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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 yarns 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., Funding Agencies|Promobilia Foundation [F17603]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO Mat LiU) [2009-00971]; Swedish Research CouncilSwedish Research Council [2014-3079]; Carl Trygger Foundation [CTS:17-215]; European UnionEuropean Union (EU) [825232]; University of Wollongongs Visiting International Scholar Award

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.

Artificial muscles are devices or materials which can contract, expand, or rotate when acted upon by an external stimulus (such as electricity, pH, pressure, magnetic field, or temperature). The applications of artificial muscles are versatile because they can exhibit linear actuation as in hydraulic rams, torsional actuation like electric motors, and bending actuation as seen in nature. Artificial muscles have also exhibited great potential in robot fabrication and in surgery tools due to their resemblance to biological muscles along with high actuation force per unit mass. One successful type of artificial muscle uses a braided bladder that generates muscle-like contractions when the bladder is pressurised with gas or liquid. These systems are used commercially in industry, but are not useful in portable applications, such as robotics, because of the need for an external pump or compressor. This thesis investigated the use of a volume-changing hydrogel material as a means for pressurizing and depressurizing a braid. The hydrogel has the potential to replace the pump/compressor and make possible a smaller, lighter artificial muscle. For further investigation of these artificial muscles as linear actuators and for the practical application of linear actuators, it was imperative to standardize methods for characterizing their performance. This thesis introduces such an integrated characterisation method and demonstrates its use in the determination of the free stroke of a hydraulic artificial muscle (HAM); the stroke while operating against an externally applied force (isotonic); the blocked force of these muscles upon applying constant length (isometric); force and displacement change at constant pressure (isobaric); and actuation against a return spring (variable force, pressure). The linear mechanics approach has been verified and allows the prediction of fundamental characteristics of the actuator: free stroke, blocked force and stiffness while varying the preloa

© 2020 IOP Publishing Ltd. Braided (McKibben) artificial muscles are one of the most attractive biomimetic actuators since they exhibit similar static and dynamic performance to skeletal muscles. One disadvantage of these systems, when intended for portable applications, is the need for a compressor or pump to provide pressurised fluid for muscle activation. An alternative is to use an expandable material, such as a hydrogel. This work investigates the development of hydrogel-based braided artificial muscles which can produce mechanical work through controlled hydrogel swelling in the presence of water. Hydrogel bead-filled braided meshes were prepared where no internal bladder was needed; since the bead size was larger than the holes in the braided mesh. A spring test method was introduced to measure force generation and strain developed by the braided mesh when the thermo-responsive gel was cooled from 60 °C to 5 °C-8 °C. Reducing the temperature resulted in hydrogel swelling and braided mesh length contraction due to the internal pressure generated. Blocked forces and actuation free strokes of 5-6 N and 7%-8% were observed, respectively. A long response time was the limiting factor of these actuators due to the slow diffusion properties of the hydrogel.

Many different test methods are currently used to characterise the output of artificial muscle materials but few studies report the full range of possible force and displacements that can be generated by a given material when activated with a given input stimulus but when operated against different external loads. The measurement of the loading and unloading force extension curves in tension in both the un-activated and activated states is investigated as a means for efficiently characterising the full range of outputs for three different types of artificial muscles: pneumatically operated braided muscle and thermally operated shape memory alloy spring and twisted / coiled polymer fiber. A graphical method of analysis was applied whereby the force-extension curves obtained before and after actuator activation were plotted on the same axes. By overlaying the external loading conditions, the graphical method provided the equilibrium starting and finishing forces and displacements and successfully predicted the isotonic strokes, isometric forces and combined force and displacement generated when the actuator was operated against an external spring. Complications in the interpretation of the force-stroke curves were encountered as all three artificial muscles displayed a degree of loading-unloading hysteresis and non-ideal mechanical behavior.

Biodiesel/diesel blends (BDB) were prepared using different biodiesel percentages (10, 15 and 20% v/v) namely B10, B15 and B20, respectively. A high energy emulsification method was employed for this purpose. An engine test bed was utilized to combust the emulsion in order to investigate emission gas concentrations such as CO, NOx, CO2, O2 and smoke. The emission concentrations of NOx and O2 were decreased with increasing biodiesel concentration. However, the emission of CO2 was increased with the increasing amounts of water. The highest concentration of NOx was found for B15. The physicochemical properties of BDB emulsion fuel in terms of viscosity and calorific value were also measured and investigated. Furthermore, biodiesel showed the highest viscosity compared to diesel and BDB fuels. The viscosity of BDB fuels was increased from B10 to B20. The increasing biodiesel concentration showed a decrease in calorific value. Hence, emulsified biodiesel fuel is a promising alternative fuel for reducing harmful emissions.

Water-in-diesel nanoemulsions are considered as alternative fuels for internal combustion engines, to enhance combustion efficiencies and reduce exhaust emissions. A high energy emulsification process using a range of ultrsonication amplitudes (20 to 35 % with 10 minutes processing time) was employed to prepare nanoemulsion fuels. Nanoemulsion fuels were formulated by using a range of surfactant (Triton X-100) concentrations (0.31 % to 0.49 % w/w) with varying water concentrations (0.80% to 1.15% w/w). Cerium oxide (CeO2) was also incorporated into the nanoemulsion fuels in order to evaluate the effect of fuel additive on the nanoemulsion properties. A screening method was carried out to determine the most suitable experimental conditions for the formation of nanoemulsion fuel in terms of improved combustion and emission properties. The screening process was conducted by analysing the emission of fuels from an engine test bed, namely CO2, CO and NOx. It was found that nanoemulsion fuels have the ability to reduce exhaust emissions compared to that of neat diesel. The exhaust temperature of neat diesel was found to be 290 °C along with the CO2, CO and NO emission concentrations of 21784, 766, and 276 ppm, respectively. A significant reduction of exhaust temperature (up to 33%) as well as NOx emission (up to 61%) was obtained during the combustion of cerium oxide enriched nanoemulsions compared to those without. The physico-chemical properties of screened nanoemulsions such as color, density,fuel stability, kinematic viscosity, flash point, pour point, acid number, calorific value and cetane number were determined and comparison was made to neat diesel. The destabilization methods; mainly Ostwald ripening was discussed to investigate the stability of nanoemulsions. The morphology of the nanoemulsions was studied by using the micrographs obtained from transmission electron microscopy (TEM). The size of the droplets formed in the prepared nanoemulsion fuel was found in