Mathematical modeling of drop mixing in a slit-type microchannel

Fast solute mixing can be achieved in a microchannel by rapid unidirectiona l displacement of a discrete liquid drop. The recirculation streamlines cre ated within the liquid during the drop's motion cause the solute to interla yer across the channel depth, provided the interlayer diffusion of the solu te is small. Uniform interlayering appears when the drop is displaced by mo re than three drop lengths in a slit-type microchannel, thereby reducing th e solute diffusion distances to a fraction of the channel depth. By fabrica ting the microchannel to a depth of less than 50 mum even large molecules w ith a low diffusivity (D < 10(-8) cm(2) s(-1)) can be mixed in seconds. The above strategy is shown by modeling the mixing of solutes present in a dro p moving in a slit-type microchannel.