Investigation of the Y-Mixer Junction for Generating Non-Linear Chemical Gradients

This project focuses on the geometry of Y-mixer junctions in microfluidic devices (MFDs) designed for the generation of non-linear chemical gradients to study the chemotaxis of live cancer cells. The MFD’s input concentrations (0% and 100% of a cancer-relevant chemical) are deployed through a series of microchannels that are repeatedly assembled into bifurcations, trifurcations, and mixing junctions, ultimately delivering a two-dimensional chemical landscape for the cells of interest. When both inputs are equal, i.e. they are symmetrical, the chemical gradient produced is considered linear and varies proportionally with distance across the top of the chamber (where lie the ends of the mixing channels). We can change the dimensions of one side of the mixer arms to introduce a bias in concentration output by widening one of the mixer input channels. However, doing this has introduced a surprising issue where backwards diffusion occurs within the mixing channels, causing the resulting gradient to have a limited range of concentrations. The new project designs address this issue by creating a bottleneck-like feature at each mixer junction to mitigate the unwanted diffusion, as well as using different shapes for the biased mixer channel to study how geometry affects flow through the channels