Liquid gradient refractive index

Tunable Liquid Gradient Refractive Index Lens... 

All the in-plane tunable microlenses discussed to this point are classical refractive types. Mao et al. reported a tunable microlens configuration based on a liquid gradient refractive index (L-GRIN) lens mechanism [20]. 

In these chapters, most emerging tunable and non-tunable microlenses based on various mechanisms have their optical axes perpendicular to their substrates, thus requiring optical alignments of different layers. This means that complicated structures are required for applications such as labs on chips. Chapter 7, Horizontal Microlenses Integrated in Microfluidics, presents examples of microlenses whose optical axes are parallel to substrates of microfluidic networks. These horizontal microlenses include two-dimensional polymer lenses tunable and movable liquid droplets as lenses hydrodynamically tuned cylindrical lenses liquid core and liquid cladding lenses air-liquid interface lenses and tunable liquid gradient refractive index lenses. 

A second method utilizes the Fresnel principle (Figure 19-44), which relates the transmittance of a dielectric interface to the refractive indices of the interface materials. Such an interface may be formed between a glass prism of selected optical properties and the liquid whose refractive index is to be measured. These detectors are difficult to use with gradient elution systems, and temperature control of the solvents is critical. 

J. Li, S. Gauza, and S. T. Wu, High temperature-gradient refractive index liquid crystals. Opt. Express 12, 2002 (2004). 

Renn, C. N. and Synovec, R. E., Refractive index gradient detection of biopolymers separated by high-temperature liquid chromatography, /. Chromatogr., 536, 289, 1991. 

Sugars were estimated by using a Beckman 344 gradient high-pressure liquid chromatograph with an Altex 156 refractive index detector and a Spherogel 7.5% carbohydrate column with a flow rate of 0.5 ml/min in the mobile phase of water at 80 C. The sugar samples were appropriately diluted before injection. 

Hancock DO, Synovec RE. Microbore liquid-chromatography and refractive-index gradient detection of low-nanogram and low-ppm quantities of carbohydrates. Journal of Chromatography 464, 83-91, 1989. 

The results for the TEA--water mixtures at atmospheric pressure are shown in Figure 6. These are for TEA mole fractions of x 0.05 and 0.59. The LOST is 18.2 at x - 0.09. We also obtained a very similar data set at the latter mole fraction, but we omitted it for clarity. For contrast and comparison, a data set for pure water is shown. These mixture results again show a sharp rise in heat transfer coefficient as condensate first appeared. In fact, the appearance was remarkably similar to the n-decane--C02 results for x - 0.973 discussed above, but the visibility of the phase separation was enhanced by the presence of a fine emulsion at the phase interface and the absence of strong refractive index gradients characteristic of the supercritical systems. This permitted the structure of the interface to be seen more clearly. In Figure 7 we show photographs that typify the appearance of the two phases. In all cases observed here, both in supercritical vapor--liquid and in liquid--liquid systems, the dense phase appears to wet the cylinder surface regardless of composition. 

Combined measurements of the surface tension, concentration gradient, and mass transfer coefficients on the liquid-vapor interface (P < Pm) and also measurements of the solution refractive index in the vapor or liquid phase (9,1 0). 

J.E. Stewart, Refractive index gradients in stopped-flow and temperature-jump kinetics and liquid chromatography, Anal. Chem. 53 (1981) 1125. 

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