Nanoparticle-Stabilized Porous Composite Architectures for Ultrasound-Driven Triboelectric Energy Harvesters in Soft Implantable Electronics

Wireless powering of implantable medical devices (IMDs) using triboelectric nanogenerators (TENGs) has gained attention as a sustainable and battery-free energy strategy. Ultrasound-driven TENGs (US-TENGs) offer favorable biocompatibility and deep tissue accessibility, but their practical application remains limited by unstable acoustic vibration, filler aggregation at low contents, and complex electrode integration. Here, we report a porous polyimide composite-based TENG (PPC-TENG) designed to overcome these limitations through material and structural innovations. The triboelectric layer is fabricated via a Pickering emulsion templating approach using a water-borne poly(amic acid) salt (W-PAAS) and high-permittivity CaCu₃Ti₄O₁₂ (CCTO) nanoparticles, enabling homogeneous dispersion up to 10 wt % without aggregation. The resulting porous architecture concentrates mechanical deformation at branch-like pore supports, promoting uniform vibration and enhancing charge generation under acoustic actuation. A laser-induced graphene (LIG) electrode is directly patterned on the porous surface, enabling a double-electrode configuration through a simplified, metal-free process. The PPC-TENG exhibits high electrical output, stable capacitor and battery charging performance, and confirmed biocompatibility in both in vitro and in vivo tests. This work presents a scalable and structurally adaptive triboelectric platform for wirelessly powered biomedical electronics.