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LC Droplet (lc + droplet)
Selected AbstractsLiquid Crystal Emulsions as the Basis of Biological Sensors for the Optical Detection of Bacteria and VirusesADVANCED FUNCTIONAL MATERIALS, Issue 14 2009Sri Sivakumar Abstract A versatile sensing method based on monodisperse liquid crystal (LC) emulsion droplets detects and distinguishes between different types of bacteria (Gram +ve and ,ve) and viruses (enveloped and non-enveloped). LCs of 4-cyano-4'-pentylbiphenyl transition from a bipolar to radial configuration when in contact with Gram ,ve bacteria (E. coli) and lipid-enveloped viruses (A/NWS/Tokyo/67). This transition is consistent with the transfer of lipid from the organisms to the interfaces of the micrometer-sized LC droplets. In contrast, a transition to the radial configuration is not observed in the presence of Gram +ve bacteria (Bacillus subtilis and Micrococcus luteus) and non-enveloped viruses (M13 helper phage). The LC droplets can detect small numbers of E. coli bacteria (1,5) and low concentrations (104,pfu mL,1) of A/NWS/Tokyo/67 virus. Monodisperse LC emulsions incubated with phosholipid liposomes (similar to the E. coli cell wall lipid) reveal that the orientational change is triggered at an area per lipid molecule of ,46,Å2 on an LC droplet (,1.6,×,108 lipid molecules per droplet). This approach represents a novel means to sense and differentiate between types of bacteria and viruses based on their cell-wall/envelope structure, paving the way for the development of a new class of LC microdroplet-based biological sensors. [source] Surfactant Effects on Morphology and Switching of Holographic PDLCs Based on Polyurethane Acrylates,CHEMPHYSCHEM, Issue 1 2007Ju Yeon Woo Abstract Effects of octanoic acid (OA) on the morphology, diffraction efficiency, and electro-optic properties of the transmission mode of holographic polymer,dispersed liquid crystals (HPDLC) are studied. Droplet size decreases with increasing OA content (0,9,%), and this leads to a monotonic increase in off-state diffraction with increasing OA content. However, on-state diffraction decreases with increasing applied voltage and shows a minimum at 6,% OA, for which minimum switching voltage (5 V,,m,1) and maximum contrast ratio (10) are obtained. Rise time and decay time decrease with increasing OA content. Interposition of OA between polymer and LC droplet is theoretically predicted by the spreading coefficient (,>0) calculated on the basis of the solubility parameter, while the coalescence behavior of droplets is described by a dimensionless group () called coalescence number. [source] Liquid Crystal Emulsions as the Basis of Biological Sensors for the Optical Detection of Bacteria and VirusesADVANCED FUNCTIONAL MATERIALS, Issue 14 2009Sri Sivakumar Abstract A versatile sensing method based on monodisperse liquid crystal (LC) emulsion droplets detects and distinguishes between different types of bacteria (Gram +ve and ,ve) and viruses (enveloped and non-enveloped). LCs of 4-cyano-4'-pentylbiphenyl transition from a bipolar to radial configuration when in contact with Gram ,ve bacteria (E. coli) and lipid-enveloped viruses (A/NWS/Tokyo/67). This transition is consistent with the transfer of lipid from the organisms to the interfaces of the micrometer-sized LC droplets. In contrast, a transition to the radial configuration is not observed in the presence of Gram +ve bacteria (Bacillus subtilis and Micrococcus luteus) and non-enveloped viruses (M13 helper phage). The LC droplets can detect small numbers of E. coli bacteria (1,5) and low concentrations (104,pfu mL,1) of A/NWS/Tokyo/67 virus. Monodisperse LC emulsions incubated with phosholipid liposomes (similar to the E. coli cell wall lipid) reveal that the orientational change is triggered at an area per lipid molecule of ,46,Å2 on an LC droplet (,1.6,×,108 lipid molecules per droplet). This approach represents a novel means to sense and differentiate between types of bacteria and viruses based on their cell-wall/envelope structure, paving the way for the development of a new class of LC microdroplet-based biological sensors. [source] Preparation and characterization of PDLC films formed using a two-step procedureADVANCES IN POLYMER TECHNOLOGY, Issue 1 2007Yu-Che Hsiao Abstract A novel polymer-dispersed liquid crystal composite film was prepared using liquid crystal and dual resins, namely, UV-curable urethane diacrylate and thermo-curable epoxy, with a fixed LC content of 50 wt%. A combination treatment of UV irradiation and heat was performed in sequential steps. At first, the urethane diacrylate resin was cross-linked through UV irradiation and a pre-UV-cured film was formed. Then, the pre-UV-cured film was heat treated for curing the thermo-curable epoxy resin. As the thermal polymerization continued, LC droplets were formed and became embedded within the polymer matrix. PDLC films obtained from the polymer matrix with refractive indices in a range from 1.511 to 1.523 (1.517 ± 0.006) have optimal electro-optical properties. Films with a refractive index higher than 1.523 have high contrast ratio (CR), threshold voltage (Vth), and V90, whereas those with a low refractive index of 1.508 have low CR, Vth, and V90. In this study, we found that PDLC composite films with optimal compositions prepared by dual resins (UV/thermal) have good electro-optical properties. © 2007 Wiley Periodicals, Inc. Adv Polym Techn 26:14,20, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20087 [source] |