Researchers are developing a safer “artificial muscle” material that can mimic the smooth expansion and contraction of human muscles. Currently, some polymers can act as artificial muscles but only respond to dangerously high voltages.

A breakthrough has been reported by scientists in ACS Applied Materials & Interfaces, who have developed a range of thin, flexible films that react to much lower electrical charges than previously possible. This innovation marks a significant stride towards creating artificial muscles that could operate safely in medical devices in the future.

In the realm of movable soft robotic implants and functional artificial organs, artificial muscles are set to become a crucial component. Electroactive elastomers, specifically bottlebrush polymers, are highly desirable materials for this application due to their unique property of being soft initially but stiffening when stretched.

Furthermore, these polymers can alter their shape in response to electrical charge. Nonetheless, the currently available bottlebrush polymer films require voltages exceeding 4,000 V to move, which goes beyond the maximum safe level of 50 V recommended by the U.S. Occupational Safety & Health Administration.

Lowering the thickness of these films to under 100 µm is a potential solution to reduce the required voltages. However, achieving this with bottlebrush polymers has not yet been successful. In light of this, Dorina Opris and her team aimed to devise a straightforward approach to producing thinner films.

To accomplish this, the researchers created a range of bottlebrush polymers by reacting norbornene-grafted polydimethylsiloxane macromonomers and then cross-linking the resultant products using ultraviolet light.

Among the various thicknesses tested, the most electroactive material was found to be 60 µm thick. It exhibited greater expansion than the previously reported elastomers and operated with a voltage of 1,000 V. A circular actuator composed of this material also demonstrated remarkable performance, undergoing over 10,000 cycles of expansion and contraction before degrading.

In a separate series of experiments, they incorporated polar side chains into the polymers, resulting in materials that responded to voltages as low as 800 V. However, the expansion achieved by these materials was not as significant as that of the team’s most electroactive film.

The researchers concluded that, with some modifications, the material holds promise for the development of long-lasting implants and other medical devices that can operate using safer voltage levels.

Source: 10.1021/acsami.2c23026

Image Credit: shutterstock