Viscosity measurement optical detection

Negative adsorption is in most cases very small compared to positive adsorption and therefore not easily detected directly. A sophisticated optical technique (evanescent-wave-induced fluorescence, EWIF) has been used to prove the reduction in segment concentration close to a non-adsorbing surface Depletion also has an effect on the flux of polymer solutions through pores since the viscosity of the liquid near the non-adsorbing surface is lower than that of the polymer solution, the flux is then higher than would be expected on the basis of the bulk viscosity. Negative adsorption at a liquid-air interface leads to a measurable increase In surface tenslon ... 

The applications of the SFM include force measurement between surfaces in liquid and vapor, adhesion between similar or dissimilar materials, contact deformation, wetting and capillary condensation, viscosity in thin films, forces between surfactant and polymer-coated surfaces, and surface chemistry. Fluid-electrolyte interactions between conductive surfaces can also be measured [Smith, et. al., 1988]. A typical microforce of 10 nN can be detected over separation distances to a resolution of 0.1 nm with optical interoferometry between reflective surfaces. With electrostatic forces, relatively large separation are measured 1-100 nm, whereas, short range forces such as van der Waals forces take place over distances of less than 3.0 nm. Ultrasmooth and electrically conductive surfaces can be formed by the deposition of a metal film (40 nm thickness) such as Pt on a smooth substrate of mica [Smith, et. al., 1988]. The separation distance between the two surfaces is controlled by a... 

Since their invention, optical tweezers have proved themselves to be very powerful interdisciplinary tools. Today they are used extensively in biophysics, as they serve as delicate tools to manipulate and study single molecules of DNA [8, 9]. Optically trapped beads have been successfully used to measure local elasticities and viscosities, for example inside cells. Ashkin [5] provides an overview of the diverse uses of optical traps as an important tool in the important areas of research. Isolation and detection of sparse cells concentration of cells from dilute suspensions separation of cells according to specific properties and trapping and positioning of individual cells for characterization are the key areas of research due to their possible impact. The non-invasive nature of particle manipulation being a key requirement, forces like hydrodynamic, optical, ultrasonic and electromagnetic have been employed for such purposes. Successful examples of the use of these optical forces for biological applications are determination... 

The contribution of translational order parameters to the anisotropy of physical properties of liquid crystals has not been studied in detail. Evidence suggests that there is a very small influence of translational ordering on the optical properties, but effects of translational order can be detected in the measurement of dielectric properties. There are strong effects in both elastic properties and viscosity, but the statistical theories of these properties have not been extended to include explicitly the effects of translational order. 

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