2026-09-21T21:44:17Z https://www.ideals.illinois.edu/oai-pmh

oai:www.ideals.illinois.edu:2142/132805 2026-03-24 col_2142_5131 col_2142_8888 com_2142_5130 com_2142_8887 com_2142_234

application/pdf en text Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2027-12-01 The student, Akshit Mahajan, accepted the attached license on 2025-12-12 at 12:14. The student, Akshit Mahajan, submitted this Thesis for approval on 2025-12-12 at 12:25. This Thesis was approved for publication on 2025-12-12 at 13:19. DSpace SAF Submission Ingestion Package generated from Vireo submission #23098 on 2026-02-19 at 20:10:06 Long silicon microfluidic needles for VTA and in-vivo differential neurochemical measurement Mahajan, Akshit 2025-12-12 Vlasov, Yurii Neural Probe Process Development Aluminum oxide Silicon Nitride VTA eng 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. 2025-12 Thesis https://hdl.handle.net/2142/132805 Copyright 2025 Akshit Mahajan Electrical & Computer Eng Electrical & Computer Engr University of Illinois Urbana-Champaign M.S. Thesis