Coiled Thermoplastic Actuator Fiber for Wearable Flexibility
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Solution Overview
Problem
Existing polymer actuator materials face challenges in flexibility and integration into fiber products like clothes, with issues such as hard springs and poor flexibility, limiting their practical application.
Innovation Solution
An actuator fiber with a coil spring shape made of thermoplastic resin, featuring a spring index of 1.7 or more, glass transition temperature of 150°C or lower, crystallinity between 5% to 95%, and birefringence between 1.0 × 10^-3 to 5.0 × 10^-1, utilizing thermoplastic resins like nylon 6,10, nylon 6,12, and nylon 10,10 for enhanced flexibility and integration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the average diameter of the coil is smaller than the fiber diameter (creating a hard spring), then the actuator achieves high variation rate, but flexibility is poor and it cannot be easily incorporated into fiber products like clothes
Solution Approach 1:
The patent applies parameter changes by optimizing the spring index (D/d) to be within 0.5 to 2.0, where D is the average diameter of the coil and d is the fiber diameter. This parameter optimization transforms the actuator from a hard spring configuration to a flexible spring configuration, enabling it to be incorporated into fiber products while maintaining high variation rate for actuation performance
2Weight of moving object
If polymer actuator materials are used to reduce size and weight, then the actuator becomes more compact, but displacement or force generated is small and electrolytic solution supply tanks are required which restrict further size reduction
Solution Approach 1:
The patent extracts and eliminates the electrolytic solution supply tank from the actuator system by using a shape memory alloy material that generates actuation force through thermal expansion and contraction alone. This extraction removes the harmful factor (electrolytic solution tank) that restricted size reduction, enabling compact actuator design while maintaining sufficient generated force
Solution Approach 2:
The patent employs composite material strategy by using shape memory alloy material that combines metallic properties with shape memory functionality. This material can generate significant displacement and force through phase transformation during heating and cooling cycles, overcoming the limitation of polymer materials that produce small force
3Volume of moving object
If the actuator is miniaturized to reduce load on the person wearing it, then size and weight are reduced, but making it more precise and smaller meets a limit only by extension in the related art
Solution Approach 1:
The patent applies parameter changes by utilizing the phase transformation temperature characteristics of shape memory alloy material. By controlling the heating and cooling cycles to match the phase transformation points, the actuator achieves reliable and precise actuation at miniaturized dimensions, overcoming the limitations of conventional actuator scaling
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
The actuator fiber achieves flexible expansion and contraction motions suitable for fiber products, maintaining wearability and stability, with improved flexibility and reduced oppressive feeling.
Implementation Method 1
a glass transition point measured by a differential scanning calorimeter is 150°C or lower
Implementation Method 2
an actuator fiber having a coil spring shape capable of expanding and contracting by heating and cooling
Data Source
Figure 1~2
Figure 3~4
AI summary
The present invention provides a fiber for flexible actuators that reversibly stretches and contracts by means of heating and cooling as a soft actuator. The fiber for actuators according to the present invention includes a thermoplastic resin, has a coil-spring shape, and has a spring index D/d of at least 1.7 where D is the average diameter of a coil part and d is the diameter of the fiber.