Chemistry: electrical and wave energy – Processes and products – Electrophoresis or electro-osmosis processes and electrolyte...
Patent
1995-09-26
1998-09-29
Warden, Robert J.
Chemistry: electrical and wave energy
Processes and products
Electrophoresis or electro-osmosis processes and electrolyte...
204643, G01N 2726, G01N 27447, G01N 27453
Patent
active
058142002
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to improvements in separators and more particularly to improvements in dielectrophoretic separators.
BACKGROUND OF THE INVENTION
Dielectrophoretic (DEP) separators rely on the phenomenon that substances within a non uniform DC or AC electric field experience a dielectrophoretic (DEP) force. The (DEP) force causes the substance, which may gaseous, liquid, solid, or dissolved in solution, to move within the field.
A DEP field can have different effects upon different substances. This effect has been used to filter or separate substances, usually solids in suspension, from a liquid for the purposes of analysis.
A study carried out by Gascoyne, Huang et al. and reported in "Meas. Sci. Technol. 3 (1992), at pages 439 to 445", describes the separation of mixed population of mammalian cells and more particularly the separation of leukaemic cells from normal blood cells. However, separation was only achieved locally on electrodes.
A further study by Pethig, Huang et al. in J. Phys. D Appl. Phys. 24 (1992) 881 to 888 describes an arrangement for positive and negative dielectrophoretic collection of colloidal particles using interdigitated, castellated microelectrodes. The arrangement described enables a colloidal suspension to be separated locally. However, permanent separation of a colloid from the liquid in which it was suspended was not possible.
U.S. Pat. No. 4,390,403 (Batchelder) describes and claims an arrangement for filtering a species from a liquid. This describes a method which employs DC non-uniform electrical fields to manipulate one or more chemicals within a multi-electrode chamber so as to promote chemical reactions between the chemical species.
German Offenlegungsschrift DE-A-4127405 purports to describe an arrangement for continuous separation of microscopic particles. It is stated that the arrangement overcomes the problem of convectional drift within a separator. The arrangement allegedly overcomes this problem by applying a high frequency, electric travelling wave between rows of electrodes, which themselves are positioned between two additional electrodes which are electrically isolated from the aforementioned rows of electrodes. The two additional electrodes (5 and 6 in FIG. 1) of that document are arranged substantially parallel to one another. The description of the aforementioned Offenlegungsschrift refers to "an additional force field" which exists because of an electrophoretic effect upon the particles. Electrophoresis relies upon particles being charged. The present invention utilises DEP only. Other examples of forces are mentioned. However, the disclosure is considered not to be sufficiently clear and complete to be an enabling, in respect of these.
SUMMARY OF THE INVENTION
The present invention arose from a consideration of the problem of permanent separation of two substances, which may be in suspension in a fluid, which may be a liquid.
According to a first aspect of the present invention there is provided apparatus for separating first and second particles from a fluid comprising: disposed in the path of the fluid supporting the first and second particles, such that the fluid may flow over the electrodes, the electrodes being adapted to be placed in a filter chamber; first and second groups of electrodes; experienced by the particles, such that the first particles are confined; and
Preferably control means is provided for establishing the dielectrophoretic field and for activating the means for selectively removing the second particles from the chamber.
Preferably the control means comprises means for synchronizing one or more valves located at the or each outlet of the filter chamber, arranged to permit fluid to exhaust from the chamber, with a respective fluid pressurizing means.
Variation of the effect of the field is preferably achieved by varying the frequency of a signal applied across the electrodes. Different frequencies may be imposed simultaneously across different groups or sub-groups of electrodes.
A fluid pressurizi
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Markx Gerardus Hendricus
Pethig Ronald
British Technology Group Limited
Starsiak Jr. John S.
Warden Robert J.
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