How do you flex an artificial muscle? Using liquid crystal elastomers

Materials World magazine
1 Mar 2014

The properties of liquid crystal elastomers (LCEs) have been improved by University of Cambridge researchers, based in the UK – a development that could broaden the application of these artificial muscle materials.

At present, LCE materials boast similar stress and strain ranges to biological muscle and have excellent fatigue resistance. However, LCE components are difficult to synthesise and their actuation temperature is high, which limits their use in environments where water is the temperature carrier. Maintaining consistent alignment during cross-linking is also an issue. By introducing co-monomer molecules to disrupt the order of molecules in a crystalline state, the UK-based team managed to lower the operating temperature from 80–120°C to 58°C. The team embedded LCE precursor droplets into the polymer matrix, which was then stretched at high temperature. By confining the LCE droplets in spaces less than 20μ wide, the researchers managed to maintain molecule alignment, which simplifies the synthesis procedure.

Lead researcher Stoyan Smoukov explains how the temperature-sensitive materials work. ‘You start with an ellipsoid. When you heat it up, it becomes very close to a sphere. When you cool it, it becomes an ellipsoid again.’

Smoukov says the artificial muscle technology could be used in microfluidics, sensors and temperature-sensitive valves.