Manipulating nanoparticles and macromolecules with light patterned microfluidic flow

We present a novel light-actuated ac electroosmosis (LACE) mechanism allowing concentrating and transporting micro-, nano-scale particles including macromolecules using light-patterned, dynamically reconfigurable microfluidic vortices on a photoconductive surface. LACE is realized by sandwiching an aqueous liquid medium between a featureless photoconductive surface and a transparent ITO electrode. Under the application of an ac bias with a frequency close to the electric double layer relaxation frequency, a light beam can create a microfluidic vortex flow around the illuminated area through ac electroosmosis. By integrating with a spatial light modulator such as a DMD microdisplay, LACE allows the creation of 31,000 microfluidic vortices on a 1.3 times 1 mm2 area for massively parallel trapping of 2-mum, 1 mum, 500 nm, 200 nm, and 50 nm polystyrene beads. We have also demonstrated LACE concentration and transportation of lambda-phage DNA molecules, and quantum dots.