Coffee Ring Effect Induced Selective Wetting of Liquid Metal for High-Resolution Stretchable Bioelectrodes

Liquid metals (LM) exhibit great potential in stretchable bioelectronic devices due to their exceptional deformability, excellent conductivity, biocompatibility, and environmental stability. However, their high surface energy poses challenges for fabricating high-resolution and multichannel bioelectrodes. In this study, high-resolution (10 μm) and multichannel (16-channel) LM bioelectrodes were prepared by inducing the alignment of Ag NPs through the coffee ring effect and utilizing the selective wetting of LM on Ag NPs. The bioelectrodes exhibit excellent tensile conductivity (600% strain) and cyclic stability (1 × 10⁴ cycles in 100% strain). The recording sites of the prepared multichannel electrode arrays were encapsulated with conductive ionic gel, which significantly reduces interfacial impedance (4.14 kΩ at 1 kHz) and enhances the long-term stability of the electrodes (35 days), enabling acquisition of high-quality electrophysiological signals. Additionally, the bioelectrodes have been successfully applied in human motion detection, handwriting recognition, and Joule heating. This study provides a promising strategy for fabricating high-resolution and highly stretchable electrodes with enormous potential for application in flexible electronics.