A 1280-Channel Neural Microelectrode Array With Complementary Wedge-Shaped 3-D Assembly Interfaces

This article presents a novel 1280-channel 3-D neural microelectrode array with a complementary wedge-shaped interface. The microelectrode array consists of five 256-channel neural microelectrode chips, which are precisely stacked in three dimensions. The bonding interface between the microelectromechanical systems (MEMS) neural microelectrode and the flexible printed circuit (FPC) comprises a set of complementary wedge-shaped bonding interfaces that exhibit mirror symmetry to each other. These interfaces are encapsulated together to form a complete sensor using the anisotropic conductive film (ACF) thermocompression bonding process. This bonding interface eliminates the need for any post-processing on the bonding pads, ensuring excellent consistency and achieving 100% bonding efficiency, while facilitating high-density microelectrode integration. The neural microelectrode chip adopts a composite metal layer structural design, which integrates 256 recording microelectrodes in a 1.33 mm2 area. This design reduces the width of the needle beam while maintaining the density of the recording electrodes. Characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry, microelectrodes modified with electroplated gold exhibited a significant reduction in ac impedance from 1
$\text{M}\Omega $
to 10
$\text{k}\Omega $
at 1 kHz, demonstrating enhanced capacitive properties with improved charge storage capacity and charge transfer efficiency.