Driving characteristics of the electrowetting-on-dielectric device using atomic-layer-deposited aluminum oxide as the dielectric

• Published in: Microfluidics and nanofluidics Vol. 8; no. 2; pp. 269 - 273
• Main Authors: Chang, Jong-hyeon, Choi, Dae Young, Han, Seungoh, Pak, James Jungho
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.02.2010; Springer; Springer Nature B.V
• Subjects: Aluminum; Analytical Chemistry; Applied fluid mechanics; Biomedical Engineering and Bioengineering; Condensed matter: structure, mechanical and thermal properties; Electrodes; Engineering; Engineering Fluid Dynamics; Exact sciences and technology; Fluid dynamics; Fluidics; Fundamental areas of phenomenology (including applications); Nanotechnology and Microengineering; Physics; Short Communication; Solid-fluid interfaces; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Wetting; Digital microfluidics; Single-plate configuration; Electrowetting on dielectric (EWOD); ); Aluminum oxide (Al; O; Atomic layer deposition (ALD); Aluminium oxide; Actuators; Atomic layer method; Wetting; Design; Electrocapillarity; Fabrication; Droplets; Microfluidics; Digital microftuidics; Dielectric devices
• ISSN: 1613-4982; 1613-4990
• DOI: 10.1007/s10404-009-0511-9

Electrowetting on dielectric (EWOD) is useful in manipulating droplets for digital (droplet-based) microfluidics, but its high driving voltage over several tens of volts has been a barrier to overcome. This article presents the characteristics of EWOD device with aluminum oxide (Al 2 O 3 , ε r  ≈ 10) deposited by atomic layer deposition (ALD), for the first time as the high-k dielectric for lowering the EWOD driving voltage substantially. The EWOD device of the single-plate configuration was fabricated by several steps for the control electrode array of 1 mm × 1 mm squares with 50 μm space, the dielectric layer of 1,270 Å thick ALD Al 2 O 3 , the reference electrode of 20 μm wide line electrode, and the hydrophobic surface treatment by Teflon-AF coating, respectively. We observed the movement of a 2 μl water droplet in an air environment, applying a voltage between one of the control electrodes and the reference electrode in contact with the droplet. The droplet velocity exponentially depending on the applied voltage below 15 V was obtained. The measured threshold voltage to move the droplet was as low as 3 V which is the lowest voltage reported so far in the EWOD researches. This result opens a possibility of manipulating droplets, without any surfactant or oil treatment, at only a few volts by EWOD using ALD Al 2 O 3 as the dielectric.