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Proceedings Paper

Reversible wetting of titanium dioxide films
Author(s): A. G. G. Toh; M. G. Nolan; R. Cai; D. L. Butler
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Paper Abstract

Titanium dioxide (TiO2) films were rendered hydrophilic through ultraviolet (UV) light irradiation (254nm) and returned to their previous hydrophobic condition when exposed to a sealed pressurized nitrogen atmosphere. UV light irradiation on TiO2 films resulted in super-hydrophilic surfaces with water contact angles of <5°. Alternatively, exposure of the films to an N2 environment resulted in relatively hydrophobic surfaces with water contact angles of >40°. The switching of TiO2 surface wettability could be repeated on the same surface with little hysteresis in water contact angle values. The mechanism behind the hydrophilic and hydrophobic reversal in TiO2 surfaces is proposed to be due to UV light mediated photocatalysis and physio- adsorption of N2 molecules respectively. The non-intrusive control of TiO2 surface wettability could be an attractive alternative to other wettability-based microfluidic valving strategies like electrowetting and photochromic wetting variation. The above results are discussed in terms of the potential use of the films in wettability based valving and repeated wettability patterning of TiO2 surfaces for open and sealed microfluidic systems.

Paper Details

Date Published: 11 January 2008
PDF: 11 pages
Proc. SPIE 6800, Device and Process Technologies for Microelectronics, MEMS, Photonics, and Nanotechnology IV, 680004 (11 January 2008); doi: 10.1117/12.759438
Show Author Affiliations
A. G. G. Toh, Singapore Institute of Manufacturing Technology (Singapore)
M. G. Nolan, Singapore Institute of Manufacturing Technology (Singapore)
R. Cai, Singapore Institute of Manufacturing Technology (Singapore)
D. L. Butler, Singapore Institute of Manufacturing Technology (Singapore)
Nanyang Technological Univ. (Singapore)


Published in SPIE Proceedings Vol. 6800:
Device and Process Technologies for Microelectronics, MEMS, Photonics, and Nanotechnology IV
Hark Hoe Tan; Jung-Chih Chiao; Lorenzo Faraone; Chennupati Jagadish; Jim Williams; Alan R. Wilson, Editor(s)

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