Liquid crystal (LC) is a intermediate phase of matter possessing both the mobility of liquids and the long-range molecular ordering of crystal. Due to the unique combination of properties, LC has been widely used to create Responsive Materials (also known as Smart or Functional Materials) that optically report information about their environment, such as changes in electric field (Smart-Window; Smart-Phone Displays), temperature (Medical Thermography; Thermo Paint) or mechanical shear (Aerodynamics), and the arrival of chemical and biological stimuli (Sensors). Research in our laboratory seeks to understand how the unique characteristics of LC mediate intermolecular / interparticle / interfacial phenomena and leverage the knowledge to design New Class of Smart Materials that will enable applications in a variety of fields, including Drug delivery/release system, Sensors, Actuator (micromachine), Microfluidics, and Molecular/colloidal self-assembly.
Current Research Topics
1. Design of Smart Soft Material
Summary : Due to the anisotropic elasticity inherent to liquid crystals (LCs), microparticles, when dispersed in LCs, are trapped within the LC bulk, while the microparticles in isotropic liquids will diffuse into surrounding environments (e.g, air, water). By leveraging the elastic sequestration of microparticles and anisotropic optical properties unique to LC, we have designed a new class of smart materials that not only optically report a targeted stimulus but also transform their environments via triggered release of microcargo (e.g., cleaning agent, antibacterial agent) that were initially trapped within LCs (NATURE, 557, 539 (2018)). For example, we have designed LC systems that are triggered by the touch of a human finger and the arrival of motile bacteria. Most importantly, this is the first example of material that responds to living cells like human immune system. In this research project, we will explore how the self-reporting and self-regulating functions of new responsive soft materials can be programmed through an interplay of intermolecular and interfacial forces in diverse geometries.
2. Molecular / Colloidal Self-Assembly Mediated by Liquid Crystallinity
Summary : The anisotropic mechanical properties of liquid crystals (LCs) give rise to unique interparticular and interfacial interactions involving guest species, raging from small molecules to micrometer-sized colloid dispersed in the bulk LCs or assembled at LC interfaces, thus permitting the formation of programmable molecular / colloidal assemblies with organizations not found in isotropic liquids. For example, we demonstrated that chemical vapor polymerization can be performed on surfaces coated with thin films of liquid crystals to synthesize organized assemblies of end-attached polymer nanofibers with programmable size, shape, and chemical functionality (SCIENCE, 362, 804 (2018)). In addition, we showed topological defects induced in the bulk LC or around colloids can be exploited to program assemblies of small molecules and colloids into two- or three- dimensional ordered structures (PRL, 116, 147801 (2016)). In this research, we will explore how the anisotropic interactions between guest species in LCs are mediated by the ordering of LCs that can be manipulated by weak cues (e.g., electromagnetic field, pressure, molecular binding). This study will provide new design rules for molecular / colloidal self-assemblies with a wide range of organizations and functionalities.