Polymer Dispersed Liquid Crystal (PDLC) films are composite materials consisting of LC droplets embedded in polymers. In order to decrease the switching voltage of these devices, we prepared PDLC films doped with single wall carbon nanotubes (SWCNTs). The mesomorphic properties of the films were investigated by polarizing optical microscopy (POM). The electrical characteristics have been investigated using a Broadband Dielectric Spectrometer in a frequency domain (0.01-107) Hz and a temperature range (280-350) K. Some key aspects of an optical model for the analysis of the coherent transmittance of PDLC - NP films are presented.
Polymer Dispersed Liquid Crystals (PDLC) are composite materials consisting of small liquid crystal (LC) droplets surrounded by a polymer matrix. Due to their relatively easy preparation and processing, the PDLC devices found many applications such as displays, architectural windows, energy control devices, projection displays, spatial light modulators, polarizers.
Carbon nanotubes (CNT) have excellent mobility and are suitable as doping nanoparticles in order to improve the electrically- controlled orientation of LC.
This paper presents the methods of preparation of PDLC doped with CNT. Experimental results are presented for the films obtained by solvent induced polymerization method, using polymethyl methacrylate and a nematic LC, E7. The obtained films are characterized by polarized optical microscopy, differential scanning calorimetry and electro-optical transmission.
A method to retrieve radius from 0.6 mkm up to 13.6 mkm and relative refractive index from 1.015 up to 1.28 of
spherical homogeneous non-absorbing particles by multi-angle scattering is proposed. It is based on the formation of
noise resistant functionals of the scattered intensity, which are invariant relatively linear homogeneous transformations of
an intensity-based signal, and on the approximation of the retrieved parameters dependence on the functionals by a feed
forward neural network. The values of intensity of light scattered in the interval of angles 10° - 60° are used. At 20%
measurement errors the mean errors of the retrieval of radius and relative refractive index are 0.8% and 7%, respectively.
Light scattering patterns have been calculated for a simple optical model constructed for single smooth and nonsmooth
lymphocytes of healthy and infected individuals. It has been shown that the smooth and nonsmooth cells can be resolved
using the intensities of the sideward and backward scattered light. We have found by calculations and validated by the
flow-cytometer experiments that intensity distributions for the cells of lymphocyte populations can be used as a
preliminary signatures of some virus infections. Potential biomedical applications of the findings for label-free flowcytometry
detecting of individuals infected with viruses of hepatitises B or C and some others viruses are presented.
A simple optical model of single lymphocytes with smooth and nonsmooth surfaces has been developed for healthy and infected individuals. The model can be used for rapid (in the real-time scale) solution of the inverse light-scattering problem on the basis of optical data measured by label-free flow cytometry. Light scattering patterns have been calculated for the model developed. It has been shown that the smooth and nonsmooth cells can be resolved using the intensities of the sideward- and backward-scattered light. We have found by calculations and validated by the flow cytometer experiments that intensity distributions for the cells of lymphocyte populations can be used as a preliminary signatures of some virus infections. Potential biomedical applications of the findings for label-free flow cytometry detection of individuals infected with viruses of hepatitises B or C and some others viruses are presented.
Quantitative data on cell structure, shape, and size distribution are obtained by optical measurement of normal peripheral blood granulocytes and lymphocytes in a cell suspension. The cell nuclei are measured in situ. The distribution laws of the cell and nuclei sizes are estimated. The data gained are synthesized to construct morphometric models of a segmented neutrophilic granulocyte and a lymphocyte. Models of interrelation between the cell and nucleus metric characteristics for granulocyte and lymphocyte are obtained. The discovered interrelation decreases the amount of cell-nucleus size combinations that have to be considered under simulation of cell scattering patterns. It allows faster analysis of light scattering to discriminate cells in a real-time scale. Our morphometric data meet the requirements of scanning flow cytometry dealing with the high rate analysis of cells in suspension. Our findings can be used as input parameters for the solution of the direct and inverse light-scattering problems in scanning flow cytometry, dispensing with a costly and time-consuming immunophenotyping of the cells, as well as in turbidimetry and nephelometry. The cell models developed can ensure better interpretations of scattering patterns for an improvement of discriminating capabilities of immunophenotyping-free scanning flow cytometry.
A method for calculating scattering cross-sections and characteristics of polarization state of light transmitted through
polymer film with fine liquid crystal droplets at the independent scattering regime implementation is proposed. It is
based on the Rayleigh-Gans approximation to describe scattering by an individual droplet, and the Foldy-Twersky
equation to determine a coherent field transmitted through the polymer dispersed liquid crystal film. The results obtained
relate the morphological characteristics ofa film to its electro-optical response.
A method for calculation ellipsometrical parameters of light transmitted through a polymer dispersed liquid-crystal film is proposed. It is based on the Rayleigh-Gans approximation for independent scattering regime. Functional dependencies of ellipticity and azimuth of polarization ellipse of scattered light on liquid-crystal droplets' order parameter are presented.
The investigation of light propagation in the polymer dispersed liquid crystal film in its isotropic phase is carried out. The propagation of coherent (direct) component of the transmitted and reflected light in the film with high concentration of spherical scatters is considered by using the adding method. The calculation results of coherent transmittance, reflectance, and phases of transmitted and reflected waves are presented.
Normal human leukocytes have been investigated in suspension by methods of the specialized light microscopy. On the
basis of the obtained experimental data the histograms of the size distributions of lymphocytes, their nuclei, and
granulocytes are constructed.
The retrieval of size and refractive index of a spherical nonabsorbing particle by angular dependence of scattered light in application to the scanning flow cytometry is considered We consider the range of angles available for measurement from 10° to 60°. For the problem solution the high-order neural networks are used. The retrieval errors were investigated at the ranges of the radius and relative refractive index 0.6 - 10.6 microns, and 1.02 - 1.38, respectively.
The optical method to retrieve order parameter of liquid crystal droplets with rigidly fixed poles has been developed. The method is based on measurement of coherent transmittance of a monolayer of polymer-dispersed liquid crystal droplets and comparison with the results of coherent transmittance calculation. To calculate coherent transmittance of a polymer -dispersed liquid crystal monolayer the anomalous diffraction approximation and the approximation of effective refractive indexes for liquid crystal droplets are used.
A method for calculating transmission coefficient and characteristics of polarization state of light transmitted through polymer film with fine liquid crystal droplets is proposed. It is based on the Rayleigh-Gans approximation to describe scattering by an individual droplet, and the Foldy-Twersky equation to determine a coherent field transmitted through the polymer dispersed liquid crystal film. The results obtained relate the morphological characteristics of a film to its electro-optical response. The simple equations for scattering cross-sections are obtained. The accuracy of the method is estimated.
Electrooptical response of a cell based on monolayer film of polymer dispersed nematic liquid crystal is studied experimentally and theoretically both in light scattering mode and in geometry with crossed polarizers. Interference effects revealing in the light passed straightforward through the cells can be used to develop color filters with the spectral characteristics varied due to an applied voltage.
The coherent transmittance of polymer dispersed liquid crystal monolayer with bipolar nematic droplets have been investigated. Two kinds of electrooptical response (S- formed response and oscillation response) at transition of droplets directors structure from planar to homeotropic have been found. The influence of the order parameter of droplets and droplet polydispersity on the quenching conditions are analyzed.
A new method is proposed for increasing contrast and modulation depth of liquid-crystal electrooptical materials on the basis of the production of a polymer dispersed liquid crystal monolayer in which the interference effect of quenching for coherently scattered light is realized. A dramatic increase in the contrast ratio at viewing angles up to 5 degree(s) is predicted theoretically. The results of calculations for surface ferroelectric liquid crystal droplets films in the anomalous diffraction approach are presented.
A theoretical model for the description of noise properties of polymer dispersed liquid crystal monolayers is proposed. A signal-noise ratio and a coherent transmittance of a monolayer with spherical nematic droplets have been analyzed as a function of a size parameter at different concentration of droplets and refractive index of polymer matrix. Radial and homeotropic uniformity oriented nematic director structures of droplets have been investigated. The radial distribution function is described in the hard discs approximation. Numerical result are obtained in the anomalous-diffraction approach.
An analytical expression for the coherent transmittance of the polymer-dispersed ferroelectric liquid crystal monolayer at oblique illumination by linearly polarized plane wave has been obtained. Within the framework of the anomalous diffraction approach the conditions for coherent transmission quenching have been determined. It is shown that for the PDFLC monolayer on the basis of bistable smectic liquid crystals it is possible to provide a coherent transmittance equal to zero and unity for two stable states of droplet directors in the electric field.
Theoretical and experimental studies of passage of light through a layer with a high concentration of dispersion material have been made. The conditions for the disappearance of the coherent component from the radiation passed through the monolayer of particles have been found. Their dependence on the parameters of layer and particles have been analysed.
This paper gives an approximate theoretical model to forecast the noise spectrum of thin covers of polymeric material and analytical relation for Wiener's spectrum taking into account the near topological ordering of drop locations, the cooperative optical effects and the features of scattering by nematic drops allowing for the high electrical field. The relation for the spectrum is derived on the basis of the simulation of a thin polymeric film by an effective two- dimensional medium in the form of a stochastic amplitude-phase screen with the transmission function of an equivalent screen identified as a microdrop, the function being determined by illumination conditions and scattered radiation in the far field. The effective transmission function is inferred by comparing the results, obtained for the model proposed, with that of the anomalous diffraction. Approximation for scattering by a thin film of nematic drops that takes the configuration of a nematic director under high electrical field into account was used.
A multipurpose automated photometer designed for controlling the sharpness and noise characteristics of photolayers and their spatial homogeneity is described. The photometer's specifications are given and the results are reported of the investigation of the bright strip contrast function and modulation transfer function of undeveloped course- and fine-grain laboratory-cast photographic films in the passed radiation.
The laws of the change in the spectral power density of optical noise (Wiener spectrum) of a monolayer of particles depending on their optical properties and concentration have been studied from the view point of the model amplitude-phase screen. It is shown that the account of the spatial correlation in the positioning of inhomogeneities and of the interference between scattered waves leads to qualitatively different laws of optical noise behavior in comparison with rarefied optical image recording systems.
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