Room-temperature fabrication of anodic tantalum pentoxide for low-voltage electrowetting on dielectric (EWOD)

Yifan Li, William Parkes, Les Haworth, A. Ross, J. Stevenson, Anthony Walton

Research output: Contribution to journalArticlepeer-review

54 Citations (Scopus)

Abstract

This paper presents a robust anodic Ta2O5 dielectric as an alternative insulator for fabricating low-voltage electrowetting on dielectric (EWOD) systems. Previously reported low-voltage EWOD technologies require high-temperature processes ( > 435degC), which unlike this room temperature technology, are not compatible with standard copper and aluminum integrated circuit interconnect technology as well as polymer-based substrates. The anodized Ta2O5 forms a uniform pinhole free layer with a surface roughness (R a) of 0.6 nm. This robust film enables an ultrathin amorphous FluoroPolymer layer to be employed to reduce the EWOD driving voltage to 13 V. Both sub-20-nm Teflon-AF and CYTOP layers have been successfully coated on top of Ta2O5 with good adhesion. Applying voltages of 6-15 V significantly modified the contact angles of droplets in air on these samples (121deg to 81deg on Teflon-AF at 13 V and 114deg to 95deg on CYTOP at 6 V). Successful 14-V EWOD manipulation involving droplets being dispensed from a reservoir, their movement, followed by merging them together has been demonstrated using devices using a Teflon-AF + Ta2O5 dielectric.
Original languageEnglish
Pages (from-to)1481-1488
JournalJournal of Microelectromechanical Systems
Volume17
Issue number6
DOIs
Publication statusPublished - Nov 2008

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