Strain Response from Polypyrrole Actuators under Load

Spinks, Geoffrey M.; Liu, L.; Wallace, Gordon G.; Zhou, Dezhi

doi:10.1002/1616-3028(20020618)12:6/7<437::aid-adfm437>3.0.co;2-i

Cited by 175 publications

(149 citation statements)

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“…1,2 CP actuators have been demonstrated comprising many different conducting polymers (polyaniline, polypyrrole, poly (3,4-ethylenedioxythiophene)) and dopants. [3][4][5][6] They have been fabricated in a variety of sizes, 7 from nano-and microscale 8,9 to centimeters scale 1,2 and in different configurations offering different kind of movements such as fibers or films producing linear movements, [10][11][12] bilayers and trilayers producing angular movements, 1,2,13 and as bulk material producing perpendicular expansion. [14][15][16] Polypyrrole (PPy) doped with dodecylbenzenesulfonate (DBS) is one of the most studied materials for actuators due to its good mechanical properties and the great volume changes occurring when the electrochemical reaction (1) occurs: 8 …”

Section: Introductionmentioning

confidence: 44%

Effect of the Electrolyte Concentration and Substrate on Conducting Polymer Actuators

2014

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ABSTRACT:The effect of the electrolyte concentration (NaCl aqueous electrolyte) on the dimensional variations of films of polypyrrole doped with dodecylbenzenesulphonate PPy(DBS) on Pt and Au wires was studied. Any parallel reaction that occurs during the redox polymeric reaction that drives the mechanical actuation, as detected from the coulovoltammetric responses, was avoided by using Pt wires as substrate and controlling the potential limits, thus significantly increasing the actuator lifetime. The NaCl concentration of the electrolyte, when studied by cyclic voltammetry or chronoamperometry, has a strong effect on the performance as well. A maximum expansion was achieved in 0.3 M aqueous solution. The consumed oxidation and reduction charges control the fully reversible dimensional variations: PPy(DBS) films are faradaic polymeric motors. Parallel to the faradaic exchange of the cations, osmotic, electrophoretic, and structural changes play an important role for the water exchange and volume change of PPy(DBS).

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Section: Introductionmentioning

confidence: 44%

Effect of the Electrolyte Concentration and Substrate on Conducting Polymer Actuators

2014

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“…The higher strains at higher loads also produce significantly higher work per cycle, so that the more the gels are compressed the more effectively and efficiently they operate as contractile actuators. This feature is in contrast to the case in tension and other polymer actuators (notably conducting polymers) where the change in modulus tends to partly cancel the actuation strain so that the net actuation becomes smaller at higher loads 6 . In practical devices, a mechanical system could be devised to ensure the gel always operated under compressive loads and to maximize the actuation strain generated.…”

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confidence: 43%

“…The modulus-induced contraction partially counteracts the natural expansion of the gel leading to lower net expansions when higher tensile stresses were applied. The effect of changing modulus on the pH-induced actuation can be calculated using models described elsewhere 5,6 and is illustrated schematically in Fig. 2a.…”

mentioning

confidence: 49%

“…Tensile testing of the gels showed that the Young's modulus of the gel increased from 1.0 to 1.2 MPa when the pH was switched from 7 to 2. This increase in modulus causes an axial contraction of the gel by an amount proportional to the applied stress 6 . The modulus-induced contraction partially counteracts the natural expansion of the gel leading to lower net expansions when higher tensile stresses were applied.…”

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confidence: 50%

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Surprising shrinkage of expanding gels under an external load

et al. 2005

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H ydrogels are fascinating and useful in that they can show large volume changes in response to various stimuli, such as temperature or chemical environment 1 . Here we report the peculiar observation that chemically crosslinked hydrogels that normally expand owing to a change in electrolyte pH can be made to shrink in certain circumstances. Specifically, these hydrogels contract when tested at a constant compressive force and subjected to a pH change that causes expansion in the absence of the applied load. When tested under tension, the gels always expand. Although the effects of external stress on the swelling of gels is known 2-4 , the concomitant change in gel mechanical properties during pH switching was found to be a more dominant effect in our studies. However, existing mechanical models 5,6 used to predict dimensional changes in actuator materials could not explain both the tensile and compression results. In addition, we show that the friction between metal plates of the apparatus and the gel is a key factor in explaining the contractile actuation under compressive loads. The observations reported in this paper are important for the successful design and use of hydrogel actuators in devices such as valves for microfluidics.Volume changes occur in polyelectrolyte hydrogels when the thermodynamic balance between expansion forces (electrostatic repulsion and osmotic pressure of counterions) and contractile forces (stretching of elastically active network chains) is shifted by changes in the chemical environment. Hydrogel 'artificial muscles' 7 can generate huge dimensional changes in response to changes in temperature 8 , pH 9 , solvent 10 and electric fields 11 . Polymer conformation changes are also accompanied by large changes in equilibrium water content (EWC) of the gel, which can conveniently be measured gravimetrically. Many examples of changes in EWC with changes in pH are available in the literature, for example in the gels based on chitosan 12 .Various applications for actuating gels have been proposed, with the microscopic devices seeming most promising owing to their reasonable response times 13 . In practical applications, the influence of the external stresses on the operation of actuators cannot be neglected. Changes in mechanical properties such as

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“…The relationship between actuation strain and applied isotonic stress has been analysed previously for neat PPy actuators. 35,36 In these systems the change in elastic modulus of the PPy before and after actuation causes a length strain that usually opposes the inherent actuation. The analysis described by equation (b) suggests that increasing applied pre-strain/stress will decrease the actuation strain linearly.…”

Section: Resultsmentioning

confidence: 46%

Polypyrrole stretchable actuators

Zheng

Alici

Clingan

et al. 2012

J Polym Sci B Polym Phys

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Here, we report a simple way to prepare stretchable polypyrrole (PPy)-based actuator materials that can be operated over a wide dynamic strain range and generate useable actuation displacements and pressures. The stretchable actuators were prepared as a laminated composite of PPy and a gold-coated roughened rubber sheet. By manipulating the corrugated surface of the rubber substrate, the stretchability of PPy was greatly improved. Gold-coated rubbers could be stretched to 30 percent without significant change in electrical resistance. The corrugated PPy/gold/rubber laminates successfully showed -1 percents of actuation strain even when prestretched to 24 percent. The actuation strains were smaller than for similar free-standing PPy films and a detailed analysis of the effects of corrugation and of the rubber substrate are presented to predict actuation strain under various prestretch strains. Correspondence to: Geoffrey M Spinks (E-mail: gspinks@uow.edu.au) (Additional Supporting Information may be found in the online version of this article.) ABSTRACTHere we report a simple way to prepare stretchable polypyrrole (PPy) based actuator materials that can be operated over a wide dynamic strain range and generate useable actuation displacements and pressures. The stretchable actuators were prepared as a laminated composite of polypyrrole and a gold-coated roughened rubber sheet. By manipulating the corrugated surface of the rubber substrate, the stretchability of PPy was greatly improved. Gold-coated rubbers could be stretched to 30% without significant change in electrical resistance. The corrugated PPy/gold/rubber laminates successfully showed ~1% of actuation strain even when pre-stretched to 24%. The actuation strains were smaller than for similar free-standing PPy films and a detailed analysis of the effects of corrugation and of the rubber substrate are presented to predict actuation strain under various pre-stretch strains.

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Strain Response from Polypyrrole Actuators under Load

Cited by 175 publications

References 0 publications

Effect of the Electrolyte Concentration and Substrate on Conducting Polymer Actuators

Effect of the Electrolyte Concentration and Substrate on Conducting Polymer Actuators

Surprising shrinkage of expanding gels under an external load

Polypyrrole stretchable actuators

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