Towards automated optoelectrowetting on dielectric devices for multi-axis droplet manipulation

Lab-on-a-chip technology scales down multiple laboratory processes to a chip capable of performing automated biochemical analyses. Electrowetting on dielectric (EWOD) is a digital microfluidic lab-on-a-chip technology that uses patterned electrodes for droplet manipulation. The main limitations of EWOD devices are the restrictions in volume and motion of droplets due to the fixed size, layout, and addressing scheme of the electrodes. Optoelectrowetting on dielectric (OEWOD) is a recent technology that uses optical sources and electric fields for droplet actuation on a continuous surface. We describe an open surface light-actuated OEWOD device that can manipulate droplets of multiple volumes ranging from 1 to 50 μL at voltages below 45 V. To achieve lower voltage droplet actuation than previous open configuration devices, we added a dedicated dielectric layer of high dielectric constant (Al₂O₃ with ε_r of 9.1) and significantly reduced the thickness of the hydrophobic layer. The device is capable of transporting droplets at speeds as high as 12 mm/sec using a data projector as an optical source. We developed a multiple axis contact pad design to apply lateral electric fields along different axes to achieve multi-axis droplet movement. We demonstrated microfluidic operations including droplet merging, mixing, and parallel droplet motion. Further, the OEWOD device is capable of droplet transportation using a tablet computer´s LCD screen as an optical source.