PRESSUR ISED INFLAT IONWITH ELECTR ICALACTUAT ION OFD IELECTR IC ELASTOMERabhishek saini* & k.patra1

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AbstractDielectric elastomers (DE) are incompressible polymeric solids having fi-nite deformation in planar direction when applying voltage on compliantelectrodes. Dielectric elastomers have received a great deal of attention re-cently due to large strains which make them enticing materials for manynew types of sensors, actuators and future energy generators. When subjectto an electric field through the thickness of the membrane, the material be-comes polarized and contracts mechanically to reduce the electrical energystored in the material. Because these materials are nearly incompressible,they expand in-plane in response to a transverse electric field.This work intends to extend the electromechanical characterisation of dielec-tric elastomer actuators; we investigate electromechanical behaviour of cir-cular actuator. Tests were conducted on a predesigned experimental setuphaving cylindrical vessel with pressure sensor, DAQ etc. at different pres-sure and voltage values. Actuation results show their large strain capacitywhich can be used on miniaturized pumps and in other application.

1 introductionPolymers have many advantages such as low manufacturing cost, lightweight,compliant nature, fracture tolerant, can be made in different shape or size,easy handling etc [3]. Today dielectric elastomers are enticing area in thefield of sensors, actuators and energy generation. DE is used in a widevariety of application including robotics, adaptive optics, Braille displays,micro-fluidics, prosthetics, biomedical etc. [4, 5, 6]. The wide range ofapplication of dielectric elastomers justifies a high research interest in its ex-perimental and analytical characterization. The mechanical tests frequentlyperformed on rubbers are of two types: compression and tension; while thecompression state is always uniaxial, tension can be applied in a uniaxial,planar or equi-biaxial state [1, 2].In this paper we have tested the bi-axially pre-stretched circular planar ac-tuator with different pre-strained values through bulge test. Also as DEare very permissible for the actuator purpose like micro-pumps. So herewe have tested the coated planar actuator by applying pressure and checkthe electromechanical characterization at different pressure ratings whichis an extended form of equibiaxial stress and strain. Burst test was alsoperformed to find out the maximum deflection and failure of the sample.In addition to this as the actuator actuates/inflate continuously, to checkits response we have performed cyclic/ hysteresis test to determine its vis-coelastic behaviour.

2 experiments2.1 Circular planar actuator preparationA bi-axially pre-strained circular planar actuator used here consists of di-electric elastomer sandwiched between two compliant electrodes. The activearea is defined by the region where the circular electrodes overlap across thedielectric film; conducting path is arranged on opposite sides of the activearea. When a high voltage is applied to the conducting path the active areawill expand in plane and reduce in thickness. Circular active area of 20 mm

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in diameter was used in this work.

In this work we have used the carbon conducting grease for the activeregion. Circular frame of diameter 50 mm was designed to hold the pre-strained DE actuator; high voltage power supply was used for giving elec-trical actuation to the

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3 references1. K. Miller, Testing elastomer for hyperelastic material models in finite

element analysis. Axel Products Testing and Analysis Report, 2000.2. I. Pearson, M. Pickering, The determination of a highly elastic adhe-

sives material properties and their representation in finite elementanalysis, Finite Elements in Analysis and Design 37 (2001) 221232.

3. Vlad Crlescu., mechanical testing of elastomers for sensor and actua-tor applications

4. Shankar R., Ghosh T. K., Spontak R. J., Dielectric Elastomers as Next-generation Polymeric Actuators, Soft Matter, 3, 1116-1129, 2007.

5. Carpi, F., Rossi, D. D., Kornbluh, R., Pelrine, R., Larsen, P. S. Dielec-tric Elastomers as Electromechanical Transducers, Elsevier, OxfordUK, 1st Edition, 2008.

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1 Introduction2 Experiments2.1 Circular planar actuator preparation

3 References