Development and Optical Analysis of a Microfluidic Point-of-Care Diagnostic Device

Remote health monitoring and disease detection in the developing world are hampered by a lack of accurate and convenient diagnostic tools. The sensitive and quantitative tests run in well-funded clinical laboratories are inappropriate to the requirements of the point-of-care (POC) setting, demanding tradeoffs in performance to achieve operational simplicity in devices like the lateral flow strip. One approach to bridging the gap between rapid diagnostics and clinical standards is to apply low-cost instrumentation to the operation and analysis of disposable test devices. Using a microfluidic assay card and an external reader, complex tests can be operated and interpreted with minimal user intervention.;This work explored one approach to an instrumented microfluidic assay for the point of care: the flow-though membrane immunoassay, or FMIA. The assay takes place on a microporous membrane enclosed in a channel that directs fluid through its pores. The high surface area and small diffusion distances in the membrane favor rapid and sensitive assays, while the microfluidic channels allow easily programmable fluidic manipulation Microfluidic FMIA cards were developed to run an automated assay for a malarial biomarker in nine minutes with an external pumping system, giving a detection limit similar to benchtop standards that take hours to run. The system's fluidic flexibility enabled it to perform assays with amplified signals, using either enzyme labels or autocatalytic deposition of gold. To allow unrefrigerated storage of the devices, a method was developed for dry storage and on-card rehydration of assay reagents, providing several months of reagent stability. Low-cost fluid actuation was achieved by designs that enabled pneumatic operation of the FMIA. To demonstrate an approach to low-cost quantification of the colorimetric results, a cell phone camera and a video analysis algorithm were developed to automate result interpretation.;This work has produced an immunoassay format for the point of care, while providing methods for sensitive analyte detection and solutions for the needs of low-resource settings. By addressing problems related to a wide field of detection efforts, these results have advanced our understanding of how POC detection technologies can be improved to address health care needs across the globe.