Needle-Like Multifunctional Biphasic Microfiber for Minimally Invasive Implantable Bioelectronics

Implantable bioelectronics has attracted significant attention in electroceuticals and clinical medicine for precise diagnosis and efficient treatment of target diseases. However, conventional rigid implantable devices face challenges such as poor tissue-device interface and unavoidable tissue damage during surgical implantation. Despite continuous efforts on utilizing various soft materials to address such issues, their practical applications are still limited. Here, we report a needle-like stretchable microfiber comprised of a phase-convertible liquid metal (LM) core and a multifunctional nanocomposite shell for minimally invasive soft bioelectronics. The sharp tapered microfiber can be stiffened by freezing like a conventional needle to penetrate the soft tissue with minimal incision. Once implanted in vivo where the LM melts, unlike conventional stiff needles, it recovers soft mechanical properties facilitating a seamless tissue-device interface. The nanocomposite incorporated with functional nanomaterials can both exhibit low impedance and detect physiological pH, which confers biosensing and stimulation capabilities. The fluidic liquid metal embedded in the nanocomposite shell enables high stretchability and strain-insensitive electrical properties. This multifunctional biphasic microfiber conforms to the surface of the stomach, muscle, and heart and offers a promising approach for electrophysiological recording, pH sensing, electrical stimulation, and radiofrequency ablation in vivo