Scientists have created thin, elastic bottlebrush polymer films that can function as artificial muscles at significantly lower voltages than currently available materials, potentially enabling their use in safer medical devices and artificial organs.

Whether wriggling your toes or lifting groceries, muscles in your body smoothly expand and contract. Some polymers can do the same thing — acting like artificial muscles — but only when stimulated by dangerously high voltages. Now, researchers in ACS Applied Materials & Interfaces report a series of thin, elastic films that respond to substantially lower electrical charges. The materials represent a step toward artificial muscles that could someday operate safely in medical devices.

Artificial muscles could become key components of movable soft robotic implants and functional artificial organs. Electroactive elastomers, such as bottlebrush polymers, are attractive materials for this purpose because they start soft but stiffen when stretched. And they can change shape when electrically charged. However, currently available bottlebrush polymer films only move at voltages over 4,000 V, which exceeds the 50 V maximum that the U.S. Occupational Safety & Health Administration states is safe. Reducing the thickness of these films to less than 100 µm could lower the required voltages, but this hasn’t been done successfully yet for bottlebrush polymers. So, Dorina Opris and colleagues wanted to find a simple way to produce thinner films.