Flexible piezoelectrics: integration of sensing, actuating and energy harvesting

npj | flexible electronics Review Published in partnership with Nanjing Tech University https://doi.org/10.1038/s41528-025-00432-5 Flexible piezoelectrics: integration of sensing, actuating and energy harvesting Check for updates 1234567890():,; 1234567890():,; Binjie Chen1,2, Zimin Feng1, Fang-Zhou Yao1,3 Wen Gong1,6 & Jürgen Rödel7 , Mao-Hua Zhang1, Ke Wang4, Yan Wei5 , Piezoelectric materials are capable of converting between mechanical and electrical energy, and are suitable for sensing, actuating and energy harvesting. While most conventional piezoelectric materials are brittle solids, flexible piezoelectric materials (FPM) retain functionality even under bending and stretching conditions. This characteristic has garnered increasing attention in recent years, particularly for wearable devices, where the ability to adapt to dynamic human movements is essential. In addition, wearable devices also demand excellent conformability, durability, and adaptability to miniaturization. FPM emerge as a promising solution that meet all these requirements. This review thus aims to offer a comprehensive summary of recent advances in the field of FPM, including piezoelectric polymers, composites, and inorganic flexible films. We introduce and categorize the specific features of these materials and highlight their emerging applications in electronic devices, and comment on the prospect of FPM as well as their potential challenges. Piezoelectric materials are capable of converting between mechanical energy and electrical energy. When mechanical deformation occurs, they produce an electrical signal, facilitating follow-up processing, and when an electric field is applied, they produce a strain, effecting desired motions. Compared with other devices or mechanisms that implement this conversion, piezoelectric materials have high electromechanical efficiency and remarkable scalability, allowing for miniaturization even down to the scale of microelectromechanical systems (MEMS)1–4. For this reason, they are very widely used in sensing and actuating5–8. Recently, in contrast to its brittle solid counterparts, flexible piezoelectric materials (FPM) are gaining attention for applications where flexibility is a primary metric, such as wearable devices. These devices are commonly designed to be compact and lightweight to meet portability needs and to include various functional modules for sensing and for feedback of multiple signals9–11. Typical applications include motion sensing12–15, physiological monitoring16–19, human-machine interaction20–22, and wearable transducers for on-body imaging and diagnosis23–25. To be able to adapt to the moving human body, some flexibility of the involved functional materials becomes highly desirable. In addition to sensing and actuating, harvesting energy from the motions of humans requires devices that can withstand large deformations that are no possible with brittle piezoelectric materials26. Hence, FPM can also be used for harvesting kinetic energy from heartbeat27,28, breathing29,30, pulse31, and even gastrointestinal peristalsis32 in some wearable devices, making energy harvesting another major use in the application of FPM in wearable devices. There are three main approaches to achieving the flexibility of piezoelectric materials: intrinsically flexible piezoelectric polymers33, flexible piezoelectric composites (FPC) formed by combining piezoelectric ceramics with flexible materials34, and inorganic flexible piezoelectric films fabricated on flexible substrates through direct deposition35 or film transfer techniques36,37. Figure 1 presents a radar chart summarizing the distinct physical properties of these three materials, as well as their best suited application scenarios. Piezoelectric polymers, such as polyvinylidene fluoride (PVDF), offer excellent flexibility and ease of processing, often fabricated in the form of sheets and fibers that can be integrated into devices through textile techniques. However, their piezoelectric performances are typically weak; although there are several attempts to enhance them38–40, they still fall short compared to the other types of FPM. Research on these materials usually focused on developing new processing methods41–44 and exploring novel applications15,17,45. Piezoelectric composites are composed of high-performance piezoelectric ceramics (e.g., lead zirconate titanate (PZT)) and flexible polymers, aiming to combine the benefits of the two. 1 Research Center for Advanced Functional Ceramics, Wuzhen Laboratory, Jiaxing, China. 2School of Materials Science and Engineering, Shaanxi Normal University, Xi’an, China. 3Center of Advanced Ceramic Materials and Devices, Yangtze Delta Region Institute of Tsinghua University, Jiaxing, China. 4State Key Laboratory of New Ceramic Materials, School of Materials Science and Engineering, Tsinghua University, Beijing, China. 5Beijing Laboratory of Biomedical Materials, Department of Geriatric Dentistry, Peking University School and Hospital of Stomatology, Beijing, China. 6Tongxiang Tsingfeng Technology Co. Ltd, e-mail: ; Jiaxing, China. 7Institute of Materials Science, Technische Universität Darmstadt, Darmstadt, Germany. ; npj Flexible Electronics | (2025)9:58 1 https://doi.org/10.1038/s41528-025-00432-5 Review Fig. 1 | Materials, properties and applications of flexible piezoelectrics. The radar chart at the center of the figure illustrates the performance characteristics of the three types of flexible piezoelectric materials (FPM). The blue legend represents polymers, the red represents inorganic flexible thin films, and the green represents composites. The middle ring (gray shading) shows schematics of the three types of FPM, while the outer ring (pink shading) shows their respective application areas. Schematics of composite is reproduced with permission from ref. 250. Copyright 2017 Wiley-VCH GmbH. Schematics of flexible film is reprinted with permission from ref. 215. Copyright 2020 American Chemical Society. Images arranged clockwise starting from the 12 o’clock are reprinted with permission from ref. 61. Copyright 2015 Wiley-VCH GmbH, ref. 196. Copyright 2021 Wiley-VCH GmbH, ref. 27. Copyright 2014 National Academy of Sciences, ref. 251. Copyright 2022 Elsevier, ref. 204. Copyright 2018 Wiley-VCH GmbH, ref. 206. Copyright 2014 IOP Publishing, ref. 45. Copyright 2021 Springer Nature, ref. 252. Copyright 2016 Cambridge University Press, ref. 253. Copyright 2021 Elsevier, ref. 17. Copyright 2023 Springer Nature, ref. 176. Copyright 2023 American Chemical Society, and ref. 254. Copyright 2024 Springer Nature. However, there is a significant trade-off between performance and flexibility, and having a good compromise through material modification or composite structure design can be complicated46,47. Inorganic piezoelectric thin films form a new class of FPM that have emerged alongside advances in thin-film fabrication technology. They are basically composed of inorganic piezoelectr (...truncated)