Light actuated microfluidic devices

A light-actuated microfluidic device has been successfully fabricated to inject, move, separate, and merge liquid droplets with nano-liter volumes. Light actuation is realized by sandwiching the liquid droplets between two photosensitive surfaces whose wettability can be changed by light. By integrating a photoconductor with an electrowetting electrode, the surface tension at the liquid/solid interface above the electrode can be modified by shining an optical beam on the photoconductor. The surface tension change is reversible and has a fast response time (millisecond). The liquid droplets follow the optical beam path up to a speed of 78 nm/sec. All optical actuation for complete liquid droplet functions has been achieved. Simultaneous manipulation of multiple droplets is also demonstrated.