Electroactive Polymers

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Electroactive polymers (EAP) are polymers that change their shape when an electrical voltage is applied. These materials are used as actuators or sensors . Due to the similarity of their functioning to that of natural muscles , they are often also called "artificial muscles".

A general distinction is made between ionic EAP and electronic EAP .

In ionic EAP, the mechanism of action is based on mass transport (diffusion) of ions. Subgroups of such EAP are conductive polymers, ionic metal-polymer composites and ionic gels .

The mode of operation of electronic EAP, however, is based on electronic charge transport. This group includes electrostrictive and ferroelectric polymers as well as dielectric elastomers .

Advantages of EAP compared to other actuator materials, such as B. piezoelectric ceramics, are the high elongations that can be achieved (up to 380%), as well as the low density of the polymers and the free formability.

history

The first scientific work on EAP was published in 1880 by Wilhelm Conrad Röntgen . He conducted an experiment with a rubber band that he hung on one side and stretched with weights. After being electrically charged, he observed an increase in length of several percent, which could be reversed by discharging the rubber.

There are many practical uses for this technology. According to a patent application published in June 2014, Apple is planning an adjustable optical shutter made of electroactive polymers for the main camera of its iPhone .

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Individual evidence

  1. ^ Yoseph Bar-Cohen (Ed.): Electroactive Polymer (EAP) Actuators as Artificial Muscles: Reality, Potential, and Challenges . 2nd Edition. SPIE Press, Bellingham 2004, ISBN 978-0-8194-8112-2 , doi : 10.1117 / 3.547465 .
  2. ↑ Tiesheng Wang, Meisam Farajollahi, Yeon Sik Choi, I-Ting Lin, Jean E. Marshall, Noel M. Thompson, Sohini Kar-Narayan, John DW Madden, Stoyan K. Smoukov: Electroactive polymers for sensing . In: Interface Focus . tape 6 , no. 4 , 2016, 20160026, doi : 10.1098 / rsfs.2016.0026 , PMID 27499846 (free full text).
  3. ^ Wilhelm Conrad Röntgen: About the changes in shape and volume of dielectric bodies caused by electricity . In: Annals of Physics . tape 247 , no. 11 , 1880, p. 771-786 ( digitized on Gallica ).
  4. ↑ Patent US20140168799 : Artificial muscle camera lens actuator. Published July 19, 2014 , Inventors: Aurelien R. Hubert, Douglas S. Brodie, Iain A. McAllister, Jeffrey N. Gleason. ‌

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