Dielectric elastomers as next-generation polymeric actuators

Abstract

Due to their versatile properties, robust behavior, facile processability and low cost, organic polymers have become the material of choice for an increasing number of mature and cutting-edge technologies. In the last decade or so, a new class of polymers capable of responding to external electrical stimulation by displaying significant size or shape change has emerged. These responsive materials, collectively referred to as electroactive polymers (EAPs), are broadly classified as electronic or ionic according to their operational mechanism. Electronic EAPs generally exhibit superior performance relative to ionic EAPs in terms of actuation strain, reliability, durability and response time. Among electronic EAPs, dielectric elastomers exhibit the most promising properties that mimic natural muscle for use in advanced robotics and smart prosthetics, as well as in haptic and microfluidic devices. Elastomers derived from homopolymers such as acrylics and silicones have received considerable attention as dielectric EAPs, whereas novel dielectric EAPs based on selectively swollen nanostructured block copolymers with composition-tailorable properties have only recently been reported. Here, we provide an overview of various EAPs in terms of their operational mechanisms, uses and shortcomings, as well as a detailed account of dielectric elastomers as next-generation actuators.

Mechanics of dielectric elastomers: materials, structures, and devices

“…et al, 2013) (Li T.F. et al, 2012a;Wang J. et al, 2014) Modulus 20-2000kPa (Morrow et al, 2010 20-2000 kPa (Sheng et al, 2012) (Kornbluh et al, 2002) 0.94 kg/L (Shankar et al, 2007) et al ., 2014). This type of DE actuator usually consists of an initially curved membrane made of a circular membrane with its boundary constrained to a rigid frame.…”

“…Various types of smart materials have been used as artificial muscles with assumed response to external stimuli, including dielectric elastomers (DEs), ferroelectric polymers (FPs), ionic polymer-metal composites (IPMCs), and shape-memory polymers (SMPs). Among those listed, DEs that are usually made of electroactive polymers can readily transform electric energy into mechanical work, enabling them to mimic the function and performance of natural muscles (Shankar et al, 2007;Brochu and Pei, 2010;Kornbluh et al, 2012;Suo, 2012;Zhao and Wang, 2014). Specific examples of DEs include acrylics, silicones, polyurethanes, fluoroelastomers, and ethylene-propylene rubbers.…”

Investigation into the electromechanical properties of dielectric elastomers subjected to pre-stressing

“…It is minimally affected by the compliant electrodes, power supplies, counter electrodes and packaging and can be calculated directly from experimentally measured quantities including the electrostatic stress and thickness strain. The equations representing these relations are as follows [33]:…”

Towards materials with enhanced electro-mechanical response: CaCu3Ti4O12–polydimethylsiloxane composites

“…In general, and based on the random spatial arrangements of the filler, it is expected that the effective dielectric permittivity of a composite, 3 c , will be somewhere between these two extremes. One of the oldest and most popular effective medium theories is the Maxwell-Garnett approximation, which assumes a twophase isotropic dielectric component with spherical shaped inclusions ideally dispersed, thus defining the effective dielectric permittivity as follows: 35 3 cðMaxwellÀGarnettÞ ¼ 3 1 …”

“…1 Given their excellent properties, this class of materials enable a wide range of interesting applications, such as arm-wrestling robots, 2 fish-like propellers in airships, 3 refreshable tactile displays 4 or microactuators for mecano-transduction of individual cells, 5 to name but a few.…”