EAPs ElectroActive Polymers

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.
Wikipedia

Types

  • Dielectric
    • Ferroelectric polymers
    • Electrostrictive graft polymers
    • Liquid crystalline polymers
  • Ionic
    • Electrorheological fluid
    • Ionic polymer-metal composite
    • Stimuli-responsive gels

Dielectric polymers are able to hold their induced displacement while activated under a DC voltage. This allows dielectric polymers to be considered for robotic applications. These types of materials also have high mechanical energy density and can be operated in air without a major decrease in performance. However, dielectric polymers require very high activation fields (>10 V/┬Ám) that are close to the breakdown level.

The activation of ionic polymers, on the other hand, requires only 1-2 volts. They however need to maintain wetness, though some polymers have been developed as self-contained encapsulated activators which allows their use in dry environments. Ionic polymers also have a low electromechanical coupling. They are however ideal for bio-mimetic devices.

Applications

Artificial muscles

As the most prospective practical research direction, EAPs have been used in artificial muscles. Their ability to emulate the operation of biological muscles with high fracture toughness, large actuation strain and inherent vibration damping draw the attention of scientists in this field.

Tactile displays

In recent years, “electro active polymers for refreshable Braille displays” has emerged to aid the visually impaired in fast reading and computer assisted communication. This concept is based on using an EAP actuator configured in an array form. Rows of electrodes on one side of an EAP film and columns on the other activate individual elements in the array. Each element is mounted with a Braille dot and is lowered by applying a voltage across the thickness of the selected element, causing local thickness reduction. Under computer control, dots would be activated to create tactile patterns of highs and lows representing the information to be read.

Microfluidics

EAP materials have huge potential for microfluidics e.g. as drug delivery systems, microfluidic devices and lab-on-a-chip. A first microfluidic platform technology reported in literature is based on stimuli-responsive gels. To avoid the electrolysis of water hydrogel-based microfluidic devices are mainly based on temperature-responsive polymers with lower critical solution temperature (LCST) characteristics, which are controlled by an electrothermic interface. Two types of micropumps are known, a diffusion micropump and a displacement micropump. Microvalves based on stimuli-responsive hydrogels show some advantageous properties such as particle tolerance, no leakage and outstanding pressure resistance. Besides these microfluidic standard components the hydrogel platform provides also chemical sensors and a novel class of microfluidic components, the chemical transistors (also referred as chemostat valves). These devices regulate a liquid flow if a threshold concentration of certain chemical is reached. Chemical transistors form the basis of microchemomechanical fluidic integrated circuits. “Chemical ICs” process exclusively chemical information, are energy-self-powered, operate automatically and are able for large-scale integration. Read more

Wikipedia

Share