Long silicon microfluidic needles for VTA and in-vivo differential neurochemical measurement
Mahajan, Akshit
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https://hdl.handle.net/2142/132805
Description
Title
Long silicon microfluidic needles for VTA and in-vivo differential neurochemical measurement
Author(s)
Mahajan, Akshit
Issue Date
2025-12-12
Director of Research (if dissertation) or Advisor (if thesis)
Vlasov, Yurii
Department of Study
Electrical & Computer Eng
Discipline
Electrical & Computer Engr
Degree Granting Institution
University of Illinois Urbana-Champaign
Degree Name
M.S.
Degree Level
Thesis
Keyword(s)
Neural Probe
Process Development
Aluminum oxide
Silicon Nitride
VTA
Abstract
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.
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