Helically Wrapped Supercoiled Polymer (HW-SCP) Artificial Muscles: Design, Characterization, and Modeling

Tsabedze, Thulani; Mullen, Christopher; Coulter, Ryan; Wade, Scott A; Zhang, Jun

doi:10.1109/icra40945.2020.9197330

Cited by 8 publications

(7 citation statements)

References 26 publications

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“…As the polymer melt flows through the mandrel, the polymer chains within the melt align to the longitudinal direction of the helical flute of the mandrel. SMPs with anisotropic coefficients of thermal expansion benefit greatly from this polymer alignment and helical geometry, allowing for larger contraction strains and forces, as well as fewer muscles within an artificial muscle array to produce the desired muscle contractions [ 17 , 18 , 34 ].…”

Section: Resultsmentioning

confidence: 99%

“…Despite their advantages, exoskeletons using pneumatic artificial muscles require heavy pumps to drive the system and compressed air that could be better allocated for sustaining astronauts, making them costly for transport and resource inefficient for human space exploration. Shape memory alloy (SMA) [ 8 , 9 ] and shape memory polymer (SMP) [ 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ] based artificial muscles do not require heavy motors or pumps to actuate. Instead, shape memory materials use external stimuli, such as temperature, magnetic field, or pH level changes, to alter the shape and/or mechanical properties of a structure.…”

Section: Introductionmentioning

confidence: 99%

“…To form artificial muscles by twisting, nylon fibers are twisted at different tensions to form twisted fibers. Then, the twisted fiber is either coiled around other twisted fibers or a mandrel to generate supercoiled polymers (SCPs) [ 18 ]. Lastly, the fibers are temperature annealed to hold a desired helical shape.…”

Section: Introductionmentioning

confidence: 99%

“…Lastly, the fibers are temperature annealed to hold a desired helical shape. After fabrication, when heat is applied to twisted SMP artificial muscles through joule heating or convection, the fibers contract because of the material’s anisotropic thermal expansion and helical shape [ 17 , 18 ]; generating a pulling force. Like spinning, producing SMP artificial muscles through twisting requires highly trained operators for fabrication and multiple machines for twisting and annealing, which may occupy the limited room within a spacecraft.…”

Section: Introductionmentioning

confidence: 99%

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Material Extrusion of Helical Shape Memory Polymer Artificial Muscles for Human Space Exploration Apparatus

et al. 2022

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Astronauts suffer skeletal muscle atrophy in microgravity and/or zero-gravity environments. Artificial muscle-actuated exoskeletons can aid astronauts in physically strenuous situations to mitigate risk during spaceflight missions. Current artificial muscle fabrication methods are technically challenging to be performed during spaceflight. The objective of this research is to unveil the effects of critical operating conditions on artificial muscle formation and geometry in a newly developed helical fiber extrusion method. It is found that the fiber outer diameter decreases and pitch increases when the printhead temperature increases, inlet pressure increases, or cooling fan speed decreases. Similarly, fiber thickness increases when the cooling fan speed decreases or printhead temperature increases. Extrusion conditions also affect surface morphology and mechanical properties. Particularly, extrusion conditions leading to an increased polymer temperature during extrusion can result in lower surface roughness and increased tensile strength and elastic modulus. The shape memory properties of an extruded fiber are demonstrated in this study to validate the ability of the fiber from shape memory polymer to act as an artificial muscle. The effects of the operating conditions are summarized into a phase diagram for selecting suitable parameters for fabricating helical artificial muscles with controllable geometries and excellent performance in the future.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Material Extrusion of Helical Shape Memory Polymer Artificial Muscles for Human Space Exploration Apparatus

et al. 2022

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“…In the simulations, the molten SMP and the body of the printhead was set as PLA and 6061-T6 aluminum, respectively. The selection of suitable SMPs is of great significance in the proposed method because the materials must possess shape memory effects to achieve the desired linear actuation under prevalent stimuli, such as temperature change [22,23]. Herein, PLA, a widely used thermoplastic for biomedical devices, was selected as the exemplary SMP for validating the method for extruding artificial muscles in this study because of its thermal shape memory actuation properties, extrusion characteristics, and biocompatibility [32,[42][43][44].…”

Section: Printhead Design Using Numerical Simulationmentioning

confidence: 99%

Material Extrusion Advanced Manufacturing of Helical Artificial Muscles from Shape Memory Polymer

2022

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Rehabilitation and mobility assistance using robotic orthosis or exoskeletons have shown potential in aiding those with musculoskeletal disorders. Artificial muscles are the main component used to drive robotics and bio-assistive devices. However, current fabrication methods to produce artificial muscles are technically challenging and laborious for medical staff at clinics and hospitals. This study aims to investigate a printhead system for material extrusion of helical polymer artificial muscles. In the proposed system, an internal fluted mandrel within the printhead and a temperature control module were used simultaneously to solidify and stereotype polymer filaments prior to extrusion from the printhead with a helical shape. Numerical simulation was applied to determine the optimal printhead design, as well as analyze the coupling effects and sensitivity of the printhead geometries on artificial muscle fabrication. Based on the simulation analysis, the printhead system was designed, fabricated, and operated to extrude helical filaments using polylactic acid. The diameter, thickness, and pitch of the extruded filaments were compared to the corresponding geometries of the mandrel to validate the fabrication accuracy. Finally, a printed filament was programmed and actuated to test its functionality as a helical artificial muscle. The proposed printhead system not only allows for the stationary extrusion of helical artificial muscles but is also compatible with commercial 3D printers to freeform print helical artificial muscle groups in the future.

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Soft Wearable Rehabilitation Robots with Artificial Muscles based on Smart Materials: A Review

Gonzalez-Vazquez

Garcia

Kilby

et al. 2023

Advanced Intelligent Systems

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During the past decade, wearable devices such as exoskeletons have gained popularity [1] in different fields, such as the military, [2] industry, [3] and rehabilitation. [4] In the latter, rehabilitation exoskeletons are used to restore or maintain the functionality and mobility of people with physical disabilities. [5] These are receiving greater attention as the number of people with disabilities affecting physical performance will increase in the following decades as the population ages and individuals live longer with noncommunicable conditions (e.g., cerebral palsy, stroke, acquired brain injuries, and muscular dystrophies). [6][7][8] Most current exoskeletons use electric motors and rigid links to realize actuation and often have heavy and bulky designs that are difficult to safely wear outside clinical facilities. [9] Hence, researchers in this area are working to develop soft wearable rehabilitation robots (SWRRs), featuring soft actuators that are agreeable to the users as they have increased compliance, adaptability, comfort, safety, and less weight. [10][11][12] Currently, SWRR relies mainly upon two soft robotic technologies, cable-driven and fluidic actuators. For a cable-driven system, the wire is embedded into clothes or tubes and attached to an anchor point. The other side of the wire is connected to an electric motor to generate the desired movement and force by pulling the cable [13,14] (Figure 1a). Alternatively, in fluidic actuation (Hydraulic/Pneumatic), a pressurized fluid is inserted into a chamber made of highly deformable material to generate a displacement [11,15,16] (Figure 1b). However, these require large and heavy external pumps and valves to compress the fluid. [17] Unfortunately, cable-driven and fluidic actuation need cumbersome components (e.g., electric motors, pumps, and valves) to work, compromising the portability of the systems when used in daily life. [18] Therefore, in recent years, research has been committed to developing new actuator technologies that can overcome the drawbacks of the current actuators used in SWRR. These technologies include artificial muscles based on smart materials (AMSMs). AMSMs are soft actuators composed primarily of material with a low Young's modulus similar to that of soft biological materials (10 ^4-10 ^9 Pa) that can sense and directly convert physical stimulus (e.g., light, electrical, heat) into physical displacement. [19][20][21][22][23] Some examples of smart materials are shape-memory alloy (SMA), [24] dielectric elastomer actuators (DEAs), [25] ionic polymer-metal composites (IPMC), [26] shapememory polymers (SMPs), [27] and twisted and coiled polymer actuators (TCPs). [28] Due to their inherent properties and manufacturing processes, AMSM can be fabricated in various shapes, allowing them to be embedded into flexible and deformable wearable devices. [29][30][31][32] Furthermore, it is possible to fabricate robots with a relatively small weight and volume as they present a power density comparable to the skeletal muscles. [33] Neverthe...

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Helically Wrapped Supercoiled Polymer (HW-SCP) Artificial Muscles: Design, Characterization, and Modeling

Cited by 8 publications

References 26 publications

Material Extrusion of Helical Shape Memory Polymer Artificial Muscles for Human Space Exploration Apparatus

Material Extrusion of Helical Shape Memory Polymer Artificial Muscles for Human Space Exploration Apparatus

Material Extrusion Advanced Manufacturing of Helical Artificial Muscles from Shape Memory Polymer

Soft Wearable Rehabilitation Robots with Artificial Muscles based on Smart Materials: A Review

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