The interaction of water droplets with hydrophobic or rough, superhydrophobic solid surfaces has been studied. Such surfaces may be found in the natural world and their potential applications range from waterproof and self-cleaning surfaces to droplet microfluidics. A measure of hydrophobicity is obtained from the angle between the liquid and solid surface measured from the solid through the liquid, known as the contact angle. Variations in this angle can indicate not only a level of ‘wetting’ of the surface but also small amounts of droplet movement and may be achieved by electrowetting, the application of a voltage between a liquid droplet and a substrate, and/or by varying the local topography of the surface. Photolithography and thin-film deposition fabrication techniques have been used to create hydrophobic and superhydrophobic surfaces for use in electrowetting experiments. Both AC and DC electrowetting behaviour has been investigated and the results have been shown to be in agreement with past work and well established theory. Liquid marbles have been investigated as water drops displaying extreme non-wetting behaviour, with conformal coatings forming textures similar to those formed by the topography of a super-hydrophobic surface. It has been demonstrated that for such marbles both AC and DC reversible electrowetting may be achieved and shape oscillations may be observed having nodal patterns of these oscillations which are due to stationary capillary surface waves which are accurately described by theory. Electrostatic actuation of controllable, bi-directional motion of liquid marbles has also been demonstrated on a patterned electrode structure with and without an insulating layer. Electrodeposited rough copper surfaces were created with a surface topography gradient to control the directional movement of water drops and collect them with a view to applications in large scale water harvesting. The effects of surface roughness on the sensor response to liquid loading of a Quartz Crystal Microbalance (QCM) has also been investigated using three different surface coating materials. Liquid penetration between surface features differed between the materials and those upon which the liquid penetrated exhibited a characteristic low slip length or trapped mass type effect whereas those upon which it did not exhibited a slip length introduced by the air layer between the liquid and the crystal.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:629135 |
| Date | January 2009 |
| Creators | Elliott, S. J. |
| Publisher | Nottingham Trent University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://irep.ntu.ac.uk/id/eprint/63/ |
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