Deep-brain silicon multielectrodes for simultaneous in vivo neural recording and drug delivery

In this paper, the fabrication method, electrical and fluidic characterization and in vivo testing of the first deep brain silicon multielectrode with monolithically integrated fluidic channel are presented in details. Micromachined silicon probes with monolithically integrated microfluidic channels up to 70 mm length have been realized to perform simultaneous electrical recording and drug delivery in deep brain regions. The achieved cross-sectional dimension of the microchannels is in the range of 5–30 μm, while the length of the channel can be even 70 mm long.Fabrication process and integration of the drug delivery channels and the Pt recording sites are described. Electrical characterization and impedance tuning of the developed probes are also demonstrated. The functionality of the microfluidic channels is verified and the hydrodynamic characteristics (flow rate vs. injection pressure) are measured in the case of several length and cross-sections.Feasibility of our integration concept is proved by locally injected bicuculline in the cortex and in the thalamical regions of rat brain in vivo, while simultaneously recording the electrical signals of the stimulated neurons on four different electrical channels.