Suresh Sruthi, Athira B S, Akhila N S, Vijaya Lakshmi, Chandran Achu, Gowd E Bhoje
Materials Science and Technology Division, CSIR-National Institute for Interdisciplinary Science and Technology, Trivandrum 695 019, Kerala, India.
Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201 002, India.
ACS Appl Mater Interfaces. 2025 Feb 12;17(6):9818-9829. doi: 10.1021/acsami.4c19733. Epub 2025 Jan 28.
Lightweight flexible piezoelectric devices have garnered significant interest over the past few decades due to their applications as energy harvesters and wearable sensors. Among different piezoelectrically active polymers, poly(vinylidene fluoride) and its copolymers have attracted considerable attention for energy conversion due to their high flexibility, thermal stability, and biocompatibility. However, the orientation of polymer chains for self-poling under mild conditions is still a challenging task. Herein, anisotropic poly(vinylidene fluoride--trifluoroethylene) (PVDF-TrFE)/MXene aerogel-based piezoelectric generators with highly oriented MXene fillers are fabricated. The unidirectional freezing of a hybrid solution facilitates the strain-induced alignment of MXene nanosheets and polymer chains along the solvent crystal growth direction due to the robust interactions between the MXene nanosheets (O-H/F groups) and PVDF-TrFE chains (F-C/C-H groups). Consequently, this process fosters the development of abundant electroactive β crystals with preferred alignment characteristics, leading to the formation of intrinsic self-oriented dipoles within the PVDF-TrFE aerogel. As a result, the piezoelectric properties of PVDF-TrFE are fully harnessed without any complex poling process, resulting in an open-circuit voltage of around 40 V with MXene loading of 3 wt % in anisotropic aerogel, which is 2-fold higher than that of the corresponding isotropic aerogel where the MXene nanosheets and polymer chains are randomly aligned. Furthermore, the developed piezoelectric nanogenerator was demonstrated as a tactile sensor which showed a high sensitivity of 9.6 V/N for lower forces (less than 2 N) and a sensitivity of 1.3 V/N in the higher force regime (2 N < force < 10 N). The strategy adopted here not only provides the enhancement of the piezoelectric crystalline form for self-poling but also paves an avenue toward developing self-powered energy harvesters using piezoelectric polymers.
在过去几十年中，轻质柔性压电器件因其作为能量收集器和可穿戴传感器的应用而备受关注。在不同的压电活性聚合物中，聚偏二氟乙烯及其共聚物因其高柔韧性、热稳定性和生物相容性而在能量转换方面受到了相当大的关注。然而，在温和条件下实现聚合物链的自极化取向仍然是一项具有挑战性的任务。在此，制备了具有高度取向的MXene填料的各向异性聚偏二氟乙烯-三氟乙烯（PVDF-TrFE）/MXene气凝胶基压电发电机。混合溶液的单向冷冻促进了MXene纳米片和聚合物链沿溶剂晶体生长方向的应变诱导排列，这是由于MXene纳米片（O-H/F基团）与PVDF-TrFE链（F-C/C-H基团）之间存在强相互作用。因此，该过程促进了具有优先取向特性的大量电活性β晶体的形成，导致在PVDF-TrFE气凝胶中形成内在的自取向偶极子。结果，在没有任何复杂极化过程的情况下充分利用了PVDF-TrFE的压电性能，在各向异性气凝胶中MXene负载量为3 wt%时，开路电压约为40 V，这比MXene纳米片和聚合物链随机排列的相应各向同性气凝胶高出2倍。此外，所开发的压电纳米发电机被证明是一种触觉传感器，在较低力（小于2 N）下显示出9.6 V/N的高灵敏度，在较高力范围（2 N < 力 < 10 N）下灵敏度为1.3 V/N。这里采用的策略不仅增强了用于自极化的压电晶体形式，还为开发使用压电聚合物的自供电能量收集器铺平了道路。
