Droplet manipulation with light on optoelectrowetting device

We have demonstrated a 2-D droplet manipulation platform allowing fully optical manipulation of droplets on a photosensitive surface. Optically controlled injection, transport, separation, and multiple droplet manipulation have been achieved for nanoliter-size droplets. These functions are realized by sandwiching the droplets between two optoelectrowetting (OEW) surfaces. Optical illumination on OEW surfaces changes the surface wettability locally through the electrowetting mechanism. Optical illumination turns the initially Teflon-coated surface from hydrophobic to hydrophilic. This process is reversible and can be controlled in real time. We have achieved a maximum transport speed of 78 mm/s for a 100-nL droplet using a scanning laser beam. We have also demonstrated a fully decoupled 2-D multidroplet manipulation on the OEW surfaces. Potentially, the OEW mechanism can be scaled up to process a large number of liquid droplets using projected optical images for high throughput applications.