Integration of silicon-via electrodes with different recording characteristics on a glass microprobe using a glass reflowing process.

Electrodes on planar type microelectromechanical system (MEMS) microprobes mainly record neurons on the top-side of probe shaft (called a top-side electrode). However, it is often necessary to record neurons other than those on the top-side of the probe shaft. This study uses the glass reflowing technique to embed silicon-vias in a glass probe to implement a microprobe capable of recording neurons around the shaft. The proposed technology makes it possible to fabricate, distribute, and integrate four types of electrodes on the shaft: top-side, back-side, double-side, and sidewall electrodes. These electrodes have different recording characteristics. The in vitro and in vivo (using crayfish and rat brain) experiments in this study shows that the top-side and back-side electrodes are respectively more sensitive to neurons on the top-side and back-side of the probe shaft. In contrast, signals recorded by double-side electrode and sidewall electrode are equally sensitive to neurons around the probe shaft. This study enables the implementation and integration of these four types of electrodes, meeting the requirements of various neural applications.