Modeling mechanochromatic lamellar gels

Consisting of alternating swelling and nonswelling polymeric layers (SLs and NLs), lamellar gels are one-dimensional photonic crystals with mechanically tunable optical properties. The lamellar structure induces a constraint between the SLs and the NLs, resulting in a highly anisotropic swelling behavior that is coupled with deformation. The coupling gives rise to the mechanochromatic effect, i.e., the color change in the material in response to mechanical deformations. A quantitative understanding of the coupling behavior is the key to many applications. This paper formulates a nonlinear continuum model for lamellar gels by considering the constrained swelling and anisotropic deformation in both layers. A finite-element method is further developed to simulate the mechanochromatic response of a lamellar gel undergoing a nonuniform field.