Cavatappi artificial muscles from drawing, twisting, and coiling polymer tubes

Area of Science:

• Robotics and Biomimetic Engineering
• Materials Science and Engineering

Background:

• Development of compliant, efficient, and powerful actuation technologies is crucial for advanced robotic systems capable of human interaction and integration.
• Existing actuation methods often face limitations in bandwidth, efficiency, controllability, and practical implementation.

Purpose of the Study:

• To introduce a novel fluid-driven muscle-like actuator, termed 'cavatappi artificial muscles', fabricated from inexpensive polymer tubes.
• To demonstrate the actuation principles and performance capabilities of these artificial muscles.

Main Methods:

• Polymer tubes undergo drawing to enhance microstructural anisotropy, followed by twisting to create torsional actuators.
• Twisted tubes are helically coiled into linear actuators, which contract upon internal hydraulic or pneumatic pressure application.
• The localized untwisting of the helical microstructure under pressure leads to actuator contraction.

Main Results:

• Cavatappi artificial muscles achieve contractions exceeding 50% of their initial length.
• Mechanical contractile efficiencies approach 45%.
• Maximum specific work and power demonstrated are 0.38 kJ/kg and 1.42 kW/kg, respectively.

Conclusions:

• Cavatappi artificial muscles present a promising alternative to thermally activated systems, offering superior actuation bandwidth, efficiency, modeling, controllability, and practical implementation.
• The demonstrated performance metrics indicate significant potential for future advancements in soft robotics and human-robot interfaces.
• The use of inexpensive materials and simple fabrication processes makes this technology scalable and cost-effective.