In nature, movement is a feature commonly associated with intelligent behavior. Memory is another such feature. Though polymers are known to exhibit these functions separately, they have not been so far incorporated in the same material. Such multi-functionality in a material promises applications such as adaptive building facades with autonomous regulation of temperature without electronics, interactive surfaces, and even powering mini-robots.
We have demonstrated the realization of electro-mechanical memory (EMM) – a type of actuator material that incorporates memory and motion control in the material itself. Thus its actuation can be manipulated, stored, read, and restored independently.
The first material used for the demonstration is based on Nafion, commonly used in battery and fuel cell separators. It can be used to program shapes at multiple temperatures, which could later be recovered one by one on demand. In this work the researchers programmed not only the shapes but also 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. We also analyzed the dependence of the electrical actuation on the amount of mechanical programming, and the mechanism behind the behavior.
The conceptual combination of separate functions in the same material has led to synthetic efforts in the Active and Intelligent Materials (AIM) lab, where separate material functionalities can be confined to nanoscale structure morphologies. We are working on demonstrating other complementary functionalities as well. One of the synergistic results from this combination has been a two-way linear shape-memory actuation, in addition to the ionic actuation.