Fabrication of Multichannel Neural Microelectrodes with Microfluidic Channels Based on Wafer Bonding Technology

We have proposed the intelligent Si neural probe which can realize high density and multifunctional recording of neuronal behaviors. In this device, LSI chips such as amplifiers, A/D converters, and multiplexers are integrated on the Si neural probe. In this paper, we report the development of a novel multichannel Si neural microelectrode with microfluidic channels which is the key part of the intelligent Si neural probe. The microelectrode has microfluidic channels fabricated using a wafer bonding technology to deliver drugs into the brain when neuronal action potentials are recorded. And also, our microelectrode has recording sites on both front- and backside of Si to realize high density recording. We fabricated the carefully-designed multichannel Si neural microelectrode, and we evaluated characteristics of both recording sites and microfluidic channels. From the liquid ejection test, we confirmed that there was no void at bonding faces. We observed the liner relationship between the flow rate and the pressure drop, and the relationship was identical to that from the calculation, which indicated that the microfluidic channel was successfully formed. Moreover, both front- and back-side recording sites had impedance values of 2.5 MΩ and 2.7 MΩ at 1 kHz, respectively, which indicated that both recording sites had equivalent characteristics. The neuronal action potentials from CA1 area in a hippocampal slice were successfully recorded by using the fabricated microelectrode.