Helen Gleeson (University of Leeds): New metamaterials from soft matter physics

Liquid crystals are a type of soft matter perhaps best known for their use in displays (LCDs) and much of the research in the area over the past 30 years or so has been focused on achieving faster switching and more complex images in flat panel TVs. However, such technology is now mature and for some time now new, exciting properties of liquid crystals that might lead to rather futuristic applications have been emerging.

This talk concentrates on the physics of liquid crystal elastomers. These materials are rubbers formed from liquid crystal units that have remarkable properties because of the interaction of the polymer network with the ordered liquid crystal units. Suggested applications include artificial irises, self-cleaning surfaces for solar panels and artificial muscles. Thin films of these materials have been shown to lift many times their own weight. We recently discovered that some liquid crystal elastomers are metamaterials – they exhibit auxetic behaviour whereby the material gets thicker when stretched rather than thinner. The talk will describe the physics behind these metamaterials including how and why the molecular rearrangement that occurs on stretching causes the materials to expand in one direction. There are many exciting uses that have been suggested for auxetic materials and the talk will consider possible applications.