Poroelastic relaxation indentation of thin layers of gels

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. (C) 2011 American Institute of Physics. [doi:10.1063/1.3647758]