Electrowetting on a Polymer Microlens Array

• Published in: Langmuir 2010-07, Vol.26 (14), p.12443-12447
• Main Authors: Im, Maesoon, Kim, Dong-Haan, Lee, Joo-Hyung, Yoon, Jun-Bo, Choi, Yang-Kyu
• Format: Article
• Language: English
• Subjects: Chemistry; Devices and Applications: Sensors, Fluidics, Patterning, Catalysis, Photonic Crystals; Dimethylpolysiloxanes - chemistry; Electricity; Electrodes; Exact sciences and technology; General and physical chemistry; Hydrophobic and Hydrophilic Interactions; Lenses; Microarray Analysis - instrumentation; Microarray Analysis - methods; Solid-liquid interface; Surface physical chemistry; Surface Properties; Water - chemistry
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la101339t

This paper reports on the electrowetting behavior of a flexible poly(dimethylsiloxane) (PDMS) microlens array. A Cr and Au double-layered electrode was formed on an array of microlenses with diameters of 10 μm and heights of 13 μm. A deposition of parylene and a coating of Teflon were followed for electrical insulation as well as for enhancement of the hydrophobicity. On the nearly superhydrophobic microlens array surface, the electrowetting of a deionized water droplet was observed over the contact angle range of ∼140° to ∼58° by applying 0−200 V, respectively. The electrowetting phenomenon was reversible even in air environment with applied voltages of less than 100 V. The electrowetting on the microlens array surface lost its reversibility after the microlens array surface was completely wetted when the water meniscus touched the bottom of the microlens array. Analysis of meniscus shapes and net force direction follows to elucidate the reversibility. The convex curvature of the microlens caused gradual rather than abrupt impalement of water into the gap among the microlenses.