan University","correspondingAuthor":false,"prefix":"","firstName":"Yi","middleName":"","lastName":"Chen","suffix":""},{"id":476864832,"identity":"ff8c1ab2-29a4-4d9d-b581-e11c6f85bb5b","order_by":5,"name":"Yingfei Hu","email":"","orcid":"","institution":"School of Materials and Energy, Yunnan University","correspondingAuthor":false,"prefix":"","firstName":"Yingfei","middleName":"","lastName":"Hu","suffix":""},{"id":476864833,"identity":"e1a1025d-1314-4782-ba62-00317682dc5f","order_by":6,"name":"Qiang Wu","email":"","orcid":"","institution":"School of Materials and Energy, Yunnan University","correspondingAuthor":false,"prefix":"","firstName":"Qiang","middleName":"","lastName":"Wu","suffix":""},{"id":476864834,"identity":"01d80834-82cb-4653-8b7e-3c2545552bd0","order_by":7,"name":"Yilan Yang","email":"","orcid":"","institution":"School of Materials and Energy, Yunnan University","correspondingAuthor":false,"prefix":"","firstName":"Yilan","middleName":"","lastName":"Yang","suffix":""},{"id":476864835,"identity":"d7375f21-16e1-48c2-82c0-b839bf37e489","order_by":8,"name":"Hongyao Luo","email":"","orcid":"","institution":"School of Materials and Energy, Yunnan University","correspondingAuthor":false,"prefix":"","firstName":"Hongyao","middleName":"","lastName":"Luo","suffix":""},{"id":476864836,"identity":"f8c8c8ac-fa1b-4881-b440-0f3ba3281e1a","order_by":9,"name":"Peng Yang","email":"","orcid":"https://orcid.org/0000-0002-5473-5454","institution":"Yunnan University","correspondingAuthor":false,"prefix":"","firstName":"Peng","middleName":"","lastName":"Yang","suffix":""},{"id":476864837,"identity":"240a9d03-f192-458d-8728-3c2fc957c2b1","order_by":10,"name":"Yanfen Wan","email":"","orcid":"","institution":"Yunnan University","correspondingAuthor":false,"prefix":"","firstName":"Yanfen","middleName":"","lastName":"Wan","suffix":""}],"badges":[],"createdAt":"2025-04-17 14:45:40","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6472763/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6472763/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":85547311,"identity":"8800d048-bf15-440b-916c-d7a74fa10189","added_by":"auto","created_at":"2025-06-27 08:52:10","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":508317,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eDesign and mechanism of LMBG\u003c/strong\u003e. \u003cstrong\u003ea\u003c/strong\u003e Schematic of LMBG device for pipeline leakage visual monitoring. \u003cstrong\u003eb\u003c/strong\u003e The natural core-layer structure of a liquid metal material whose oxide layer is vulnerable to external disturbances and then rapidly oxidized. \u003cstrong\u003ec\u003c/strong\u003e Current generation mechanism of galvanic cell based on different interfaces of liquid metal core metal and oxide layer.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-6472763/v1/3d18640bbc60298aadf5ce40.png"},{"id":85547988,"identity":"3167af35-31a8-44f0-a786-e89ce83cda83","added_by":"auto","created_at":"2025-06-27 09:00:10","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":646783,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eCharacterization of core, layer materials and adhesion to pipe surface\u003c/strong\u003e. \u003cstrong\u003ea\u003c/strong\u003eThe photographs of the device (the inset below shows an optical microscope image of the surface core metal and oxide micro zone in detail). \u003cstrong\u003eb\u003c/strong\u003e TEM images, EDS elemental mapping images, SAED, and HRTEM images of oxide layer. \u003cstrong\u003ec\u003c/strong\u003eXRD patterns of oxide layer and core material of liquid metal. \u003cstrong\u003ed\u003c/strong\u003e Raman spectrum of the oxide layer and core material of liquid metal. \u003cstrong\u003ee-f\u003c/strong\u003eHigh-resolution XPS spectrum of Ga 2p of the oxide layer and core material of liquid metal. \u003cstrong\u003eg\u003c/strong\u003e Spread-ability of liquid metal coatings on typical types of plate surfaces: glass fiber and HDPE. \u003cstrong\u003eh\u003c/strong\u003e Contact angle of liquid metal drop before and after spreading on typical glass fiber and HDPE plate. \u003cstrong\u003ei\u003c/strong\u003e Liquid metal coatings slip at different angles on a glass fibersurface. \u003cstrong\u003ej-k\u003c/strong\u003e Stability testing of liquid metal coatings on glass fiber surfaces subjected to fluid flushing at different angles. \u003cstrong\u003el\u003c/strong\u003e Stability testing of liquid metal coatings on glass fiber surfaces subjected to fluid washout at different flow velocities.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-6472763/v1/dbe745a007f8a125f01d28ae.png"},{"id":85547309,"identity":"fab36c93-3b0a-4537-9166-4be85422ac13","added_by":"auto","created_at":"2025-06-27 08:52:10","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":561670,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eGeneration and dynamics of LMB.\u003c/strong\u003e \u003cstrong\u003ea\u003c/strong\u003e The gas-liquid-liquid bubble model is proposed in this work. \u003cstrong\u003eb\u003c/strong\u003e The morphology of LMBs generated by different pipe diameters. \u003cstrong\u003ec\u003c/strong\u003e Simulated snapshots of bubble generation inside liquid metal at different pipe diameters. \u003cstrong\u003ed\u003c/strong\u003e The morphology of LMBs generated at different flow velocity. \u003cstrong\u003ee\u003c/strong\u003e “Core metal columns” generated by upward agitation of the core metal at the moment of LMB bursting at different flow velocity. Volume \u003cstrong\u003ef\u003c/strong\u003e of single bubbles generated by different flow velocity and frequency \u003cstrong\u003eg\u003c/strong\u003e of bubble generation (counting the number of bubbles generated per minute). Experimental and simulated curves of the volume \u003cstrong\u003eh\u003c/strong\u003e and frequency \u003cstrong\u003ei\u003c/strong\u003e of bubbles generated. \u003cstrong\u003ej\u003c/strong\u003eSchematic diagram of bubble shear and “liquid metal droplet-gas-solution” mixtures obtained by “laminar three-phase. flow-phase field” modesimulation. \u003cstrong\u003ek\u003c/strong\u003e Simulated and experimental path and morphology of bubble generation with different surface tensions. The yellow dashed outline shows the path of bubble generation. \u003cstrong\u003el\u003c/strong\u003e The surface tension of liquid metal before and after oxidation, the inset shows an image of the measured profile of a liquid metal droplet.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-6472763/v1/df83f62623988689944a6ec5.png"},{"id":85547989,"identity":"2247cbe0-d9a0-4fcc-aea2-73062913cc3d","added_by":"auto","created_at":"2025-06-27 09:00:10","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":399201,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eElectrical and bubble sensing performance of LMBG.\u003c/strong\u003e \u003cstrong\u003ea\u003c/strong\u003eConductivity tests of ionic liquids with different volume concentrations. \u003cstrong\u003eb-c\u003c/strong\u003eThe open-circuit voltage and short circuit current generated at different flow velocities. \u003cstrong\u003ed\u003c/strong\u003e Schematic diagram of different tube diameters for gas injection. \u003cstrong\u003ee-f\u003c/strong\u003e The open-circuit voltage and short circuit current generated at different tube sizes. \u003cstrong\u003eg\u003c/strong\u003e Mathematical relationship between flow velocity to voltage signal amplitude and frequency. \u003cstrong\u003eh\u003c/strong\u003e Mathematical relationship between bubble volume to voltage signal amplitude and frequency. \u003cstrong\u003ei\u003c/strong\u003e Response and recovery sensing time. \u003cstrong\u003ej\u003c/strong\u003e Sensitivity results between open-circuit voltage and LMB volumes. \u003cstrong\u003ek\u003c/strong\u003e Comparison of the detection resolution and sensitivity of LMBG with other reports. \u003cstrong\u003el-m\u003c/strong\u003e Schematic diagrams and output electrical signal of bubbles generated and bursted at different time intervals. \u003cstrong\u003en-o\u003c/strong\u003e Schematic diagrams and output electrical signal of switchable voltage mode induced by changing the direction of anode and cathode bubble burst.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-6472763/v1/b221e91a7c53e64a8da12777.png"},{"id":85547991,"identity":"afd6704c-c85e-48c2-b513-9d562166b120","added_by":"auto","created_at":"2025-06-27 09:00:10","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":490858,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eLMBG for pipeline leak detection.\u003c/strong\u003e \u003cstrong\u003ea\u003c/strong\u003e Schematic diagrams of different degrees of leakage in pipelines. \u003cstrong\u003eb\u003c/strong\u003e Schematic diagram of the device for gas leakage detection in a real pipeline, inset showing the simulated leakage points on a silicone pipe, schematic diagram of the detection device and the system processing logic. \u003cstrong\u003ec\u003c/strong\u003e Comparison of gas leakage detection signals from intact and damaged pipelines with actual simple devices. \u003cstrong\u003ed\u003c/strong\u003e Future application of the system for gas leakage detection in extreme environments.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-6472763/v1/281b1c0e29169e49f8f5294d.png"},{"id":85548766,"identity":"aa8c3b41-0ac7-4cec-a47d-71a775e16830","added_by":"auto","created_at":"2025-06-27 09:16:12","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3544876,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6472763/v1/a25ec97f-3de7-47f2-a93e-913e4448d4b0.pdf"},{"id":85547987,"identity":"2eb88c18-2f14-451e-ac15-1553cf80050e","added_by":"auto","created_at":"2025-06-27 09:00:10","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":1097054,"visible":true,"origin":"","legend":"Supplementary Information - Figures and Table","description":"","filename":"SupplementaryInformation.docx","url":"https://assets-eu.researchsquare.com/files/rs-6472763/v1/ec433d1cf96be02a6b5a740b.docx"},{"id":85547314,"identity":"a5374c12-96ad-4f1b-8a54-9db2d88c5973","added_by":"auto","created_at":"2025-06-27 08:52:10","extension":"mp4","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":5427234,"visible":true,"origin":"","legend":"Supplementary Information - Movie S1","description":"","filename":"MovieS1.mp4","url":"https://assets-eu.researchsquare.com/files/rs-6472763/v1/39ef799fabccb94394161fd5.mp4"},{"id":85547994,"identity":"6f482af0-2c21-4ee1-b624-e7a2f3ff54e3","added_by":"auto","created_at":"2025-06-27 09:00:10","extension":"mp4","order_by":3,"title":"","display":"","copyAsset":false,"role":"supplement","size":26315371,"visible":true,"origin":"","legend":"Supplementary Information - Movie S2","description":"","filename":"MovieS2.mp4","url":"https://assets-eu.researchsquare.com/files/rs-6472763/v1/38bc053caee3f83e6f262e25.mp4"},{"id":85547333,"identity":"71059b08-f906-43a5-a754-7c66733ec8ff","added_by":"auto","created_at":"2025-06-27 08:52:11","extension":"mp4","order_by":4,"title":"","display":"","copyAsset":false,"role":"supplement","size":37113761,"visible":true,"origin":"","legend":"Supplementary Information - Movie S3","description":"","filename":"MovieS3.mp4","url":"https://assets-eu.researchsquare.com/files/rs-6472763/v1/1e9feb0fa307654a1dd467a0.mp4"},{"id":85547334,"identity":"daa6f96c-655b-4f7e-b396-1d8fc4a27c93","added_by":"auto","created_at":"2025-06-27 08:52:11","extension":"mp4","order_by":5,"title":"","display":"","copyAsset":false,"role":"supplement","size":25791612,"visible":true,"origin":"","legend":"Supplementary Information - Movie S4","description":"","filename":"MovieS4.mp4","url":"https://assets-eu.researchsquare.com/files/rs-6472763/v1/c65c4460f549c02a903f0231.mp4"},{"id":85547332,"identity":"b059d835-98d1-45ab-a3cc-f4f3e48abe56","added_by":"auto","created_at":"2025-06-27 08:52:10","extension":"mp4","order_by":6,"title":"","display":"","copyAsset":false,"role":"supplement","size":24893316,"visible":true,"origin":"","legend":"Supplementary Information - Movie S5","description":"","filename":"MovieS5.mp4","url":"https://assets-eu.researchsquare.com/files/rs-6472763/v1/62f263430e02c8027269a560.mp4"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Self-Powered Liquid Metal Interfaces Enable Autonomous Electrochemical Sensing of Pipeline Microleaks in Extreme Environments","fulltext":[{"header":"Introduction","content":"\u003cp\u003eThe global network of energy pipelines \u0026ndash; spanning deep-sea trenches, urban undergrounds, and permafrost regions \u0026ndash; forms the circulatory system of modern industrial civilization, yet suffers annual economic losses exceeding \u003cspan\u003e$\u003c/span\u003e10\u0026nbsp;billion due to undetected leaks.\u003csup\u003e1\u0026ndash;5\u003c/sup\u003e Conventional detection technologies, relying on pressure differentials or acoustic signatures, face inherent limitations in micro-leakage resolution, response latency, and environmental interference resistance.\u003csup\u003e6, 7\u003c/sup\u003e These shortcomings become critically pronounced in extreme environments.\u003c/p\u003e \u003cp\u003eBubble formation is the typical physical signature of pipeline leakage, presenting significant potential for mechano-electrical energy conversion in extreme environments.\u003csup\u003e8\u0026ndash;11\u003c/sup\u003e Bubble-driven nanogenerators based on liquid-solid triboelectric mechanisms have been studied for leakage sensing, but their practical deployment still faces fundamental limitations such as the interfacial adhesion and the essential energy supply.\u003csup\u003e12\u0026ndash;15\u003c/sup\u003e In contrast, liquid metals (LMs) offer transformative advantages through their intrinsic fluidic adaptability and self-healing oxide interfaces, enabling seamless integration with complex substrates while maintaining electrochemical activity in extreme environments.\u003csup\u003e16\u0026ndash;20\u003c/sup\u003e This unique combination addresses the longstanding trade-off between interfacial compliance and sensing reliability in conventional systems. More importantly, the intrinsic reduction potential differences between LM and its oxide can form a built-in electric field. When the LM coating broken, an electrochemical cell is established between the bubble-exposed core metal and the oxidized layer on the intact coating. An electrical signal may be generated from the mechanical energy of the breakage. Here in this work, we designed a novel liquid metal chamber on the pipeline for the autonomous leakage detection. When the pipeline ruptures, the bubble bursts and leads to the destruction of the thin oxide layer on the liquid metal surface. The oxidation layer and the exposed LM formed a galvanic cell at the instant of bubble burst, and the current signal can be detected (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The systemic studies indicate the liquid metal bubble (LMB) can distinguish the size and the form of leakage point with a superhigh sensitivity. The voltage-volume sensitivity has been enhanced by one order, and the minimum threshold volume is better than the triboelectric ones commonly used nowadays, and is even comparable to the best sensing level of capacitive sensors. This new technician based on the self-powered galvanic cell shows great potential for bubble-related monitoring, especially for the equipment safety in the extreme environment.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Results and Discussions","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003ePreparation of LM coating\u003c/h2\u003e \u003cp\u003eThe surface of the original liquid metal material has a silvery-white appearance with metallic luster and smooth topography, while the surface is quickly to form an obvious thin layer of oxides after contacting of air (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea, the insert diagram shows an optical microscope image of the original liquid metal surface and an obvious oxide layer).\u003csup\u003e21, 22\u003c/sup\u003e SEM images clearly show a large number of folds of the oxide layer (Supplementary Fig. \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e), which is also evident from the low contrast appearance and pronounced stacking from the TEM images (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb). In addition, the elemental composition and distribution were investigated employing EDS spatial maps, indicating the formation of Ga\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e thin layers. Ga and O were discovered to be uniformly distributed throughout the film. Selected area electron diffraction pattern indicates that the oxide layer has a low degree of crystallinity, which is consistent with the reported oxide surface on liquid metal surfaces.\u003csup\u003e23, 24\u003c/sup\u003e AFM image shows that the thickness of the oxide layer is about 4.8 nm, which satisfies the typical thickness characteristics of 2D nanosheets (Supplementary Fig. S2).\u003csup\u003e24\u003c/sup\u003e To detect and infer these two different core and layer materials at the interface, XRD analysis was adopted (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec). The XRD results also proved the low crystallinity of both the liquid metal and its oxide.\u003csup\u003e25, 26\u003c/sup\u003e Raman spectra showed that the characteristic peak positions of Ga\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e were 88.1, 121.2, 151.1, 208.6, and 248.3 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, whereas core metal surfaces are mainly interactions between metal atoms and show no characteristic peaks (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed).\u003csup\u003e27\u0026ndash;29\u003c/sup\u003e High resolution XPS spectra of the split Ga 2p orbitals show that the surface composition of the oxide layer and core metal samples was mainly Ga and Ga\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e due to the relatively high Ga ratio in the liquid metal. In the 2p orbital, a clear spin-orbit splitting (SS) is observed, where the peak at 1145.1 eV points to elemental Ga\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e 2p3/2 and the peak at 1118.3 eV points to Ga\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e 2p3/2 (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ee-f).\u003csup\u003e30, 31\u003c/sup\u003e In addition, the XPS results comprehensively show that the proportion of oxides on the oxide layer is considerably increased compared to the core metal.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eTypically, we spread the liquid metal on the widely used substrates as glass fiber and HDPE (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eg). The contact angle of liquid metal on them were 85.0\u003csup\u003eo\u003c/sup\u003e and 94.2\u003csup\u003eo\u003c/sup\u003e, respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eh). However, after we spread the liquid metal on the glass fiber and steel plate by scraping, the contact angle decreased to 7.1\u003csup\u003eo\u003c/sup\u003e and 10.3\u003csup\u003eo\u003c/sup\u003e significantly (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eh). Notably, the coating will not rebound or shrink, which is attributed to the oxidation of gallium in the liquid metal in air, forming a stable oxide layer that secures the internal liquid metal and prevents shrink. Meanwhile, when we change the tilt angles of substrates from 15\u003csup\u003eo\u003c/sup\u003e to 150\u003csup\u003eo\u003c/sup\u003e, the LM coating shows the excellent adhesion stability (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ei). With the protection of the oxide layer, the core metal did not rupture and flow out or slip off. When we further applied different speeds of flowing water to the liquid metal coating, it also shows a good stability. The LM coating can even tolerate a flow velocity of 30 cm\u0026middot;s\u003csup\u003e-1\u003c/sup\u003e with a tilt angle smaller than 60\u003csup\u003eo\u003c/sup\u003e. The liquid metal coating maintains excellent stability under scouring at different flow velocities with a small shear angle (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ej-l).\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eGeneration and dynamics of LMB\u003c/h3\u003e\n\u003cp\u003eWhen a leakage appeared in the pipe, bubble will nucleate and grow up at the interface between the pipeline and LM core (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea). LMB is thermodynamically unstable that are extremely prone to burst.\u003csup\u003e32, 33\u003c/sup\u003e High-speed imaging results show that the duration of a single LMB from generation to burst is extremely short (~\u0026thinsp;300 ms, Supplementary Fig. S3 and Supplementary Movie S1). Further, we captured finite element simulation images of individual bubble generation to burst in order to better investigate the bubble development and morphology inside the liquid metal (Supplementary Fig. S4). The results show that the volume of LMB increases with the increase of the broken area under the same gas flow velocity (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb-c, Supplementary Movie S2). While the volume and morphology of LMBs unchanged for different flow velocities under the same pipe diameter conditions, indicating it is independent of the flow velocity (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed, Supplementary Fig. S5 and Supplementary Movie S3). It is worth noting that the transient pattern of LMB generation is consistent across different gas source areas and air velocity conditions. When a LMB burst, not only does the oxide layer at the top of the bubble rupture, exposing the core metal, but it also causes the core metal inside the LMB to surge upward, forming a \u0026ldquo;core metal column\u0026rdquo; as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ee. The volume and frequency of bubbles generation at different flow velocity were counted in the experiment, where the volume of bubbles was obtained by multiplying the duration of bubble generation until burst and the gas flow velocity, and the frequency was the number of bubbles produced per unit time (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ef-i). The simulation group shows a relationship where the bubble volume increases with the increase in gas flow velocity for bubble volumes generated by various gas flow velocity (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eh). The relationship between bubble frequency and gas flow velocity in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ei shows the same linear correlation for both experimental and simulation groups, meaning that the frequency rises as gas flow velocity increases.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eWhen the internal pressure reaches its limit, the bubble starts to burst with an instantaneous energy release at the gas-liquid interface.\u003csup\u003e34, 35\u003c/sup\u003e The gas-liquid interface generates a high-intensity shear force that shears the bulk liquid metal into many tiny droplets covering the liquid metal surface, resulting in a gas-liquid metal droplet-liquid mixture on the liquid metal surface (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ej, Supplementary Fig. S6 shows the entire process of liquid metal breaking by bubble shear stress). Further, it was found that the surface tension also has a great influence on the path and morphology of bubble generation (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ek). The bubble generation follows the three processes of: lateral escape of bubbles due to the large surface of the liquid metal in the initial state; intermediate arching of bubbles when the surface tension is reduced to about half of the initial one; and normal ellipsoidal LMB that can be generated smoothly when the surface tension is reduced by a factor of about 10 (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ek, Movie S4). The presence of surface oxides leads to significant decrease in the surface tension of liquid metals (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003el), which will decrease the energy barrier of bubble generation.\u003csup\u003e36\u0026ndash;39\u003c/sup\u003e\u003c/p\u003e\n\u003ch3\u003eElectrical and bubble sensing performance of LMBG\u003c/h3\u003e\n\u003cp\u003e[EMIM]CL ionic liquids with a volume concentration of 40% are chosen as electrolytes because of its relatively high conductivity (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea). Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb-c present the output voltage and current performance curves for different flow velocities with a tube diameter of 510 \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\mu\\:\\)\u003c/span\u003e\u003c/span\u003em. As the flow velocity increases, the frequency of the output open-circuit voltage and current signals increases significantly, while the amplitude of the corresponding electrical signals little changed (Supplementary Fig. S7). Subsequently, we changed the diameters of the pipelines and found the factor of pipe diameter is strong related to the voltage amplitude, while the current amplitude remains constant (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ed-f, Supplementary Movie S5). We further map the relationship between dynamical behavior of bubbles and electrical signals, and found the flow velocity shows a good linear correlation with the frequency of the electrical signal and little correlation with the change in amplitude (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eg-h). On the contrary, the bubble diameter does not correlate well with the frequency variation of the electrical signal, while it shows a good linear correlation with the amplitude. Above all, we can make a conclusion that the voltage\u0026rsquo;s amplitude is mainly related to the volume size of the LMBs, while the pulse frequency of voltage and the current intensity is mainly related to the frequency of the bubble generation, which is also verified by the kinetic process of bubble generation. The output electrical performance is affected by the volume of LMBs, electrolyte, etc. in addition to the upper limit of the redox potential of core metal.\u003csup\u003e36, 40\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe rupture of the surface oxide layer of LMBs triggers the activation of a localized galvanic cell reaction, realizing the conversion of mechanical energy to electrical energy, which in turn can be used as bubble sensor to realize the detection of bubble motion patterns and morphology. The response time was short as 0.33 s. While the response time was longer than 20 s can be attributed to the gradual convergence of the asymmetric potential difference to symmetry caused by re-oxidation of the core metal (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ei, Supplementary Fig. S8a-c). Then we defined the voltage-volume dependent sensitivity as \u003cb\u003eS1\u003c/b\u003e and the frequency-flow velocity dependent sensitivity as \u003cb\u003eS2\u003c/b\u003e to study the sensitivity of the bubble sensor (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ej). The device exhibits a superb high sensitivity of 319.9 V\u0026middot;cm\u003csup\u003e3\u003c/sup\u003e to the small bubble below 1.1\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e cm\u003csup\u003e3\u003c/sup\u003e, which is one order better than the best reported work based on our knowledge (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ej-k, Supplementary Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e).\u003csup\u003e14, 41\u0026ndash;50\u003c/sup\u003e And the minimum threshold volume for bubbles leakage detecting is only 1\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e cm\u003csup\u003e3\u003c/sup\u003e, which matches the resolution of the best reported work (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ej-k, Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e).\u003csup\u003e14, 41\u0026ndash;50\u003c/sup\u003e It also shows a good linear relationship between volume of bubble and voltage for different volume ranges of bubbles, with linear relationships of 0.9738 and 0.9955, respectively. Meanwhile, the frequency-flow velocity correlation with a sensitivity of 0.25 Hz\u0026middot;cm\u003csup\u003e-1\u003c/sup\u003e\u0026middot;s and a good linear relationship between signal frequency and flow velocity with a linearity of 0.9997 (Supplementary Fig. S9).\u003c/p\u003e \u003cp\u003eIn addition to intuitively reflecting the macroscopic LMB volume and frequency of generation through electrical signals, more microscopic detection of bubble motion patterns can be realized. Scenarios involving a single bubble, two consecutive bubbles, and two bubbles fusion in LM are further explored (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003el). As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003em, a single bubble produced a signal sharp peak, while the fast bubble generation will also shorten the time interval of the series of peaks. In addition, when two bubbles are closely generated, they will merge together and present two consecutive peak\u0026rsquo;s signal. Interestingly, since the spacer in chamber divided the cell into a cathode and an anode, the voltage direction can reflect the position of bubble (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003en-o). For instance, if the bubble generation on left chamber is specified to be negative, then the corresponding right-one will output positive. When we sequentially blew bubbles in the left and right chamber, an alternating voltage can be detected with a good stability (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eo).\u003c/p\u003e\n\u003ch3\u003eLMBG for pipeline rupture leak detection\u003c/h3\u003e\n\u003cp\u003eBeneath urban soils and oceans, the complex networks of pipelines serve as the lifeline of human beings, transporting fluids such as liquids and gases, and the severity of the pipeline leakage can be visually indicated by different colored warnings (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea).\u003csup\u003e50\u003c/sup\u003e In order to verify the effectiveness of this system for application in real scenarios, a pipe pre-buried through the bottom of the left and right chambers was designed (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb). Based on the monitoring device, the circuit and equipment for collecting data will transmit the data to the computer visualization display interface for real-time monitoring, and the monitoring interface will alarm and alert when an inconspicuous gas leakage occurs, and the manager staff will carry out post-processing according to this information (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb iii). When the gas is intermittently blown in, a series of sharp electrical signals can be detected immediately as expected (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eBecause of the establish of the connection between three parameters, including the electrical signal, the leakage of pipeline, and the flow of gas, we can prospect this technician can be expended to the gas pipeline in the deep sea, under the ground, or other extreme environments (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ed). Besides, gases originate from multiple sources in daily life, including air exhaled by the human body, the exhaust from machinery and appliances, and gases leaking from conveyor pipelines, etc. This provides possible future application scenarios for LMBG and bubble detection.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003e\u003cstrong\u003eMaterials:\u003c/strong\u003e The liquid metal, Galinstan (Ga\u003csub\u003e61.5\u003c/sub\u003eIn\u003csub\u003e25\u003c/sub\u003eSn\u003csub\u003e13.5\u003c/sub\u003e) alloy was purchased from Dongguan Dingguan Metal Technology Co. Ltd, China. Ionic liquid ([EMIM]BF\u003csub\u003e4\u003c/sub\u003e: 1-Ethyl-3-methylimidazolium tetrafluoroborate, 98%; [EMIM]DCA: 1-Ethyl-3-methylimidazolium Dicyanamide, 98%; [EMIM]CL: 1-Ethyl-3-methylimidazolium Chloride, 98%) used were of reagent grade obtained from Aladdin. Ionic liquid solutions of different concentrations are prepared by mixing the original ionic liquid and DI-water in different volume ratios. Unless stated otherwise all chemicals and reagents were used as received.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCharacterization and measurements of oxide layer and core metal of liquid metal:\u0026nbsp;\u003c/strong\u003eOptical micrographs of liquid metal surfaces obtained with an Olympus optical microscope. The TEM image, energy-dispersive X-ray spectroscopy (EDS) elemental mapping image, selected area electron diffraction (SAED) pattern image, high-resolution TEM (HRTEM) image of oxide layer was characterized by field emission transmission electron microscope (JEM-F200, Japan Electronics Co., Ltd.). The thickness of oxide layer is obtained by atomic force microscopy (NX10, Park, Korea). The SEM microscopic morphology of the oxide layer on the liquid metal surface was obtained by the Phenom Pro X, and its crystal structure composition and bonding fraction was obtained by X-ray diffraction (XRD, K-Alpha+, Thermo Fisher Scientific) and Raman spectroscopy (Raman, XperRam200VN, Nanobase, Korea). X-ray photoelectron spectroscopy (XPS) was adopted to analyze the composition of oxidation of the liquid metal surface before and after bubble generation. Full spectrum and narrow spectrum of gallium, indium, and oxygen were measured.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAdhesion and stability testing of liquid metal coatings on piping materials:\u003c/strong\u003eMechanical scraping was used to verify the spreading of the liquid metal coating on the pipe material. The stability of the coating is verified by observing the liquid metal liquid at different angles to see if there is any slippage and cracking out of the liquid. Liquid metal coatings were flushed with water at different angles and flow velocities to simulate the actual fluid flow environment they may be subjected to.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eLiquid metal bubble generation and bursting:\u003c/strong\u003e Liquid metals were injected into a 3D-printed container (HALOT-SKY, Shenzhen Creality 3D Technology Co., LTD) with left and right chambers, the bottoms of which are pre-punched with microscopic holes for connecting thin silicone tubes for aeration. The ionic liquid was poured into the container and fully covered the surfaces of liquid metals. The syringe pump (TL-F6, TONGLi Tech Co., LTD, Shenzhen) was used for air intake into the liquid metal, and the gas path is connected between the syringe pump and the bottom of the liquid metal by a silicone tube. The characteristics of the bubbles, including size, duration, and burst time, were then analyzed based on the photographs acquired by high-speed camera. The experiment was conducted at room temperature.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFinite element simulation:\u003c/strong\u003e For simplicity, a two-dimensional simulation model was built, whose dimensional proportions between its parts were kept consistent with the actual experimental setup, to investigate the generation of bubbles inside a liquid metal. The “laminar two-phase. flow-phase field” model of fluid flow affiliation was selected to investigate the bubble generation and the “laminar three-phase. flow-phase field” model was selected to explore the shear effect of gas on liquid metal. The corresponding bubble generation can be obtained by varying different air flow velocities and surface tension of liquid metal.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSurface tension and contact angle measurement:\u0026nbsp;\u003c/strong\u003eThe surface tension of the liquid metal as is and after oxidation of the LMB burst was carried out on a contact angle tester (SDC-350KS) by the hanging drop method and the angle measurement method was fitted to the Young-Laplace equation. A contact angle analyzer (FCA2000A, AFES) was used to determine the contact angle of liquid metal with four pipe materials.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eElectrical measurements of LMBG:\u003c/strong\u003eThe copper wire is inserted into the liquid metal, in direct contact with the liquid metal core, and the entire process of generating bubbles is insulated from the ionic liquid electrolyte. A digital multimeter (2400, Keithley) was used to record the voltage or current between the liquid metals in the two chambers through tinned copper wires. The conductivity data of ionic liquids was obtained by a conductivity meter (SANXIN SX813, Shanghai Sanxin Co. Ltd, China). The syringe pump is fed with different flow velocities of gas to produce bubbles of different volumes and frequencies so that voltage and current signals of different amplitudes and frequencies can be obtained. Cyclic performance testing was completed by continuous aeration with a syringe pump for some time with continuous bubble production.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eElectrochemical characterization:\u003c/strong\u003e An electrochemical workstation (CHI-660e, Shanghai Chenhua Co. Ltd, China) was adopted to test the electrochemical impedance and cyclic voltammetric curves of the oxide layer on the liquid metal surface between the left and right chambers within a frequency range from 0.01 to 100000 Hz and scan rate range from 0.01 V/s to 0.5 V/s.\u0026nbsp;\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eIn this work, we establish a new approach for autonomous leakage detection through the electrochemical regulation of liquid metal interface. The developed liquid metal bubble generator exploits the symbiotic relationship between LM\u0026rsquo;s intrinsic fluidity and the self-limiting oxide layer\u0026rsquo;s fracture-reconstruction behavior, creating a self-sustaining electrochemical transducer that operates without external energy input. Our device presents an ultra-high selectivity and performs excellent to the small leakage. Furthermore, a mathematical relationship between breakage size-flow velocity-electrical signals is established, and a multi-dimensional mapping between physical parameters and electrical signals is realized. In this case, our work opens a new class of intelligent flow electronics with transformative applications ranging from industrial microleakage prevention to biomechanical sensing. This fundamental advancement in material-enabled transduction physics opens avenues for developing self-powered monitoring networks in next-generation energy and space exploration infrastructure.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003ch2\u003eCompeting interests\u003c/h2\u003e \u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eAuthor contributions\u003c/h2\u003e \u003cp\u003eX. Wang carried out the experiment, analyzed the data, and wrote the manuscript. G. Ye managed the validation, methodology, and data curation. X. Zhang embellished the visual processing of the figure. Y. Chen, Y. Hu, Q. Wu, Y. Yang, H. Luo were involved in device fabrications and material testing and characterization analysis. N. Yang, P. Yang, Y. Wan. supervised this research and revised the manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgments\u003c/h2\u003e \u003cp\u003eThis work was financially supported by the National Natural Science Foundation of China (No. 12264053, 52271241 and 92163209), the Scientific Research and Innovation Project of Postgraduate Students in the Academic Degree of Yunnan University (No. KC-23234366) and Beijing Natural Science Foundation (JQ22004). The authors thank the Advanced Analysis and Measurement Centre of Yunnan University for the sample testing service and Advanced Computing Centre of Yunnan University. The authors thank the software support from Prof. Yingtang Zhou from Zhejiang Ocean University.\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that the main data supporting the findings of this study are contained within the paper and its associated Supplementary Information. All other relevant data are available from the corresponding author upon reasonable request.\u0026nbsp;\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eCostello SB, Chapman DN, Rogers CDF, Metje N. 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Herein, we present an intelligent liquid metal bubble generator (LMBG) chamber capable of converting mechanical leakage signals into real-time electrical feedback through a self-powered transduction mechanism. The proposed system exploits the intrinsic electric potential difference of liquid metal (LM) and its oxide. The rupture of LM bubbles at leakage site activates a built-in galvanic cell between the metallic core and its oxide shell, achieving direct mechanoelectrical energy conversion without external power input. Notably, the system demonstrates ultrahigh sensitivity with linear voltage-volume (319.9 V·cm\u003csup\u003e-3\u003c/sup\u003e) and frequency-flow velocity (0.25 Hz·cm\u003csup\u003e-1\u003c/sup\u003e·s) correlations, rapid response characteristics (0.33 s latency). Meanwhile, the exceptional detection resolution for micro-leakages as small as 1.0×10\u003csup\u003e-3\u003c/sup\u003e cm\u003csup\u003e3\u003c/sup\u003e. This achievement in active sensing technology establishes a new route for intelligent infrastructure monitoring, particularly addressing the critical need for robust leakage detection systems in next-generation deep-sea exploration and space habitat applications.\u003c/p\u003e","manuscriptTitle":"Self-Powered Liquid Metal Interfaces Enable Autonomous Electrochemical Sensing of Pipeline Microleaks in Extreme Environments","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-06-27 08:52:05","doi":"10.21203/rs.3.rs-6472763/v1","editorialEvents":[],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"nature-communications","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"NCOMMS","sideBox":"Learn more about [Nature Communications](http://www.nature.com/ncomms/)","snPcode":"","submissionUrl":"https://mts-ncomms.nature.com/","title":"Nature Communications","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Nature Communications","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"2dd4281f-a670-4d5c-a597-d631de470940","owner":[],"postedDate":"June 27th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[{"id":50638171,"name":"Physical sciences/Materials science/Nanoscale materials"},{"id":50638172,"name":"Physical sciences/Chemistry/Electrochemistry"},{"id":50638173,"name":"Physical sciences/Engineering/Electrical and electronic engineering"},{"id":50638174,"name":"Physical sciences/Nanoscience and technology/Nanoscale devices"}],"tags":[],"updatedAt":"2026-04-29T05:00:31+00:00","versionOfRecord":[],"versionCreatedAt":"2025-06-27 08:52:05","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6472763","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6472763","identity":"rs-6472763","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}