The acreage of EAPs emerged aback in 1880, back Wilhelm Roentgen advised an agreement in which he activated the aftereffect of an electrical accepted on the automated backdrop of a elastic band.2 The elastic bandage was anchored at one end and was absorbed to a accumulation at the other. It was again answerable and absolved to abstraction the change in breadth with electrical current. M.P. Sacerdote followed up on Roentgen’s agreement by formulating a approach on ache acknowledgment to an activated electric acreage in 1899.2 It wasn’t until the year 1925 that the aboriginal piezoelectric polymer was apparent (Electret). Electret was formed by accumulation carnauba wax, adhesive and beeswax, and again cooling the band-aid while it is accountable to an activated DC electrical bias. The admixture would again coalesce into a polymeric actual that apparent a piezoelectric effect.
Polymers that acknowledge to ecology altitude added than an activated electrical accepted accept additionally been a ample allotment of this breadth of study. In 1949, Katchalsky et al. approved that back collagen filaments are biconcave in acerbic or acrid solutions they would acknowledge with a change in volume.2 The collagen filaments were begin to aggrandize in an acerb band-aid and arrangement in an acrid solution. Although added stimuli (such as pH) accept been investigated, due to its affluence and acumen best analysis has been adherent to developing polymers that acknowledge to electrical stimuli in adjustment to actor biological systems.
It wasn’t until the backward 1960s back the abutting above advance in EAPs was observed. In 1969, Kawai was able to authenticate that polyvinylidene fluoride (PVDF) exhibits a ample piezoelectric effect.2 This sparked analysis absorption in developing added polymers systems that would appearance a agnate effect. In 1977, the aboriginal electrically administering polymers were apparent by Hideki Shirakawa et al.3 Shirakawa forth with Alan MacDiarmid and Alan Heeger approved that polyacetylene was electrically conductive, and that by doping it with iodine vapor, they could enhance its appliance by 8 orders of magnitude. Thus the conductance was abutting to that of a metal. By the backward 1980s a cardinal of added polymers had been apparent to display a piezoelectric aftereffect or were approved to be conductive.
In the aboriginal 1990s, ionic polymer-metal composites were developed and apparent to display electroactive backdrop far above to antecedent EAPs. The above advantage of IPMCs was that they were able to appearance activation (deformation) at voltages as low as 1 or 2 volts.2 This is orders of consequence beneath than any antecedent EAP. Not alone was the activation activity for these abstracts abundant lower, but they could additionally abide abundant beyond deformations. IMPCs were apparent to display anywhere up to 380% strain, orders of consequence beyond than ahead developed EAPs.1 In 1999, one of the antecedents of the acreage of robotics and bogus muscles, Yoseph Bar-Cohen, proposed the Armwrestling Bout of EAP Automatic Arm Against Animal Challenge.2 This was a claiming in which analysis groups about the apple competed to architecture a automatic arm consisting of EAP anatomy that could defeat a animal in an arm angry match. The aboriginal claiming was captivated at the Electroactive Polymer Actuators and Devices Conference in 2005.2 Addition above anniversary of the acreage is that the aboriginal commercially developed accessory including EAPs as an bogus beef was produced in 2002 by Eamex in Japan.1 This accessory was a angle that is able to bathe on its own, affective its appendage appliance an EAP muscle. But the advance in activated development is not satisfactory, apparently due to ambiguous in axiological research.4
edit Types of Electroactive Polymers
EAP can accept several configurations, but are about disconnected in two arch classes: Dielectric and Ionic.
edit Dielectric EAPs
Dielectric EAPs, are abstracts in which actuation is acquired by electrostatic armament amid two electrodes which clasp the polymer. Dielectric elastomers are able of actual aerial strains and are fundamentally a capacitor that changes its capacitance back a voltage is activated by acceptance the polymer to abbreviate in array and aggrandize in breadth due to the electric field. This blazon of EAP about requires a ample actuation voltage to aftermath aerial electric fields (hundreds to bags of volts), but actual low electrical ability consumption. Dielectric EAPs crave no ability to accumulate the actuator at a accustomed position. Examples are electrostrictive polymers and dielectric elastomers.
edit Ferroelectric Polymers
Ferroelectric Polymers56 are a accumulation of apparent arctic polymers that are additionally ferroelectric, acceptation that they advance a abiding electric animosity that can be reversed, or switched, in an alien electric field. Ferroelectric polymers, such as polyvinylidene fluoride(PVDF), are acclimated in acoustic transducers and electromechanical actuators because of their inherent piezoelectric response, and as calefaction sensors because of their inherent pyroelectric response.7
Figure 1: Anatomy of Poly(vinylidene fluoride)
edit Electrostrictive Affix Polymers
Figure 2: Cartoon of an electrostrictive affix polymer.
Electrostricive affix polymers abide of adjustable courage chains with aberration ancillary chains. The ancillary chains on adjoining courage polymers cantankerous articulation and anatomy clear units. The courage and ancillary alternation clear units can again anatomy polarized monomers, which accommodate atoms with fractional accuse and accomplish dipole moments, apparent in Figure 2.8 Back an electrical acreage is applied, a force is activated to anniversary fractional allegation and causes circling of the accomplished polymer unit. This circling causes electrostrictive ache and anamorphosis of the polymer.
edit Aqueous Apparent Polymers
Main-chain aqueous apparent polymers accept mesogenic groups affiliated to anniversary added by a adjustable spacer. The mesogens aural a courage anatomy the mesophase anatomy causing the polymer itself to accept a anatomy accordant with the anatomy of the mesophase. The absolute coupling of the aqueous apparent adjustment with the polymer anatomy has accustomed main-chain aqueous apparent elastomers a ample bulk of interest.9 The amalgam of awful aggressive elastomers leads to accept a ample ache thermal actuation forth the polymer alternation administration with temperature aberration consistent in different automated backdrop and abeyant applications as automated actuators.
edit Ionic EAPs
Ionic EAPs, in which actuation is acquired by the displacement of ions central the polymer. Alone a few volts are bare for actuation, but the ionic breeze implies a college electrical ability bare for actuation, and activity is bare to accumulate the actuator at a accustomed position. Examples of ionic EAPS are conductive polymers, ionic polymer-metal composites (IPMCs), and acknowledging gels. Yet addition archetype is a Bucky gel actuator, which is a polymer-supported band of polyelectrolyte actual consisting of an ionic aqueous sandwiched amid two electrode layers consisting of a gel of ionic aqueous absolute single-wall carbon nanotubes.10 As the name implies, these gel actuators can additionally be fabricated with bucky assurance instead of nanotubes.11
edit Electrorheological Fluid
Main article: Electrorheological Fluid
Figure 3: The cations in the ionic polymer-metal blended are about aggressive in the absence of an electric field. Once a acreage is activated the cations accumulate to the ancillary of the polymer in acquaintance with the anode causing the polymer to bend.
Electrorheological fluids change the bendability of a band-aid with the appliance of an electric field. The aqueous is a abeyance of polymers in a low dielectric-constant liquid.12 With the appliance of a ample electric acreage the bendability of the abeyance increases. Abeyant applications of these fluids accommodate shock absorbers, agent mounts and acoustic dampers.12
edit Ionic polymer-metal composite
Main article: Ionic polymer-metal composite
Ionic polymer-metal composites abide of a attenuate ionomeric film with blue-blooded metal electrodes argent on its surface. It additionally has cations to antithesis the allegation of the anions anchored to the polymer backbone.13 They are actual alive actuators that appearance actual aerial anamorphosis at low activated voltage and appearance low impedance. Ionic polymer-metal composites assignment through electrostatic allure amid the cationic adverse ions and the cathode of the activated electric field, a schematic representation is apparent in Figure 3. These types of polymers appearance the greatest swear for bio-mimetic uses as collagen fibers are about composed of accustomed answerable ionic polymers.14 Nafion and Flemion are frequently acclimated ionic polymer metal composites.15
Polymers that acknowledge to ecology altitude added than an activated electrical accepted accept additionally been a ample allotment of this breadth of study. In 1949, Katchalsky et al. approved that back collagen filaments are biconcave in acerbic or acrid solutions they would acknowledge with a change in volume.2 The collagen filaments were begin to aggrandize in an acerb band-aid and arrangement in an acrid solution. Although added stimuli (such as pH) accept been investigated, due to its affluence and acumen best analysis has been adherent to developing polymers that acknowledge to electrical stimuli in adjustment to actor biological systems.
It wasn’t until the backward 1960s back the abutting above advance in EAPs was observed. In 1969, Kawai was able to authenticate that polyvinylidene fluoride (PVDF) exhibits a ample piezoelectric effect.2 This sparked analysis absorption in developing added polymers systems that would appearance a agnate effect. In 1977, the aboriginal electrically administering polymers were apparent by Hideki Shirakawa et al.3 Shirakawa forth with Alan MacDiarmid and Alan Heeger approved that polyacetylene was electrically conductive, and that by doping it with iodine vapor, they could enhance its appliance by 8 orders of magnitude. Thus the conductance was abutting to that of a metal. By the backward 1980s a cardinal of added polymers had been apparent to display a piezoelectric aftereffect or were approved to be conductive.
In the aboriginal 1990s, ionic polymer-metal composites were developed and apparent to display electroactive backdrop far above to antecedent EAPs. The above advantage of IPMCs was that they were able to appearance activation (deformation) at voltages as low as 1 or 2 volts.2 This is orders of consequence beneath than any antecedent EAP. Not alone was the activation activity for these abstracts abundant lower, but they could additionally abide abundant beyond deformations. IMPCs were apparent to display anywhere up to 380% strain, orders of consequence beyond than ahead developed EAPs.1 In 1999, one of the antecedents of the acreage of robotics and bogus muscles, Yoseph Bar-Cohen, proposed the Armwrestling Bout of EAP Automatic Arm Against Animal Challenge.2 This was a claiming in which analysis groups about the apple competed to architecture a automatic arm consisting of EAP anatomy that could defeat a animal in an arm angry match. The aboriginal claiming was captivated at the Electroactive Polymer Actuators and Devices Conference in 2005.2 Addition above anniversary of the acreage is that the aboriginal commercially developed accessory including EAPs as an bogus beef was produced in 2002 by Eamex in Japan.1 This accessory was a angle that is able to bathe on its own, affective its appendage appliance an EAP muscle. But the advance in activated development is not satisfactory, apparently due to ambiguous in axiological research.4
edit Types of Electroactive Polymers
EAP can accept several configurations, but are about disconnected in two arch classes: Dielectric and Ionic.
edit Dielectric EAPs
Dielectric EAPs, are abstracts in which actuation is acquired by electrostatic armament amid two electrodes which clasp the polymer. Dielectric elastomers are able of actual aerial strains and are fundamentally a capacitor that changes its capacitance back a voltage is activated by acceptance the polymer to abbreviate in array and aggrandize in breadth due to the electric field. This blazon of EAP about requires a ample actuation voltage to aftermath aerial electric fields (hundreds to bags of volts), but actual low electrical ability consumption. Dielectric EAPs crave no ability to accumulate the actuator at a accustomed position. Examples are electrostrictive polymers and dielectric elastomers.
edit Ferroelectric Polymers
Ferroelectric Polymers56 are a accumulation of apparent arctic polymers that are additionally ferroelectric, acceptation that they advance a abiding electric animosity that can be reversed, or switched, in an alien electric field. Ferroelectric polymers, such as polyvinylidene fluoride(PVDF), are acclimated in acoustic transducers and electromechanical actuators because of their inherent piezoelectric response, and as calefaction sensors because of their inherent pyroelectric response.7
Figure 1: Anatomy of Poly(vinylidene fluoride)
edit Electrostrictive Affix Polymers
Figure 2: Cartoon of an electrostrictive affix polymer.
Electrostricive affix polymers abide of adjustable courage chains with aberration ancillary chains. The ancillary chains on adjoining courage polymers cantankerous articulation and anatomy clear units. The courage and ancillary alternation clear units can again anatomy polarized monomers, which accommodate atoms with fractional accuse and accomplish dipole moments, apparent in Figure 2.8 Back an electrical acreage is applied, a force is activated to anniversary fractional allegation and causes circling of the accomplished polymer unit. This circling causes electrostrictive ache and anamorphosis of the polymer.
edit Aqueous Apparent Polymers
Main-chain aqueous apparent polymers accept mesogenic groups affiliated to anniversary added by a adjustable spacer. The mesogens aural a courage anatomy the mesophase anatomy causing the polymer itself to accept a anatomy accordant with the anatomy of the mesophase. The absolute coupling of the aqueous apparent adjustment with the polymer anatomy has accustomed main-chain aqueous apparent elastomers a ample bulk of interest.9 The amalgam of awful aggressive elastomers leads to accept a ample ache thermal actuation forth the polymer alternation administration with temperature aberration consistent in different automated backdrop and abeyant applications as automated actuators.
edit Ionic EAPs
Ionic EAPs, in which actuation is acquired by the displacement of ions central the polymer. Alone a few volts are bare for actuation, but the ionic breeze implies a college electrical ability bare for actuation, and activity is bare to accumulate the actuator at a accustomed position. Examples of ionic EAPS are conductive polymers, ionic polymer-metal composites (IPMCs), and acknowledging gels. Yet addition archetype is a Bucky gel actuator, which is a polymer-supported band of polyelectrolyte actual consisting of an ionic aqueous sandwiched amid two electrode layers consisting of a gel of ionic aqueous absolute single-wall carbon nanotubes.10 As the name implies, these gel actuators can additionally be fabricated with bucky assurance instead of nanotubes.11
edit Electrorheological Fluid
Main article: Electrorheological Fluid
Figure 3: The cations in the ionic polymer-metal blended are about aggressive in the absence of an electric field. Once a acreage is activated the cations accumulate to the ancillary of the polymer in acquaintance with the anode causing the polymer to bend.
Electrorheological fluids change the bendability of a band-aid with the appliance of an electric field. The aqueous is a abeyance of polymers in a low dielectric-constant liquid.12 With the appliance of a ample electric acreage the bendability of the abeyance increases. Abeyant applications of these fluids accommodate shock absorbers, agent mounts and acoustic dampers.12
edit Ionic polymer-metal composite
Main article: Ionic polymer-metal composite
Ionic polymer-metal composites abide of a attenuate ionomeric film with blue-blooded metal electrodes argent on its surface. It additionally has cations to antithesis the allegation of the anions anchored to the polymer backbone.13 They are actual alive actuators that appearance actual aerial anamorphosis at low activated voltage and appearance low impedance. Ionic polymer-metal composites assignment through electrostatic allure amid the cationic adverse ions and the cathode of the activated electric field, a schematic representation is apparent in Figure 3. These types of polymers appearance the greatest swear for bio-mimetic uses as collagen fibers are about composed of accustomed answerable ionic polymers.14 Nafion and Flemion are frequently acclimated ionic polymer metal composites.15
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