Characterization and Biocompatibility Study of Nematic and Cholesteryl Liquid Crystals.

noIntensive research in bio-engineering has been conducted in the search for flexible biomaterials that could support cell growth and cells attachment. Flexible synthetic materials that support cell growth without the aid of synthetic extracellular matrix proteins are still rare. Cholesteryl liquid crystal containing cholesteryl moieties may have suitable biological affinity. Human keratinocytes (HaCat) were cultured with a nematic liquid crystal and three cholesteryl liquid crystals of different formulation. Subsequently, the trypan blue dye exclusion assay was used to determine cell viability in the liquid crystals. The two classes of liquid crystal were characterized by Differential Scanning Calorimeter (DSC) and polarizing microscope (POM) to understand the nature of the interface material. The cell viability study in medium containing liquid crystals verified that liquid crystals had no effects on cell viability. However, only the surface of cholesteryl liquid crystal has shown affinity to HaCat cells. In addition, cells continued to proliferate in the presence of liquid crystals without a change of medium for eight days. No sign of exothermic and endothermic activities at 370C were observed from the DSC test results for the three samples. Biological and mechanical test result of the cholesteryl liquid crystals has shown that cholesteryl liquid crystals are non toxic and support cell attachment without extracellular matrix protein at very low elasticity

Environmental effects of natural dyes and syntetic dyes: a comparison

Dyes is important to add colorant on fabrics. The dyeing process makes a fabric colourful and attractive. However, the waste disposed by dyeing process was hazard to environment especially synthetic dyes. Most of the textile industry uses synthetic dyes compared to natural dyes. This happens because natural dyes are difficult to extract its colour. Four types of natural and synthetic dyes were reviewed in this study. It was understood that all types of dyes have its advantages and disadvantages. Natural dyes have poor colour fastness compared to synthetic dyes. Besides, natural dyes can combine with synthetic dyes for greater commercial dyeing. Dyeing is one of the method to beautify the appearance of fabrics. It is a process to add colour to textile products like yarn, fiber and fabrics. Dyeing can be divided into synthetic dyes and natural dyes whereas can be produced either chemically or by plants. Synthetic dyes are man-made and normally made from synthetic resources such as petroleum by-products and earth minerals while natural dyes are from plant and animal sources. Most of the textile industry is using synthetic dyes compared to natural dyes. Natural dyes are hardly to extract their colour and environmentally friendly. Synthetic dyes can be extracted easily but brings harmful effect to environment. Unfortunately, the exact amount of dyes produced in the world is still unknown. It is estimated that the production of dyes to be over 10,000 tons per year. Exact data on the quantity of dyes discharged in the environment are also not available (Forgacs and Cserhátia, 2004)

Exploratory investigation on the measurement of skin friction by means of liquid crystals

Direct measurement of skin friction in wind tunnel testing by using cholesteric liquid crystal

Mechanisms for the effect of electric and magnetic fields on biological systems Semiannual status report, Jun. - Dec. 1969

Electric and magnetic field effects on structure and properties of cholesteric liquid crystal

Effective index of refraction, optical rotation, and circular dichroism in isotropic chiral liquid crystals

This paper concerns optical properties of the isotropic phase above the isotropic-cholesteric transition and of the blue phase BP III. We introduce an effective index, which describes spatial dispersion effects such as optical rotation, circular dichroism, and the modification of the average index due to the fluctuations. We derive the wavelength dependance of these spatial dispersion effects quite generally without relying on an expansion in powers of the chirality and without assuming that the pitch of the cholesteric $P$ is much shorter than the wavelength of the light $\lambda$, an approximation which has been made in previous studies of this problem. The theoretical predictions are supported by comparing them with experimental spectra of the optical activity in the BP III phase.Comment: 15 pages and 7 figures. Submitted to PR

LC nanocomposites: induced optical singularities, managed nano/micro structure, and electrical conductivity

Microstructure, phase transitions, electrical conductivity, and optical and electrooptical properties of multiwalled carbon nanotubes (NTs), dispersed in the cholesteric liquid crystal (cholesteryl oleyl carbonate, COC), nematic 5CB and their mixtures, were studied in the temperature range between 255 K and 363 K. The relative concentration X=COC/(COC+5CB)was varied within 0.0-1.0. The concentration $C_p$ of NTs was varied within 0.01-5% wt. The value of X affected agglomeration and stability of NTs inside COC+5CB. High-quality dispersion, exfoliation, and stabilization of the NTs were observed in COC solvent ("good" solvent). From the other side, the aggregation of NTs was very pronounced in nematic 5CB solvent ("bad" solvent). The dispersing quality of solvent influenced the percolation concentration $C_p$, corresponding to transition between the low conductive and high conductive states: e.g., percolation was observed at $C_p=1$ and $C_p=0.1$ for pure COC and 5CB, respectively. The effects of thermal pre-history on the heating-cooling hysteretic behavior of electrical conductivity were studied. The mechanism of dispersion of NTs in COC+5CB mixtures is discussed. Utilization of the mixtures of "good" and "bad" solvents allowed fine regulation of the dispersion, stability and electrical conductivity of LC+NTs composites. The mixtures of COC and 5CB were found to be promising for application as functional media with controllable useful chiral and electrophysical properties.Comment: 10 pages, 9 figure

Influence of Time Dependent Factors To The Phases and Poisson's Ratio of Cholesteryl Ester liquid crystals

Liquid crystal based biosensors detect physical restructuring of cells via changes in the birefringence property or orientation order of the liquid crystal molecules. The strain induced in the liquid crystal molecules is closely associated with the liquid crystalline phases and Poisson’s ratio of the liquid crystals. Cholesteryl ester liquid crystals (CELC) and CELC based lyotropic liquid crystals (LLC) that were regarded as viscoelastic materials are subjected to time-dependent factors (a fluidic environment, incubation time, and temperature). The effects of these factors, qualitatively and quantitatively, were investigated by using cross-polarising microscopy and a uniaxial micro-tensile technique. More lyotropic phases were observed in the liquid crystals as the incubation time in cell culture media was increased. Poisson’s ratio of approximately 0.58 and 0.6 were determined for CELC and LLC, respectively, at room (25 oC) and incubation (37 oC) temperatures over a period of 3 days