Abstract
Flexible piezoelectric energy harvesters have been regarded as an overarching candidate for achieving self-powered electronic systems for environmental sensors and biomedical devices using the self-sufficient electrical energy. In this research, we realize a flexible high-output and lead-free piezoelectric energy harvester by using the aerosol deposition method and the laser lift-off process. We also investigated the comprehensive biocompatibility of the lead-free piezoceramic device using ex-vivo ionic elusion and in vivo bioimplantation, as well as in vitro cell proliferation and histologic inspection. The fabricated LiNbO3-doped (K,Na)NbO3 (KNN) thin film-based flexible energy harvester exhibited an outstanding piezoresponse, and average output performance of an open-circuit voltage of ∼130 V and a short-circuit current of ∼1.3 μA under normal bending and release deformation, which is the best record among previously reported flexible lead-free piezoelectric energy harvesters. Although both the KNN and Pb(Zr,Ti)O3 (PZT) devices showed short-term biocompatibility in cellular and histological studies, excessive Pb toxic ions were eluted from the PZT in human serum and tap water. Moreover, the KNN-based flexible energy harvester was implanted into a porcine chest and generated up to ∼5 V and 700 nA from the heartbeat motion, comparable to the output of previously reported lead-based flexible energy harvesters. This work can compellingly serve to advance the development of piezoelectric energy harvesting for actual and practical biocompatible self-powered biomedical applications beyond restrictions of lead-based materials in long-term physiological and clinical aspects.
Highlights
Several researchers have reported that PZT might be used for biological and in vivo applications, but these reports were only based on cell viability or histology over shortterm periods,[18,24,25] which cannot guarantee actual biocompatibility for long-term periods or repeated exposures.[26]
A maximum instantaneous power of ∼30 μW was elicited at ∼150 MΩ. This matching impedance was too high to be compared with conventional electronic components, due to the high internal resistance of the IDE-type piezoelectric devices,[64] our result demonstrates that lead-free piezoceramics can replace lead-based piezoelectric energy harvesters, even for mechanically flexible manner
The high performance in this work is even comparable to that of prior high-performance lead-based flexible piezoelectric energy harvester (f-PEH) made by sol-gel PZT films,[11,65] AD-formed PZT thick film,[55] and solid-grown Pb(Mg1/3Nb2/3)O3-PZT (PMN-PZT) thick film[66] with IDEs under similar deformations. This remarkable output performance of our lead-free f-PEH stems from the high-quality and dense AD-formed L-KNN piezoceramic thin film
Summary
Piezoelectric devices have been regarded as plausible mechanical energy harvesting concepts due to simple structures and environmental stability without concerns about abrasion, humidity, and bulky heaviness.[1,2,3,4,5,6,7,8,9,10] flexible energy harvesters (nanogenerators) can be fabricated using piezoelectric materials, and they are prospective candidates for realizing self-powered flexible electronics.[11,12,13,14] In that pursuit, many researchers have demonstrated high-performance flexible energy harvesters using representative lead-based piezoelectric materials, e.g., Pb(Zr,Ti)O3 (PZT),[11,12,14,15] even for wearable/bioimplantable applications.[16,17,18,19,20]. Comprehensive biocompatibility of nontoxic and high-output flexible energy harvester using lead-free piezoceramic thin film
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