introduction
illustration 1: Representation of an EAP gripper. (a) Tension is applied, both fingers in EAP deform to circumnavigate the ball. (b) When the electrical voltage is broken, the fingers in EAP return to their original shape and catch the ball. (against).
THE electroactive polymers, or EAPS (Electroactive Polymers) are polymers that change shape or size when excited by an electric field (In physics, an electric field is a field created by particles…). The main use of this type of material (A material is a material of natural or artificial origin that man shapes…) is the manufacture of actuators and sensors (A sensor is a device that converts the state of a physical quantity observed into a . ..). An interesting property of EAPs is that they can withstand both large deformations and large forces. Most of today’s actuators are made of piezoelectric ceramics. These materials (A material is a material of natural or artificial origin that man molds…) are capable of generating very high forces, but their range of deformation does not exceed a few percent. In the 1990s, certain EAPs were shown to be capable of 380% deformation, far superior to any ceramic (First “fire art” to appear (prior to metallurgy and glassworking),…) any ceramic use. Another application of EAPs is in the development of robotics, in the development of artificial muscles. The functioning of a gripper (A gripper is a mechanical device or tool that has the function of gripping something…) in EAP is described in Figure 1.
History of EAPs
The study of EAPs began in the 1880s when Wilhelm Roentgen set up an experiment in which he tested the effect of an electric current (An electric current is a fixed displacement of charge carriers…) on the mechanical properties of a rubber band. The rubber band was attached at one end, and he hooked a mass (The term mass is used to refer to two sizes attached to one…) at the other end. An electric field (A field corresponds to a notion of defined space:) was applied to the rubber band to limit the variation in its length (The length of an object is the distance between its two most distant ends…) depending on the application investigate electric current. Sacerdote furthered Roentgen’s experiment by proposing a theory (The word theory comes from the Greek word theorein, meaning “to consider, observe…” in 1899. It was not until 1925 that the first polymer (A polymer (Etymology: from the Greek pollus, several, and meros, part) is a…) piezoelectric (electret) discovered. The electret was discovered by combining wax (chemically wax is an ester of ethylene glycol and two or one fatty acids…) of carnauba, rosin (rosin is the solid Residue obtained after the distillation of turpentine,…), beeswax (Bee is an ambiguous popular name denoting certain insects in French…), and by cooling the mixture (A mixture is a combination of two or more solid substances, liquids or gases…) while a continuous electrical voltage was applied to it to polarize it.The material solidified into a polymer with piezoelectric properties properties.
Polymers whose properties change in response to stimuli other than an electric field are part of this field of study. 1949 Katchalsky et. Abs. showed that collagen filaments (Collagen is a family of fibrous proteins that make up connective tissue…) converted into an acid (An acid is a chemical compound generally defined by its reactions…) or into an alkaline solution show a significant change Volume (Volume, in the physical or mathematical sciences, is a quantity that measures expansion…)[2]. Collagen filaments contract in alkaline solution and relax in acidic solution. Other stimuli (such as pH variation) have been tested, but research (scientific research primarily denotes any action taken to…) has focused more on electroactive polymers because these are the best contenders on mimicking complex biological systems.
Significant progress was not made until the 1960s. In 1969, Kawai was able to prove that polyvinylidene fluoride fluoride (PVDF) has a very strong piezoelectric effect[2]. This brilliant discovery enabled the search for polymers with properties similar to PVDF. In 1977 the first conductive polymers were developed by Hideki Shirakawa (Hideki Shirakawa (20 August 1936 in Tokyo) is a Japanese chemist. Alan MacDiarmid, Alan…) et.al. discovered [3]. Shirakawa, in collaboration with Alan MacDiarmid (Alan Graham MacDiarmid (April 14, 1927 in Masterton, New Zealand – February 7, 2007…) and Alan Heeger (Alan Jay Heeger (January 22, 1936 in Sioux City, Iowa, USA) is Chemist…) showed that polyacetylene is conductive and that by doping with iodine vapor () (iodine is a chemical element of the halogen family, symbol I and…) it is possible to increase its conductivity 8 orders of magnitude Its conductivity was comparable with that of a metal (A metal is a chemical element capable of donating electrons to form…) In the 1980s, a variety of polymers with conductive or piezoelectric properties are discovered.
In the early 1990s, metal-ion composite polymers (IPMC) were developed that exhibited electroactive properties far superior to those of the first EAPs. The main advantage of IPMCs is that they exhibit deformations after electrical excitations of less than 1 or 2 volts[2].