Cooling is essential for
perishable food, medicine, buildings and electronics. Current cooling
technologies exploit large thermal changes that occur in fluids when
driving liquid to gas phase transitions with pressure. However, these
vapour-compression technologies are harmful to the environment and
display low energy efficiencies. By contrast, cooling based on pressure
driven thermal changes in solids, i.e. barocaloric effects, promise
novel environmentally friendly cooling technologies with high energy
efficiencies close to the thermodynamic maximum limit. While several
major breakthroughs have been recently reported, solid barocaloric
materials are still in their infancy, and their thermal response is
still far from the performance of fluids, because they all operate at
solid-solid phase transitions with limited pressure-induced changes in
entropy.
The aim of the proposed project is to experimentally study
barocaloric effects in liquid crystals (LCs). LCs have properties
between those of conventional liquids and those of solid crystals, and
are widely used in displays. For instance, a LC may flow like a liquid,
but its molecules may be oriented in a crystal-like way.
Thus
far, these materials have been widely ignored by the research community
working on caloric materials, despite LCs exhibiting the key
ingredients required to achieve an outstanding barocaloric response:
they show:
extremely large (colossal) thermally driven changes in entropy;
very small thermal hysteresis; and
extremely large shifts of their transition temperatures with
pressure, which when combined all together in the same material promise
pressure-driven thermal changes similar to those observed in fluids.
This research will develop a new framework to design and optimise LCs
with colossal barocaloric properties that outperform those observed in
state-of-the-art barocaloric materials. These findings will be the
foundation for a new cooling technology that is environmentally
friendly, energy efficient and affordable.
