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Thermally Triggered Transition of Superhydrophobic Characteristics of Micro and Nano Textured Multiscale Rough Surfaces Bichitra Nanda Sahoo, Kandasubramanian Balasubramanian, and Mahesh M Sucheendran J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/acs.jpcc.5b02917 • Publication Date (Web): 22 May 2015 Downloaded from http://pubs.acs.org on May 27, 2015
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The Journal of Physical Chemistry
Thermally Triggered Transition of Superhydrophobic Characteristics of Micro and Nano Textured Multiscale Rough Surfaces Bichitra Nanda Sahoo, a Kandasubramanian Balasubramanian, a* Mahesh Sucheendran b, a
Department of Materials Engineering, Defence Institute of Advanced Technology (DIAT),
Girinagar, Pune - 411025, India b
Department of Aerospace Engineering, Defence Institute of Advanced Technology (DIAT),
Girinagar, Pune - 411025, India
To whom correspondence should be addressed Email:
[email protected], Fax: +91 (020) 2438-9509; Tel: +91 (020) 2438-9680)
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The Journal of Physical Chemistry
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ABSTRACT: In this paper, superhydrophobicity of multiscale hierarchical structures and wettability transition phenomenon of a water droplet on the superhydrophobic surface at different substrate temperature are extensively studied. Spin coating and spray coating methods have been regulated to fabricate EPF (Expanded polystyrene foam)/candle soot and EPF/camphor soot particle composites films. Maximum water contact angle of 165° and roll off angle of 2° were obtained with spray coated EPF/camphor soot composites which demonstrates their superhydrophobicity. By the measurement of water contact angle at different substrate temperature, we have demonstrated the influence of heat energy and pressure developed by micro water droplets during spreading phase. The reduction in water repellence observed on the protrusion induced hierarchical nanostructure is explained by the balancing pressure induced by a droplet of volume 4 µL and work of adhesion. The droplet contact area of hierarchical surfaces was profoundly influenced by change in viscosity of water droplets with temperature. The best performing spray coated EPF/camphor soot particle composite film impressively maintained superhydrophobicity with critical pressure of 200 Pa. The resulting insights can be used to tailor wettability of composite films, control liquid flow patterns for engineering applications such as micro-fluidics and bio-sensing devices.
Keywords: Critical pressure; protrusion; impalement; superhydrophobicity; droplet
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The Journal of Physical Chemistry
I. INTRODUCTION The nature of droplets on various surfaces has been studied extensively for a wide range of industrial and biological applications. When a droplet of any type of fluid deposited on a solid surface demonstrates the Cassie state with an apparent contact angle more than 150° and a small roll-off angle (
