Epidermal electronics with stretchable microneedle electrodes for highly reliable electrophysiological monitoring

Abstract

Flexible microneedle electrodes are promising sensors that permit skin-preparation-free, high-quality electrophysiological signal recording. However, the existing flexible microneedle electrodes cannot achieve conformal contact with the skin due to modulus mismatch, thick substrate, and lack of self-adhesion, resulting in interface failure and hindering the long wear. Here, we report a hybrid-structured stretchable microneedle electrode incorporating a low-resistance silicon microneedle array on the sub 100 μm thin electrically conductive adhesive substrate with low young's modulus. It showed 1.3 kPa of adhesion to the skin and low conductivity change even above 60% of strain. Also, the height of the needle was less than 200 μm and thus do not reach the skin pain receptors and do not cause discomfort. The performance of stretchable microneedle electrode-based wearable electronics is demonstrated through wireless, multi-channel, and real-time electromyogram (EMG) monitoring using a smartphone. These applications including strenuous ambulatory motion show the robustness of the device to various skin secretions and motion artifacts.