Platinum-nanostructured silicon microneedles with scalable fabrication for EEG biosensing

This study details the development and characterization of a silicon microneedle electrode array for enhanced biopotential recording. Fabricated using a streamlined two-step process, the device design was guided by mechanical analysis to ensure structural stability and minimize skin-electrode impedance. Structural analysis identified needle lengths of 500-700 µm as mechanically favorable for high buckling resistance, with needle spacing selected to reduce inter-needle interference and support effective skin penetration. The microneedles were subsequently modified through platinum electrodeposition to produce a nanostructured porous surface, which increased the electroactive area by approximately 15-fold compared to bare platinum microneedles, as determined from electrochemical measurements. Electrochemical characterization and proof-of-concept EEG experiments demonstrated improved signal acquisition performance, with the nanostructured electrodes yielding higher signal-to-noise ratios than bare microneedles in both SSVEP and ASSR recordings. Compared to conventional gel-based Ag/AgCl wet electrodes, the proposed device eliminates the need for conductive gel application, reduces preparation time, and improves user comfort. The work establishes a scalable, cleanroom-compatible method for fabricating nanostructured platinum-coated silicon microneedles, highlighting their potential as a user-friendly platform for next-generation wearable electrophysiological monitoring.