Electrodewetting

University Of California-Los Angeles, Los Angeles CA

Investigators

Abstract

As a simple technology for handling liquid droplets, electrically making a liquid wetting on a non-wettable surface, i.e., electrowetting, especially electrowetting-on-dielectric (EWOD) technology, has shown significant progress since the turn of the century. While major commercial products have started to emerge, the well-known reliability problem of EWOD devices is hampering the continued growth. A UCLA team from the engineering and medical school proposes to explore a phenomenon opposite to electrowetting, thus named electrodewetting, after finding it has a droplet manipulation capability similar to EWOD without the reliability problem. Noting the high reliability and easy manufacturing of electrodewetting-based devices, the team proposes to study the origin of electrodewetting, characterize the mechanism, and build the fundamental knowledge that will help design application devices. The proposed electrodewetting study is expected to significantly increase the user base of digital (droplet) microfluidics, which is powered by EWOD technology currently. Attractive to users of all levels and different goals regardless of their expertise and interests, electrodewetting devices are expected to serve both academic and industrial researchers as well as some hobbyists because of their simplicity and reliability. The proposed work requires an interdisciplinary approach in research and training on issues ranging from basic electrical engineering, surface science, and microfabrication, all the way to optical and biochemical applications. Graduate students will gain first-hand experience from this interdisciplinary research and be well prepared to be future leaders. Undergraduate and high school students will carry out tasks in a vertical team of researchers. The results will enrich the engineering curricula, including the MEMS/Nano PhD program at UCLA. While providing all the basic digital microfluidic functions of EWOD, electrodewetting avoids the key problems of EWOD. First, electrodewetting uses a hydrophilic substrate with neither the dielectric layer nor the hydrophobic topcoat. These coated layers needed for EWOD are the main culprits to its reliability problem and high manufacturing cost. Hydrophilic surfaces, such as glass, are common to many diverse applications spanning biomedical, optical, chemical, and other fields. Importantly, this simplicity would also make the design and manufacturing of electrodewetting devices easy and cheap. Second, electrodewetting typically uses only ~3 V for actuation. This low voltage allows the use off-the-shelf integrated circuits so the developers can quickly build a compact system, which is especially useful for mobile applications. Third, droplets can be split into smaller ones in an open configuration with no cover plate, allowing more flexibility in device design. In the proposed study, based on hypotheses carefully constructed from preliminary experiments and observations, the UCLA team will elucidate how the electrodewetting mechanism works, understand how it responds to device parameters, build the fundamental engineering knowledge for device design, and explore applications by developing an electronic display device. The underlying goal is to develop knowledge foundation that will assist other researchers and developers who would like to adopt this elegantly simple liquid handling technology for their own applications.