Pushing a micro droplet using a laser beam.

A weak laser beam (similar to 0.1 watt) should be able to displace a drop using the Marangoni effect (via an imposed temperature gradient). Temperature shifts of similar to 10 degrees should overcome pinning forces on the supporting surface. The expected drop speeds are rather high. The direction of motion can be monitored optically. The movement of one (or many) droplets may be controlled retroactively. This system should be efficient for drop sizes similar to 10 mu m, and less efficient for smaller drops (which do not absorb much energy).