Remote energy transfer strategies for flexible implantable bioelectronics

Abstract

Flexible wireless-powered implantable medical devices (FW-IMDs) conform to biological tissues to minimize mechanical mismatch and inflammation compared to conventional rigid, battery-powered biomedical electronic systems, while maintaining stable, healthy bioelectronic interfaces. Their stretchable, bendable, and ultrathin form enables continuous deformation within dynamic organs while maintaining stable operation. Additionally, remote energy conversion technologies enable wireless power transmission and electric charge generation, offering promising subcutaneous applications such as powering rechargeable implantable bioelectronics and direct biotherapy. Although modern implantable batteries have achieved substantial miniaturization, their long lifespans still necessitate periodic replacement surgeries, which remain a major clinical burden. In this context, wireless power transfer (WPT) technologies provide a complementary solution by enabling non-surgical energy replenishment or continuous powering. This review summarizes the functions, materials, and architectures of the FW-IMDs. It functionally classifies these devices based on WPT systems, including near-field capacitive coupling, ultrasound-driven piezoelectric and triboelectric nanogenerators, light-mediated photovoltaic generators, and near-field inductive coupling. Particular emphasis is placed on integrating flexibility, biocompatibility, output enhancement, minimization, circuit integration, bioadhesiveness, and biodegradability. Finally, the review outlines current challenges and opportunities in clinical safety and advancement, and proposes future directions for hybrid, multifunctional, and adaptive WPT platforms, thereby presenting a coherent framework for FW-IMDs that operate reliably and sustainably within the human body.