Development of a Flexible Microneedle Array Electrode with a High Signal-to-Noise Ratio for Surface Bioelectrical Signal Recording

Microneedle array (MNA) electrodes have garnered significant attention for their capacity to record high-fidelity surface bioelectrical signals over extended periods and convenience. However, accuracy limitations in 3D-printed metal MNA electrodes, particularly concerning surface roughness and insufficient tip sharpness, have been reported. Additionally, the prevalent use of nonporous metal substrates often results in poor flexibility. This study proposes a novel MNA electrode featuring a lightweight flexible substrate and sharp, smooth microneedles. Utilizing micron-level metal 3D printing with 316L stainless steel, we fabricated the electrodes in a single step. We evaluated the MNA electrode-skin interface impedance via frequency sweep and assessed mechanical properties using porcine skin, followed by the collection and analysis of bioelectrical signals. The results demonstrate that the contact impedance of the MNA electrode is comparable to that of standard gold cup electrodes, with validated flexibility and strength. Furthermore, the MNA electrodes achieved a high signal-to-noise ratio and minimal motion artifacts during recording, thereby enhancing both comfort and signal quality. The efficient production process facilitates the broader application of metal MNA electrodes.