Twisted Polymer Fiber Actuators With Thermal Coiling for Fast Stroke
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Solution Overview
Problem
Existing artificial muscles, particularly those based on carbon nanotubes, face limitations such as slow response, low stroke or force generation, short cycle life, hysteresis, need for electrolytes, and narrow temperature range of operation, making them unsuitable for advanced applications like prosthetics and humanoid robots.
Innovation Solution
Twist-spun nanofiber yarns and twisted polymer fibers that utilize a guest material for actuation, eliminating the need for electrolytes and enabling high-stroke, high-rate torsional and tensile actuation powered by electricity, photons, or chemicals, with complex coiled geometries to enhance performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If carbon nanotube actuators are used, then stress generation is enhanced, but response speed becomes slow
Solution Approach 1:
The patent changes the actuation mechanism from electrochemical to thermal by heating the carbon nanotube yarn, which fundamentally alters the response characteristics. Thermal actuation through Joule heating provides faster response compared to electrochemical processes while maintaining high stress generation capability through the inherent mechanical properties of carbon nanotubes
Solution Approach 2:
The patent replaces the electrochemical actuation system with a thermal-mechanical system. Instead of using electrolytes and electrochemical reactions, the system uses Joule heating to thermally expand the carbon nanotube yarn, converting electrical energy directly to thermal energy and then to mechanical work, thereby eliminating the slow electrochemical response
2Ease of operation
If electrolytes are used in actuators, then actuation is enabled, but device complexity and maintenance requirements increase
Solution Approach 1:
The patent extracts and removes the electrolyte component from the actuator system entirely. By using carbon nanotube yarn that can be directly heated through Joule heating, the system eliminates the need for electrolytes, electrodes, and associated containment structures, thereby simplifying the device architecture and reducing maintenance requirements
Solution Approach 2:
The carbon nanotube yarn serves multiple functions simultaneously: it acts as both the structural element and the heating element. The yarn's inherent electrical conductivity allows it to generate heat directly when current is applied, eliminating the need for separate heating systems or electrolyte-based actuation mechanisms
3Ease of operation
If conventional actuators are used, then operation is possible, but operating temperature range is limited
Solution Approach 1:
The patent uses carbon nanotube yarn as a composite material that combines electrical conductivity, mechanical strength, and thermal stability. This composite structure enables the actuator to operate across extreme temperature ranges from cryogenic to high-temperature environments, far exceeding the capabilities of conventional actuator materials
4Length of moving object
If actuator stroke is increased, then displacement capability is improved, but cycle life becomes shorter
Solution Approach 1:
The patent employs a dynamic coiled geometry that can reversibly expand and contract through thermal actuation. The coiled structure allows for large stroke during expansion while maintaining structural integrity during contraction, enabling millions of reversible cycles without degradation. The dynamic nature of the coiled geometry accommodates large displacements without creating stress concentrations that would limit cycle life
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
These actuators achieve over two million reversible cycles, generate high torque and power density, and operate at extreme temperatures, surpassing natural muscle performance in terms of power-to-weight ratio and cycle life, suitable for advanced applications like torsional motors and sensors.
Implementation Method 1
electrothermally heated to incandescent temperatures
Implementation Method 2
Large stroke pneumatic nanotube actuators have been demonstrated that use electrochemical gas generation within nanotube sheets
Data Source
AI summary
Actuators (artificial muscles) comprising twisted polymer fibers generate actuation when powered thermally. In some embodiments, the thermally-powered polymer fiber actuator can be incorporated into an article, such as a textile or garment.