Acoustic levitation of water droplets in an environmentally controlled chamber

Lead Research Organisation: University of Bristol
Department Name: Physics


This project involves building an acoustic levitator suitable for levitating
microlitre or smaller water droplets in an environmentally controlled chamber.
The benefit of having the levitator is to prevent any interactions the droplets
would have with any substrate they were sitting on. The droplets will be
cooled at a controlled rate, with measurements being made on the freezing
temperatures of water droplets with different types of ice nucleating particles,
as well as different salt concentrations. Tasks involve building a suitable
environmentally controlled chamber which can cool the droplets without
inducing air currents and therefore oscillations, as well as developing a
method to introduce droplets and detect when they have frozen. As the
droplets get smaller evaporation will also have to be taken into account, and
the humidity will have to be controlled to ensure the droplets last long
enough to freeze.


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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/N509619/1 01/10/2016 30/09/2021
1792936 Studentship EP/N509619/1 01/10/2016 30/04/2020 Fredrick Cook
Description The majority of this work involved the design and building of apparatus for ice nucleation experiments. These were as follows:
1. A pyroelectric thermal sensor the the automatic detection of phase changes. A pyroelectric material produces a change in voltage across it when it changes temperature. By freezing droplets of water on a thin pyroelectric foil the latent heat released by the freezing droplets produces a measurable change in voltage across the foil, and the temperature at which the droplet froze to be recorded.
2. Automated lag-time apparatus. This repeatedly freezes/thaws a sample between two set temperatures, allowing freezing statistics to be built up with minimal interference from the operator. The statistics tell us about the freezing effectiveness of whatever is in the sample.
3. Levitated lag-time apparatus. This is similar to the above, but instead of holding the sample in a glass vial droplets are acoustically levitated in an environmental chamber. By levitating the sample we avoid the interference of the sample holder, which will change the temperature at which droplets freeze.
Exploitation Route I hope that all of the pieces of equipment developed will be useful for future experiments.
Sectors Environment