Inertial Microfluidics with Integrated Vortex Generators Using Liquid Metal Droplets as Fugitive Ink

This work demonstrates a simple method for fabricating nearly spherical dome structures on top of lithographically defined microfluidic channels using gallium-based liquid metal droplets as fugitive ink. The droplets remain stable during the pouring and curing of polydimethylsiloxane and can be easily removed by applying a basic solution. This facilitates the formation of domes with diameters of a few hundred micrometers patterned on the desired locations of the channel. The expansion of the channel at the interface of the dome leads to formation of a large vortex inside the dome. Experiments using high-speed imaging along with numerical simulations show the utility of the vortex-induced flow rotation for orbiting of human monocytes and polystyrene microbeads inside the dome. The lateral displacement of liquids caused by the vortex is further utilized for creating controllable multiband flow/color profiles within a T-mixer. The method enables the fabrication of customized, complex, and 3D microfluidic systems utilizing planar microfabricated structures.