UC San Diego

Understanding and dissecting the dynamics of single-cell interactions is integral to immunological research. However, many of the microfluidic platforms that seek to facilitate this are constrained by strict particle size limits, low trap density, or complex multilayer fabrication processes. This thesis presents a microfluidic flow-reversal platform with a high-density trap array that hydrodynamically pairs two distinctly sized particle populations in a 1:1 ratio. Fabricated as a single layer via conventional soft lithography, the device incorporates 1,566 bidirectional traps that enable sequential loading of particles. Initially motivated by investigating host-pathogen interactions between neutrophils and Coccidioides spherules, the device was characterized using 10 µm and 20 µm fluorescent beads as model particles across operational flow rates from 75 to 200 µL/min. The results demonstrate an optimal 1:1 capture yield exceeding 40% at 125 µL/min, corresponding to an estimated over 626 paired sites per chip based on sampled fields of view. This platform serves as a high-throughput and easily fabricated framework for single-particle interaction assays with broad research applicability.