Flexible Microneedle Array Electrode with Improved Comfort, Low Impedance, and High Performance for Electrophysiological Recording

High-fidelity electrophysiological recording is critical for wearable brain-computer interfaces and human-machine interaction. However, balancing signal quality and wearing comfort remains a challenge: wet electrodes suffer from gel dehydration, whereas conventional dry electrodes often exhibit high impedance and mechanical instability. Here, we present a flexible microneedle array (fMNA) electrode fabricated using a scalable micro-electro-mechanical system process. The electrode comprises octagonal pyramidal silicon microneedles coated with Au/Cr on a flexible parylene substrate, providing high conductivity, mechanical robustness, and conformal scalp contact. Integrated with a specialized denoising algorithm, the fMNA achieved a contact impedance of 7.6 kΩ@10 Hz, 1-2 orders of magnitude lower than that of commercial wet electrodes. It also exhibited excellent durability and flexibility, with a minimum bending radius of 3 mm. Its recording performance was systematically validated through electroencephalographic visual evoked potential and cognitive engagement experiments, together with electrooculography. Compared with wet electrodes, the fMNA produced 41%-46% higher signal amplitudes, a higher signal-to-noise ratio, improved stability, lower impedance drift, and fewer motion artifacts. These results establish the fMNA as a versatile platform for high-quality electrophysiological recording and long-term wearable bioelectronic monitoring.