Unlocking the Potential of Carbon Nanotube Artificial Muscles

Artificial nanotube muscles accelerate the pace

A new conductive polymer coat allows an electrochemically powered, twisted carbon nanotube artificial muscle to contract more quickly when it is driven faster. The device was developed by Ray Baughman of University of Texas at Dallas and an international team. It overcomes many of the limitations of artificial muscles and could be used in robotics, intelligent textiles, and heart pumps.

Carbon nanotubes are carbon sheets that have walls as thin and as long as an atom. When CNTs are twisted into a yarn, and then placed in an electrodelyte, they expand and contract as a muscle in response to electrochemical inputs. A potential difference between a yarn and an electrolyte drives ions into the yarn. This causes the muscle to contract.

These CNT muscles, while extremely powerful and energy efficient – capable of lifting loads 100,000 times their weight – do have some limitations. They are bipolar. This means that their direction of movement changes when the potential falls to zero. The stroke of the actuator is reduced. The muscle’s capacity decreases when it is subjected to rapid changes in potential, which can also cause the stroke of the actuator to be reduced.