Figure 4.

Droplet transport, fluid flow, and viscous mixing on SMCs. a) Photographic time lapse taken of a glycerol droplet (labeled with rhodamine) driven over a dry SMC by a linear track of magnets. The droplet moves in the opposite direction to the magnetic track. b) Plot of the displacement of the glycerol droplet's front with time. c) Continuous flow of glycerol (fully submerged SMC) driven by a circular magnetic track. The motion is in the direction opposite to that of the track. The direction of flow was visualized by adding a droplet of rhodamine labeled glycerol. d) Sketch demonstrating how soft carpets enable spatial control over local fluid mixing. Glycerol droplets labeled with different dyes (rhodamine and green food color) are placed at opposite corners of the millifluidic chip. Active mixing takes place in one corner while the fluid in the opposite corner remains effectively unperturbed. e) Photographic time lapse taken of a local mixing experiment that demonstrates the significant enhancement of SMC‐based mixing compared to that induced by diffusion in glycerol. Scale bars are 5 mm.