Amplified and Localized Photoswitching of TiO2 by Micro- and Nanostructuring

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Amplified and Localized Photoswitching of TiO2 by Micro- and Nanostructuring. / Hoshian, Sasha; Jokinen, Ville; Hjort, Klas; Ras, Robin H. A.; Franssila, Sami.

In: ACS Applied Materials and Interfaces, Vol. 7, No. 28, 22.07.2015, p. 15593-15599.

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@article{a03d9b6d255d44d5a43512b91c90e439,
title = "Amplified and Localized Photoswitching of TiO2 by Micro- and Nanostructuring",
abstract = "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.",
keywords = "superhydrophobic, overhang structures, wetting transition, microwriting, atomic layer deposition, ATOMIC LAYER DEPOSITION, SELF-CLEANING PROPERTIES, TUNABLE WATER ADHESION, REVERSIBLE WETTABILITY, SUPERHYDROPHOBIC SURFACES, POLYMER SURFACES, NANOROD FILMS, THIN-FILMS, CONVERSION, COATINGS",
author = "Sasha Hoshian and Ville Jokinen and Klas Hjort and Ras, {Robin H. A.} and Sami Franssila",
year = "2015",
month = "7",
day = "22",
doi = "10.1021/acsami.5b04309",
language = "English",
volume = "7",
pages = "15593--15599",
journal = "ACS Applied Materials and Interfaces",
issn = "1944-8244",
publisher = "AMERICAN CHEMICAL SOCIETY",
number = "28",

}

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TY - JOUR

T1 - Amplified and Localized Photoswitching of TiO2 by Micro- and Nanostructuring

AU - Hoshian, Sasha

AU - Jokinen, Ville

AU - Hjort, Klas

AU - Ras, Robin H. A.

AU - Franssila, Sami

PY - 2015/7/22

Y1 - 2015/7/22

N2 - 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.

AB - 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.

KW - superhydrophobic

KW - overhang structures

KW - wetting transition

KW - microwriting

KW - atomic layer deposition

KW - ATOMIC LAYER DEPOSITION

KW - SELF-CLEANING PROPERTIES

KW - TUNABLE WATER ADHESION

KW - REVERSIBLE WETTABILITY

KW - SUPERHYDROPHOBIC SURFACES

KW - POLYMER SURFACES

KW - NANOROD FILMS

KW - THIN-FILMS

KW - CONVERSION

KW - COATINGS

U2 - 10.1021/acsami.5b04309

DO - 10.1021/acsami.5b04309

M3 - Article

VL - 7

SP - 15593

EP - 15599

JO - ACS Applied Materials and Interfaces

JF - ACS Applied Materials and Interfaces

SN - 1944-8244

IS - 28

ER -

ID: 1468014