Microcapillaries, wall surface

For simplicity, we consider a charged cylindrical microcapillary of radius / w packed with charged mono-sized microparticles of diameter dp. The liquid in the microcapillary is assumed to be an incompressible, Newtonian, mono-valence electrolyte of density p and viscosity p,. The zeta potentials of the inner wall surface and the particle... 

The disc-shaped plastic micoreactors, termed microcapillary films (MCFs), contain 19 parallel microchannels, each with a mean internal diameter of 142 10 pm. The material was prepared using a melt extrusion process from an ethylene-vinyl alcohol copolymer (EVOH) [28]. Immobilization of palladium(0) on the wall surface inside the MCFs was performed by simple chemical deposition techniques (Scheme 7.3). The palladium-coated capillaries were used for transfer hydrt enation of ketones, imines, nitro compounds, alkenes, and alkynes with triethylsilane under flow conditions [29]. Microcapillaries whose inside surfaces were coated with copper or gold were also utilized for the continuous-flow reactions [30]. 

Scheme 7.3 Wall surface functionalization of microcapillaries (EVOH-MCF) inside and schematic illustration of a wall-coated microcapillary.

Figure 7.25 Capillary electrophoresis, (a) Schematic of microcapillary dimensions, (b) Ion-solute structure at the capillary wall, (c) Schematic illustration of electro-osmotic flow (EOF) created in the microcapillary as a result of capillary bore surface charges.

Satisfactory formulations of pheromones that afford a constant release rate over a long period of time are not likely to be achieved without the cooperation of the chemical industry. Controlled release of pheromones is discussed in the Proceedings of a recent symposium (623). Fortunately, several organizations in the U. S. have been interested in the possibilities of the use of pheromone formulations on a commercial basis. One company (605) has supplied formulations for several investigators, and in addition has carried out extensive field tests with their own personnel. It has developed the use of hollow fibers, which are simply microcapillary reservoirs that serve to contain a vaporizable material and mediate evaporation of the material into the atmosphere . The fiber wall is essentially impermeable. One end is sealed, and the release rate essentially depends on diffusion from the surface of the liquid-vapor interface to the open end of the hollow fiber. Fibers are supplied in two forms. A tape form consists of a parallel array of fibers on an adhesive tape this form is used to establish point-source evaporators. The chopped fiber form is used for dissemination with a ground rig or from the air. 

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