Light-Actuated Digital Microfluidics for Large-Scale Droplet Manipulation

Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific permission. Abstract The ability to quickly perform a large number of chemical or biological reactions in parallel using low reagent volumes is a field well addressed by electrowetting-based digital microfluidics. Here we report on a new light-actuated digital microfluidics device which uses on-demand, 'virtual' electrodes defined by light patterns from a data projector for the large-scale, parallel manipulation of arbitrarily sized droplets. The device features a thin, high-quality aluminum oxide film deposited via atomic layer deposition (ALD), which allows aggressive scaling of the dielectric thickness while maintaining high device reliability. Due to the thin ALD dielectric layer, a significantly higher actuation force is imparted on droplets, which results in actuation speeds of up to 2 cm/s. Compared to our previous device, the actuation speed is 20x faster, but achieved at 250x lower optical power and 5x lower voltage. In this paper, we demonstrate the device's ability to perform all the critical digital microfluidics functionalities: transport, creation, merging, and splitting. In addition, the ability to easily achieve parallel manipulation and array formation (8 by 12, 96 droplet format) of droplets will be presented.