Multi-functional piezoelectric energy harvesters based on porous PLLA/BaTi₂O₅ piezocomposite films

Flexible piezoelectric energy harvesters (PEHs) have attracted considerable attention in self-powered systems due to their unique ability to convert mechanical energy into electrical energy. However, PEHs still face several challenges for further practical applications, such as low energy conversion, limited signal recognition, and biomechanical incompatibility. In this study, three-dimensional (3D) network-structured poly(l-lactic acid)/BaTi₂O₅ (PLLA/BT2) piezocomposite films are successfully prepared through thermally induced phase separation. Benefiting from the design of the 3D porous PLLA matrix, the PEHs achieve excellent deformability and can generate significant longitudinal deformation. Notably, the optimized PLLA/BT2 PEH exhibits an open-circuit voltage of 49.0 V and a short-circuit current of 4.2 μA, achieving a power density of 15.6 μW cm⁻² when connected to an external resistance of 1 × 10⁷ Ω. In practical application, it easily illuminates 36 light-emitting diodes and generates different electrical signals in response to various physiological signals. When utilized as an implantable medical device, it facilitates the proliferation of bone marrow mesenchymal stem cells while inhibiting the growth of Staphylococcus aureus by reconstructing the local electric fields, thereby promoting bone repair. This work provides a promising strategy for the fabrication of multifunctional flexible PEHs with high piezoelectric performance and biomechanical compatibility.