Three-dimensional Printing of High-Performance Hydrogel Bioelectronic Implants

Implantable hydrogel bioelectronics are promising candidates for seamlessly bridging biological systems with intelligent devices. However, sustaining stable communication between hydrogel electronics and biological systems in complex physiological environments remains a critical challenge, primarily due to the swelling-induced degradation of mechanical properties of hydrogel encapsulation and reduced electrical performance of the conductive networks. To address this, we developed a micelle-assembly approach to synthesize soft and highly stretchable hydrogels with swelling-resistant performance. Moreover, these hydrogels show alleviated foreign body reactions during long-term implantation, serving as valuable implant materials. Through embedded 3D printing technology, we engineered ultrasoft (~ 40 kPa) and stretchable (over 1,000%) hydrogel electronics with unprecedented conductivity retention in aqueous environment – conductivity over 9,000 S cm-1 post-printing and 4,000 S cm-1 even after swollen. We further printed three different types of invasive implants, including brain-computer interfaces, implantable wirelessly-powered optoelectronics and sciatic nerve stimulators. These devices can either perceive physiological signals or receive electronic orders and respond accordingly with extraordinary robustness and longevity in vivo. We believe that such technological advances hold great promise for the development of human-computer interfaces.