Abstract
We propose a planar 3D microfluidic flow-focusing device (MFFD) that can produce monodisperse single/double emulsions in a closed/open microfluidic system. By confining droplets to the central axis of the microchannel, we avoid the problem of wetting and successfully produced single emulsions for both water-in-oil (W/O) and oil-in-water (O/W) droplets utilizing the same device as well as double emulsions containing one to several internal droplets inside in the closed channel configuration. We also demonstrated the feasibility of forming W/O droplets and polymer microspheres in an open channel configuration by withdrawing fluid from the outlet channel. The unique fabrication provides flexibility for Lab-on-Chip microsystem. © 2006 Society for Chemistry and Micro-Nano Systems.