Microdroplet manipulation device

A device for manipulating microdroplets using optically-mediated electrowetting is provided and characterised by consisting essentially of: 5 a first composite wall comprised of: * a first transparent substrate * a first transparent conductor layer on the substrate having a thickness in the range 70 to 250nm; * a photoactive layer activated by electromagnetic radiation in the 10 wavelength range 400-1000nm on the conductor layer having a thickness in the range 300-1000nm and * a first dielectric layer on the conductor layer having a thickness in the range 120-160nm; * a second composite wall comprised of: 15 * a second substrate; * a second conductor layer on the substrate having a thickness in the range 70 to 250nm and * optionally a second dielectric layer on the conductor layer having a thickness in the range 120-160nmnm 20 wherein the exposed surfaces of the first and second dielectric layers are disposed less than 10pm apart to define a microfluidic space adapted to contain microdroplets; * an A/C source to provide a voltage across the first and second composite walls connecting the first and second conductor layers; 25 * at least one source of electromagnetic radiation having an energy higher than the bandgap of the photoexcitable layer adapted to impinge on the photoactive layer to induce corresponding ephemeral electrowetting locations on the surface of the first dielectric layer and * means for manipulating the points of impingement of the electromagnetic 30 radiation on the photoactive layer so as to vary the disposition of the ephemeral electrowetting locations thereby creating at least one electrowetting pathway along which the microdroplets may be caused to move.