Department of Materials Science & Metallurgy: Research paper of the month

Department of Materials Science & Metallurgy

Research paper of the month

September 2014 - Artificial Muscles with Muscle Memory

In nature, movement is a feature commonly associated with intelligent behavior. Memory is another such feature. Although polymers are known to exhibit each of these functions separately, they have not so far been incorporated in the same material. Researchers at the Department of Materials Science and Metallurgy at the University of Cambridge have produced, for the first time, a polymeric electro-mechanical memory (EMM) - a type of actuator material that incorporates memory and motion control in the same material. Thus its actuation can be manipulated, stored, read, and restored independently. The conceptual separation has led to synthetic efforts in the Active and Intelligent Materials (AIM) lab, where separate material functionalities can be confined to nanoscale structure morphologies. Researchers are working on demonstrating other complementary functionalities as well.

The first material used for the demonstration is based on Nafion®, a membrane separator commonly used in batteries and fuel cells. It can be used to programme shapes at multiple temperatures, which can later be recovered one-by-one, on demand. In this work, the researchers programmed not only different shapes but also various actuation responses, which could be tuned or completely switched off. The shape transformations are reversible, and upon recall, the EMM’s programmed function and actuation amplitude are recovered. The restored states can be cycled thousands of times using low voltage inputs. The researchers also analysed the dependence of the electrical actuation on the amount of mechanical programming, and the mechanism underlying the behaviour.

Figure: Illustration of the electro mechanical memory effect – programming and recovery of both shape and actuation modes.

Khaldi, A., Elliott, J. A., Smoukov, S. K., "Electro-mechanical actuator with muscle memory", J. Mater. Chem. C, (2014)

doi: 10.1039/c4tc00904e