Ionic‐Electronic Hydrogel‐Liquid Metal Composite Bilayer with Tissue‐Adaptive and Adhesive Properties for Closed‐Loop Neuroprosthetic System

ABSTRACT Peripheral nerve injuries caused by trauma, such as laceration or amputation, can result in severe sensory and motor dysfunction. However, conventional neural interfaces for diagnosing and treating these injuries often lack the mechanical softness, biocompatibility, and electrical stability required to safely interface with sensitive, injured nerves. Here, we present a hydrogel‐liquid metal composite bilayer peripheral nerve interface (HLB‐PNI) that combines a screen‐printed eutectic gallium‐indium (EGaIn)‐based composite electrode with a phenylboronic‐acid‐conjugated alginate (AlBA) hydrogel layer. The composite provides thin (∼30 µm), conformable electrodes with excellent stretchability, stress relaxation, electrical durability, and self‐healability. The AlBA hydrogel offers strong, conformal adhesion via dynamic covalent bonding, minimizing delamination and fibrotic responses in vivo. Implanted on the sciatic nerve of rats, the HLB‐PNI enables reliable sensory neural signal recording and electrical stimulation, facilitating the precise diagnosis of sensory–motor pathway disruptions corresponding to varying degrees of nerve injury states. Furthermore, integration with a closed‐loop robotic assistance system enables voluntary hindlimb movement in rats with severe nerve pathway disconnection. These findings underscore the potential of this tissue‐adaptive and adhesive PNI platform for personalized neuroprosthetic systems and rehabilitation following early peripheral nerve damage.