A new technique for maximizing the energy harvested using electrostrictive polymer composite Adil Eddiai a,b,⇑ , Mounir Meddad a,c , Khalid Sbiaai b , Yahia Boughaleb b,e , Abdelowahed Hajjaji d , Daniel Guyomar a a Laboratoire de Génie Electrique et Ferroélectricité (LGEF), INSA LYON, Bat. Gustave Ferrie, 69621 Villeurbanne Cedex, France b Université Chouaib Doukkali, Faculté des Sciences, Laboratoire de Physique de la Matière Condensée (LPMC), 24000 El Jadida, Morocco c DAC HR Laboratory, Université Ferhat Abbas, 19000 Sétif, Algeria d Ecole Nationale des Sciences Appliquées d’El Jadida, Université Chouaib Doukkali, El Jadida, Morocco e Université Hassan II Mohammedia, Faculté des Sciences Ben M’sik, Casablanca, Morocco article info Article history: Available online 22 August 2013 Keywords: Electrostrictive polymer Energy harvesting Reversal of polarization abstract Recent trends in electromechanical conversion have demonstrated the advantages of using electrostric- tive polymers for actuation or energy harvesting. At present, the investigation of using electrostrictive polymers for energy harvesting (a conversion of mechanical to electrical energy) is beginning to show potential for this application. This paper investigates the effects of different signals of electrical field E in order to develop a more in-depth understanding of the changes in electrostrictive polymers compos- ites (EPCs) response for increased current and energy harvesting. Results relating strain and electric field provide a framework for developing energy harvesting techniques which improve the overall perfor- mance of the system. In the present paper the theory is detailed then, with the reversal of polarization in the half period by applying signals electrical field of 10 V/lm and transverse strain of 0.5% and consid- ering a phase shift between them. The obtained power density for u ¼ p 2 , is 7 times higher than the one corresponding of classical techniques. The simulation results are compared with experimental ones and good agreements are found. Ó 2013 Elsevier B.V. All rights reserved. 1. Introduction With the development in the last decade of microelectronic and mechanical technology, the request in wearable electronical de- vices and in cordless detectors is increasing. These wearable de- vices need more autonomy in energy in order to feed continuously deployed sensor networks and mobile electronics [1]. Electroactive polymers belong to an important class of poly- mers due to their widespread use in industrial applications like sensors [2,3], electrochromic devices [4–6], actuators [7], and bat- teries [8,9]. Among these materials, electrostrictive polymers can be em- ployed to convert the mechanical energy, such as ambient vibra- tion in electric energy or in a large number of areas such as artificial muscles or vibration control [10,11]. In order to achieve this purpose, many studies on the material itself have been de- voted to increasing the power harvesting [12–15]. Thanks to their flexibility, processability, high productivity, high transparency and optical quality even in great thickness, electrostrictive polymers have been of particular interest over the last few years in order to replace piezoelectric elements as actuators and transducers [16–22]. A lot of effort has been devoted recently in developing device configurations and concepts in the energy harvesting with electro- active materials with the objective of achieving high electric power output [23–26]. This energy can be stored and used in place of con- ventional battery. From the Devonshire formalism of thermody- namic phenomenology describing the coupling between dielectric and elastic properties of solids, electrostriction is a fourth rank tensor property relating the mechanical strain S to an applied electric field E or to the polarization P [27]. From earlier publica- tions [19,25], it has been shown that electrostrictive materials may also be used in pseudo-piezoelectric mode, the increase in the electric field of electroactive polymers (EAPs) and the quadratic dependence of the strain with electric field is one of the key factors for increasing the energy conversion. Hence the purpose of this pa- per is to expose the application of such an approach for increasing the conversion abilities of electrostrictive materials. It will be shown that by the reversal of polarization in the half period and by applying a phase shift, the electric power harvesting increases relatively to conventional system bias DC. 0925-3467/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.optmat.2013.07.014 ⇑ Corresponding author at: Université Chouaib Doukkali, Faculté des Sciences, Laboratoire de Physique de la Matière Condensée (LPMC), 24000 El Jadida, Morocco. Tel.: +212 663540999. E-mail addresses: aeddiai@gmail.com, adil_edd@hotmail.fr (A. Eddiai). Optical Materials 36 (2014) 13–17 Contents lists available at ScienceDirect Optical Materials journal homepage: www.elsevier.com/locate/optmat