Consisting of alternating swelling and nonswelling polymeric layers (SLs and NLs), lamellar gels are 1D photonic crystals with tunable optical properties.  The lamellar structure induces a constraint between the SLs and the NLs, resulting in an anisotropic swelling behavior coupled with deformation.  The coupling gives rise to the mechano-chromatic effect, and quantitative understanding of it is the key to many applications.  This letter formulates a nonlinear continuum model for lamellar gels by considering the constrained swelling of SLs and the anisotropic deformation in both types of layers.  A finite-element method is further developed to simulate the response to non-uniform deformation.

Magneto-rheological elastomers (MREs), a class of polymer-based composites with dispersed magnetic filler particles, are known for their tunable stiffness.  The magnetic-field-induced stiffening effect, namely the magneto-rheological (MR)effect, is often attributed to the magnetic dipolar interaction.  The direct attraction between two magnetic dipoles could increase the shear modulus of the material, but not the tensile modulus, while experiments showed increases in both.  In this paper, we investigate the possible mechanisms of the MR effect using two different methods: a dipolar interaction model and a micromechanics model based on a continuum field the

Ionic polymer conductor network composite (IPCNC) is a mixed conductor consisting of a network of loaded ionomer and another network of metallic particles. It is known that the microstructure of the composite, especially that of the electrodes, plays a dominating role in the performance of an IPCNC. However the microstructures of IPCNC have seldom been addressed in theoretical models. This letter formulates a continuum field theory for IPCNC by considering a supercapacitor-like microstructure with a large distributed interface area. The theory is then applied to the study of the equilibrium deformation and electrochemistry in a thin-sheet IPCNC actuator.

Dielectric elastomer, as an important category of electroactive polymers, is known to have viscoelastic properties that strongly affect its dynamic performance and limit its application. Very few models accounting for the effects of both electrostatics and viscoelasticity exist in the literature, and even fewer are capable of making reliable predictions under general loads and constraints. Based on the principals of nonequilibrium thermodynamics, this paper develops a field theory that fully couples the large inelastic deformations and electric fields in deformable dielectrics. Our theory recovers existing models of elastic dielectrics in the equilibrium limit.

Due to the migration of mobile molecules and ions, a thin diffusive layer of distributed charge - the electric double layer - forms at the interface between a polyelectrolyte gel and a liquid ionic solution.  When two polyelectrolyte gels are brought closely together, the electric double layers overlap and interact with each other, resulting in an effective repulsion.  The multiphysics coupling nature of soft gels makes their surface interactions significantly different from the interactions between rigid solids.

The electric-field-induced phase transition was investigated under mechanical confinements in bulk samples of an antiferroelectric perovskite oxide at room temperature. Profound impacts of mechanical confinements on the phase transition are observed due to the interplay of ferroelasticity and the volume expansion at the transition. The uniaxial compressive prestress delays while the radial compressive prestress suppresses it. The difference is rationalized with a phenomenological model of the phase transition accounting for the mechanical confinement.

When a block of an elastomer is bent, the compressed surface may form a crease. This paper analyzes the critical condition for creasing by comparing the elastic energy in a creased body and that in a smooth body. This difference in energy is expressed by a scaling relation. Critical conditions for creasing are determined for elastomers subject to general loads and gels swelling under constraint. The theoretical results are compared with existing experimental observations.

Immersed in an ionic solution, a network of polyelectrolyte polymers imbibes the solution and swells, resulting in a polyelectrolyte gel. The swelling is reversible, and is regulated by ionic concentrations, mechanical forces, and electric potentials. This paper develops a field theory to couple large deformation and electrochemistry. A specific material model is described, including the effects of stretching the network, mixing the polymers with the solvent and ions, and polarizing the gel. We show that the notion of osmotic pressure in a gel has no experimental significance in general, but acquires a physical interpretation within the specific material model.