Analysis of the Internal Configurations of Droplets of Liquid Crystal Using Flow Cytometry

Abstract

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 comprised 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.

Liquid crystal droplet-based amplification of microvesicles that are shed by mammalian cells

“…31 Here we first address the use of FC to characterize the size distributions and more importantly changes in the size distributions due to coalescence of LC droplets during experiments. Specifically, we speculated that the presence of amphiphilic components of the MVs within the LC droplets could potentially influence the sizes and stability of the LC droplets formed by emulsification.…”

“…In particular, a recent study has demonstrated that a population of LC droplets in the radial configuration generates a light scatter plot (Figure 1f) that is distinct from that measured for bipolar droplets (Figure 1c). 31 Specifically, when compared to bipolar droplets, radial droplets generate a narrower distribution of side scattering intensities (SSC, large angle light scattering) for a fixed intensity of forward light scattering (FSC, small angle light scattering). This difference in scatter plots arises from the different rotational symmetries of the refractive index profiles presented to the laser of the FC by the two configurations.…”

Liquid Crystal Interfaces Programmed with Enzyme‐Responsive Polymers and Surfactants

“…[ 2f , 2i , 2j , 4,10 ] We focus, however, on results obtained using LC microdroplets because i) in contrast to micrometer-thick fi lms of LCs, the use of microdroplets eliminates the need for a chemically functionalized solid to support the LC, [ 4 ] ii) microdroplets can be rapidly screened (10 000 microdroplets in less than one minute) using the light scattering mode of a fl ow cytometer, [ 5 ] and iii) elastic strain of the LC within the droplet geometry can trigger ordering transitions at low concentrations of analytes. [ 6 ] We note that a number of past studies, by us and others, have reported investigations of stimulisensitive LC microdroplets.…”

“…[ 6 ] We note that a number of past studies, by us and others, have reported investigations of stimulisensitive LC microdroplets. [ 2,5,6,11 ] PPAs were synthesized via ring-opening metathesis polymerization (ROMP) [ 12 ] using norbornene-based monomers containing either biphenyl moieties or peptidic moieties (GPLGLAGK for PPA1, GPLGLAG for PPA2) to form hydrophobic and hydrophilic blocks, respectively (resulting ring-opened products as polymers are shown in Figure 1 and Supporting Information). [ 8,13 ] The biphenyl group was used as the hydrophobic block to promote the coassembly of the PPA at the interface of the biphenyl-based LC.…”

A Quantitative Analysis of an Oil Component in an Emulsion by Multiphoton Ionization Mass Spectrometry

“…Emulsions are used in diverse applications such as foods, cosmetics, and pharmaceuticals. Many studies have been carried out concerning emulsions; in recent years, novel techniques for the preparation [1][2][3][4] and measurement/evaluation [5][6][7][8][9][10][11][12] of emulsions or droplets have been reported. Chen et al reported in situ monitoring of emulsion polymerization by Raman spectroscopy using a homopolymer as an internal standard, although the absolute Raman intensity depends on many factors, such as the solution turbidity and the particle size distribution of the dispersed phase.…”