|M.Sc Student||Horesh Amihai|
|Subject||Manipulation of Multiphase Systems under MHz Acoustics|
|Department||Department of Chemical Engineering||Supervisor||Professor Ofer Manor|
|Full Thesis text|
Manipulation of liquids over solids has an important role in both industry and science. The phenomenon, also known as acoustic streaming, has been studied since the end of the 19th century. Despite great progress and discoveries that have been made over the years, still it is not fully understood.
It was recently found that thin films of oil and water can be significantly manipulated by imposing MHz frequency vibration in the solid substrate in the form of surface acoustic waves (SAWs). This manipulation has a strong relation to the contact angle be- tween the liquid and the substrate and the thickness of the films. However, all of the previous work in the field were done in cases when the film is much larger than the wavelength of the SAWs, (h >> λ),
This work presents an initial study on the interaction between Rayleigh SAW, propagating in the solid substrate of a microfluidic chamber, and a film of silicon oil, confined between a quiescent bubble and the solid substrate of the channel. Theoretical and experimental analysis indicates that the thickness of the film is about or smaller than the viscous penetration length, (h < λ), which is at order of magnitude of 1 µm. Light microscopy techniques were used in order to capture the dynamic variations in the film geometry by capturing the interference of a monochromatic light on the air-oil interface, (i.e. light fringes). By converting the light fringes to dynamic and spatial variations in the film thickness we investigate the mechanisms by which MHz SAWs interact with thin films and interfaces and show that further employing a basic theoretical analysis we may infer the physical properties of the liquid.