Staggered trap arrays for robust microfluidic sample digitization

A sample digitization method that exploits the controlled pinning of fluid at geometric discontinuities within an array of staggered microfluidic traps is presented. The staggered trap design enables reliable sample filling within high aspect ratio microwells, even when employing substrate materials such as thermoplastics that are not gas permeable. A simple geometric model is developed to predict the impact of device geometry on sample filling and discretization, and validated experimentally using fabricated cyclic olefin polymer devices. Using the developed design guidelines, a 768-element staggered trap array is demonstrated, with reliable passive loading and discretization achieved within 5 min. The resulting discretization platform offers a simplified workflow with flexible trap design, reliable discretization, and repeatable operation using low-cost thermoplastic substrates.