Amplified and Localized Photoswitching of TiO2 by Micro- and Nanostructuring
2015 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 7, no 28, 15593-15599 p.Article in journal (Refereed) Published
Fast photoswitching of wetting properties is important for the development of micro/nanofluidic systems and lab-on-a-chip devices. Here, we show how structuring the surface amplifies photoswitching properties. Atomic layer-deposited titanium dioxide (TiO2) has phototunable hydrophilic properties due to its surface chemistry, but microscale overhang pillars and additional nanoscale topography can override the chemistry and make the surface sup erhydrophobic. Three switching processes are achieved simply by controlling the UV exposure time: from (1) rolling superhydrophobic to sticky superhydrophobic (Cassie-Baxter to Wenzel), (2) sup erhydrophobic to hydrophilic, and (3) superhydrophobic to superhydrophilic after 1, 5, and 10 min of UV exposure, respectively. We report the fastest reversible switching to date: 1 min of UV exposure is enough to promote a rolling-to-sticky transition, and mild heating (30 min at 60 degrees C) is sufficient for recovery. This performance is caused by a combination of the photoswitching properties of TiO2, the micropillar overhang geometry, and surface nanostructuring. We demonstrate that the switching also can be performed locally by introducing microwriting under a water droplet.
Place, publisher, year, edition, pages
2015. Vol. 7, no 28, 15593-15599 p.
superhydrophobic, overhang structures, wetting transition, microwriting, atomic layer deposition
Materials Engineering Computer Engineering
IdentifiersURN: urn:nbn:se:uu:diva-260855DOI: 10.1021/acsami.5b04309ISI: 000358558300055PubMedID: 26115550OAI: oai:DiVA.org:uu-260855DiVA: diva2:848820
Funding: Academy of Finland (PROWET project nos. 263538, 263560, and 266820)2015-08-262015-08-252015-08-26Bibliographically approved