Studies of photo-thermal deformations of liquid crystal elastomers under local illumination

ABSTRACT

In this work we present studies of micron scale deformations of dye doped liquid crystal elastomers (LCEs) subject to localized laser illumination. Due to coupling between orientational order of mesogenic units and shape of polymer backbone of the LCE, reduction of the nematic order in the illuminated region produced local stress favoring material contraction along the director and expansion in the perpendicular plane. As a result, a nonuniform bulk deformation and a micron scale undulation of the sample surface was induced, which we studied via observation of the far field diffraction of the illuminating beam. We concluded that the light induced deformation of the studied samples was driven primarily by heating rather than by photoisomerization of the dye molecules. Additionally, we reproduced experimental results by numerical calculation of the optical diffraction, and by finite difference simulation of LCE deformation based on nonlocal elasticity model.

KEYWORDS:

• Liquid crystal elastomers
• light induced deformation
• nonlinear reflection