Comprehensive Engineering of PVA-Based Gel Probes for Scanning Gel Electrochemical Microscopy

Scanning Gel Electrochemical Microscopy (SGECM) is a novel tool for microscale electrochemical imaging and patterning. In this study, poly(vinyl alcohol)-borate (PVA-borate) gel probes, the core component of SGECM, are developed through an integrated approach combining electrochemistry, polymer science, and fluid mechanics. Two types of gel probes are engineered with distinct fabrication strategies. Type I gel probes are formed by electrodeposition of PVA-borate on platinum micro-disk electrodes. The deposition potential controls the gel's shape, while co-deposition with poly(ethylene oxide) enhances its stiffness and toughness via the Double Network strategy. These probes enable precise topography and current mapping, with reusability ensured by re-soaking in electrolyte. Type II gel probes are fabricated on etched tungsten wires using a "deposition + pulling" technique. By exploiting the viscous-to-viscoelastic transition of the precursor solution at high pulling velocities, precise shape control is achieved despite the slow electrodeposition kinetics of PVA-borate. The optimized Type II probes achieve a spatial resolution of 2.1 mu m, demonstrated through SGECM patterning of silver. This work underscores the powerful synergy between electrochemistry, polymer science, and fluid mechanics in advancing electrodeposition processes engineering, ultimately leading to the creation of novel gel probes for spatially localized electrochemical analysis.