A Highly Conductive and Deformable Hydrogel for Chronically Stable Neural Interfaces

Chronic neural interfaces are essential for advancing brain-computer interfaces, neuroprosthetics, and neuromodulation technologies. However, a fundamental trade-off between performance and longevity persists, primarily due to the limited availability of materials that simultaneously exhibit exceptional electrical properties, mechanical compliance, and biocompatibility. We present a deformable and chronically stable electrocorticography (ECoG) electrode array capable of efficient ionic-electronic signal transduction, sustaining functionality for over 550 days in vivo. Central to this design is a conductive hydrogel with interfacial percolation (CHIP), achieving a record-high electrical conductivity of 2512 S cm–1 while maintaining mechanical flexibility and biocompatibility. The implementation of in-plane swelling control combined with a dry, soft-protective etching strategy further enhances structural integrity during hydrogel processing and supports long-term stability in biotic environments. The CHIP-based ECoG array provides precise mapping of behaviorally relevant neural dynamics across a broad frequency range and supports microampere-scale stimulation, enabling stable bidirectional neural interfacing over extended periods.