Smart+Materials+and+applications+4

Electroactive Polymers, or EAPs, are polymers that exhibit a change in size or shape when stimulated by an electric field. The most common applications of this type of material are in actuators and sensors. A typical characteristic property of an EAP is that they will undergo a large amount of deformation while sustaining large forces. The majority of historic actuators are made of ceramic piezoelectric materials. While these materials are able to withstand large forces, they commonly will only deform a fraction of a percent . In the late 1990s, it has been demonstrated that some EAPs can exhibit up to a 380% strain, which is much more than any ceramic actuator. Another one of the most common applications for EAPs is in the field of robotics  in the development of artificial muscles. Due to this being one of the most common and attractive applications, EAPs are often referred to as artificial muscles.
 * Electro active polymers **
 * Characteristics of EAPs **


 * History of EAPs **

The field of EAPs emerged back in 1880, when Wilhelm Roentgen  designed an experiment in which he tested the effect of an electrical current  on the mechanical properties of a rubber band . Later on, in 1899, M.P. Sacerdote followed up on Roentgen’s experiment by formulating a theory on strain response to an applied electric field <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">. In 1925, the first <span style="color: windowtext; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;">piezoelectric <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">polymer was discovered ( Electret ). In 1949, Katchalsky demonstrated that when <span style="color: windowtext; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;">collagen filaments are dipped in <span style="color: windowtext; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;">acid <span style="font-family: 'Times New Roman','serif'; font-size: 16px;"> or <span style="color: windowtext; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;">alkali <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">solutions they would respond with a change in <span style="color: windowtext; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;">volume <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">.

<span style="font-family: 'Times New Roman','serif'; font-size: 16px;">It wasn’t until the late 1960s when the next major breakthrough in EAPs was observed. In 1969, Kawai was able to demonstrate that <span style="color: windowtext; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;">polyvinylidene fluoride <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">(PVDF) exhibits a large piezoelectric effect. This sparked research interest in developing other polymers systems that would show a similar effect. In 1977, the first electrically <span style="color: windowtext; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;">conducting polymers <span style="font-family: 'Times New Roman','serif'; font-size: 16px;"> were discovered by <span style="color: windowtext; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;">Hideki Shirakawa //<span style="font-family: 'Times New Roman','serif'; font-size: 16px;">. //<span style="font-family: 'Times New Roman','serif'; font-size: 16px;"> Shirakawa along with <span style="color: windowtext; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;">Alan MacDiarmid <span style="font-family: 'Times New Roman','serif'; font-size: 16px;"> and <span style="color: windowtext; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;">Alan Heeger <span style="font-family: 'Times New Roman','serif'; font-size: 16px;"> demonstrated that <span style="color: windowtext; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;">polyacetylene <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">was electrically conductive, and that by doping it with <span style="color: windowtext; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;">iodine <span style="font-family: 'Times New Roman','serif'; font-size: 16px;"> vapor, they could enhance its <span style="color: windowtext; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;">conductivity <span style="font-family: 'Times New Roman','serif'; font-size: 16px;"> by 8 orders of magnitude. Thus the <span style="color: windowtext; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;">conductance <span style="font-family: 'Times New Roman','serif'; font-size: 16px;"> was close to that of a metal. By the late 1980s a number of other polymers had been shown to exhibit a <span style="color: windowtext; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;">piezoelectric effect <span style="font-family: 'Times New Roman','serif'; font-size: 16px;"> or were demonstrated to be conductive.

<span style="font-family: 'Times New Roman','serif'; font-size: 16px;">In the early 1990s, <span style="color: windowtext; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;">ionic polymer-metal composites <span style="font-family: 'Times New Roman','serif'; font-size: 16px;"> were developed and shown to exhibit electroactive properties far superior to previous EAPs. The major advantage of IPMCs was that they were able to show activation (deformation) at <span style="color: windowtext; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;">voltages <span style="font-family: 'Times New Roman','serif'; font-size: 16px;"> as low as 1 or 2 <span style="color: windowtext; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;">volts <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">. This is orders of magnitude less than any previous EAP. Not only was the activation energy for these materials much lower, but they could also undergo much larger deformations. IMPCs were shown to exhibit anywhere up to 380% strain, orders of magnitude larger than previously developed EAPs. In 1999, one of the pioneers of the field of <span style="color: windowtext; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;">robotics <span style="font-family: 'Times New Roman','serif'; font-size: 16px;"> and artificial muscles, <span style="color: windowtext; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;">Yoseph Bar-Cohen <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">, proposed the <span style="color: windowtext; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;">Armwrestling Match of EAP Robotic Arm Against Human <span style="font-family: 'Times New Roman','serif'; font-size: 16px;"> Challenge.


 * <span style="font-family: 'Times New Roman','serif'; font-size: 19px;">Types of EAPs **

<span style="font-family: 'Times New Roman','serif'; font-size: 16px;">Dielectric EAPs, Ferroelectric Polymers , Electrostrictive Graft Polymers

<span style="font-family: 'Times New Roman','serif'; font-size: 16px;">Liquid Crystalline Polymers, Ionic EAPs , Electrorheological Fluid ,

<span style="font-family: 'Times New Roman','serif'; font-size: 16px;">Ionic polymer-metal composite


 * <span style="font-family: 'Times New Roman','serif'; font-size: 19px;">Industrial applications **

<span style="font-family: 'Times New Roman','serif'; font-size: 16px;">1-M <span style="color: windowtext; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;">icroelectromechanical systems <span style="font-family: 'Times New Roman','serif'; font-size: 16px;"> (MEMS) to produce smart actuators.

<span style="font-family: 'Times New Roman','serif'; font-size: 16px;">2-EAPs have been utilized in artificial muscles.

<span style="font-family: 'Times New Roman','serif'; font-size: 16px;">3-Small pumps can also be achieved by applying EAP materials. These pumps could be used for <span style="color: windowtext; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;">drug delivery <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">, <span style="color: windowtext; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;">microfluidic devices <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">, active flow control, and a multitude of consumer applications

<span style="font-family: 'Times New Roman','serif'; font-size: 16px;">4-EAP materials show potential in <span style="color: windowtext; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;">biomimetic <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">-robot research, stress sensors and <span style="color: windowtext; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;">acoustics <span style="font-family: 'Times New Roman','serif'; font-size: 16px;"> field

<span style="font-family: 'Times New Roman','serif'; font-size: 16px;">5-optical membranes


 * <span style="font-family: 'Times New Roman','serif'; font-size: 19px;">links to videos and pictures to illustrate how they work: **

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<span style="font-family: 'Times New Roman','serif'; font-size: 16px;">[|www.youtube.com/watch?v=R6ufLXGm_94]

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