Stretchable artificial muscles from coiled polymer fibers

Spinks, Geoffrey M.

doi:10.1557/jmr.2016.316

Cited by 29 publications

(21 citation statements)

References 30 publications

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“…Heating the twist‐oriented polymer fibers induces a partial untwisting due to their anisotropic thermal volume expansion . When formed into coils, this fiber untwist causes length changes in the coil and similar behavior has been observed in twisted and coiled carbon nanotube yarns and by using chemical or electrochemical stimuli to generate the volume changes. The relationship between fiber twist and fiber volume has been successfully modeled based on the geometry of a single helix .…”

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confidence: 67%

“…Several wet/dry cycles were performed to assess the reversibility of the actuation and each sample was also subjected to a load/unload sequence in both the wet and dry states to determine the respective stiffnesses. Changing material stiffness is known to affect the actuation stroke so the measured actuation stroke (Δ L A ) was converted to the free stroke (Δ L 0 ) using Equation

Δ L_{0} = F_{normalA} (\frac{1}{k_{A}} - \frac{1}{k'_{A}}) + Δ L_{normalA}

where F A is the applied constant tensile load, and k A and k ′ A are the sample stiffnesses in the dry and wet states, respectively. The stiffness values are reported in Table S1 (Supporting Information) and show a decrease in stiffness when the samples were hydrated of up to 30%.…”

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confidence: 99%

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Double Helix Actuators

Shepherd

Spinks

2018

Adv Materials Technologies

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Tensile actuators that reversibly generate large length change strokes are of great interest in many biomedical and robotic applications. Guest–host composite materials comprising volume change guests with multi‐filament yarn hosts can be exploited as large stroke tensile actuators when the fiber host is formed into helices. Here, a new type of double helix actuator is introduced by plying two yarns together. The helical geometry suggests large length contractions are possible when the ply angle approaches the limit of 45° and when the yarn swells predominantly in the diameter direction as it occurs when reinforcing filaments are aligned in the yarn direction. Prototype double helix actuators are constructed from cotton yarn infused with a water‐swellable hydrogel. A series of actuator samples are made with differing ply angles and the length changes monitored during repeated hydration/dehydration cycles. Water swelling causes length contractions of up to 9% and it increases in magnitude with an increase in ply twist. The experimental results are in good agreement with those calculated using the helical geometry model.

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confidence: 67%

Δ L_{0} = F_{normalA} (\frac{1}{k_{A}} - \frac{1}{k'_{A}}) + Δ L_{normalA}

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confidence: 99%

Double Helix Actuators

Shepherd

Spinks

2018

Adv Materials Technologies

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“…[22] Next, we investigated the yarn's actuation ability upon on electrochemical charge injection. In general, the stiffness (S) of helical coils is defined by the contributing yarn diameter (d), coil diameter (D), number of turns in the coil (N), and the material's shear modulus (G) [23]…”

Section: Electrochemical Characteristicsmentioning

confidence: 99%

Artificial Muscles from Hybrid Carbon Nanotube‐Polypyrrole‐Coated Twisted and Coiled Yarns

Aziz

Martínez

Foroughi

et al. 2020

Macro Materials & Eng

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in the significant progress in soft-robotics, flexible prosthetics, and exoskeletons that either boost human performance or assist disabled people in carrying out day-today tasks. One of the significant innovations is introducing soft and lightweight actuating materials (artificial muscles) that can mimic biological muscles and operate smoothly and silently. [1] The current materials of interest for artificial muscles are carbon nanotubes (CNT), [2] graphene, [3] shape memory alloys (SMA), [4] shape memory polymers (SMP), [5] conductive polymers, [6] and highly oriented polymer yarns [7] that can be induced thermally, chemically, photonically, or electrochemically to obtain muscle-like actuation. Artificial muscles made from polymeric or nano-carbon-based yarns can find versatile applications ranging from assistive wearable artificial muscles for biomedical rehabilitation or assistance for daily activities, bioinspired and biomimetic systems, for handling delicate objects, and on-demand movement. [8] CNT yarn actuators are of great interest in the field of electrochemically or electrothermally induced wearable artificial muscle technologies. [2a,9] These actuators exhibit excellent mechanical properties needed for wearable textile exoskeletons. [2c,10] Recently, the feasibility of using multi-walled CNT forest drawn twisted or coiled yarns was demonstrated in terms of both tensile and rotational actuation. As high as 3% tensile actuation and 12.6° mm-1 rotational actuation was reported from an electrothermally activated twist-spun wax-filled CNT yarn when subjected to 25-210 °C temperature variations. [9c] On the other hand, electrochemically induced twist-spun CNT yarns have shown a maximum of 180° mm-1 torsional rotation and 0.7% axial strain in an organic electrolyte (0.2 m tetrabutylammonium hexafluorophosphate (TBA.PF6) in acetonitrile) when pulsed from-2.0 to +2.0 V versus Ag/Ag + reference. [9b] However, due to the reasonably high cost associated with their fabrication, these CNT yarn actuators have limited practicability in smart textiles where low cost is desirable. Therefore, the interest in using inexpensive textile yarns has grown. Several researchers have shown the feasibility of using such yarns to construct simple textile actuators actuated by thermal, [7b] electrothermal, [9a] electronic, [11] electrochemical, [9b,12] or electrical [9c] energy inputs. Similar to CNT yarn muscles, twisted and coiled textile yarns Electrochemically or electrothermally driven twisted/coiled carbon nanotube (CNT) yarn actuators are interesting artificial muscles for wearables as they can sustain high stress. However, due to high fabrication costs, these yarns have limited their application in smart textiles. An alternative approach is to use off-the-shelf yarns and coat them with conductive polymers that deliver high actuation properties. Here, novel hybrid textile yarns are demonstrated that combine CNT and an electroactive polypyrrole coating to provide both high strength and good actuation properties. CNT-coated po...

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“…Conventionally, coils are formed by twisting of the fiber under the action of tensile force. Ross 47,48 defined the critical torque (τ c ) that initiates coiling in anisotropic fibers under a tensile force (F t ) as:…”

Section: Fabrication Of 3d Hcsmentioning

confidence: 99%

Architectured helically coiled scaffolds from elastomeric poly(butylene succinate) (PBS) copolyester via wet electrospinning

Sonseca¹,

Sahay²,

Stępień³

et al. 2019

Preprint

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<div><div><div><p>Electrospinning is one of the most investigated methods used to produce polymeric fiber structures that mimic the morphology of native extracellular matrix. These structures have been extensively studied in the context of scaffolds for tissue regeneration. However, the compactness of materials obtained by traditional electrospinning, collected as two-dimensional non-woven scaffolds, can limit cell infiltration and tissue ingrowth. In addition, for applications in smooth muscle tissue engineering, highly elastic scaffolds capable of withstanding cyclic mechanical strains without suffering significant permanent deformations are preferred. In order to address these challenges, we report the fabrication of microscale 3D helically coiled structures (referred as 3D-HCS) by wet-electrospinning method, a modification of the traditional electrospinning process in which a coagulation bath (non-solvent system for the electrospun material) is used as the collector. The present study, for the first time, successfully demonstrates the feasibility of using this method to produce various architectures of 3D-HCS from segmented copolyester of poly(butylene succinate-co- dilinoleic succinate) (PBS-DLS), a thermoplastic elastomer. A mechanism for the HCS formation is proposed and verified with experimental data. Fabricated 3D-HCS showed high specific surface area, high porosity, and good elasticity. Further, the marked increase in cell proliferation on 3D-HCS confirmed the suitability of these materials as scaffolds for soft tissue engineering.</p></div></div></div>

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Stretchable artificial muscles from coiled polymer fibers

Cited by 29 publications

References 30 publications

Double Helix Actuators

Double Helix Actuators

Artificial Muscles from Hybrid Carbon Nanotube‐Polypyrrole‐Coated Twisted and Coiled Yarns

Architectured helically coiled scaffolds from elastomeric poly(butylene succinate) (PBS) copolyester via wet electrospinning

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