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.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Electrical & Computer Engr

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Mahajan, Akshit

Contributors dc:contributor

• Vlasov, Yurii

• Neural Probe
• Process Development
• Aluminum oxide
• Silicon Nitride
• VTA

Statement dc:rights

• Copyright 2025 Akshit Mahajan

Language dc:language

en

Handle dc:identifier

https://hdl.handle.net/2142/132805

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/132805