Analysis of the internal configurations of droplets of liquid crystal using flow cytometry.

We report the use of flow cytometry to identify the internal ordering (director configurations) of micrometer-sized droplets of thermotropic liquid crystals (LCs) dispersed in aqueous solutions of adsorbates (surfactants and phospholipids). We reveal that changes in the configurations of the LC droplets induced by the adsorbates generate distinct changes in light scattering plots (side versus forward scattering). Specifically, when compared to bipolar droplets, radial droplets generate a narrower distribution of side scattering intensities (SSC, large angle light scattering) for a given intensity of forward scattering (FSC, small angle light scattering). This difference is shown to arise from the rotational symmetry of a radial LC droplet which is absent for the bipolar configuration of the LC droplet. In addition, the scatter plots for radial droplets possess a characteristic "S-shape", with two or more SSC intensities observed for each intensity of FSC. The origin of the experimentally observed S-shape is investigated via calculation of form factors and established to be due to size-dependent interference effects that differ for the forward and side scattered light. Finally, by analyzing emulsions composed of mixtures of bipolar and radial droplets at rates of up to 10,000 droplets per second, we demonstrate that flow cytometry permits precise determination of the percentage of radial droplets within the mixture with a coefficient of determination of 0.98 (as validated by optical microscopy). Overall, the results presented in this paper demonstrate that flow cytometry provides a promising approach for high throughput quantification of the internal configurations of LC emulsion microdroplets. Because large numbers of droplets can be characterized, it enables statistically robust analyses of LC droplets. The methodology also appears promising for quantification of chemical and biological assays based on adsorbate-induced ordering transitions within LC droplets.

[1]  Peter C. Mushenheim,et al.  Introduction to optical methods for characterizing liquid crystals at interfaces. , 2013, Langmuir : the ACS journal of surfaces and colloids.

[2]  N. Abbott,et al.  Influence of droplet size, pH and ionic strength on endotoxin-triggered ordering transitions in liquid crystalline droplets. , 2013, Soft matter.

[3]  Tanmay Bera,et al.  Optical detection of lithocholic acid with liquid crystal emulsions. , 2013, Langmuir : the ACS journal of surfaces and colloids.

[4]  Vera Joanne Aliño,et al.  Detecting proteins in microfluidic channels decorated with liquid crystal sensing dots. , 2012, Langmuir : the ACS journal of surfaces and colloids.

[5]  Saif A. Khan,et al.  Inkjet printing and release of monodisperse liquid crystal droplets from solid surfaces. , 2012, Langmuir : the ACS journal of surfaces and colloids.

[6]  Tanmay Bera,et al.  Polyelectrolyte-coated liquid crystal droplets for detecting charged macromolecules , 2012 .

[7]  N. Abbott,et al.  Liquid Crystalline Materials for Biological Applications. , 2012, Chemistry of materials : a publication of the American Chemical Society.

[8]  Vera Joanne Aliño,et al.  Liquid crystal droplets as a hosting and sensing platform for developing immunoassays. , 2011, Langmuir : the ACS journal of surfaces and colloids.

[9]  C. Murphy,et al.  Endotoxin-Induced Structural Transformations in Liquid Crystalline Droplets , 2011, Science.

[10]  N. Abbott,et al.  Recent advances in colloidal and interfacial phenomena involving liquid crystals. , 2011, Langmuir : the ACS journal of surfaces and colloids.

[11]  J. Als-Nielsen,et al.  Elements of Modern X-ray Physics: Als-Nielsen/Elements , 2011 .

[12]  M. E. Buck,et al.  Immobilization of polymer-decorated liquid crystal droplets on chemically tailored surfaces. , 2010, Langmuir : the ACS journal of surfaces and colloids.

[13]  Sri Sivakumar,et al.  Liquid Crystal Emulsions as the Basis of Biological Sensors for the Optical Detection of Bacteria and Viruses , 2009 .

[14]  N. Abbott,et al.  Characterization of adsorbate-induced ordering transitions of liquid crystals within monodisperse droplets. , 2009, Langmuir : the ACS journal of surfaces and colloids.

[15]  Xinyan Bi,et al.  Liquid crystal multiplexed protease assays reporting enzymatic activities as optical bar charts. , 2009, Analytical chemistry.

[16]  N. Abbott,et al.  Size-dependent ordering of liquid crystals observed in polymeric capsules with micrometer and smaller diameters. , 2009, Angewandte Chemie.

[17]  Chang Lu,et al.  Microfluidic electroporative flow cytometry for studying single-cell biomechanics. , 2008, Analytical chemistry.

[18]  N. Abbott,et al.  Self-assembly of amphiphiles, polymers and proteins at interfaces between thermotropic liquid crystals and aqueous phases , 2008 .

[19]  N. Abbott,et al.  Preparation of microscopic and planar oil-water interfaces that are decorated with prescribed densities of insoluble amphiphiles. , 2008, Journal of the American Chemical Society.

[20]  N. Abbott,et al.  Tailoring the interfaces between nematic liquid crystal emulsions and aqueous phases via layer-by-layer assembly. , 2006, Nano letters (Print).

[21]  Alex Groisman,et al.  High-throughput and high-resolution flow cytometry in molded microfluidic devices. , 2006, Analytical chemistry.

[22]  A. Shabanov,et al.  Director configurations in nematic droplets with inhomogeneous boundary conditions. , 2005, Physical review. E, Statistical, nonlinear, and soft matter physics.

[23]  A. Shabanov,et al.  Transformation of director configuration upon changing boundary conditions in droplets of nematic liquid crystal , 2004 .

[24]  N. Abbott,et al.  Biomolecular Interactions at Phospholipid-Decorated Surfaces of Liquid Crystals , 2003, Science.

[25]  M. McClain,et al.  Flow cytometry of Escherichia coli on microfluidic devices. , 2001, Analytical chemistry.

[26]  E. Gartland,et al.  Fine structure of defects in radial nematic droplets , 2000, Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics.

[27]  E. Gartland,et al.  INSTABILITY OF RADIAL HEDGEHOG CONFIGURATIONS IN NEMATIC LIQUID CRYSTALS UNDER LANDAU-DE GENNES FREE-ENERGY MODELS , 1999 .

[28]  P. Poulin,et al.  Rotational Diffusion of Monodisperse Liquid Crystal Droplets , 1998 .

[29]  O. D. Lavrentovich,et al.  Topological defects in dispersed words and worlds around liquid crystals, or liquid crystal drops , 1998 .

[30]  E. Terentjev.  Stability of Liquid Crystalline Macroemulsions , 1995, mtrl-th/9509003.

[31]  Paul Drzaic,et al.  Liquid Crystal Dispersions , 1995 .

[32]  C. Chiccoli,et al.  Computer simulations of nematic droplets with bipolar boundary conditions. , 1994, Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics.

[33]  Slobodan Žumer,et al.  Microscope textures of nematic droplets in polymer dispersed liquid crystals , 1991 .

[34]  Zumer,et al.  Light scattering from nematic droplets: Anomalous-diffraction approach. , 1988, Physical review. A, General physics.

[35]  Doane,et al.  Light scattering from a small nematic droplet. , 1986, Physical review. A, General physics.

[36]  Robert B. Meyer,et al.  Piezoelectric Effects in Liquid Crystals , 1969 .