| 1. |
- Aziz, Shazed, et al.
(author)
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Artificial Muscles from Hybrid Carbon Nanotube-Polypyrrole-Coated Twisted and Coiled Yarns
- 2020
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In: Macromolecular materials and engineering. - : WILEY-V C H VERLAG GMBH. - 1438-7492 .- 1439-2054. ; 305:11
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Journal article (peer-reviewed)abstract
- 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 polyester yarns are twisted and coiled and subjected to electrochemical coating of polypyrrole to obtain the hierarchical soft actuators. When twisted without coiling, the polypyrrole-coated yarns produce fully reversible 25 degrees mm(-1)rotation, 8.3x higher than the non-reversible rotation from twisted CNT-coated yarns in a three-electrode electrochemical system operated between +0.4 and -1.0 V (vs Ag/AgCl). The coiled yarns generate fully reversible 10 degrees mm(-1)rotation and 0.22% contraction strain, 2.75x higher than coiled CNT-coated yarns, when operated within the same potential window. The twisted and coiled yarns exhibit high tensile strength with excellent abrasion resistance in wet and dry shearing conditions that can match the requirements for using them as soft actuators in wearables and textile exoskeletons.
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| 2. |
- Aziz, Shazed, et al.
(author)
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Characterisation of torsional actuation in highly twisted yarns and fibres
- 2015
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In: Polymer testing. - : Elsevier. - 0142-9418 .- 1873-2348. ; 46, s. 88-97
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Journal article (peer-reviewed)abstract
- Highly twisted oriented polymer fibres and carbon nanotube yarns show large scale torsional actuation from volume expansion that can be induced, for example, thermally or by electrochemical charging. When formed into spring-like coils, the torsional actuation within the fibre or yarn generates powerful tensile actuation per muscle weight. For further development of these coil actuators and for the practical application of torsional actuators, it is important to standardise methods for characterising both the torsional stroke (rotation) and torque generated. By analogy with tensile actuators, we here introduce a method to measure both the free stroke and blocked torque in a one-end-tethered fibre. In addition, the torsional actuation can be measured when operating against an externally applied torque (isotonic) and actuation against a return spring fibre (variable torque). A theoretical treatment of torsional actuation was formulated using torsion mechanics and evaluated using a commercially available highly-oriented polyamide fibre. Good agreement between experimental measurements and calculated values was obtained. The analysis allows the prediction of torsional stroke under any external loading condition based on the fundamental characteristics of the actuator: free stroke and stiffness.
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| 3. |
- Aziz, Shazed, et al.
(author)
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Controlled and scalable torsional actuation of twisted nylon 6 fiber
- 2016
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In: Journal of Polymer Science Part B. - : John Wiley & Sons. - 0887-6266 .- 1099-0488. ; 54:13, s. 1278-1286
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Journal article (peer-reviewed)abstract
- Large‐scale torsional actuation occurs in twisted fibers and yarns as a result of volume change induced electrochemically, thermally, photonically, and other means. A quantitative relationship between torsional actuation (stroke and torque) and volume change is here introduced. The analysis is based on experimental investigation of the effects of fiber diameter and inserted twist on the torsional stroke and torque measured when heating and cooling nylon 6 fibers over the temperature range of 26–62 °C. The results show that the torsional stroke depends only on the amount of twist inserted into the fiber and is independent of fiber diameter. The torque generated is larger in fibers with more inserted twist and with larger diameters. These results are successfully modeled using a single‐helix approximation of the twisted fiber structure
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| 4. |
- Aziz, Shazed, et al.
(author)
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Effect of anisotropic thermal expansion on the torsional actuation of twist oriented polymer fibres
- 2017
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In: Polymer. - : Elsevier. - 0032-3861 .- 1873-2291. ; 129, s. 127-134
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Journal article (peer-reviewed)abstract
- Torsional actuation of twisted polymer fibres is the basis for high performance tensile actuation when these fibres are formed into coils. The thermally-induced torsional actuation of twisted polyamide-6 fibres can be predicted by a single helix approximation when the measured diameter and length direction thermal expansion coefficients are known. The single helix model illustrates the sensitivity of the magnitude of torsional actuation to the volume expansion anisotropy for a given volume change. The applicability of the model has been further assessed by investigating three polymer fibres that display different thermal expansion anisotropies. Commercially available polyethylene, polypropylene and polyamide-6 fibres were twisted to the maximum extent without coiling and then heat treated to fix the twisted structure. Heating the twisted fibres between 26 and 62 °C resulted in a partial untwist which was reversed during cooling. The single-helix model of the twisted fibres was used to accurately predict the torsional stroke based on the measured fibre length and diameter change during heating. Comparative torsional stroke of twisted polyamide-6, polyethylene and polypropylene was explained in terms of materials thermo-physical properties. Generated blocked torques was also correctly predicted by the single-helix model when combined with the measured fibre torsional stiffness. Variances between torsional stiffnesses were found to be dependent of different anisotropic thermal properties of tested fibres.
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| 5. |
- Aziz, Shazed, et al.
(author)
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Effect of fibre coating and geometry on the tensile properties of hybrid carbon nanotube coated carbon fibre reinforced composite
- 2014
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In: Materials & Design. - : Elsevier. - 0261-3069. ; 54, s. 660-669
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Journal article (peer-reviewed)abstract
- Hierarchically structured hybrid composites are ideal engineered materials to carry loads and stresses due to their high in-plane specific mechanical properties. Growing carbon nanotubes (CNTs) on the surface of high performance carbon fibres (CFs) provides a means to tailor the mechanical properties of the fibre–resin interface of a composite. The growth of CNT on CF was conducted via floating catalyst chemical vapor deposition (CVD). The mechanical properties of the resultant fibres, carbon nanotube (CNT) density and alignment morphology were shown to depend on the CNT growth temperature, growth time, carrier gas flow rate, catalyst amount, and atmospheric conditions within the CVD chamber. Carbon nanotube coated carbon fibre reinforced polypropylene (CNT-CF/PP) composites were fabricated and characterized. A combination of Halpin–Tsai equations, Voigt–Reuss model, rule of mixture and Krenchel approach were used in hierarchy to predict the mechanical properties of randomly oriented short fibre reinforced composite. A fractographic analysis was carried out in which the fibre orientation distribution has been analyzed on the composite fracture surfaces with Scanning Electron Microscope (SEM) and image processing software. Finally, the discrepancies between the predicted and experimental values are explained.
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| 6. |
- Aziz, Shazed, et al.
(author)
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Experimental evaluation of the interfacial properties of carbon nanotube coated carbon fiber reinforced hybrid composites
- 2015
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In: Polymer Composites. - : John Wiley & Sons. - 0272-8397 .- 1548-0569. ; 36:10, s. 1941-1950
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Journal article (peer-reviewed)abstract
- A floating catalyst chemical vapor deposition (CVD) unit was utilized to grow CNT onto the surface of carbon fiber (CF). The surface morphology of the resultant fibers, CNT population density and alignment pattern were found to be depended on the CNT growth temperature, growth time, and atmospheric conditions within the CVD chamber. In contrast to the neat‐CF reinforced composites, improved interfacial shear strength (IFSS) between CF and matrix were obtained when the surface of CF was coated by CNT. Particularly, CF treatment condition for CNT‐coating with 700°C reaction temperature and 30 min reaction time has shown a considerable increase in IFSS approximately of 45% over that of the untreated fiber from which it was processed. The proper justification of fiber–matrix adhesion featured by composite interfacial properties was explained through IFSS.
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| 7. |
- Aziz, Shazed, et al.
(author)
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Fast and High-Strain Electrochemically Driven Yarn Actuators in Twisted and Coiled Configurations
- 2021
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In: Advanced Functional Materials. - : John Wiley & Sons. - 1616-301X .- 1616-3028. ; 31:10
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Journal article (peer-reviewed)abstract
- Commercially available yarns are promising precursor for artificial muscles for smart fabric-based textile wearables. Electrochemically driven conductive polymer (CP) coated yarns have already shown their potential to be used in smart fabrics. Unfortunately, the practical application of these yarns is still hindered due to their slow ion exchange properties and low strain. Here, a method is demonstrated to morph poly-3,4-ethylenedioxythiophene:poly-styrenesulfonate (PEDOT:PSS) coated multifilament textile yarns in highly twisted and coiled structures, providing >1% linear actuation in <1 s at a potential of +0.6 V. A potential window of +0.6 V and -1.2 V triggers the fully reversible actuation of a coiled yarn providing >1.62% strain. Compared to the untwisted, regular yarns, the twisted and coiled yarns produce >9x and >20x higher strain, respectively. The strain and speed are significantly higher than the maximum reported results from other electrochemically operated CP yarns. The yarn’s actuation is explained by reversible oxidation/reduction reactions occurring at CPs. However, the helical opening/closing of the twisted or coiled yarns due to the torsional yarn untwisting/retwisting assists the rapid and large linear actuation. These PEDOT:PSS coated yarn actuators are of great interest to drive smart textile exoskeletons.
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| 8. |
- Aziz, Shazed, 1985-, et al.
(author)
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PEDOT:PSS coated twisted and coiled yarn actuators
- 2021
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In: EuroEAP 2021.
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Conference paper (other academic/artistic)abstract
- Commercial yarns can be functionalized with conducting polymers (CPs) todevelop yarn and textile actuators. Here we show a method of functionalizationof commercial polyamide yarns by poly-3,4-ethylenedioxythiophene:polystyrenesulfonate (PEDOT:PSS) coating. Aftercoating, while PEDOT:PSS is drying, it is possible to twist and coil the yarns,resulting in a major improvement of their linear strain and speed of movement.By using a potential window between +0.6 V and -1.2 V vs Ag/AgCl it waspossible to obtain a fully reversible actuation of a coiled yarn providing up to1.62% strain. A strain higher than 1% was achieved in less than 1 second.Compared to the untwisted, regular yarns, the twisted and coiled yarns produce>9× and >20× higher strain, respectively. These results are a step forward towardsthe development of soft, silent and compliant smart textile exoskeletons.
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| 9. |
- Aziz, Shazed, et al.
(author)
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Plant-Like Tropisms in Artificial Muscles
- 2023
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In: Advanced Materials. - : WILEY-V C H VERLAG GMBH. - 0935-9648 .- 1521-4095.
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Journal article (peer-reviewed)abstract
- Helical plants have the ability of tropisms to respond to natural stimuli, and biomimicry of such helical shapes into artificial muscles has been vastly popular. However, the shape-mimicked actuators only respond to artificially provided stimulus, they are not adaptive to variable natural conditions, thus being unsuitable for real-life applications where on-demand, autonomous operations are required. Novel artificial muscles made of hierarchically patterned helically wound yarns that are self-adaptive to environmental humidity and temperature changes are demonstrated here. Unlike shape-mimicked artificial muscles, a unique microstructural biomimicking approach is adopted, where the muscle yarns can effectively replicate the hydrotropism and thermotropism of helical plants to their microfibril level using plant-like microstructural memories. Large strokes, with rapid movement, are obtained when the individual microfilament of yarn is inlaid with hydrogel and further twisted into a coil-shaped hierarchical structure. The developed artificial muscle provides an average actuation speed of approximate to 5.2% s(-1) at expansion and approximate to 3.1% s(-1) at contraction cycles, being the fastest amongst previously demonstrated actuators of similar type. It is demonstrated that these muscle yarns can autonomously close a window in wet climates. The building block yarns are washable without any material degradation, making them suitable for smart, reusable textile and soft robotic devices.
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| 10. |
- Aziz, Shazed, et al.
(author)
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Theoretical Prediction of CNT-CF/PP Composite Tensile Properties Using Various Numerical Modeling Methods
- 2013
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In: Fullerenes, nanotubes, and carbon nanostructures. - : Taylor & Francis. - 1536-383X .- 1536-4046. ; 21:5, s. 411-416
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Journal article (peer-reviewed)abstract
- Development of effective models to predict tensile properties of ‘carbon nanotube coated carbon fibre reinforced polypropylene (CNT-CF/PP)’ composites is briefly discussed. The composite taken as the reference is based on the highest growth mechanism of CNTs over carbon fibres. Halpin-Tsai and Combined Voigt-Reuss model has been implemented. Young's modulus for CNT-CF/PP composites has been found 4.5368 GPa and the tensile strength has been estimated 45.367 MPa considering the optimum operating condition of chemical vapor deposition (CVD) technique. Stiffness of the composite is represented through the stress-strain plots; stiffness is proportional to the steepness of the slope. There are slight deviations of results that have been found theoretically over the experimental issues.
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