Long silicon microfluidic needles for VTA and in-vivo differential neurochemical measurement
This thesis presents the design, fabrication, and preliminary in vivo evaluation of long silicon microfluidic neural probes intended for high-resolution neurochemical sampling from deep brain nuclei such as the ventral tegmental area in mice. The work first analyzes stress-induced bending in thinfilm cantilever structures on silicon-on-insulator substrates and develops a multilayer stress-balancing strategy using plasma-enhanced chemical vapor deposited silicon nitride to compensate compressive stress from the buried oxide, enabling fabrication of 8–10 mm needles with sub-100 µm tip deviation in the best cases. Further on, I explore aluminum oxide hard mask integration processes, and its etch characterization to provide high etch selectivity over silicon nitride and silicon oxide and to improve channel yield by mitigating photoresist-induced clogging in buried microfluidic networks. Finally, I propose and test out several probe architectures for differential in-vivo nanodialysis measurements. Collectively, these advances in stress engineering, hard mask integration, and probe-level fluidic design establish a robust platform for future long-term, multi-state neurochemical recordings and for combining localized drug delivery with mass-spectrometry-based analysis in deep brain regions.
Neural Probe, Process Development, Aluminum oxide, Silicon Nitride, VTA
University of Illinois - Urbana-Champaign
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