Modern medicine has detailed 70,000 different diagnoses; the 21st century challenge is bringing those diagnoses to over 7 billion people. This phenomenal feat requires precision biosensing strategies that minimize necessary training and manual effort while maximizing portability and affordability. Microfluidic strategies, both fabricated chips and paper-based devices, held the promise to facilitate point-of-care diagnostics but have been inadequate for many applications due to the trade-off between bulky pumps or limited control and complexity. This dissertation details novel strategies that control the progression of biochemical reactions with high functionality, portability, and ease-of-use.

First, I will describe an amplified signaling reaction that leverages both positive and negative feedback loops to achieve optically-regulated control. This assay, termed “Peroxidyme-Amplified Radical Chain Reaction” enables naked-eye detection of catalytic reporter DNA structures at concentrations across five orders of magnitude down to 100 pM while eliminating the need for manual addition of hydrogen peroxide common to other such detection reactions.

Next, I will describe the development of a platform for thermal regulation of generic reactions. To address the need for a broadly capable automation platform that provides equal utility in the lab and field alike, we recently developed “phase-change partitions”. In our system, purified waxes segregate reagents until incremental heating melts the partitions one by one, causing the now-liquid alkane to float and allowing the desired reagents to interact with the sample on demand. This tight control over reaction progression enabled us to construct hands-free detection systems for isothermal DNA amplification, heavy metal contamination, and antibiotic resistance profiling. My work has demonstrated a broadly capable suite of assay control systems with the potential to enable simple, inexpensive automation of a broad array of chemical and biological analysis across human medicine, environmental surveillance, and industrial chemical synthesis.