Self-shaping Liquid Crystals: This research demonstrates a fully reversible transformation, addressing a longstanding problem in the controlled shape transformation of liquid crystals, where LC droplets transform into fibers. This transformation is achieved by finely tuning the internal forces in the LCs and adjusting the surface tension, all controlled by changes in temperature. Distinct surfactants, one in the LC phase and another in the surrounding water, facilitate this process. These surfactants lower the surface tension, enabling the LC droplets to reshape into either straight or branched fibers while maintaining their original volume. This capability is applicable across various LC phases.
Experimentally accessible macroscopic negative nematic order parameter: Our research utilizing microfluidic techniques has led to the innovative realization of LCE shells with both positive (S > 0) and negative (S < 0) nematic order parameters, a measure of the alignment of LC molecules. The nematic scalar order parameter is described as S=1/2 〈3cos^2 θ-1〉, where θ indicates the angle between the long axis of the LC molecule and director n. The S value lies between -0.5 and 1. The negative order parameter value is considered inaccessible due to a big difference between local and global free energy minimums in nematics. Our breakthrough involves stretching LCE shells outward with water osmosis and a two-step polymerization process. This process locks the positive uniaxial anisotropy molecules into the in-plane state, allowing osmotic stretching to force the molecules to be tangential to the surface, thus achieving a state where no preferred in-plane orientation (θ=90°) is possible. Catalyst-initiated polymerization makes the local energy minimum state achievable, and UV-initiated polymerization permanently locks the anti-ordered state, inverting the actuation mechanism compared to positive-order nematic LCE shells.
Light guiding liquid crystal fibers: Another focused research direction is demonstrating the potential of LC fibers’ light guiding by total internal reflection at the LC-water interface. This unique setting paves a new direction in LC photonics, particularly in developing soft topological photonic actuators for structured photonics.
Education and Outreach: Our lab is committed to providing hands-on training in Experimental Soft Matter Physics. We welcome students and early-stage researchers interested in exploring the field of interfacial soft matter. Join us in our journey to advance the understanding and application of LC soft matter science and technology.