&lt;title&gt;Nonhomogeneous large-deformation theory of ionic polymeric gels in electric and pH fields&lt;/title&gt;

Shahinpoor, Mohsen

doi:10.1117/12.148499

Cited by 10 publications

(6 citation statements)

References 17 publications

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“…Kent, Hamlen and Shafer 10 were also the first to report the electrochemical transduction of PVA-PAA polyelectrolyte system. Recently revived interest in this area concentrates on artificial muscles which can be traced to Shahinpoor and co-workers and other researchers u~14 ' 22 have been experimenting with various chemically active as well as electrically active ionic polymers and their metal composites as artificial muscle actuators.…”

Section: Introductionmentioning

confidence: 99%

Ionic Polymer-Metal Composites as Biomimetic Sensors and Actuators-Artificial Muscles

Shahinpoor

Bar‐Cohen

Xue

et al. 1999

ACS Symposium Series

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This chapter presents an introduction to ionic-polymer-metal composites and some mathematical modeling pertaining to them. It further discusses a number of recent findings in connection with ion-exchange polymer metal composites (IPMC) as biomimetic sensors and actuators. Strips of these composites can undergo large bending and flapping displacement if an electric field is imposed across their thickness. Thus, in this sense they are large motion actuators. Conversely by bending the composite strip, either quasi-statically or dynamically, a voltage is produced across the thickness of the strip. Thus, they are also large motion sensors. The output voltage can be calibrated for a standard size sensor and correlated to the applied loads or stresses. They can be manufactured and cut in any size and shape. In this paper first the sensing capability of these materials is reported The preliminary results show the existence of a linear relationship between the output voltage and the imposed displacement for almost all cases. Furthermore, the ability of these IPMC's as large motion actuators and robotic manipulators is presented. Several muscle configurations are constructed to demonstrate the capabilities of these IPMC actuators. This paper further identifies key parameters involving the vibrational and resonance characteristics of sensors and actuators made with IPMC's. When the applied signal frequency is varied, so does the displacement up to a point where large deformations are observed at a critical frequency called resonant frequency where maximum deformation is observed. Beyond which the actuator response is diminished. A data acquisition system was used to measure the parameters involved and record the results in real time basis. Also the load characterization of the IPMC's were measured and showed that these actuators exhibit good force to weight characteristics in the presence of low applied voltages. Finally, reported are the cryogenic properties of these muscles for potential utilization in an outer space environment of few Torrs and temperatures of the order of -140 degrees Celsius. These muscles are shown to work 26 quite well in such harsh cryogenics environments and thus present a great potential as sensors and actuators that can operate at cryogenic temperatures.

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Section: Introductionmentioning

confidence: 99%

Ionic Polymer-Metal Composites as Biomimetic Sensors and Actuators-Artificial Muscles

Shahinpoor

Bar‐Cohen

Xue

et al. 1999

ACS Symposium Series

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“…It is the surplus or deficiency of such ions which determines osmotic pressure, free volume, and therefore deformation. Shahinpoor [19] has presented a dual theory for the behavior of ionic gel strips in the presence of a pH as well as an electric field. He discusses the possibilities of existence of two distinct mechanisms for the deformation of an ionic gel in a solution subject to an electric field.…”

Section: Fixed Chargesmentioning

confidence: 99%

<title>Relationship between the volumetric strain and the pH in ionic polymeric gels</title>

Shahinpoor¹

1993

SPIE Proceedings

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A theoretical model is presented for the derivation of a mathematical relationship between the volumetric strain, c, of an ionic polymeric gel and its pH. The model presented also applies to polyelectrolytes in aqueous solutions. The derivation uses an expression for the total electrostatic free energy per single polyelectrolyte molecule which involves a quasi-Debye curvature, the local absolute temperature, the geometric features of polyelectrolyte molecule, the dielectric constant of the gel as well as the local ionic concentrations for the fixed and the mobile charges. The gradient of the free energy with respect to the number of fixed ions is then related to the pH, i.e., the local concentration of hydrogen ions H+, the absolute temperature T and the degree of ionization a which is defined as the ratio of the number of moles of 11+ to the number of moles of the ionizable groups fixed to the ionic gel network. Subsequently, the gradient of the free energy is related to the volumetric strain, v' of the ionic gel network. The relationship obtained between the pH and the volumetric strain, v' of the ionic gel is highly nonlinear and does depict a trend compatible with experimental evidence on rapid phase transformation in ionic gels at certain critical values of the pH. For infinitesimal strains, the derived expression between the pH and the volumetric strain fv is shown to become approximately linear. 2-INTRODUCTIONIonizable polymeric gels composed of ionic networks of randomly cross-linked macromolecules of polyelectrolytes have recently been investigated as electrically controllable artificial muscles and smart materials for medical, robotic, and other engineering applications. A polymer gel is defined as a cross-linked polymer network swollen in a liquid medium. These gels possess an ionic structure in the sense that they are generally composed of a number of fixed ions pertaining to sites of various polymer cross-links and segments and mobile ions (counter ions) due to the presence of a solvent which is electrolytic. Figure 1 below depicts a very simplistic molecular picture of such ionic gels. Katchalsky [1], and Kuhn[2] originally reported on the possibility that certain copolymers . can be chemically contracted or swollen like a synthetic muscle (pH muscle) by changing the pH of the solution containing them. As originally reported by Kuhn, Horgitay, Katchalsky, and Eisenberg [3], a three-dimensional network, consisting of polyacrylic acid, can be obtained by heating a foil of polyacrylic acid containing a polyvalent alcohol such as glycerol or polyvinyl alcohol. The resulting three-dimensional networks are insoluble in water but swell enormously in water on addition of alkali and contract enormously on addition of acids. Linear reversible dilations and contractions of the order of more than 1000 percent has been observed for ionic gel muscles made with polyacrylonitrile (PAN) fibers (Shahinpoor and Mojarrad [4]). Furthermore, as reported recently by Li and Tanaka [5], the structural deformation (swelling ...

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“…Under these conditions the transport of ions and water across the membrane is one of the main processes responsible for the resulting deformation and subsequent strain relaxation observed in experiments. Shahinpoor proposed one of the first models based on the large deformation theory of ionic polymeric gels in an electric field and a pH gradient [8]. This model considers the effect of the internal electric charge redistribution of fixed and mobile ions due to the presence of the electric field, and describes a purely electrostatic process.…”

Section: Actuator Mechanismmentioning

confidence: 99%

Time Evolution of Current and Deformation of Ion‐Exchange Polymer/metal Composite Actuators

Enikov

Seo

2006

Multidiscipline Modeling in Materials and Structures

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This paper describes the development and the numerical analysis of an electrochemical model for the analysis of a novel polymer/metal composite actuator. A general continuum model describing the transport and deformation processes of these actuators is briefly presented, along with a detailed description of the simulation scheme used to predict deformation, current, and mass transport. The predictions of the model are compared with experimental data, indicating a significant role of water transport in the large‐scale deformation. Comparison of the simulations and experimental data showed good agreement confirming the central role of water transport in the deformation process. For the sake of completeness the fabrication process and testing apparatus are also described.

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<title>Nonhomogeneous large-deformation theory of ionic polymeric gels in electric and pH fields</title>

Cited by 10 publications

References 17 publications

Ionic Polymer-Metal Composites as Biomimetic Sensors and Actuators-Artificial Muscles

Ionic Polymer-Metal Composites as Biomimetic Sensors and Actuators-Artificial Muscles

<title>Relationship between the volumetric strain and the pH in ionic polymeric gels</title>

Time Evolution of Current and Deformation of Ion‐Exchange Polymer/metal Composite Actuators

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