Optical levitation and transport of microdroplets: Proof of concept

A new technique for microfluidic transport of liquid droplets in “lab-on-a-chip” (LOC) applications is described in which droplets are levitated above or between solid planar surfaces through the use of thermocapillarity, the variation in a liquid’s surface tension with temperature. Levitated liquid droplets are not in contact with solid surfaces and so may be transported from point-to-point along arbitrary paths with little friction. In addition, the lack of liquid-solid contact virtually eliminates the potential for sample-to-sample contamination. The new technique therefore addresses three issues associated with existing LOC devices employing microchannels: droplet pathway constraints, transport speed, and sample-to-sample contamination.