Electropolymers for mechatronics and artificial muscles

Abstract

This chapter covers the main features and material examples of the electric fieldactivated electropolymers used for electromechanical applications. This class of electropolymers is very attractive in performing the energy conversion between the electric and mechanical forms and hence can be utilized as both solid-state electromechanical actuators and motion sensors. These polymers are also attractive for artificial muscles and for energy-harvesting applications. As will be discussed, the electromechanical response in this class of polymers can be linear, as in typical piezoelectric polymers and electrets, or nonlinear, as the electrostrictive polymers and Maxwell stress-induced response. Most of the piezoelectric polymers under investigation and in commercial use are based on poled ferroelectric (FE) polymers, including poly(vinylidene fluoride) (PVDF) and related copolymers. This chapter will discuss in detail the properties of these FE polymers. In comparisonwith the electromechanical responses in inorganic materials, the electromechanical activity in these polymers is relatively low. To significantly improve the electromechanical properties in these electropolymers, new avenues or approaches have to be explored. From the basic material consideration, these approaches include the strain change accompanied with the molecular conformation change, due to the polar vector reorientation, from the morphology change due to the ordering degree change in the interfacial layer between crystalline and amorphous regions, and from the Maxwell stress effect in soft polymer elastomers. This chapter will discuss the recent advances based on those approaches, which have produced remarkable improvements in terms of the electric field-induced strain level, elastic energy density, and electromechanical conversion efficiency in the electropolymers. © 2008 Springer-Verlag US.