Fabrication, Electrochemical Characterization, and In Vivo Validation of a Flexible Neural Probe

Abstract

The use of flexible neural probes for brain recordings presents several advantages compared to rigid neural probes. The main advantage is related to the reduction of damage to the neural tissue when using a flexible invasive neural probe. This work presents the fabrication, characterization, and in vivo validation of a flexible neural probe fabricated with photosensitive and low-temperature cured polyimide. The neural probe was fabricated with standard microfabrication technologies, and its dimensions are approximately $130~\mu $ m in width, $9~\mu $ m in thickness, and 6 mm in shaft length. The device has 11 platinum microelectrodes, deposited by direct current sputtering. Electrochemical characterization of the microelectrodes was performed immediately after fabrication and again after six months, showing a final mean impedance in the range of 200-400 k $\Omega $ at 1 kHz, demonstrating their suitability for neural signal detection. Then, insertion tests were performed using an agar phantom and a mouse brain, considering two approaches for implantation. After choosing the best approach, acute in vivo electrophysiological recordings were performed in an anesthetized mouse, successfully recording spikes and local field potential neural activity from the hippocampus.[2025-0034]