The 26th issue of the WW-EAP Newsletter is now available at:
http://ndeaa.jpl.nasa.gov/nasa-nde/newsltr/WW-EAP_Newsletter13-2.pdf
This newsletter on the field of electroactive polymers, edited by Dr. Yoseph Bar-Cohen, addresses the need for rapid communication of progress in the field and state-of-the-art capabilities.
For a dielectric elastomer membrane we show giant voltage-triggered expansion of area by 1692%, far beyond the largest values reported in the literature.
Abstract:A hydrostatically coupled dielectric elastomer (HCDE) actuator consists of two membranes of a dielectric elastomer, clamped with rigid circular rings. Confined between the membranes is a fixed volume of a fluid, which couples the movements of the two membranes when a voltage or a force is applied. This paper presents a computational model of the actuator, assuming that the membranes are neo-Hookean, capable of large and axisymmetric deformation. The voltage-induced deformation is described by the model of ideal dielectric elastomer. The forc
We develop a method of poroelastic relaxation indentation (PRI) to characterize thin layers of gels. The solution to the time-dependent boundary-value problem is obtained in a remarkably simple form, so that the force-relaxation curve obtained by indenting a gel readily determines all the poroelastic constants of the gel—the shear modulus, Poisson’s ratio, and the effective diffusivity. The method is demonstrated with a layer of polydimethylsiloxane immersed in heptane.
I gave a seminar at Xian Jiaotong University on 27 October 2009. I recently found the video of the seminar online. The seminar was in Chinese, but the slides were in English.
If the subject interests you, the following papers will lead you to the literature.
This paper uses the thermodynamic data of aqueous solutions of uncrosslinked poly(N-isopropylacrylamide) (PNIPAM) to study the phase transition of PNIPAM hydrogels. At a low temperature, uncrosslinked PNIPAM can be dissolved in water and form a homogenous liquid solution. When the temperature is increased, the solution separates into two liquid phases with different concentrations of the polymer. Covalently crosslinked PNIPAM, however, does not dissolve in water, but can imbibe water and form a hydrogel. When the temperature is changed
