Microfluidic platform for selective microparticle parking and paired particle isolation in droplet arrays.

Immobilizing microscale objects (e.g., cells, spheroids, and microparticles) in arrays for direct observation and analysis is a critical step of many biological and chemical assays; however, existing techniques are often limited in their ability to precisely capture, arrange, isolate, and recollect objects of interest. In this work, we present a microfluidic platform that selectively parks microparticles in hydrodynamic traps based on particle physical characteristics (size, stiffness, and internal structure). We present an accompanying scaling analysis for the particle parking process to enable rational design of microfluidic traps and selection of operating conditions for successful parking of desired particles with specific size and elastic modulus. Our platform also enables parking of encoded particle pairs in defined spatial arrangements and subsequent isolation of these pairs in aqueous droplets, creating distinct microenvironments with no cross-contamination. In addition, we demonstrate the ability to recollect objects of interest (i.e., one particle from each pair) after observation within the channel. This integrated device is ideal for multiplexed assays or microenvironment fabrication for controlled biological studies.