Conformal Thermoreversible Gelatin-Based Gel for High-Fidelity Electrophysiological Recording and Acute Peripheral Nerve Interfacing.

Conformal and tissue-adaptive bioelectronic interfacing remains a challenge for electrophysiological recording and nerve stimulation, particularly on irregular or hair-covered surfaces where conventional electrodes fail to maintain intimate, low-impedance contact. Here, we report a thermoreversible gelatin-based gel that transitions from a flowable precursor to a conformal conductive interface layer upon cooling, enabling both in situ formation on skin and use as a preformed compliant interlayer between metal electrodes and neural tissue. The gel integrates a uniformly dispersed carbon nanotube network with mobile ions from sodium chloride to support coexisting ionic and electronic transport pathways, while the gelatin-based matrix provides moisture retention and mechanical compliance. It achieves low interface impedance on hairless and hairy skin, outperforming commercial electrocardiogram gels, and electroencephalogram pastes. The gel's versatility is demonstrated across multiple modalities and species, including electrocardiography and acute peripheral nerve stimulation in rats, compound muscle action potential and sensory nerve action potential recordings in rhesus monkeys, and electroencephalography in humans. Beyond these cross-sectional assessments, repeated short-term recordings using the gel enable longitudinal evaluation of peripheral nerve functional recovery in nerve injury models. Together, this work establishes a tissue-adaptive and reconfigurable strategy for achieving stable, low-impedance bioelectronic interfacing across complex biological environments.