Manta-Ray-Inspired Bump Geometry for Enhanced Mixing in a Straight Microchannel

Slow diffusion in laminar microchannels limits assay speed, so a simple passive way to enhance mixing isuseful. This study tests whether smooth, periodic wall bumps inspired by manta rays can outperform astraight Y-junction of the same footprint. Both geometries were built, 3D computational fluid dynamics(CFD) was conducted in Ansys Student 2025 R2 with laminar flow and species transport, and mixing wascompared at inlet flow ratios of 1:1, 1:2, and 1:3 for water with dilute fluorescein. The bumped channelshowed earlier and broader regions of intermediate concentration and a more uniform outlet profile acrossall ratios, with a higher but manageable pressure drop. Velocity maps were consistent with low Reynoldsnumber flow, while pressure fields showed small local rises before bumps and dips after them. Mesh sizeand solver settings may soften gradients near bumps, but trends were consistent. These results supportfabrication and testing of the bumped design for low-flow lab-on-a-chip applications that need bettermixingwithoutaddedhardware.