Enhanced Energy Conversion Efficiency in PVDF/WS 2 Hybrid Piezoelectric Nanogenerators

Enhanced Energy Conversion Efficiency in PVDF/WS 2 Hybrid Piezoelectric Nanogenerators | 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 Research Article Enhanced Energy Conversion Efficiency in PVDF/WS 2 Hybrid Piezoelectric Nanogenerators Munni Panwar, Himani Kaninwal, Shilpa Rana, Jasvir Dalal, Bharti Singh This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6801588/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 18 Aug, 2025 Read the published version in Discover Materials → Version 1 posted 10 You are reading this latest preprint version Abstract Energy harvesting from ambient sources, particularly human motion is gaining considerable interest because of its potential to efficiently convert environmental mechanical energy into usable electrical power. Ongoing research is exploring piezoelectric nanogenerators (PENGs) as a means to convert vibrational mechanical energy into functional electrical output. Here in, we report the fabrication of PENG based on PVDF/WS 2 nanocomposite thin films. WS 2 nanosheets are synthesized by exfoliation method. Further, WS 2 with different weight percentages was incorporated in PVDF and the resulting thin films are analysed using XRD and FTIR. The output of nanogenerator is finally examined, determining the maximum output voltage (V OC ) without an external load and the maximum current (I SC ) when the output terminals were shorted. The results indicate that the incorporation of WS 2 nanosheets led to enhanced output of piezoelectric nanogenerator, exhibiting an elevated voltage of 19.6 V and a peak current of 11.03 µA corresponding to 2 wt% filler concentration of WS 2 and shows significant potential for renewable energy conversion and self-sustaining electronic devices. Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 1. Introduction The continuous evolution of autonomous sensor networks, portable devices and IoT (Internet of Things) platforms has emphasized the significance of developing self-sustaining energy solutions. Although batteries have traditionally met this demand, their limited lifespan and frequent need for replacement pose major drawbacks. To address these concerns, harnessing energy from surrounding environmental sources has emerged as an effective alternative[ 1 , 2 , 3 ]. There are several sources of energy present in our surrounding, such as, sunlight[ 4 ], wind[ 5 ], human motion, and water, to produce clean, renewable energy[ 6 ]. With growing interest in sustainable and portable power sources, piezoelectric nanogenerators have become one of the most viable technologies for harvesting energy from ambient mechanical stimuli and are beneficial in designing self-powered wearable and portable electronic device[ 7 ]. Zhong Lin Wang et. al. [ 8 ] first introduced piezoelectric nanogenerators (PENGs) in the year 2006. By exploiting the characteristics of piezoelectric materials, these devices generate electrical energy by harnessing mechanical inputs, useful for powering small scale electronics. Mechanical deformation in piezoelectric transducers polarizes the crystal lattice structure, separating positive and negative charge carriers and creating an electrical potential. Piezoelectric materials have attracted significant interest for their incredible ability to harness ambient mechanical energy and generate useful electrical energy [ 9 , 10 , 11 ]. Various materials including lead zirconate titanate (PZT), barium titanate (BaTiO 3 ), lithium niobate (LiNbO 3 ) and sodium niobate (NaNbO 3 ) have been widely explored for piezoelectric applications, but these inorganic materials have a high energy conversion rate but because of its high toxicity, lack of durability and biocompatibility, they are less selected for use in the flexible nanogenerator. On the contrary, polyvinylidene fluoride (PVDF) and other piezoelectric polymers and copolymers offer potential for mechanical-to-electrical energy conversion applications owing to their elevated piezoelectric coefficient, thermal and chemical durability, biocompatibility, and lightweight structure[ 12 , 13 , 14 ]. In its semicrystalline form, this polymer frequently exhibits in several structural forms, including α, β, γ, and δ. The β-phase, characterized by the all-trans (TTTT) conformation, offers maximum piezoelectric response as a consequence of its higher dipole moment per unit volume, whereas the α-phase (TGTG conformation) is non-polar, while the γ-phase (T3GT3G conformation) has a weak piezoelectric coefficient. In comparison to PENGs constructed from inorganic piezoelectric materials, PENGs utilizing PVDF exhibit reduced electrical output efficiency[ 14 , 15 , 16 , 17 , 18 ]. The electrical output characteristics of piezoelectric nanogenerators utilizing PVDF has been significantly enhanced through the application of thermal, mechanical, and electrical treatments, which effectively increases β-phase crystallization and stabilization in PVDF. Moreover, the β-phase of PVDF may be enhanced through the incorporation nanofillers into the PVDF matrix, resulting in a flexible nanocomposite that exhibits improved piezoelectric output without sacrificing flexibility. The appropriate selection of fillers and their uniform integration into PVDF not only facilitates the nucleation of β-crystals but also augments the dielectric characteristics by increasing electric dipoles through significant interfacial polarization. To improve the ferroelectric characteristics of PVDF, nanofillers such as ZnO, RGO, BaTiO3 and various 2D materials like hBN, MXenes and TMDs are often introduced, as they facilitate β-phase crystallization by disrupting PVDF’s symmetry [ 19 , 20 ]. Herein, chemically exfoliated WS 2 nanosheets were utilized to boost the piezoelectric output characteristics of PVDF films. To determine the optimum concentration of nanofillers, PVDF nanocomposite film with different content (1,2,3, and 5%) were synthesised using drop-casting technique and were used to fabricate PENG. Among all fabricated devices, the PENG with 2% of WS 2 produce a maximum voltage 19.6 Volts and a maximum current of 11.09 µA at a tapping frequency of 7 Hz. Thus, the PENG is designed to extract mechanical energy from subtle human motions including finger tapping, foot tapping. These results demonstrate a practical approach for biomechanical energy harvesting from everyday human activities, highlighting the potential for sustainable applications in wearable electronics and portable systems. 2. Experimental Section 2.1. Materials Tungsten disulphide, Lithium bromide, Hexane and PVDF powder were acquired from Sigma Aldrich, whereas N, N-Dimethylformamide (DMF) was obtained from Fisher. The chemicals were directly used as provided, without any further processing. 2.2. Exfoliation of WS 2 nanosheets To synthesize WS 2 nanosheets, 1 gram of tungsten (IV) sulphide was incorporated into a combination of lithium bromide and hexane, maintaining a molar ratio of 1:2. The combination was thereafter subjected to sonication for 5 hours. Following sonication, the solution darkened, ensuring exfoliation. To facilitate separation, the solution was subjected to centrifugation at 6000 rpm for 45 minutes. The resulting sample was then washed many times with dimethylformamide (DMF) to eliminate any residual lithium bromide or hexane. After processing, the sample underwent oven drying at 90⁰C to yield WS 2 nanosheets powder. The synthesis process of WS 2 nanosheets is shown in Fig. 1 . 2.3. Synthesis of PVDF/WS 2 nanocomposite thin films The process of nanocomposite films fabrication includes mixing of 1g of PVDF powder with 10 ml of DMF and agitated until a homogenous mixture was achieved. Subsequently, exfoliated WS 2 nanosheets were added into the PVDF solution at different weight percentages (1%, 2%, 3% and 5%). The solutions were sonicated for about an hour to ensure uniform distribution of nanosheets. Subsequently, each solution was drop-casted onto pristine glass slides and subsequently exposed to thermal treatment at 80⁰C in an oven for a duration of 2 hours to facilitate drying. Upon cooling, the thin films were carefully peeled off from the substrate using deionised water. Pure PVDF films were fabricated using the same method, except the addition of WS 2 nanosheets. The synthesis process is illustrated in Fig. 2 . These were subsequently used for the fabrication of piezoelectric nanogenerators. 2.4. Characterization techniques and electrical measurements To analyse the exfoliated WS 2 nanosheets, X-ray diffraction (Bruker D8 Advance with Cu Kα X-ray source, 3.0 KW) was utilized for structural identification and scanning electron microscopy (JEOL Japan Model: JSM 6610LV) for evaluating surface morphology. PVDF/WS 2 thin films were characterized using XRD for phase determination, while Fourier Transform Infrared (Nicolet iS50 FTIR Tri-detector) spectrometer for investigating chemical bond structures and functional group distributions. An electrodynamic shaker (Micron MEV-0025) was employed to induce mechanical deformations in the piezoelectric devices, where parameters such as tapping frequency were varied to test the device performance. The electrical response was assessed by measuring open-circuit voltage with an oscilloscope (Tektronix MD034) and short-circuit current using an electrometer (Keysight B2985B). 3. Results and discussion XRD analysis of exfoliated WS 2 nanosheets is illustrated in Fig. 3 (a). In the XRD spectra peaks at 2θ 14.86°, 29.43°, 44.58°, and 60.46°, are attributed to the (002), (004), (100) and (006) planes, respectively indicative of a hexagonal crystalline phase consistent with JCPDS card no. 08-0237. The (002) peak exhibits significantly greater intensity than the others, indicating a strong preferred orientation along its crystallographic plane during exfoliation. This strong peak suggests the well-defined crystalline nature of the WS 2 nanosheets[ 21 ]. The surface morphology of WS 2 samples was characterized using SEM. The SEM micrograph of WS 2 is illustrated in Fig. 3 (b) demonstrated that the sample exhibits thin sheet structure which are well dispersed without any aggregation. The crystallinity and phase evolution of PVDF and PVDF/WS 2 nanocomposite films were characterized through XRD analysis. Figure 4 (a) displays the XRD pattern of PVDF and its nanocomposite films, where the peak associated with PVDF are indicated by * in the XRD pattern, while WS 2 -associated peaks are marked by #. The XRD spectra of pure PVDF film exhibits two characteristic peaks, the peak at 18.66° corresponding to (020) plane is attributed to non-polar α-phase, while the second peak at 20.32° corresponding to (110) plane is associated with polar β-phase of PVDF. While, PVDF/WS 2 nanocomposite films exhibits additional peak at 14.86⁰, which is identical to bare WS 2 , which demonstrates that PVDF/WS 2 nanocomposite films were successfully synthesized without affecting the crystallinity of WS 2 . Further, Fig. 4 (b) presents the FTIR spectra of PVDF and PVDF/WS 2 nanocomposite films, revealing characteristics absorption peaks corresponding to α and β phases of PVDF [ 22 , 23 ]. The β-phase fraction can be calculated using Lambert-Beer law-based equation, which is related to characteristic IR absorbance peaks to phase content, given by the following mathematical expression [ 23 ]: $$\:F\left(\beta\:\right)=\:\frac{A\beta\:}{\left(\frac{K\beta\:}{K\alpha\:}\right)A\alpha\:\text{+}A\beta\:\text{}}\:\times\:100\%$$ In this equation, the absorption coefficients K α and K β corresponds to 6.1×10 4 cm 2 /mol and 7.7×10 4 cm 2 /mol at wavenumbers 762 cm − 1 and 840 cm − 1 respectively. The absorbance values at these wavenumbers are represented by A α and A β respectively [ 24 ]. Analysis indicates that the pure PVDF exhibits approximately 64% β-phase, whereas the fraction of electroactive β phase increases to 86% for PVDF/WS 2 nanocomposite films. The results show that, incorporation of 2 wt % WS 2 results in highest β-phase content of 86%, suggesting that WS 2 nanosheets effectively enhance development of β-phase crystallization in PVDF. For the evaluation of the piezoelectric behaviour of nanocomposite films, a nanogenerator device was constructed by making electrodes onto both surfaces of the films. Each film was initially trimmed into dimensions of 2x1 cm 2 and thereafter, aluminium tape is attached on both sides of the films for the fabrication of PENG devices. Finally, the copper wires were drawn from the electrodes for making necessary electrical connections, and the entire device was encapsulated using Kapton tape for insulation. Thereafter, the piezo response of the fabricated PENGs, was assessed by continuously tapping the device using an electrodynamic shaker unit. Figure 5 and 6 displays the electrical output characteristics, specifically the generated open-circuit voltage and short-circuit current for nanogenerators based on PVDF and PVDF/WS 2 nanocomposite films. The results indicate that the incorporation of WS 2 significantly produces higher voltage than pure PVDF-based nanogenerators. PVDF film generates only 8 V whereas, the nanocomposites films with filler concentration of 1%, 2%, 3% and 5% executed the output voltage of 11.8V, 19.6V, 14.8V and 8.6V respectively. The output voltage from PVDF/WS 2 device initially increases with increase in WS 2 filler concentration, but its value start decreasing after 2% of filler concentration. The device with 2wt% filler concentration yields the maximum open-circuit output voltage of 19.6 V. The results demonstrate that the device with a 2% filler concentration exhibits optimal performance, as confirmed by the XRD and FTIR analysis. The short-circuit current data follows the voltage trend. The pure PVDF film yielded a current of 3µA, while the nanocomposite films exhibited significantly improved performance 7.28 µA, 11.03 µA, 6.52 µA, and 6.1 µA for 1 wt%, 2 wt%, 3 wt%, and 5 wt %, respectively. The maximum current was achieved at 2 wt% filler concentration, reflecting the most efficient conversion of mechanical into electrical signals. Table 1 presents a concise summary of the β-phase content and the corresponding electrical output values for each composition. The strong correlation between the electroactive phase and output parameters further validates the critical role of the β-phase in enhancing piezoelectric performance. Overall, these results provide the valuable insight into the material optimization strategies required for the development of high-performance flexible nanogenerators intended for wearable electronics and self-powered sensors. Table 1 Calculated β-phase content, open circuit voltage (V OC ) and short circuit current (I SC ) for fabricated nanogenerators at a tapping frequency of 7 Hz. S no. Sample β-phase (in %) V OC (in V) I SC (in µA) 1. PVDF 64 8 3 2. 1 wt% 82 11.8 7.28 3. 2 wt% 86 19.6 11.03 4. 3 wt % 84 14.8 6.52 5. 5 wt% 81.9 8.6 6.1 Piezoelectric-nanogenerator (PENG) functions on the basis of mechanical-to-electrical energy conversion, as depicted in Fig. 7 . Initially, in the absence of mechanical input, the internal dipoles within the piezoelectric film remain randomly oriented, resulting in no electrical signal, as depicted in Fig. 7 (a). When mechanical stress is introduced, the film undergoes deformation, aligning the dipoles and generating a polarization field. As a result of polarization, electric charges accumulate on the electrode surfaces. As the charges accumulate, voltage is generated, prompting charge flow between the electrodes, as depicted in Fig. 7 (b). When the mechanical force is released, the film returns to its original shape, causing the dipoles to relax and charges to flow in the opposite direction, as depicted in Fig. 7 (c). This repetitive cycle of mechanical deformation and relaxation results in an alternating output voltage from the PENG. 4. Piezoelectric Nanogenerators Application Furthermore, to validate the real-world applicability of the fabricated PENG devices, the capability to harvest mechanical energy was examined through various human motions. These tests aim to demonstrate the functional performance of the nanogenerator under low-frequency, low-force stimuli that are typically encountered in daily activities. In the present study, controlled tapping motions, including finger tapping and thumb tapping, were performed manually to stimulate realistic inputs. As shown in Fig. 8 , the electrical response of the PVDF/WS 2 (2 wt%) nanocomposite-based device under these stimuli indicates promising energy harvesting characteristics. An open-circuit voltage 2.54V was observed from the PENG device when subjected to single-finger tapping as shown in Fig. 8 (a). A more forceful thumb motion yielded a higher voltage output of 3.78 V, as illustrated in Fig. 8 (b). These results demonstrate the device’s high sensitivity and its effective conversion of mechanical deformations into electrical. The enhanced output is primarily due to the optimal dispersions of WS 2 within the PVDF matrix at 2 wt% concentration, which stimulates the formation of β-phase and facilitating efficient mechanical-to-electrical energy conversion. Along with, voltage generation, the practical utility of the device was further demonstrated through a visual experiment involving the illumination of commercial light-emitting diodes (LEDs). The circuit configuration used for this demonstration is shown in Fig. 8 (c). Upon mechanical actuation using an electrodynamic shaker, the stored energy from the PENG was successfully utilized to power LEDs, as illustrated in Fig. 8 (d). This validates the device’s potential to serve as a practical energy source for low-power electronic devices. These findings reinforce the potential of PVDF/WS 2 nanocomposite-based PENGs for integration into self-powered electronic systems. The ability to harvest and convert mechanical energy, such as simple human motions, into useful electrical energy highlights their suitability for wearable electronics, portable sensors, and next generation energy-autonomous devices. Moreover, the simplicity of the device architecture and cost-effective fabrication process makes it a viable candidate for scalable energy harvesting solutions. 5. Conclusions PVDF, PVDF/WS 2 flexible thin films with varying filler contents (0%, 1%, 2%, 3% and 5%) have been synthesised, and their piezoelectric responses have been examined. The PENG device incorporating 2 wt% WS 2 exhibited superior performance, producing a voltage output of 19.6 V and a corresponding current of 11.03 µA. The enhanced piezoelectric output performance is ascribed to WS 2 influence in the alignment of β-phase dipoles in PVDF. The incorporation of WS 2 provides a conductive pathway that facilitate charge transport within the films, hence enabling the alignment PVDF dipoles and enhancing the overall piezo response. Finally, the potential application of the PVDF/WS 2 film (with 2% filler concentration) based PENG device was demonstrated by harvesting energy from human actions like single finger tapping and thumb tapping. The PENG device with 2 wt% WS 2 content exhibited superior performance, characterized by measured voltage of 19.6 V and a corresponding current of 11.03 µA. The generated voltage was also used to power LED, thereby demonstrating the real time application of fabricated nanogenerator. Declarations Contributions : Munni & Himani: Methodology, experiment, data curation, formal analysis, original draft; S. Rana: Experiment, data curation, investigation, writing; J. Dalal: Investigation, revision and editing; and B. Singh: Writing, editing, methodology, supervision. Competing interests: The authors declare no competing interests. Ethics, Consent to Participate, and Consent to Publish declarations not applicable. Clinical trial number not applicable. Funding: This research was not supported by any funding agencies. Author Contribution Munni & Himani (Both equal): Methodology, experiment, data curation, formal analysis, original draft; S. Rana: Experiment, data curation, investigation, writing; J. Dalal: Investigation, revision and editing; and B. Singh: Writing, editing, methodology, supervision. Acknowledgment The authors sincerely thank the Advanced Materials and Device Laboratory (AMDL) team for their valuable support and assistance throughout the course of this work. Data Availability The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request. References Khandelwal G, Deswal S, Shakthivel D, Dahiya R. Recent developments in 2D materials for energy harvesting applications. JPhys Energy 5. 2023. Gołąbek J, Strankowski M. 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Compos Sci Technol. 2017;149:127–33. Additional Declarations No competing interests reported. Supplementary Files SS1.mp4 Cite Share Download PDF Status: Published Journal Publication published 18 Aug, 2025 Read the published version in Discover Materials → Version 1 posted Editorial decision: Revision requested 24 Jun, 2025 Reviews received at journal 20 Jun, 2025 Reviewers agreed at journal 20 Jun, 2025 Reviews received at journal 11 Jun, 2025 Reviewers agreed at journal 11 Jun, 2025 Reviewers invited by journal 11 Jun, 2025 Editor invited by journal 06 Jun, 2025 Editor assigned by journal 03 Jun, 2025 Submission checks completed at journal 03 Jun, 2025 First submitted to journal 02 Jun, 2025 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. 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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-6801588","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":470018029,"identity":"cb0ca6c7-56ab-47bc-a8e2-2a1d6bd15764","order_by":0,"name":"Munni Panwar","email":"","orcid":"","institution":"Delhi Technological University","correspondingAuthor":false,"prefix":"","firstName":"Munni","middleName":"","lastName":"Panwar","suffix":""},{"id":470018031,"identity":"fecc7a5f-a43c-45a2-8389-69a4b3a300fa","order_by":1,"name":"Himani Kaninwal","email":"","orcid":"","institution":"Delhi Technological 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WS\u003c/strong\u003e\u003c/em\u003e\u003csub\u003e\u003cem\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e\u003cstrong\u003e nanosheets.\u003c/strong\u003e\u003c/em\u003e\u003c/p\u003e","description":"","filename":"image1.png","url":"https://assets-eu.researchsquare.com/files/rs-6801588/v1/a6500670f5f1aca52b8df109.png"},{"id":84535346,"identity":"ad5360ab-6599-4154-a748-02f9ca26c0cd","added_by":"auto","created_at":"2025-06-13 07:04:25","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":77786,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003e\u003cstrong\u003eDiagrammatic representation of the synthesis process for PVDF and PVDF/WS\u003c/strong\u003e\u003c/em\u003e\u003csub\u003e\u003cem\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e\u003cstrong\u003e films.\u003c/strong\u003e\u003c/em\u003e\u003c/p\u003e","description":"","filename":"image2.png","url":"https://assets-eu.researchsquare.com/files/rs-6801588/v1/4ed7e4e95968a697c349ec08.png"},{"id":84535092,"identity":"90168a3f-4b6d-41ea-9521-e998c64ca592","added_by":"auto","created_at":"2025-06-13 06:56:25","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":2862571,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003e\u003cstrong\u003e(a) XRD pattern, (b) SEM images of WS\u003c/strong\u003e\u003c/em\u003e\u003csub\u003e\u003cem\u003e\u003cstrong\u003e2 \u003c/strong\u003e\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e\u003cstrong\u003enanosheets.\u003c/strong\u003e\u003c/em\u003e\u003c/p\u003e","description":"","filename":"image3.png","url":"https://assets-eu.researchsquare.com/files/rs-6801588/v1/ba499eb6bd827b01e1942d12.png"},{"id":84535099,"identity":"52570fdf-220f-4a40-81da-a7f7bdcc50f6","added_by":"auto","created_at":"2025-06-13 06:56:25","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":72639,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003e\u003cstrong\u003e(a) XRD, (b) FTIR analysis for PVDF and PVDF/WS\u003c/strong\u003e\u003c/em\u003e\u003csub\u003e\u003cem\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e\u003cstrong\u003e nanocomposite films.\u003c/strong\u003e\u003c/em\u003e\u003c/p\u003e","description":"","filename":"image4.png","url":"https://assets-eu.researchsquare.com/files/rs-6801588/v1/9599fd4103f48355bc704f62.png"},{"id":84536233,"identity":"ef3e600f-d232-45bf-a0bb-80faca7e7183","added_by":"auto","created_at":"2025-06-13 07:12:25","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":47360,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003e\u003cstrong\u003eVoltage measurement outputs (a) PVDF, (b-e) PVDF/WS\u003c/strong\u003e\u003c/em\u003e\u003csub\u003e\u003cem\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e\u003cstrong\u003e nanocomposites containing 1%, 2%, 3% and 5% of WS\u003c/strong\u003e\u003c/em\u003e\u003csub\u003e\u003cem\u003e\u003cstrong\u003e2 \u003c/strong\u003e\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e\u003cstrong\u003erespectively.\u003c/strong\u003e\u003c/em\u003e\u003c/p\u003e","description":"","filename":"image5.png","url":"https://assets-eu.researchsquare.com/files/rs-6801588/v1/f3739219d1777a6de49864be.png"},{"id":84535095,"identity":"321cafde-f85b-4c0f-b0c6-23a427f01d93","added_by":"auto","created_at":"2025-06-13 06:56:25","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":61197,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003e\u003cstrong\u003eCurrent measurement outputs (a) PVDF, (b-e) PVDF/WS\u003c/strong\u003e\u003c/em\u003e\u003csub\u003e\u003cem\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e\u003cstrong\u003e nanocomposites containing 1%, 2%, 3% and 5% of WS\u003c/strong\u003e\u003c/em\u003e\u003csub\u003e\u003cem\u003e\u003cstrong\u003e2 \u003c/strong\u003e\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e\u003cstrong\u003erespectively.\u003c/strong\u003e\u003c/em\u003e\u003c/p\u003e","description":"","filename":"image6.png","url":"https://assets-eu.researchsquare.com/files/rs-6801588/v1/a299dbd2503128e902d8888a.png"},{"id":84535348,"identity":"1f5e07ee-e420-42a8-ba78-22205eff27fe","added_by":"auto","created_at":"2025-06-13 07:04:25","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":82524,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003e\u003cstrong\u003eWorking mechanism of PENG.\u003c/strong\u003e\u003c/em\u003e\u003c/p\u003e","description":"","filename":"image7.png","url":"https://assets-eu.researchsquare.com/files/rs-6801588/v1/bb9c285520436aa21d966816.png"},{"id":84535349,"identity":"6b313d9e-1610-4310-b209-c9fa5076593d","added_by":"auto","created_at":"2025-06-13 07:04:25","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":190289,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003e\u003cstrong\u003eVoltage measurements (a)single finger tapping, (b) thumb tapping; and (c) schematic circuit diagram, (d) image of lightning LED using PENG.\u003c/strong\u003e\u003c/em\u003e\u003c/p\u003e","description":"","filename":"image8.png","url":"https://assets-eu.researchsquare.com/files/rs-6801588/v1/9aea88c5a0737d90a6e9a038.png"},{"id":89847141,"identity":"2f15b96a-3702-47be-81bc-68c247bbbf73","added_by":"auto","created_at":"2025-08-25 16:41:09","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":4359260,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6801588/v1/f98142ef-0f97-4c89-8beb-0027ba8153f3.pdf"},{"id":84535094,"identity":"c9fad291-0963-4989-bd7e-945234978d27","added_by":"auto","created_at":"2025-06-13 06:56:25","extension":"mp4","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":1084959,"visible":true,"origin":"","legend":"","description":"","filename":"SS1.mp4","url":"https://assets-eu.researchsquare.com/files/rs-6801588/v1/a55a7412edf9d0617c2db425.mp4"}],"financialInterests":"No competing interests reported.","formattedTitle":"Enhanced Energy Conversion Efficiency in PVDF/WS 2 Hybrid Piezoelectric Nanogenerators","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThe continuous evolution of autonomous sensor networks, portable devices and IoT (Internet of Things) platforms has emphasized the significance of developing self-sustaining energy solutions. Although batteries have traditionally met this demand, their limited lifespan and frequent need for replacement pose major drawbacks. To address these concerns, harnessing energy from surrounding environmental sources has emerged as an effective alternative[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. There are several sources of energy present in our surrounding, such as, sunlight[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e], wind[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e], human motion, and water, to produce clean, renewable energy[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. With growing interest in sustainable and portable power sources, piezoelectric nanogenerators have become one of the most viable technologies for harvesting energy from ambient mechanical stimuli and are beneficial in designing self-powered wearable and portable electronic device[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Zhong Lin Wang et. al. [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e] first introduced piezoelectric nanogenerators (PENGs) in the year 2006. By exploiting the characteristics of piezoelectric materials, these devices generate electrical energy by harnessing mechanical inputs, useful for powering small scale electronics. Mechanical deformation in piezoelectric transducers polarizes the crystal lattice structure, separating positive and negative charge carriers and creating an electrical potential. Piezoelectric materials have attracted significant interest for their incredible ability to harness ambient mechanical energy and generate useful electrical energy [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Various materials including lead zirconate titanate (PZT), barium titanate (BaTiO\u003csub\u003e3\u003c/sub\u003e), lithium niobate (LiNbO\u003csub\u003e3\u003c/sub\u003e) and sodium niobate (NaNbO\u003csub\u003e3\u003c/sub\u003e) have been widely explored for piezoelectric applications, but these inorganic materials have a high energy conversion rate but because of its high toxicity, lack of durability and biocompatibility, they are less selected for use in the flexible nanogenerator.\u003c/p\u003e \u003cp\u003eOn the contrary, polyvinylidene fluoride (PVDF) and other piezoelectric polymers and copolymers offer potential for mechanical-to-electrical energy conversion applications owing to their elevated piezoelectric coefficient, thermal and chemical durability, biocompatibility, and lightweight structure[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. In its semicrystalline form, this polymer frequently exhibits in several structural forms, including α, β, γ, and δ. The β-phase, characterized by the all-trans (TTTT) conformation, offers maximum piezoelectric response as a consequence of its higher dipole moment per unit volume, whereas the α-phase (TGTG conformation) is non-polar, while the γ-phase (T3GT3G conformation) has a weak piezoelectric coefficient. In comparison to PENGs constructed from inorganic piezoelectric materials, PENGs utilizing PVDF exhibit reduced electrical output efficiency[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. The electrical output characteristics of piezoelectric nanogenerators utilizing PVDF has been significantly enhanced through the application of thermal, mechanical, and electrical treatments, which effectively increases β-phase crystallization and stabilization in PVDF. Moreover, the β-phase of PVDF may be enhanced through the incorporation nanofillers into the PVDF matrix, resulting in a flexible nanocomposite that exhibits improved piezoelectric output without sacrificing flexibility. The appropriate selection of fillers and their uniform integration into PVDF not only facilitates the nucleation of β-crystals but also augments the dielectric characteristics by increasing electric dipoles through significant interfacial polarization. To improve the ferroelectric characteristics of PVDF, nanofillers such as ZnO, RGO, BaTiO3 and various 2D materials like hBN, MXenes and TMDs are often introduced, as they facilitate β-phase crystallization by disrupting PVDF\u0026rsquo;s symmetry [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eHerein, chemically exfoliated WS\u003csub\u003e2\u003c/sub\u003e nanosheets were utilized to boost the piezoelectric output characteristics of PVDF films. To determine the optimum concentration of nanofillers, PVDF nanocomposite film with different content (1,2,3, and 5%) were synthesised using drop-casting technique and were used to fabricate PENG. Among all fabricated devices, the PENG with 2% of WS\u003csub\u003e2\u003c/sub\u003e produce a maximum voltage 19.6 Volts and a maximum current of 11.09 \u0026micro;A at a tapping frequency of 7 Hz. Thus, the PENG is designed to extract mechanical energy from subtle human motions including finger tapping, foot tapping. These results demonstrate a practical approach for biomechanical energy harvesting from everyday human activities, highlighting the potential for sustainable applications in wearable electronics and portable systems.\u003c/p\u003e"},{"header":"2. Experimental Section","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1. Materials\u003c/h2\u003e \u003cp\u003eTungsten disulphide, Lithium bromide, Hexane and PVDF powder were acquired from Sigma Aldrich, whereas N, N-Dimethylformamide (DMF) was obtained from Fisher. The chemicals were directly used as provided, without any further processing.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2. Exfoliation of WS\u003csub\u003e2\u003c/sub\u003e nanosheets\u003c/h2\u003e \u003cp\u003eTo synthesize WS\u003csub\u003e2\u003c/sub\u003e nanosheets, 1 gram of tungsten (IV) sulphide was incorporated into a combination of lithium bromide and hexane, maintaining a molar ratio of 1:2. The combination was thereafter subjected to sonication for 5 hours. Following sonication, the solution darkened, ensuring exfoliation. To facilitate separation, the solution was subjected to centrifugation at 6000 rpm for 45 minutes. The resulting sample was then washed many times with dimethylformamide (DMF) to eliminate any residual lithium bromide or hexane. After processing, the sample underwent oven drying at 90⁰C to yield WS\u003csub\u003e2\u003c/sub\u003e nanosheets powder. The synthesis process of WS\u003csub\u003e2\u003c/sub\u003e nanosheets is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3. Synthesis of PVDF/WS\u003csub\u003e2\u003c/sub\u003e nanocomposite thin films\u003c/h2\u003e \u003cp\u003eThe process of nanocomposite films fabrication includes mixing of 1g of PVDF powder with 10 ml of DMF and agitated until a homogenous mixture was achieved. Subsequently, exfoliated WS\u003csub\u003e2\u003c/sub\u003e nanosheets were added into the PVDF solution at different weight percentages (1%, 2%, 3% and 5%). The solutions were sonicated for about an hour to ensure uniform distribution of nanosheets. Subsequently, each solution was drop-casted onto pristine glass slides and subsequently exposed to thermal treatment at 80⁰C in an oven for a duration of 2 hours to facilitate drying. Upon cooling, the thin films were carefully peeled off from the substrate using deionised water. Pure PVDF films were fabricated using the same method, except the addition of WS\u003csub\u003e2\u003c/sub\u003e nanosheets. The synthesis process is illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. These were subsequently used for the fabrication of piezoelectric nanogenerators.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4. Characterization techniques and electrical measurements\u003c/h2\u003e \u003cp\u003eTo analyse the exfoliated WS\u003csub\u003e2\u003c/sub\u003e nanosheets, X-ray diffraction (Bruker D8 Advance with Cu Kα X-ray source, 3.0 KW) was utilized for structural identification and scanning electron microscopy (JEOL Japan Model: JSM 6610LV) for evaluating surface morphology. PVDF/WS\u003csub\u003e2\u003c/sub\u003e thin films were characterized using XRD for phase determination, while Fourier Transform Infrared (Nicolet iS50 FTIR Tri-detector) spectrometer for investigating chemical bond structures and functional group distributions. An electrodynamic shaker (Micron MEV-0025) was employed to induce mechanical deformations in the piezoelectric devices, where parameters such as tapping frequency were varied to test the device performance. The electrical response was assessed by measuring open-circuit voltage with an oscilloscope (Tektronix MD034) and short-circuit current using an electrometer (Keysight B2985B).\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results and discussion","content":"\u003cp\u003eXRD analysis of exfoliated WS\u003csub\u003e2\u003c/sub\u003e nanosheets is illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(a). In the XRD spectra peaks at 2θ 14.86\u0026deg;, 29.43\u0026deg;, 44.58\u0026deg;, and 60.46\u0026deg;, are attributed to the (002), (004), (100) and (006) planes, respectively indicative of a hexagonal crystalline phase consistent with JCPDS card no. 08-0237. The (002) peak exhibits significantly greater intensity than the others, indicating a strong preferred orientation along its crystallographic plane during exfoliation. This strong peak suggests the well-defined crystalline nature of the WS\u003csub\u003e2\u003c/sub\u003e nanosheets[\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. The surface morphology of WS\u003csub\u003e2\u003c/sub\u003e samples was characterized using SEM. The SEM micrograph of WS\u003csub\u003e2\u003c/sub\u003e is illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(b) demonstrated that the sample exhibits thin sheet structure which are well dispersed without any aggregation.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe crystallinity and phase evolution of PVDF and PVDF/WS\u003csub\u003e2\u003c/sub\u003e nanocomposite films were characterized through XRD analysis. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e(a) displays the XRD pattern of PVDF and its nanocomposite films, where the peak associated with PVDF are indicated by * in the XRD pattern, while WS\u003csub\u003e2\u003c/sub\u003e -associated peaks are marked by #. The XRD spectra of pure PVDF film exhibits two characteristic peaks, the peak at 18.66\u0026deg; corresponding to (020) plane is attributed to non-polar α-phase, while the second peak at 20.32\u0026deg; corresponding to (110) plane is associated with polar β-phase of PVDF. While, PVDF/WS\u003csub\u003e2\u003c/sub\u003e nanocomposite films exhibits additional peak at 14.86⁰, which is identical to bare WS\u003csub\u003e2\u003c/sub\u003e, which demonstrates that PVDF/WS\u003csub\u003e2\u003c/sub\u003e nanocomposite films were successfully synthesized without affecting the crystallinity of WS\u003csub\u003e2\u003c/sub\u003e.\u003c/p\u003e \u003cp\u003eFurther, Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e(b) presents the FTIR spectra of PVDF and PVDF/WS\u003csub\u003e2\u003c/sub\u003e nanocomposite films, revealing characteristics absorption peaks corresponding to α and β phases of PVDF [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. The β-phase fraction can be calculated using Lambert-Beer law-based equation, which is related to characteristic IR absorbance peaks to phase content, given by the following mathematical expression [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]:\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$\\:F\\left(\\beta\\:\\right)=\\:\\frac{A\\beta\\:}{\\left(\\frac{K\\beta\\:}{K\\alpha\\:}\\right)A\\alpha\\:\\text{+}A\\beta\\:\\text{}}\\:\\times\\:100\\%$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eIn this equation, the absorption coefficients K\u003csub\u003eα\u003c/sub\u003e and K\u003csub\u003eβ\u003c/sub\u003e corresponds to 6.1\u0026times;10\u003csup\u003e4\u003c/sup\u003e cm\u003csup\u003e2\u003c/sup\u003e/mol and 7.7\u0026times;10\u003csup\u003e4\u003c/sup\u003e cm\u003csup\u003e2\u003c/sup\u003e/mol at wavenumbers 762 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 840 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e respectively. The absorbance values at these wavenumbers are represented by A\u003csub\u003eα\u003c/sub\u003e and A\u003csub\u003eβ\u003c/sub\u003e respectively [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. Analysis indicates that the pure PVDF exhibits approximately 64% β-phase, whereas the fraction of electroactive β phase increases to 86% for PVDF/WS\u003csub\u003e2\u003c/sub\u003e nanocomposite films. The results show that, incorporation of 2 wt % WS\u003csub\u003e2\u003c/sub\u003e results in highest β-phase content of 86%, suggesting that WS\u003csub\u003e2\u003c/sub\u003e nanosheets effectively enhance development of β-phase crystallization in PVDF.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFor the evaluation of the piezoelectric behaviour of nanocomposite films, a nanogenerator device was constructed by making electrodes onto both surfaces of the films. Each film was initially trimmed into dimensions of 2x1 cm\u003csup\u003e2\u003c/sup\u003e and thereafter, aluminium tape is attached on both sides of the films for the fabrication of PENG devices. Finally, the copper wires were drawn from the electrodes for making necessary electrical connections, and the entire device was encapsulated using Kapton tape for insulation. Thereafter, the piezo response of the fabricated PENGs, was assessed by continuously tapping the device using an electrodynamic shaker unit.\u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e and \u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e displays the electrical output characteristics, specifically the generated open-circuit voltage and short-circuit current for nanogenerators based on PVDF and PVDF/WS\u003csub\u003e2\u003c/sub\u003e nanocomposite films. The results indicate that the incorporation of WS\u003csub\u003e2\u003c/sub\u003e significantly produces higher voltage than pure PVDF-based nanogenerators. PVDF film generates only 8 V whereas, the nanocomposites films with filler concentration of 1%, 2%, 3% and 5% executed the output voltage of 11.8V, 19.6V, 14.8V and 8.6V respectively. The output voltage from PVDF/WS\u003csub\u003e2\u003c/sub\u003e device initially increases with increase in WS\u003csub\u003e2\u003c/sub\u003e filler concentration, but its value start decreasing after 2% of filler concentration. The device with 2wt% filler concentration yields the maximum open-circuit output voltage of 19.6 V. The results demonstrate that the device with a 2% filler concentration exhibits optimal performance, as confirmed by the XRD and FTIR analysis. The short-circuit current data follows the voltage trend.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe pure PVDF film yielded a current of 3\u0026micro;A, while the nanocomposite films exhibited significantly improved performance 7.28 \u0026micro;A, 11.03 \u0026micro;A, 6.52 \u0026micro;A, and 6.1 \u0026micro;A for 1 wt%, 2 wt%, 3 wt%, and 5 wt %, respectively. The maximum current was achieved at 2 wt% filler concentration, reflecting the most efficient conversion of mechanical into electrical signals. Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e presents a concise summary of the β-phase content and the corresponding electrical output values for each composition. The strong correlation between the electroactive phase and output parameters further validates the critical role of the β-phase in enhancing piezoelectric performance. Overall, these results provide the valuable insight into the material optimization strategies required for the development of high-performance flexible nanogenerators intended for wearable electronics and self-powered sensors.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003e\u003cb\u003eCalculated β-phase content, open circuit voltage (V\u003c/b\u003e\u003csub\u003e\u003cb\u003eOC\u003c/b\u003e\u003c/sub\u003e\u003cb\u003e) and short circuit current (I\u003c/b\u003e\u003csub\u003e\u003cb\u003eSC\u003c/b\u003e\u003c/sub\u003e\u003cb\u003e) for fabricated nanogenerators at a tapping frequency of 7 Hz.\u003c/b\u003e\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eS no.\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSample\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eβ-phase (in %)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eV\u003csub\u003eOC\u003c/sub\u003e (in V)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eI\u003csub\u003eSC\u003c/sub\u003e (in \u0026micro;A)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePVDF\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e64\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1 wt%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e82\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e11.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e7.28\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e3.\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e2 wt%\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e86\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e19.6\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e11.03\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3 wt %\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e84\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e14.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e6.52\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e5.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5 wt%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e81.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e8.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e6.1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003ePiezoelectric-nanogenerator (PENG) functions on the basis of mechanical-to-electrical energy conversion, as depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e. Initially, in the absence of mechanical input, the internal dipoles within the piezoelectric film remain randomly oriented, resulting in no electrical signal, as depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e(a). When mechanical stress is introduced, the film undergoes deformation, aligning the dipoles and generating a polarization field. As a result of polarization, electric charges accumulate on the electrode surfaces. As the charges accumulate, voltage is generated, prompting charge flow between the electrodes, as depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e(b). When the mechanical force is released, the film returns to its original shape, causing the dipoles to relax and charges to flow in the opposite direction, as depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e(c). This repetitive cycle of mechanical deformation and relaxation results in an alternating output voltage from the PENG.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"4. Piezoelectric Nanogenerators Application","content":"\u003cp\u003eFurthermore, to validate the real-world applicability of the fabricated PENG devices, the capability to harvest mechanical energy was examined through various human motions. These tests aim to demonstrate the functional performance of the nanogenerator under low-frequency, low-force stimuli that are typically encountered in daily activities. In the present study, controlled tapping motions, including finger tapping and thumb tapping, were performed manually to stimulate realistic inputs. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e, the electrical response of the PVDF/WS\u003csub\u003e2\u003c/sub\u003e (2 wt%) nanocomposite-based device under these stimuli indicates promising energy harvesting characteristics.\u003c/p\u003e \u003cp\u003eAn open-circuit voltage 2.54V was observed from the PENG device when subjected to single-finger tapping as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e(a). A more forceful thumb motion yielded a higher voltage output of 3.78 V, as illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e(b). These results demonstrate the device\u0026rsquo;s high sensitivity and its effective conversion of mechanical deformations into electrical. The enhanced output is primarily due to the optimal dispersions of WS\u003csub\u003e2\u003c/sub\u003e within the PVDF matrix at 2 wt% concentration, which stimulates the formation of β-phase and facilitating efficient mechanical-to-electrical energy conversion.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAlong with, voltage generation, the practical utility of the device was further demonstrated through a visual experiment involving the illumination of commercial light-emitting diodes (LEDs). The circuit configuration used for this demonstration is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e(c). Upon mechanical actuation using an electrodynamic shaker, the stored energy from the PENG was successfully utilized to power LEDs, as illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e(d). This validates the device\u0026rsquo;s potential to serve as a practical energy source for low-power electronic devices. These findings reinforce the potential of PVDF/WS\u003csub\u003e2\u003c/sub\u003e nanocomposite-based PENGs for integration into self-powered electronic systems. The ability to harvest and convert mechanical energy, such as simple human motions, into useful electrical energy highlights their suitability for wearable electronics, portable sensors, and next generation energy-autonomous devices. Moreover, the simplicity of the device architecture and cost-effective fabrication process makes it a viable candidate for scalable energy harvesting solutions.\u003c/p\u003e"},{"header":"5. Conclusions","content":"\u003cp\u003ePVDF, PVDF/WS\u003csub\u003e2\u003c/sub\u003e flexible thin films with varying filler contents (0%, 1%, 2%, 3% and 5%) have been synthesised, and their piezoelectric responses have been examined. The PENG device incorporating 2 wt% WS\u003csub\u003e2\u003c/sub\u003e exhibited superior performance, producing a voltage output of 19.6 V and a corresponding current of 11.03 \u0026micro;A. The enhanced piezoelectric output performance is ascribed to WS\u003csub\u003e2\u003c/sub\u003e influence in the alignment of β-phase dipoles in PVDF. The incorporation of WS\u003csub\u003e2\u003c/sub\u003e provides a conductive pathway that facilitate charge transport within the films, hence enabling the alignment PVDF dipoles and enhancing the overall piezo response. Finally, the potential application of the PVDF/WS\u003csub\u003e2\u003c/sub\u003e film (with 2% filler concentration) based PENG device was demonstrated by harvesting energy from human actions like single finger tapping and thumb tapping. The PENG device with 2 wt% WS\u003csub\u003e2\u003c/sub\u003e content exhibited superior performance, characterized by measured voltage of 19.6 V and a corresponding current of 11.03 \u0026micro;A. The generated voltage was also used to power LED, thereby demonstrating the real time application of fabricated nanogenerator.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003cb\u003eContributions\u003c/b\u003e: Munni \u0026amp; Himani: Methodology, experiment, data curation, formal analysis, original draft; S. Rana: Experiment, data curation, investigation, writing; J. Dalal: Investigation, revision and editing; and B. Singh: Writing, editing, methodology, supervision.\u003c/p\u003e\u003cp\u003e \u003ch2\u003eCompeting interests:\u003c/h2\u003e \u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e \u003c/p\u003e\u003cp\u003e \u003ch2\u003eEthics, Consent to Participate, and Consent to Publish declarations\u003c/h2\u003e \u003cp\u003enot applicable.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eClinical trial number\u003c/strong\u003e \u003cp\u003enot applicable.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eFunding:\u003c/h2\u003e \u003cp\u003eThis research was not supported by any funding agencies.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eMunni \u0026amp; Himani (Both equal): Methodology, experiment, data curation, formal analysis, original draft; S. Rana: Experiment, data curation, investigation, writing; J. Dalal: Investigation, revision and editing; and B. Singh: Writing, editing, methodology, supervision.\u003c/p\u003e\u003ch2\u003eAcknowledgment\u003c/h2\u003e \u003cp\u003eThe authors sincerely thank the Advanced Materials and Device Laboratory (AMDL) team for their valuable support and assistance throughout the course of this work.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eKhandelwal G, Deswal S, Shakthivel D, Dahiya R. Recent developments in 2D materials for energy harvesting applications. JPhys Energy 5. 2023.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGołąbek J, Strankowski M. A Review of Recent Advances in Human-Motion Energy Harvesting Nanogenerators, Self-Powering Smart Sensors and Self-Charging Electronics. 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ACS Appl Mater Interfaces. 2016;8:16876\u0026ndash;84.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJaleh B, Jabbari A. Evaluation of reduced graphene oxide/ZnO effect on properties of PVDF nanocomposite films. Appl Surf Sci. 2014;320:339\u0026ndash;47.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMartins P, Lopes AC, Lanceros-Mendez S. Electroactive phases of poly(vinylidene fluoride): Determination, processing and applications. Prog Polym Sci. 2014;39:683\u0026ndash;706.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSingh HH, Singh S, Khare N. Design of flexible PVDF/NaNbO3/RGO nanogenerator and understanding the role of nanofillers in the output voltage signal. Compos Sci Technol. 2017;149:127\u0026ndash;33.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"discover-materials","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"dime","sideBox":"Learn more about [Discover Materials](https://www.springer.com/journal/43939)","snPcode":"","submissionUrl":"","title":"Discover Materials","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Discover Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-6801588/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6801588/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eEnergy harvesting from ambient sources, particularly human motion is gaining considerable interest because of its potential to efficiently convert environmental mechanical energy into usable electrical power. Ongoing research is exploring piezoelectric nanogenerators (PENGs) as a means to convert vibrational mechanical energy into functional electrical output. Here in, we report the fabrication of PENG based on PVDF/WS\u003csub\u003e2\u003c/sub\u003e nanocomposite thin films. WS\u003csub\u003e2\u003c/sub\u003e nanosheets are synthesized by exfoliation method. Further, WS\u003csub\u003e2\u003c/sub\u003e with different weight percentages was incorporated in PVDF and the resulting thin films are analysed using XRD and FTIR. The output of nanogenerator is finally examined, determining the maximum output voltage (V\u003csub\u003eOC\u003c/sub\u003e) without an external load and the maximum current (I\u003csub\u003eSC\u003c/sub\u003e) when the output terminals were shorted. The results indicate that the incorporation of WS\u003csub\u003e2\u003c/sub\u003e nanosheets led to enhanced output of piezoelectric nanogenerator, exhibiting an elevated voltage of 19.6 V and a peak current of 11.03 \u0026micro;A corresponding to 2 wt% filler concentration of WS\u003csub\u003e2\u003c/sub\u003e and shows significant potential for renewable energy conversion and self-sustaining electronic devices.\u003c/p\u003e","manuscriptTitle":"Enhanced Energy Conversion Efficiency in PVDF/WS 2 Hybrid Piezoelectric Nanogenerators","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-06-13 06:56:20","doi":"10.21203/rs.3.rs-6801588/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-06-24T09:01:09+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-06-20T09:04:01+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"224911513326623642505588590684540972655","date":"2025-06-20T08:39:57+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-06-11T21:35:34+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"71831176080335640838654324366099629087","date":"2025-06-11T11:04:18+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-06-11T10:30:26+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-06-06T09:36:18+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-06-03T14:51:45+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-06-03T14:49:35+00:00","index":"","fulltext":""},{"type":"submitted","content":"Discover Materials","date":"2025-06-02T11:04:36+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"discover-materials","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"dime","sideBox":"Learn more about [Discover Materials](https://www.springer.com/journal/43939)","snPcode":"","submissionUrl":"","title":"Discover Materials","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Discover Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"a9d18170-17b9-4c49-ae6b-607d4266bee5","owner":[],"postedDate":"June 13th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-08-25T16:31:39+00:00","versionOfRecord":{"articleIdentity":"rs-6801588","link":"https://doi.org/10.1007/s43939-025-00334-3","journal":{"identity":"discover-materials","isVorOnly":false,"title":"Discover Materials"},"publishedOn":"2025-08-18 16:28:58","publishedOnDateReadable":"August 18th, 2025"},"versionCreatedAt":"2025-06-13 06:56:20","video":"","vorDoi":"10.1007/s43939-025-00334-3","vorDoiUrl":"https://doi.org/10.1007/s43939-025-00334-3","workflowStages":[]},"version":"v1","identity":"rs-6801588","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6801588","identity":"rs-6801588","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}