Strain-durable and stretchable electrodes with low interfacial impedance using liquid metal/PEDOT:PSS fiber mats for multifunctional epidermal bioelectronics

Abstract

Stretchable electronics afford unprecedented opportunities for continuous and real-time monitoring of electrophysiological signals and human motions. However, maintaining mechanical robustness, stable electrical performance, and low interfacial impedance under dynamic environments remains challenging. Herein, we report a strain-durable and stretchable electrode with low interfacial impedance, enabled by the synergistic combination of ion–electronic hybrid conduction, mechanical interlocking and asymmetric encapsulation. Specifically, a porous thermoplastic polyurethane (TPU) fiber mat is coated with liquid metals (LMs), followed by asymmetric encapsulation using Ecoflex and a poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS)-based gel. Benefiting from this judicious material selection and structure design, the as-prepared electrodes exhibit superior performance with a low leakage ratio of LMs (<0.1%), high conductivity (∼111.07 S m⁻¹), low resistance change of only ∼2.1 at 153% strain, low electrode–skin interfacial impedance (108.88 kΩ at 10 Hz and 39.24 kΩ at 100 Hz), and remarkable durability (enduring 10 000 cycles of stretch–release process at 30% strain with a fatigue coefficient below 3%). Important applications of multifunctional electrodes in physiological–electrical interfaces, triboelectric sensors, and capacitive sensors have been demonstrated for monitoring physiological motions and electrophysiological activities. This work demonstrates the potential for developing multifunctional epidermal bioelectronics with superior performance through material selection and structure design.