Microfluidic Chain Reaction: Exploration, Expansion, and Application

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Microfluidic Chain Reaction: Exploration, Expansion, and Application Ultrasensitive immunoassays reveal hitherto undetectable features, and are poised to advance early diagnosis and monitoring of COVID19, HIV, neurological disease and injury, and cancer. Their impact would be greatest at the point-of-care (POC), but they remain dependent on complex instrumentation housed in laboratories, and are stifled by a trade-off between assay performance and time-to-result. We propose to study and develop two lab discoveries: Microfluidic chain reactions (MCRs) and Brownian affinity trap (BAT) arrays, and integrate them on 3D printed capillary microfluidic chips for minimally instrumented, ultrasensitive (zeptomolar), and fast (<30 min) POC testing. We previously introduced capillaric circuits (CCs) that use capillary phenomena to (i) execute up to 8 fluidic operations structurally encoded in the surface microarchitecture, and (ii) for pumping. We recently discovered MCR that introduce conditional, event-based programmability (i.e. chain reaction), and enable MCR-CCs to encode, and autonomously execute, complex algorithms (300 steps) previously requiring a computer. The BAT is a microscopic pore coated with antibodies, and traps target molecules flowing through it because of Brownian motion induced wall collisions and affinity binding. The Overall goal is to explore the MCR and the BAT, and combine them for a minimally instrumented, ultrasensitive, rapid, POC test. Aim 1: MCR Exploration, Extension and Complementation CCs and the MCR are restricted to high surface tension aqueous solutions that can `decode' the structurally encoded fluidic operations. We propose to extend CCs to low surface tensions liquids using indirect valving with aqueous solutions, and 3D printed capillary `super' valves. MCR was realized using negative pressure. We will design positive pressure MCR, and complementary n-p MCR. We will encode DNA extraction and drug screening in MCR-CCs as a proof-of-concept. Aim 2: The Brownian Affinity Trap (BAT) and its use for digital ELISA Ultrasensitive digital ELISA (dELISA) use bead encapsulation, and each bead is read out as a "0", or in case of single molecule binding a "1". We will study computationally and experimentally the BAT. Samples will be flowed through arrays of millions of BATs, and single molecule binding events detected. We predict that BAT dELISA will be more sensitive and much faster. Aim 3: Digital additive manufacturing of MCRs and BATs for POC diagnostics MCRs can readily be 3D printed, but are hydrophobic. We introduce new hydrophilic resins for direct (i.e. digital) manufacturing of MCR-CCs (incl. BATs), for distributed manufacturing with collaborators. Significance MCR-CCs could become to microfluidics what cell phones (portable computers) are to desktop computers, while they could be home-built using a $500 3D printer, and used to make ultrasensitive, rapid, point-of-care diagnostics thanks to BAT arrays.