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Proceedings Paper

Electrically stimulated bilayer hydrogels as muscles
Author(s): Paul D. Calvert; Zengshe Liu
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Paper Abstract

Muscle-like actuators have been made from bilayers of crosslinked polyacrylamide and polyacrylic acid hydrogels sandwiched between electrodes. The polyacrylic acid responds to applied positive polarity field by contracting and expelling water which is taken up by the polyacrylamide layers. Previous studies have shown that the effective swelling modulus of polyacrylamide is much lower than polyacrylic acid. Hence the polyacrylamide acts as a sponge. As the polyacrylic acid layer contracts in the x, y and z directions the polyacrylamide is also pulled in on x and y, so that the whole stack becomes narrower and expands along the z- axis. Reversing the field reverses this effect with a time constant of about 1 minute for 1 mm thick layers with a thickness change of about 10%. Linear changes up to 50% have been obtained. Other gel actuators either transfer water across a sheet and so bend, or contract by expelling water. This new system shows a linear contraction and expansion without a volume change and so can be run (sealed) in a dry environment.

Paper Details

Date Published: 28 May 1999
PDF: 6 pages
Proc. SPIE 3669, Smart Structures and Materials 1999: Electroactive Polymer Actuators and Devices, (28 May 1999); doi: 10.1117/12.349682
Show Author Affiliations
Paul D. Calvert, Univ. of Arizona (United States)
Zengshe Liu, Univ. of Arizona (United States)


Published in SPIE Proceedings Vol. 3669:
Smart Structures and Materials 1999: Electroactive Polymer Actuators and Devices
Yoseph Bar-Cohen, Editor(s)

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