Tissue-adaptive bioelectronic fibers with temperature-induced self-tightening enable ultrastable neural interface

Neural interfaces are essential for brain-machine communication and closed-loop neuromodulation. However, achieving durable interfaces between neural tissue and bioelectronics remains a key challenge, as conventional electronics do not actively conform to the soft, tortuous 3D architecture of neural tissue. We report a tissue-adaptive bioelectronic fiber that actively contracts to wrap around neural tissues, forming ultrastable neural-electronic interfaces, and enabling highly reliable neural stimulation and recording. This fiber is fabricated via wet spinning from a precursor integrating a thermoresponsive polymer and electroactive materials, and exhibits an ultralow modulus of 0.16 MPa and a phase transition temperature of 26.7 °C. Upon contact with rat tissue, the polymer chains undergo a hydrophilic-to-hydrophobic transition, expelling water and contracting the fiber to conform tightly to the sciatic nerve. This ultrastable biointerface demonstrates reliable neural stimulation, producing stable hindlimb bending responses, while sciatic nerve action potential recordings show 99.5% signal retention under successive stimulations.