Overcoming the diffusion barrier: Ultra-fast micro-scale mixing via ferrofluids

We report on the design, development, fabrication and characterization of a novel, micro-scale mixing device based on stable water suspensions of magnetic nanoparticles (i.e. ferrofluids). The micromixer prototypes are built using standard microfabrication and simple soft-lithography, and the design can be incorporated as a sub-system into any chemical micro-reactor or a miniaturized biological sensor. The devices achieve mixing virtually instantaneously and may be used to greatly increase mass transport towards chemically or biologically active sites on lab-on-a-chip devices for rapid incubation and highly improved detection sensitivity.