|M.Sc Student||Haber Elad|
|Department||Department of Mechanical Engineering||Supervisor||Professor Tal Carmon|
|Full Thesis text|
A liquid phase boundary, such as the one in a cup of water, might look like the flattest interface in nature. Nevertheless, this interface actually looks like a stormy sea if monitored with an angstrom-scale resolution. These spontaneous water waves are the result of thermal (Brownian) fluctuation of the liquid-air interface, and are inherent to any liquid interface. Unique to the liquid phase, and in contrast with solids, the restoring force for such capillary waves is by interfacial tension. Interfacial tension is a force applied by a single-molecule layer at the liquid-phase boundary where cohesive forces between nearby molecules apply net force that minimizes gas-liquid interface to be flat the cup of water example.
Here we design, fabricate and activate a device that experimentally detects capillary waves. Thermal fluctuations of liquid-phase boundaries are significant in surface science, and in particular in coalescence and fission of droplets.
Our capillary-waves detector is based on a Fabry-Perot resonator where one reflector is the total internal reflection from a liquid-phase boundary. Our system goes in and out of resonance according to the small changes in the liquid level due to the capillary waves.
These changes are optically detected, which might pave the way to filming thermal fluctuations in the future.