Microencapsulation effects on the electro-optical behavior of polymer cholesteric liquid crystal flakes

A modeling method is introduced for predicting the effect of microencapsulation on the electro-optical behavior of polymer cholesteric liquid crystal (PCLC) flakes suspended in a host fluid. The electric field acting on the flakes is significantly altered as various materials and boundary conditions are explored. The modeling predicts that test cells with multiple materials in the electric field path can have a wide range of electro-optic responses in AC electric fields. For DC drive conditions at high field strengths and test cell materials with low dielectric constants, electrophoretic behavior is observed for PCLC flakes. Prototype test cells for several encapsulation configurations are characterized for their resulting electro-optical behavior. The observed flake motions are in good agreement with the predicted results. This modeling method is shown to be a useful predictive tool for developing switchable particle devices utilizing microencapsulated dielectric particles in a host fluid medium.;This work further builds on previous research on flake motion in a host fluid suspension, exploring flake doping effects, both internal and surface coated. Host fluids were also doped for increased conductivity and are explored for their effect on PCLC flake motion. A low dielectric property host fluid doped with an aqueous salt solution and a surfactant is found to enable Maxwell-Wagner reorientation in a DC electric field. In an AC electric field the doped host fluid is found to have dual-frequency response enabling a reverse drive for PCLC flakes. Below the turnover frequency, flakes align parallel to the electric field and above the turnover frequency the flakes align perpendicular.