A Self-Expanding and Degradable Biomaterial Enabling Self-Flattening Film-Based Devices for Catheter Delivery

The post-implantation shape recovery can enable the catheter delivery of large area thin-film based bioelectronics. To be safely triggered and applying sufficient force during flattening process, we developed a water-absorbable chitosan composite that provides long-lasting interchain repulsive forces when exposed to body fluids through synergistic effects of hydrogen bonding, plasticization, and nanoscale distance confining. The water-modulated modulus and significant volume expansion were balanced to achieve the stable and strong tensile force for self-flattening process of thin film-based structures. The chitosan-based composite was biocompatible, biodegradable, and hemocompatible, proving its biosafety of implantations. The in vivo flattening capability was demonstrated using a rolled triboelectric nanogenerator (TENG) in intracardiac implantation. After a 20-min flattening period, morphological changes were clearly observed by X-ray. Additionally, the self-powered TENG, driven by heartbeats, exhibited significantly enhanced electrical performance comparable to commercial ECG signals. This minimally invasive implantation of flexible film-based devices represents an essential step toward the eventual development of advanced implantable bioelectronics. This novel coating material is expected to have immediate impacts on the catheter implantation of various other flexible, thin film-based biomedical devices, such as health monitoring sensors, drug delivery systems, and electrical stimulation electrodes.