Strain-durable and stretchable electrodes with low interfacial impedance using liquid metal/PEDOT:PSS fiber mat 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 the asymmetric encapsulation using Ecoflex and poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS)-based gel. Benefiting from these judicious material selection and structure design, the as-prepared electrodes exhibit superior performance with a low leakage ratio of LMs (<0.1%), high conductivity (~6.70 S m-1), low resistance change of only ~2.1 at 153% strain, low interfacial impedance (108.8 kΩ at 10 Hz and 41.5 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-electric interfaces, triboelectric sensors, and capacitive sensors are demonstrated to monitor physiological motions and electrophysiological activities. This work demonstrates the potential for developing multifunctional epidermal bioelectronics with superior performance by material and structure design.