Active micromixer based on artificial cilia

We propose a design for anactive micromixer that is inspired by the motion of ciliatedmicro-organisms occurring in nature. The conceptual designconsists ofan array of individually addressable artificial cilia in theform ofmicro-actuators covering the channel wall. The microactuatorscan beset into motion by an external stimulus such as an electric ora magneticfield, inducing eithera primary or secondary motion in the surrounding fluid. Tovalidate theconcept and to help to design the precise mixer configurationwe developeda computational fluid-structure model. This model is based ona fictitious domain method that couples the microactuatormotionto the concomitant fluid flow, fully capturing themutual fluid-structure interactions. The simulated flowpatternsresulting from the motion of single and multiple actuatedelements (ina microchannel filled with a Newtonian fluid) under the actionof atime-periodic forcing function are analyzed using dynamicalsystemstheory to quantify the mixing efficiency. The results showthat witha proper actuation scheme, two microactuators placed on thesamewall of a microchannel can indeed induce effective mixing bychaoticadvection; their distance should be small, but collisionsshould be avoided,and they can be actuated in a rather broad regime around 90$^\circ$ out ofphase. Placing actuators on opposite walls also inducesexponentialstretching in the fluid, but if their length is relativelysmall, of the order of 20\% of thechannel height, mixing effectiveness is higher when they arearranged on the same wall