Soft, Skin-Conformal Electronic Interfaces for Multimodal Biosignal Monitoring and Transcutaneous Stimulation

Soft, stable, and high-performance skin-electrode interfaces are essential for continuous electrophysiological recording and transcutaneous electrical stimulation. Conventional gel electrodes suffer from dehydration, unstable skin-electrode contact, reduced recording quality, and limited stimulation efficiency during prolonged use. This paper reports a soft, mixed-conducting nanocomposite electrode composed of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) integrated with hygroscopic and ionic dopants. The synergistic formulation enhances mixed ionic-electronic conduction, mechanical softness, and long-term hydration stability. A simple micromolding process enables scalable fabrication of conformal, freestanding electrodes that adhere seamlessly to the skin. The optimized composition achieves an excellent balance between conductivity and softness, exhibiting approximately a 20-fold lower interfacial impedance and a 2.6-fold higher charge injection capacity compared to gel electrodes. As a result, these nanocomposite electrodes deliver higher signal-to-noise ratios in electrocardiography and electromyography recordings and enhanced bioimpedance sensitivity and achieve a 2-fold expansion of the stimulation window. This nanocomposite design establishes a versatile materials platform for soft, durable, and high-fidelity bioelectronic interfaces, enabling advances in wearable sensing and neuromodulation technologies.