{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/132805"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/132805","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Long silicon microfluidic needles for VTA and in-vivo differential neurochemical measurement","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.","abstract_html":"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_has_math":false,"creators":["Mahajan, Akshit"],"institution":"University of Illinois Urbana-Champaign","degree_name":"M.S.","degree_level":"Thesis","degree_discipline":"Electrical & Computer Engr","degree_department":null,"school":null,"contributors":["Vlasov, Yurii"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2025,"date_issued":"2025-12","date_published":"2025-12","updated_at":"2026-07-22T22:25:07Z","subjects":["Neural Probe","Process Development","Aluminum oxide","Silicon Nitride","VTA"],"languages":["en"],"rights":["Copyright 2025 Akshit Mahajan"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://hdl.handle.net/2142/132805","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Vlasov, Yurii"]},{"key":"dc:creator","label":"Author","values":["Mahajan, Akshit"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2025-12","2025-12-12"]},{"key":"dc:type","label":"Dc Type","values":["text","Thesis"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Electrical & Computer Engr"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Thesis"]},{"key":"thesis:degree_name","label":"Degree Name","values":["M.S."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Neural Probe","Process Development","Aluminum oxide","Silicon Nitride","VTA"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 2025 Akshit Mahajan"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://hdl.handle.net/2142/132805"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["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.","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"]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Long silicon microfluidic needles for VTA and in-vivo differential neurochemical measurement"]}]}],"canonical_facts":{"dc:contributor":["Vlasov, Yurii"],"dc:creator":["Mahajan, Akshit"],"dc:date":["2025-12","2025-12-12"],"dc: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.","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"],"dc:format":["application/pdf"],"dc:identifier":["https://hdl.handle.net/2142/132805"],"dc:language":["en"],"dc:rights":["Copyright 2025 Akshit Mahajan"],"dc:subject":["Neural Probe","Process Development","Aluminum oxide","Silicon Nitride","VTA"],"dc:title":["Long silicon microfluidic needles for VTA and in-vivo differential neurochemical measurement"],"dc:type":["text","Thesis"],"thesis:degree_discipline":["Electrical & Computer Engr"],"thesis:degree_level":["Thesis"],"thesis:degree_name":["M.S."],"thesis:institution_name":["University of Illinois Urbana-Champaign"]},"updated_at":"2026-07-22T22:25:07Z"}