Liquid Crystalline Tactoidal Microphases in Ferrofluids: Spatial Positioning and Orientation by Magnetic Field Gradients

Liquid crystals form the basis of liquid crystal displays (LCDs) that are used in smartphones and computer terminals. Controlling the orientation of liquid crystals in displays and other applications is crucially important for controlling their properties. In work published this month in the journal Chem, graduate Pei-Xi Wang from the MacLachlan group showed a new method to align liquid crystals. In previous research, Pei-xi showed that liquid crystalline microdomains will exclude particles that are bigger than about 20 nanometres. When magnetic particles are combined with the liquid crystal, they are excluded from the liquid crystalline droplets. This leaves the inside and outside of the particles with different magnetic susceptibilities, or degree of attraction to magnets. By applying a magnet to the mixture of magnetic nanoparticles and liquid crystal in water, the orientation and physical properties of the liquid crystal could be controlled. This new method for aligning and controlling liquid crystals could be useful for developing materials for filtration and optics. (The image shows a magnetic trap formed using two magnets to control the nanoparticle / liquid crystal mixture.)