Long silicon microfluidic needles for VTA and in-vivo differential neurochemical measurement
type: CreativeWork
description: 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.
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.
author: Mahajan, Akshit
language: en
keywords: Neural Probe, Process Development, Aluminum oxide, Silicon Nitride, VTA
date published: 2025-12
date modified: 2026-07-22T22:25:07Z
provider: University of Illinois - Urbana-Champaign
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Illinois Urbana-Champaign

PropertyValue
property ID: Handle
value: https://hdl.handle.net/2142/132805