Functionalized EGaIn Electrodes with Tunable Reduced-Graphene-Oxide Assembled EGaIn Core–Shell Particles for Soft and Deformable Electrochemical Biosensors

Gallium-based liquid metal, eutectic gallium–indium alloy (EGaIn), is becoming a leading innovation in soft electronic devices due to its exceptional electronic conductivity and deformability. However, the formation of insulating oxide films on EGaIn surfaces poses a significant impediment to translating electrochemical reactions, thereby limiting its use as an electrochemical biosensor. Here, functionalized EGaIn electrodes with reduced-graphene-oxide assembled EGaIn core–shell particles (REGs) for soft and deformable electrochemical biosensors are presented. Exploiting EGaIn's capability as a reducing agent, REGs can undergo further modification with metal nanoparticles through additional galvanic replacement reactions. The REGs and metal-coated REGs (M-REGs) provide strong interfacial adhesion with the EGaIn current collector, exhibiting no exfoliation during and after the mechanical deformation. Moreover, RIDE and metal-decorated RIDE (M-RIDE) show excellent electrochemical sensing performances by taking advantage of the facile surface tunability of REGs, allowing simultaneous detection of ascorbic acid, dopamine, and uric acid, and enzymatic detection of glucose. The developed RIDE/M-RIDE paves the way for utilizing EGaIn in the development of soft and deformable electrochemical biosensors.