An economical self-coalescing microfluidic device with an easily observable readout.

Introduction: Self-coalescing microfluidic devices represent an exciting opportunity for leveraging viscous dominated flow phenomena to reconstitute a series of reagents with a single sample infusion. In a self-coalescing microfluidic device, spatially separated dried reagents are reconstituted using a single infusion. Due to the unique device geometry, the reagents remain spatially separated after infusion. As such, self-coalescing microfluidic devices have the potential to simplify point-of-care testing by simultaneously performing multiple colorimetric tests in one device. The current versions of these devices use standard, more costly microfabrication processes and are too small to be easily read by eye. Methods: Here, we created a low cost and scaled up version of a self-coalescing microfluidic device by using laser-cut-roll-based silicone tape. In addition to eliminating the need for cleanrooms, our approach simplifies the integration of assay reagents since they can be spotted onto a coverslip and covered with the tape microfluidic device. We empirically optimized our device, finding that flow rate significantly influenced the formation of self-coalescence as well as proper reagent reconstitution. Results and Discussion: When flow rates were too slow or fast, reagents would streak, leading to inadvertent mixing between different spatial locations. Our studies further revealed that geometry had a stronger influence on device operation in low-flow conditions. Our final optimized device exhibited a 100% success rate, demonstrated through self-coalescence with no reagent streaking at 100 μL/min, which enabled the isotropic diffusion of reagents. Furthermore, the spots are spatially separated and large enough to be visualized by the naked eye and captured by a smartphone camera for downstream analysis. Taken together, our innovative device leverages the advantages of sticker microfluidics and low-cost manufacturing methods to offer standalone functionality. This approach has the potential to significantly impact point-ofcare diagnostics, particularly in resource-limited regions. By enabling multiplexed diagnostic assays through our novel technology, we aim to provide accessible and affordable healthcare solutions. [ABSTRACT FROM AUTHOR]