Fabrication of microfluidic neural probes with in-channel electrodes

This paper reports on the design and fabrication of a neural probe for simultaneous recording of neural activity and localized drug delivery. In comparison to common microfluidic probes, additional electrodes facing the fluidic channel are integrated in the polyimide-based membrane covering the microchannels. The novel fabrication process applies two-sided deep reactive ion etching (DRIE) of silicon and the wafer-level transfer of the thin membrane cover onto patterned silicon substrates. The process to transfer the membrane uses low-temperature adhesive bonding. It allows integrated electrodes to be exposed either to the surrounding neural tissue or the fluidic channels. The electrical functionality of the probes was verified using electrochemical impedance spectroscopy of both electrode types. The fluidic function was demonstrated by injecting a dyed fluid through the integrated microchannels.