Augmenting Dynamic Light Scattering with a Mixture of Positive and Negative Dielectric Anisotropy Liquid Crystals

A device is presented, wherein the opaque/translucent state is a dynamic scattering mode which is augmented by mixing nematic liquid crystal components of opposite dielectric properties and without the use of ionic additives. A liquid crystal with negative dielectric anisotropy is used as the host to which various liquid crystals with positive dielectric anisotropy are added. On its own, owing to the inherent ionic impurities, the negative LC undergoes electrohydrodynamic instabilities, however the resultant turbulent state does not yield a dynamic scattering mode with the requisite haze for practical privacy applications at low voltage. By optimizing the concentration of the positive LC in the mixtures, a scattering mode is obtained in which the haze reaches up to >90% while the transparent, 0 V, state remains essentially haze-free. We postulate that the positive-dielectric anisotropy liquid crystal serves to disrupt the vortex motion of the host negative-dielectric anisotropy nematic liquid crystal at the onset of the electrohydrodynamic instability, resulting in a chaotic state that scatters incident light. As a smart window, the device would require a smaller amount of liquid crystal (given the small cell gap -- 10 μm or smaller) and be switchable at a lower, safer, driving voltage than conventional smart windows based on liquid crystal-polymer composite mixtures.