Date of Award
8-2026
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Bioengineering
Committee Chair/Advisor
Dr. Delphine Dean
Committee Member
Dr. Bruce Gao
Committee Member
Dr. Melinda Harman
Committee Member
Dr. Lucas Schmidt
Abstract
Cobalt exposure is a clinical concern in orthopedic implant surveillance, where cobalt-chromium wear debris can release ions detectable in blood and urine, and an environmental concern in mining-affected and industrial water systems. Reference laboratory methods, including inductively coupled plasma mass spectrometry, provide sensitive quantification but require centralized instrumentation, trained personnel, and controlled sample handling, which limits their availability for routine screening in decentralized clinical and environmental contexts. This dissertation develops a surface-bound detection architecture for label-free evanescent-wave sensing of cobalt in complex fluids. The architecture rests on a physical necessity argument grounded in interfacial optics: at physiologically and environmentally relevant cobalt concentrations, and given the measured Co-DTPA molar absorptivity of approximately 13 L/mol/cm at 503 nm, bulk-phase evanescent detection would require approximately 20 kilometers of interaction length. Surface accumulation of cobalt through an immobilized chelator reduces the required interaction length by four to five orders of magnitude to a buildable scale. Surface-bound detection is therefore not a design preference in this class of sensor; it is a physical requirement dictated by the optical properties of the analyte and the interfacial physics of the evanescent wave. We extended the existing scientific literature supporting this sensing architecture, developed the surface chemistry and instrumentation required for its implementation, and evaluated cobalt chelator-capture using two independent surface-sensitive measurements. A custom visible spectrophotometer was built as an accessible optical detection platform, using a Thorlabs broadband LED, a reflective holographic diffraction grating, and a Toshiba TCD1304DG linear CCD array controlled by an STM32F401RE Nucleo microcontroller. The piranha-APTMS-DTPA surface functionalization workflow was validated on planar silica by monitoring sequential changes in contact angle during the treatment steps. The DTPA capture chemistry was independently validated on Nicoya OpenSPR gold LSPR chips functionalized with an AHT thiol self-assembled monolayer and DTPA conjugated via EDC/Sulfo-NHS coupling, where cobalt exposure produced a retained post-wash response above the instrument noise floor. Solution-phase UV-Vis characterization of the cobalt-DTPA complex quantitatively grounds the architecture argument. Together these results establish the physical basis, the surface chemistry, and the instrumentation required to build an integrated fiber-optic evanescent-wave cobalt sensor on this architecture. Integration of these components into a functionalized fiber sensor and evaluation across drinking water, synthetic urine, and biological matrices is identified as the next research phase.
Recommended Citation
Carpenter, Jeremiah W., "A Surface-Bound Detection Architecture for Label-Free Evanescent-Wave Sensing of Cobalt in Complex Fluids" (2026). All Dissertations. 4323.
https://open.clemson.edu/all_dissertations/4323
Author ORCID Identifier
0009-0008-2576-0440