A unifying fundamental element of our research will be the harnessing of anisometric interactions in soft matter to achieve new functions. We seek to use orientation-dependent interactions to modulate self-assembly, photonic properties and active transport processes. We also employ these interactions in detection mechanisms to create a range of biologically and technologically relevant soft materials. These materials include biomimetic photonic structures, biosensors and materials for guided active transport.
Detection of coronaviruses: Today, the warming planet is playing a central role in driving the resurgence and redistribution of infectious diseases across the globe. In this context, in addition to identification of specific pathogens, it is also crucial to screen for classes of pathogens, such as enveloped viruses, to keep track of new and emerging health threats. To address this need, we employ liquid crystal-based sensing principles to detect flaviviruses and coronaviruses. These viruses include COVID-19, West Nile, Zika, Dengue and SARS, some of which are associated with widespread morbidity and mortality throughout the world. Flaviviruses and coronaviruses are both enveloped viruses, but they have complex macromolecular organizations that are distinct between themselves and different from other classes of enveloped viruses. More broadly, a range of fundamental questions regarding the interactions of virus-specific lipid/proteins with liquid crystals need to be resolved to enable rational design of biosensors for viruses based on liquid crystals. Different confined geometries of liquid crystals, including thin films, droplets and microfabricated wells will be employed to explore and optimize sensing strategies for viruses. Using anisometric mechanical strain on cell membranes for single cell analysis It is known that changes in mechanical properties of biological cells, for instance, red blood cells (RBCs), play a profound role in physiological processes. For instance, increased stiffness of sickle cells reduce the lifespan and the ability of blood cells to flow through narrow capillaries where they commonly encounter anisometric strain. Furthermore, the stiffness of mammalian cells has been shown to be a marker of the metastatic potential of cancers. We study the deformability and relaxation of cell membranes when subjected to anisometric strain using an ordered fluid, specifically, lyotropic chromonic liquid crystals (LCLCs), as a host. LCLCs are a class of polyaromatic dyes that are soluble in water and form supramolecular semi-flexible rod-like assemblies upon solvation. The water solubility and bio-compatibility of LCLCs make them suitable for biological applications. In addition we are also interested in the phase behavior of LCLCs as a function of different counter-ions will also be explored using a combination of microscopy, rheology and scattering techniques. This will enable studies of biological membranes in the presence of specific cations that are known to influence cell membrane properties. Materials: Using surface tension-driven instabilities for breaking up oil films This research theme is motivated by a simple table-top experiment wherein a large drop of oil is placed atop a petri-dish filled with water. We explore several means of creating surface tension-driven instabilities to break down the large oil drop into tiny droplets. This system will be used to model the cleaning up of oil spills. In particular, the role of orientational elasticity in influencing jet-breakup will be explored. In addition, the more general topic of droplet breakup in ordered fluids will be examined. Specific efforts are directed towards droplet breakup studies of lyotropic chromonic liquid crystals wherein open questions regarding the rheological behavior of these fluids (wormlike micellar solutions or rigid rods) remain to be answered. Biomimicry of structural color using CNCs: Natural photonic crystals present extraordinary optical properties and provide valuable design principles for applications from light harvesting devices to anticounterfeit films. Photonic crystals are abundant in several biological species including beetles, butterflies and even certain classes of berries. The remarkable ability of cellulose nanocrystals (CNC) suspensions to form helical structures that persist in solvent-free films highlights their potential for use in photonic applications. Additionally, the tunability of the physical characteristics of CNC suspensions, including their chiral pitch length via changes in ionic strength, counter-ions and temperature, make them well-suited for replication of structural color found in nature. Potential applications of research on CNCs include reflective windows and anticounterfeit materials. Specifically, we explore the fundamentals involved in the transfer of chiral structures of CNCs to organosilica substrates. Two such substrates, when sandwiched with a nematic retarder, can create energy-efficient windows capable of total reflection. We are also interested in transferring chiral structures formed by CNCs onto non-planar geometries of organosilica substrates such as hemi-spheres and toroids which have promise for omnidirectional lasing. |
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