Surface topography and its transition of nematic elastomers due to photoinduced deformation

Curvature in nematic elastica responding to light and heat

Nematic elastic bodies can develop a gradient of response to heat, light and other stimuli. They then bend and develop curvature in a complex manner depending on director field distributions, on whether they are monodomain or polydomain structures and on linear or nonlinear light absorptive processes. In each case, we derive the general weak response where bend in each direction is treated independently of that in others. In a subsequent paper, we address the reverse phenomenon, that is of strong spontaneous distortion leading to curvature suppression.

Polarization dependence of optically driven polydomain elastomer mechanics

We model how polarized and unpolarized light can cause mechanical response in polydomain nematic and related photoelastomers. The reduction of order by heating and the consequential large strains that are known from nematic elastomers can alternatively be caused by light-induced bending of rodlike dye molecules which then equally reduce the order of their nematic hosts. While there is no mechanical response to heating of polydomain elastomers, mechanical response to light is possible by the selective absorption of light according to how domains are aligned with respect to the polarization direction or with respect to the propagation direction in the case of unpolarized light. We find large contractions or elongations, depending on the nature of polarization. The responses are nonmonotonic with light intensity.

Surface deformation of nematic elastomers under striped illumination

Nematic elastomers containing azobenzene chromophores are activated upon photoabsorption. We study the surface deformation of such elastomers under striped illumination. For an arbitrary orientation of the nematic axis, we obtain an analytical solution to the problem via a phenomenological continuum model. Numerical computations indicate that the profile of the deformed surface depends not only on the stripe width but also on the orientation of the nematic axis. The result may provide a mechanism to manipulate the surface topography of elastomers.