Natural muscles show tensile actuation and realize torsional rotation by combining with the skeleton, which integrate with sensing and signaling function in a single element to form a feedback loop. The currently developed artificial muscle and sensing devices always work upon external stimuli, and a separate controlling and signal transmission system is needed, increasing the complexity of muscle design. Therefore it is highly desired to develop flexible and compact fiber artificial muscles with large strain for advanced soft robotic systems. In this paper, twisted elastomer fiber artificial muscles with tensile and torsional actuations and sensing function by a single electric signal are developed, by using twisted natural rubber fiber coated with a buckled carbon nanotube sheet. The twisted natural rubber fiber can be electrothermally actuated to show contraction and rotation by entropic elasticity. The buckled carbon nanotube sheet can transmit electric current, and the contact area between the buckled carbon nanotube sheets increased during actuation, resulting in resistance decrease by thermo-piezoresistive effect. A feedback circuit was designed to connect or disconnect the electric current by measuring the resistance change to form a feedback loop to control on/off of the muscle. The current study provides a new muscle design for soft robotics, controllers, and human-machine integration.
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Sheath-run artificial muscles
Although guest-filled carbon nanotube yarns provide record performance as torsional and tensile artificial muscles, they are expensive, and only part of the muscle effectively contributes to actuation.We describe a muscle type that provides higher performance, in which the guest that drives actuation is a sheath on a twisted or coiled core that can be an inexpensive yarn. This change from guest-filled to sheath-run artificial muscles increases the maximum work capacity by factors of 1.70 to 2.15 for tensile muscles driven electrothermally or by vapor absorption. A sheath-run electrochemical muscle generates 1.98 watts per gram of average contractile power—40 times that for human muscle and 9.0 times that of the highest power alternative electrochemical muscle.Theory predicts the observed performance advantages of sheath-run muscles.
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- NSF-PAR ID:
- 10111517
- Date Published:
- Journal Name:
- Science
- Volume:
- 365
- Issue:
- 6449
- ISSN:
- 0853-1218
- Page Range / eLocation ID:
- 150-155
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1126/science.aaw2403
