Redox cycling is an electrochemical technique that utilizes closely spaced generator and collector electrodes to cycle reversible redox species between their oxidative states. With advantages in signal amplification, selectivity of species based on their electrochemical reaction mechanism, and limited or no background subtraction, this technique is well suited for selective detection of important electrochemically active molecules such as dopamine at basal or slowly changing levels.
Miniaturized medical devices have become an area of great interest for measurement of chemicals in limited volumes with low concentrations or in sensitive tissues. A probe on a polymeric SU-8 substrate with suitable dimensions and robustness for in vivo neural measurements was developed and tested in vitro. The probe’s unique construction using microfabrication processes and a laser-machining procedure is described in detail. The probe features an array of individually addressable electrodes, each 100 μm long, 4 μm wide and with a 100 μm gap in between, on a shank that is 6 mm long and 100 μm wide. The probe is insulated by a thin layer of SU-8 with only the electrodes near the tip and the contact pads exposed. Evaluation of tissue after probe insertion into a rat brain indicates minimal damage comparable to FSCV electrodes and less extensive than the microdialysis probe.
The electrodes on the probe were characterized electrochemically and redox cycling on the array was evaluated in vitro in the presence of model compounds (potassium ferricyanide and ruthenium (III) hexamine chloride) and dopamine, and the responses were compared to theory. The amplification factors, percent collection efficiencies and detection limits are determined from calibration curves. The best detection limits obtained for dopamine at the generator electrodes and collector electrodes during redox cycling are 800 nM and 1.10 μM, respectively. These values lie in the physiological concentration range of dopamine. The features and the results suggest that the probe is ready for further analysis in vivo.
Finally, potential future designs for the probe are proposed and their expected current is calculated using theoretical approximations. All of the proposed designs fit on the same footprint as the current probe (70-μm wide and 100-μm long window) and have dimensions achievable with available micro and nanofabrication tools.
","abstract_html":"<p>Redox cycling is an electrochemical technique that utilizes closely spaced generator and collector electrodes to cycle reversible redox species between their oxidative states. With advantages in signal amplification, selectivity of species based on their electrochemical reaction mechanism, and limited or no background subtraction, this technique is well suited for selective detection of important electrochemically active molecules such as dopamine at basal or slowly changing levels.</p> <p>Miniaturized medical devices have become an area of great interest for measurement of chemicals in limited volumes with low concentrations or in sensitive tissues. A probe on a polymeric SU-8 substrate with suitable dimensions and robustness for in vivo neural measurements was developed and tested in vitro. The probe’s unique construction using microfabrication processes and a laser-machining procedure is described in detail. The probe features an array of individually addressable electrodes, each 100 μm long, 4 μm wide and with a 100 μm gap in between, on a shank that is 6 mm long and 100 μm wide. The probe is insulated by a thin layer of SU-8 with only the electrodes near the tip and the contact pads exposed. Evaluation of tissue after probe insertion into a rat brain indicates minimal damage comparable to FSCV electrodes and less extensive than the microdialysis probe.</p> <p>The electrodes on the probe were characterized electrochemically and redox cycling on the array was evaluated in vitro in the presence of model compounds (potassium ferricyanide and ruthenium (III) hexamine chloride) and dopamine, and the responses were compared to theory. The amplification factors, percent collection efficiencies and detection limits are determined from calibration curves. The best detection limits obtained for dopamine at the generator electrodes and collector electrodes during redox cycling are 800 nM and 1.10 μM, respectively. These values lie in the physiological concentration range of dopamine. The features and the results suggest that the probe is ready for further analysis in vivo.</p> <p>Finally, potential future designs for the probe are proposed and their expected current is calculated using theoretical approximations. All of the proposed designs fit on the same footprint as the current probe (70-μm wide and 100-μm long window) and have dimensions achievable with available micro and nanofabrication tools.</p>","abstract_has_math":false,"creators":["Lotfi Marchoubeh, Mahsa"],"institution":null,"degree_name":"Doctor of Philosophy in Chemistry (PhD)","degree_level":"Dissertation","degree_discipline":null,"degree_department":null,"school":null,"contributors":["Stenken, Julie A.","Wilkins, Charles L."],"advisors":["Fritsch, Ingrid"],"committee_chairs":[],"committee_members":[],"year":2021,"date_issued":"2021-07-01T07:00:00Z","date_published":"2021-07-01T07:00:00Z","updated_at":"2026-07-24T00:59:58Z","subjects":["neurotransmitters","neural probe","microelectrodes","dopamine levels","Analytical Chemistry","Animal Experimentation and Research","Animal Studies","Materials Chemistry","Molecular and Cellular Neuroscience","Organic Chemistry"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://scholarworks.uark.edu/etd/4170","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Stenken, Julie A.","Wilkins, Charles L."]},{"key":"dc:contributor.advisor","label":"Advisor","values":["Fritsch, Ingrid"]},{"key":"dc:creator","label":"Author","values":["Lotfi Marchoubeh, Mahsa"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2021"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2022-09-10T07:00:00Z"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Doctor of Philosophy in Chemistry (PhD)"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["neurotransmitters","neural probe","microelectrodes","dopamine levels","Analytical Chemistry","Animal Experimentation and Research","Animal Studies","Materials Chemistry","Molecular and Cellular Neuroscience","Organic Chemistry"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://scholarworks.uark.edu/etd/4170"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Redox cycling is an electrochemical technique that utilizes closely spaced generator and collector electrodes to cycle reversible redox species between their oxidative states. With advantages in signal amplification, selectivity of species based on their electrochemical reaction mechanism, and limited or no background subtraction, this technique is well suited for selective detection of important electrochemically active molecules such as dopamine at basal or slowly changing levels.
Miniaturized medical devices have become an area of great interest for measurement of chemicals in limited volumes with low concentrations or in sensitive tissues. A probe on a polymeric SU-8 substrate with suitable dimensions and robustness for in vivo neural measurements was developed and tested in vitro. The probe’s unique construction using microfabrication processes and a laser-machining procedure is described in detail. The probe features an array of individually addressable electrodes, each 100 μm long, 4 μm wide and with a 100 μm gap in between, on a shank that is 6 mm long and 100 μm wide. The probe is insulated by a thin layer of SU-8 with only the electrodes near the tip and the contact pads exposed. Evaluation of tissue after probe insertion into a rat brain indicates minimal damage comparable to FSCV electrodes and less extensive than the microdialysis probe.
The electrodes on the probe were characterized electrochemically and redox cycling on the array was evaluated in vitro in the presence of model compounds (potassium ferricyanide and ruthenium (III) hexamine chloride) and dopamine, and the responses were compared to theory. The amplification factors, percent collection efficiencies and detection limits are determined from calibration curves. The best detection limits obtained for dopamine at the generator electrodes and collector electrodes during redox cycling are 800 nM and 1.10 μM, respectively. These values lie in the physiological concentration range of dopamine. The features and the results suggest that the probe is ready for further analysis in vivo.
Finally, potential future designs for the probe are proposed and their expected current is calculated using theoretical approximations. All of the proposed designs fit on the same footprint as the current probe (70-μm wide and 100-μm long window) and have dimensions achievable with available micro and nanofabrication tools.
"]},{"key":"dc:title","label":"Title","values":["Microfabrication and Electrochemical Characterization of a Novel SU-8 Probe with an Array of Individually Addressable Electrodes Suitable for Redox Cycling Experiments in Ultra-small Volumes"]}]}],"canonical_facts":{"dc:contributor":["Stenken, Julie A.","Wilkins, Charles L."],"dc:contributor.advisor":["Fritsch, Ingrid"],"dc:creator":["Lotfi Marchoubeh, Mahsa"],"dc:date":["2021"],"dc:date.available":["2022-09-10T07:00:00Z"],"dc:description.abstract":["Redox cycling is an electrochemical technique that utilizes closely spaced generator and collector electrodes to cycle reversible redox species between their oxidative states. With advantages in signal amplification, selectivity of species based on their electrochemical reaction mechanism, and limited or no background subtraction, this technique is well suited for selective detection of important electrochemically active molecules such as dopamine at basal or slowly changing levels.
Miniaturized medical devices have become an area of great interest for measurement of chemicals in limited volumes with low concentrations or in sensitive tissues. A probe on a polymeric SU-8 substrate with suitable dimensions and robustness for in vivo neural measurements was developed and tested in vitro. The probe’s unique construction using microfabrication processes and a laser-machining procedure is described in detail. The probe features an array of individually addressable electrodes, each 100 μm long, 4 μm wide and with a 100 μm gap in between, on a shank that is 6 mm long and 100 μm wide. The probe is insulated by a thin layer of SU-8 with only the electrodes near the tip and the contact pads exposed. Evaluation of tissue after probe insertion into a rat brain indicates minimal damage comparable to FSCV electrodes and less extensive than the microdialysis probe.
The electrodes on the probe were characterized electrochemically and redox cycling on the array was evaluated in vitro in the presence of model compounds (potassium ferricyanide and ruthenium (III) hexamine chloride) and dopamine, and the responses were compared to theory. The amplification factors, percent collection efficiencies and detection limits are determined from calibration curves. The best detection limits obtained for dopamine at the generator electrodes and collector electrodes during redox cycling are 800 nM and 1.10 μM, respectively. These values lie in the physiological concentration range of dopamine. The features and the results suggest that the probe is ready for further analysis in vivo.
Finally, potential future designs for the probe are proposed and their expected current is calculated using theoretical approximations. All of the proposed designs fit on the same footprint as the current probe (70-μm wide and 100-μm long window) and have dimensions achievable with available micro and nanofabrication tools.
"],"dc:identifier":["https://scholarworks.uark.edu/etd/4170"],"dc:subject":["neurotransmitters","neural probe","microelectrodes","dopamine levels","Analytical Chemistry","Animal Experimentation and Research","Animal Studies","Materials Chemistry","Molecular and Cellular Neuroscience","Organic Chemistry"],"dc:title":["Microfabrication and Electrochemical Characterization of a Novel SU-8 Probe with an Array of Individually Addressable Electrodes Suitable for Redox Cycling Experiments in Ultra-small Volumes"],"thesis:degree_level":["Dissertation"],"thesis:degree_name":["Doctor of Philosophy in Chemistry (PhD)"]},"updated_at":"2026-07-24T00:59:58Z"}