Controlled generation of monodisperse discoid droplets using microchannel arrays.

We report a novel technique for generating geometrically confined droplets using a unique microstructure composed of a microchannel (MC) array and a shallow well. Silicon MC array devices were successfully used to generate monodisperse discoid droplets of oil-in-water (O/W) and W/O types by forcing a to-be-dispersed phase through channels into a well filled with a continuous phase. Monodisperse discoid droplets with sizes down to several micrometers were obtained by controlling the channel and well dimensions. The resultant discoid droplets formed a mostly close-packed array in the well. Monodisperse discoid droplets consisting of a silicone oil/water/sodium dodecyl sulfate system did not coalesce during the storage time of seven days. Additionally, MC array plates with many channels can be useful for increasing the droplet productivity of a single microfluidic device.