Flex Your Artificial Muscles: The New Low-Voltage Breakthrough

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Researchers have developed a series of thin, elastic films made from bottlebrush polymers that can act as artificial muscles, as reported in ACS Applied Materials & Interfaces. These materials can potentially be used in soft robotic implants and artificial organs. Unlike current bottlebrush polymer films that require dangerously high voltages above 4,000 V, these new films respond to substantially lower electrical charges, as low as 800 V. By synthesizing these polymers with polar side chains and producing thinner films, the researchers believe that the materials can be further improved to develop durable medical devices operating at safer voltages.

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.

The researchers synthesized a suite of bottlebrush polymers by reacting norbornene-grafted polydimethylsiloxane macromonomers and cross-linking the products by ultraviolet light. A 60-µm-thick material was the most electroactive, expanding more than previously reported elastomers, with an operating voltage of 1,000 V. And a circular actuator made out of that material expanded and contracted more than 10,000 times before degrading.

In another set of experiments, the researchers introduced polar side chains to the polymers and produced materials that responded to voltages as low as 800 V. However, they didn’t expand as much as the team’s most electroactive film.

Based on the results, the researchers say that, with some tweaks, the material could someday be used to develop durable implants and other medical devices that work at safer voltages.

Reference: “On-Demand Cross-Linkable Bottlebrush Polymers for Voltage-Driven Artificial Muscles” 12 April 2023, ACS Applied Materials & Interfaces.
DOI: 10.1021/acsami.2c23026

The authors acknowledge funding from the European Research Council under the European Union’s Horizon 2020 research and innovation program, the Swiss National Science Foundation, the Swiss Federal Laboratories for Materials Science and Technology and the China Scholarship Council.

1 Comment on "Flex Your Artificial Muscles: The New Low-Voltage Breakthrough"

  1. Desmond obanor | April 12, 2023 at 1:24 pm | Reply

    This bottle brush polymers will be a great use in the medical aspect as stated, and due to the fact that it works in a lower voltage(800v) makes it safe to be implanted

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