A planar 2-stage micromixer

The paper describes a novel micromixing concept based on two independently actuated valves in a microfluidic system. Valve actuation results in periodic redirection of the flow in the microfluidic system, which leads to substantial stretching and distortion of the fluid layers. This generates very thin layers, reducing the effective diffusion length, which significantly enhances mixing compared to pure diffusion. The active valves have been realized using integrated resistive heaters in a planar design; these trigger the reversible gelation of a thermally-responsive polymer that is dissolved in the working fluid.