Abstract:

Controlling and positioning droplets in contact with one or more surfaces has uses in a wide variety of applications such as microfluidics, inkjet printing, and heat exchangers. In this work, we show experiments on the various methods for the control and manipulation of droplets in contact with lubricant impregnated surfaces. We show that simple macro structures on a surface can interact with the characteristic wetting ridge of a droplet through an effect similar to the Cheerios effect We show that a v shaped channel created from these simple features can be used to position a droplet and that the droplet has both a local and a global equilibrium position. We show that confined droplets move when the solid boundaries of a confining wedge geometry are reconfigured. We show droplet propulsion using a dual length scale roughness and wettability gradient in a slippery surface. This surface has high mobility is due to a conformal “liquid surface” created using a nano-scale roughness imbibed with oil which prevents contact with the solid surface. We also show that it is also possible to change preferred direction of motion by further imbibing to surface with yet more liquid

Bio:

Gary Wells is a Senior Lecturer in Surfaces and Wetting and member of the Institute for Multiscale Thermofluids at the University of Edinburgh. He did his undergraduate degree in Physics and his PHD entitled “Voltage Programmable Liquid Optical Interfaces” at Nottingham Trent University. He worked as a devices and Materials researcher at the Hewlett Packard displays laboratory and later became an associate professor at Northumbria University before taking up his current post at Edinburgh. His research interests are low contact angle hysteresis surfaces, Slippery Liquid Infused Porous Surfaces (SLIPS), Passive droplet actuation on Gradient SLIPS surfaces and active actuation using Electro-wetting, Dielectrophoresis and dielectrowetting.

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