Particle filter cells

Filtering cells and cell fractions from fluid media. These particles, after concentration by filtration, may be examined through subsequent quantitative or qualitative analysis. The filtration techniques also have applications in fields related to immunology and implantation of tissues as well as in cytological evaluation of cerebrospinal, fluid. 

Fig. 11 Extraction device consisting of A CO2 cylinder, B syringe pump, C oven, D extraction cell, E particle filter, F back-pressure regulator, G sampling tube...

Vitanov R, Goranova E, Stavrov V et al (2009) Fabrication of buried contact silicon solar cells using porous silicon. Sol Energy Mater Sol Cells 93(3) 297-300 Wallner JZ, Bergstrom PL (2007) A porous silicon based particle filter for microsystem. Phys Stat Sol (a) 5 1469-1473... 

FIGURE 11.5 Simplified plan view of defoamer and filter elements in typical cardiotomy reservoir. Both defoamer elements are sponge-like open-celled polyurethane foams coated with PDMS-hydrophohed silica antifoam. Inner particle filter has pore sizes in range of 50-90 microns and outer filter has pore size of 40 microns. (After Servas, F.M., Gremel, R.F., Ryan, T.C. (assigned to Shiley Inc.), US 4,743,371 10 May 1988, filed 28 February, 1986.)... 

Filter aids are widely used in die fermentation industry to improve the efficiency of filtration. It is a pre-coated filter medium to prevent blockage or blinding of the filter by solids, which would otherwise wedge diemselves into the pores of the cloth. Filter aid can be added to the fermentation broth to increase the porosity of the cake as it formed. This is only recommended when fermentation product is extracellular. Filter aid adds to the cost of filtration. The minimum quantity needed to achieve the desired result must be established experimentally. Fermentation broths can be pretreated to improve filtration characteristics. Heating to denature proteins enhances the filterability of mycelial broths such as in penicillin production. Alternatively, electrolytes may be added to promote coagulation of colloids into larger, denser particles, which are easier to filter. The filtration process is affected by the viscosity and composition of the broth, and the cell cake.5... 

When the bacteria to be detected are less than 1% of the total population in a sample, IFAs cannot be used because of interference from unrelated particles that are concentrated when large volumes of sample are filtered. To overcome this problem, the organism of interest may be concentrated by immunomagnetic separation.10,51 62 For this procedure magnetic beads coated with monoclonal or polyclonal antibodies are mixed with the sample. The beads are collected with a magnet, and the cells attached to the beads then are removed, enumerated, and identified by IFAs. 

Several additional instrumental techniques have also been developed for bacterial characterization. Capillary electrophoresis of bacteria, which requires little sample preparation,42 is possible because most bacteria act as colloidal particles in suspension and can be separated by their electrical charge. Capillary electrophoresis provides information that may be useful for identification. Flow cytometry also can be used to identify and separate individual cells in a mixture.11,42 Infrared spectroscopy has been used to characterize bacteria caught on transparent filters.113 Fourier-transform infrared (FTIR) spectroscopy, with linear discriminant analysis and artificial neural networks, has been adapted for identifying foodbome bacteria25,113 and pathogenic bacteria in the blood.5... 

Fig. 30. Snapshot of particle volume fraction fields obtained while solving a kinetic theory-based TFM. Fluid catalytic particles in air. Simulations were done over a 16 x 16 cm periodic domain. 128 x 128 cells (shown in the figure). The average particle volume fraction in the domain is 0.05. Dark (light) color indicates regions of high (low) particle volume fractions. Squares of different sizes illustrate regions (i.e., filters) of different sizes over which averaging over the cells is performed. Source Andrews and Sundaresan (2005).

Fig. 32. Filtered particle phase pressure (in CGS units) extracted from simulations over 16 x 16 cm domain using 128 x 128 cells. Source Andrews and Sundaresan (2005). The filtered particle-phase pressure includes the Reynolds stress-like fluctuations and the kinetic theory pressure.

The final principles of back-pulse filter technology are the nature and properties of the GORE-TEX membrane. The membrane is composed of expanded polytetra-fluoroethylene, or e-PTFE. The membrane traces its roots to the invention of e-PTFE by Robert W. Gore in 1969. Since that time, e-PTFE has found application in many areas including medical devices, electronics, fabrics and fuel cells to name a few. In the filtration area, e-PTFE is used in the form of a membrane to capture and remove particles from both gaseous and liquid streams. 

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