MEAM Ph.D. Thesis Defense: “User-friendly, Low-cost, Microfluidic Devices with Capillary Circuits for Multiplexed, Isothermal, Point-of-care Nucleic Acid Amplification Tests”

Rapid, sensitive, and specific detection of causative pathogens is key to personalized medicine and the prompt implementation of appropriate mitigation measures to reduce disease transmission, mortality, morbidity, and cost. Conventional molecular detection methods require trained personnel, sophisticated equipment, and specialized laboratories, which limits their use to centralized laboratories. To enable molecular diagnostics at the point of need and in resource-poor settings, inexpensive, simple devices that combine multiple unit operations and are capable of co-detecting endemic pathogens are needed.

In this dissertation, I have developed microfluidic devices with capillary circuits to automate liquid distribution, eliminating the need for expensive equipment, sophisticated laboratory facilities, and skilled personnel to enable molecular diagnostics at the point of need. Capillary valves with different sizes were developed and implemented to aliquot samples and reagents to multiple reaction chambers and to enable draining liquids from supply lines without affecting liquids in the various reaction chambers, enabling bubble-free operation. The sealing of my microfluidic devices to prevent evaporation during incubation is facilitated with phase-change materials and capillary-induced motion. When my microfluidic chip is heated to its incubation temperature, the phase change material melts and flows to seal ports of entry and air vent. Numerical simulations were carried out to assess the viability of on-chip, in-house developed, two-stage isothermal nucleic acid amplification in the presence of diffusion and advection. An Android-based smartphone application was developed to automate real-time signal monitoring, time series image analysis, and diagnostic result interpretation. Three different 3D-printed, portable, microfluidic devices with capillary circuits were designed, fabricated, and tested for single-stage and two-stage, isothermal nucleic acid amplification with either liquid reagents or ii pre-stored dry reagents that do not require a cold chain. All devices have proved successful for rapid, sensitive, and specific multiplexed detections of human and animal pathogens.