Self-powered piezoelectric nanocomposite films for wearable health-signal monitoring

With the growing demand for flexible electronics in health monitoring, the development of sensing materials that combine environmental sustainability, biocompatibility, and high piezoelectric performance has become a major research focus. Here, we report a barium titanate (BaTiO 3 [BT])/hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 [HA])/polylactic acid (PLA) nanocomposite film fabricated via spin coating, exhibiting enhanced piezoelectric performance and durability. At a BT/HA content of 5 wt %, the composite film achieves an open-circuit voltage ( V oc ) of 8.56 V, a short-circuit current ( I sc ) of 185 nA, and a piezoelectric coefficient ( d 33 ) of 2.9 pC/N, representing a significant improvement over the pure PLA. The film also demonstrates excellent cyclic stability over 3,000 s under 20 N at 1 Hz and favorable cytocompatibility. Simulations reveal that the optimized composition shows more uniform surface potential, stress, and electric field distribution, consistent with experimental observation. Furthermore, the film enables sensitive detection of various human motions. This work provides an effective strategy for designing sustainable, self-powered flexible sensors for health-monitoring applications.