Mixing of fluids at the microscale poses a variety of challenges, many of whicharise from the fact that molecular diffusion is the dominant transport mechanism in thelaminar flow regime. The unfavorable combination of low Reynolds numbers and highP????clet numbers implies that cumbersomely long microchannels are required to achieveefficient levels of micromixing. Although considerable progress has been made towardovercoming these limitations (e.g., exploiting chaotic effects), many techniques employintricate 3-D flow networks whose complexity can make them difficult to build andoperate. In this research, we show that enhanced micromixing can be achieved usingtopologically simple and easily fabricated planar 2-D microchannels by simplyintroducing curvature and changes in width in a prescribed manner. This isaccomplished by harnessing a synergistic combination of (i) Dean vortices that arise inthe vertical plane of curved channels as a consequence of an interplay between inertial,centrifugal, and viscous effects, and (ii) expansion vortices that arise in the horizontalplane due to an abrupt increase in a conduit??????s cross-sectional area. We characterize these effects using top-view imaging of aqueous streams labeled with tracer dyes andconfocal microscopy of aqueous fluorescent dye streams, and by observing bindinginteractions between an intercalating dye and double-stranded DNA. These mixingapproaches are versatile, scalable, and can be straightforwardly integrated as genericcomponents in a variety of lab-on-a-chip systems.
展开▼
