US 3714565 A
An aperture tube for use with a Coulter type particle analyzing device is constructed with its interior surface covered with conductive material such as metal, its exterior surface covered with conductive material such as metal, the aperture being provided in a corundum wafer set into the bottom end of the tube. The conductive coating approaches the aperture as close as several aperture diameters, surrounding the aperture so that except for the path of the aperture itself, flow of aperture current through the electrolyte is minimized, thereby decreasing heating of the electrolyte with its attendant noise. The invention is primarily applicable to situations where the aperture current is a high frequency current to avoid polarization.
Description (OCR text may contain errors)
[ 1 Jan. 30, 1973 United States Patent 1191 Coulter et a1.
ABSTRACT An aperture tube for use with a Coulter type particle 5 Inventors; w n 1L m Miami Springs; analyzing device is constructed with its interior surwalter Hogg, Miami Lakes, both face covered with conductive material such as metal, its exterior surface covered with conductive material such as metal, the aperture being provided in a corundum wafer set into the bottom end of the tube. The conductive coating approaches the aperture as close as several aperture diameters, surrounding the aperture so that except for the path of the aperture itself, flow of aperture current through the electrolyte is minimized, thereby decreasing heating of the electrolyte with its attendant noise. The invention is primarily applicable to situations where the aperture P02 3 CNN m 7/ a 72m 1 H 4M2 2 v u 3 0 C WG 3 n I .1 m 7 m m P, m m c l n 7 In C 9 H e l .4 I E 9 2 M 2 Q a r 3 "n" h m m 3 "H" F u. 8 m f 01m 3 2 u m 0 CF M I u M m M e e N I f. n g d I C .1 I s P Smk A F A UIF l. 1 ll] 3 2 l 2 8 2 2 555 l. I l. .111
current is a high frequency current to avoid polarization.
The aperture tube is useful in the configuration where it is the transducer for a Coulter particle analyzing apparatus or it may be used as part of a system in which size as ascertained by use of the Coulter method is utilized in connection with a droplet forming and separating device to classify particles by size.
 References Cited UNITED STATES PATENTS 3,395,343 7/1968 Morgan............................ 3,361,965 1/1968 Coulter.... 3,539,919 11 1970 H0gg.......... 3,551,802 12/1970 Kuczynski 3,287,638 11/1966 Bolie CP Primary Examiner-Gerard R. Strecker Attorney-Silverman & Cass ELECTRONIC PARTICLE ANALYZING APPARATUS WITH IMPROVED APERTURE TUBE BACKGROUND OF THE INVENTION The invention herein relates generally to an aperture tube for use with a Coulter type particle analyzing device.
The aperture tube of a Coulter particle analyzing device has an aperture which serves as a scanner or transducer in the operation of the device by responding to the change of impedance in the aperture which is filled with electrolyte each time that a particle passes through the aperture. This change of impedance is converted into a signal whose amplitude is substantially proportional to the volume, that is the size of the particle due to the displacement of electrolyte by the particle as it passes through the aperture. The construction and operation of the device is well-known in the art of particle analysis and is disclosed in some detail in U.S. Pat. No. 2,656,508.
In its usual arrangement, the aperture is formed in a corundum wafer that is set into the wall of a glass vessel by any of several known techniques. The interior of the vessel is connected to a closed fluid system including a manometer having a mercury syphon with a stopcock and vacuum source also connected to the system so that the mercury level of the manometer may be unbalanced. The first vessel is set into a second vessel which contains particles in suspension in a diluent, the bottom of the first vessel carrying the aperture being immersed with the aperture below the fluid level in the second vessel. The return of the mercury to a balanced condition sucks suspension through the aperture from the second vessel into the interior of the first vessel. The body of liquid on the inside of the first vessel and in the second vessel have respective metallic electrodes and the electronics of the Coulter device are connected across these electrodes. The electronics provide an aperture current while the liquid is being transported through the aperture and a suitable detector responds to the changes effected in the scanning circuit by the respective changes of impedance with passage of particles.
The above-described structure and function are disclosed in US. Pat. No. 2,869,078 in addition to said US. Pat. No. 2,656,508. The aperture current in most cases comprised direct current, with polarity being reversed from time to time to decrease polarizing effects. Certain advantages were achieved by using a high frequency aperture current, one of the principles of such advantages being the decrease of polarization practically to a point of elimination. Other advantages were found to result from the use of high frequency aperture current including new methods for classifying particles.
The use of high frequency current gave new problems including at least two. The first of these was the production of heating of the diluent through the flow of high frequency current. Such heating or heat losses comprise loss of energy and are reflected into the apparent aperture impedance as resistance. This gives rise to noise and limits to some extent the usefulness of the apparatus. The second of the problems relates to capacitive losses in the walls of the aperture tube, notwithstanding that the aperture current circuit is tuned. Excessive capacitive coupling through the walls of the aperture tube gives rise to loss of signal-to-noise ratio, but can practically be cured by the use of a doublewalled aperture tube as taught in US. Pat. No. 3,539,919.
The construction of the invention contemplates decreasing the heat losses due to the flow of high frequency current in the electrolyte, either alone or in combination with the double-walled aperture tube structure. Such use is basically in connection with a Coulter particle analyzing device utilized for counting and sizing studies of particles suspended in an electrolyte, such as blood cells in saline solution.
The invention has additional advantages in connection with systems of the type disclosed in US. Pat. No. 3,380,584 where the Coulter principle is used to control the charge on a droplet formed by the apparatus and which contains the particle. Deflecting the droplet by an electric field results in the amount of deflection being a function of the charge on the particle so that it is possible to collect the droplets and hence the different sized particles at spaced apart collecting means. In this manner, microscopic particles can physically be separated, collected, and statistically classified. The invention is applicable to such a construction in the provision of an aperture tube having the advantages described above.
SUMMARY OF THE INVENTION An aperture tube is constructed in which there is an electrically insulative wafer such as, for example, made of corundum having the aperture formed therein, set into the wall of a vessel of electrically insulating material such as glass or synthetic resin. The exterior surface of the vessel is covered with a coating of conductive material such as metal and likewise the interior of the vessel is covered with a similar coating. The coatings in both cases come very close to the aperture, surrounding the same on opposite sides of the wall. The coatings serve respectively as the interior and exterior electrodes of the aperture tube when the lower end of the tube is immersed in a vessel having electrolyte therein with the aperture below the surface of the electrolyte. In the case of the ordinary Coulter particle analyzing apparatus configuration, the electrolyte in the external vessel contains the suspended particles and the interior of the aperture tube is filled with electrolyte and becomes part of a closed liquid system. The sample suspension is sucked into the aperture tube and the passing particles scanned by the aperture. In other cases the sample may flow from the aperture tube into the outer vessel, either under some pressure from the interior of the aperture tube or otherwise.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary sectional view taken through an aperture tube constructed in accordance with the invention, the upper end of the tube being of any of a number of different constructions;
FIG. 2 r is a median sectional view taken through another aperture tube constructed in accordance with the invention and arranged for use in the configuration of a Coulter particle analyzing device, the view being taken generally along the line 2-2 of FIG. 3 and in the indicated direction;
FIG. 3 is a top plan view of the aperture tube of FIG. 2 taken from just below the T-fitting;
FIG. 4 is a sectional view taken generally along the line 4-4 of FIG. 2 and in the indicated direction;
FIG. 5 is a fragmentary view of the bottom of the aperture tube of FIG. 2 on an exaggerated scale;
FIG. 6 is a somewhat diagrammatic view showing a modified form of aperture tube in median section; and
FIG. 7 is a fragmentary sectional view of the bottom end of the aperture tube of FIG. 6 on an exaggerated scale.
DESCRIPTION OF THE PREFERRED EMBODIMENTS The aperture tube of the invention is suitable for use in several different arrangements, as stated above, including the ordinary Coulter particle analyzing device configuration and that in which the Coulter principle is used for particle classification and separation. In FIG. 1 there is illustrated an aperture tube 10 which may be of any of these types. Accordingly, its upper end is not shown since it may take several forms.
The tube 10 is shown immersed in a body 12 of electrolyte, as for example saline solution which may or may not have particles suspended therein, depending upon whether the tube 10 is to be used to suck sample suspension from the body 12 or to inject sample suspension into it. The body 14 of the tube 10 is made of glass or such material of high insulating qualities. The lower end of the body tapers to a relatively narrow nozzlelike configuration l6 and a corundum wafer 18 having a minute aperture 20 in the center thereof is set into the configuration 16, this latter being called the tip of the tube 10 for explanatory purposes hereinafter. It is presumed that the connection of the wafer 18 into the tip 16 is liquid-tight so that no liquid can pass between thebody of liquid 12 on the exterior of the tube 10 and the body of liquid 22 on the interior of the tube except by way of aperture 20. The body 22 of liquid will be saline or similar electrolyte, either with or without the particles to be studied, depending upon the manner in which the tube 10 is to be used.
According to the invention, the tube 10 is expected to be used in the case that the aperture current is high frequency, say of the order of 500 kilohertz and up to several tens of megahertz. The interior of the tube 10 has its surface coated with a layer 24 of some conductive material, such as for example metal. This could be a deposit or a mechanically applied coating of the type which will not react chemically with the reagents to be used. For example, it could be platinum or other metals not readily attacked by corrosives. Likewise, there is an exterior coating 26 of the same or similar conductive material adhered to the tube 10. The coatings or layers of conductive material come quite close to the aperture, as best shown at 28 on the interior and 30 on the exterior. The purpose of this is to keep the flow of electric current in the electrolyte to a minimum whereby to prevent heating and its accompanying noise generated in the aperture. The edges 28 and 30 surround the respective interior and exterior ends of the aperture 20 and extend to a few aperture diameters from the aperture.
The aperture tube 10 could be used in the ordinary Coulter particle analyzing device configuration or it could be used in connection with a system of the type disclosed in said U.S. Pat. No. 3,380,584. In the latter instance, the sample will be expressed under pressure from the tube 10 to be formed into droplets carrying the particles for the purposes described in said U.S. Pat. No. 3,380,5 84. In the case of its use as an aperture tube in a Coulter apparatus alone, the flow of suspension could be in either direction.
It is understood that the electrical coupling of the external portion of the Coulter aperture circuit with the electrolyte in the aperture 20 will be effected by connecting conductors to the respective coatings or layers 24 and 26. In other words, these function as the electrodes of the ordinary Coulter arrangement. Each time that a particle passes through the aperture, in one direction or the other, there will be a change in the impedance of the electrolyte contained within the aperture which is converted to a voltage or current signal by the electronics of the Coulter device.
Another form of the invention is shown in FIGS. 2 to 5 wherein the aperture tube 50 is illustrated. The principal difference between the aperture tube 10 and the aperture tube 50 of FIGS. 2 to 5 lies in the mechanical construction. The tube 10 is made out of glass or the like through the use of glass blowing and forming techniques. The aperture wafer 18 is set into the tube 10 by fusing, softening the tube tip 16 and manipulating the same or by cement, the latter technique having limited application. The tube 50, on the other hand is made up of members machined and shaped and mechanically held together either by screw threads or adhesives or by both mediums. Such structure shows the versatility of the invention in practical application. The wafer 52 is mounted in a cavity cut in the parts of the tube 50.
The aperture tube 50 comprises a cylindrical interior tubular member 54 made out of some synthetic resin which has very low electrical loss characteristics. Many of the commercially available so-called plastics can be used. The lower end of the tubular member 54 is enlarged on its interior to provide an inwardly extending formation 56, this being achieved by machining or molding separate pieces and adhering them by suitable adhesive, for example. An exterior tubular cylindrical member of metal is shown at 58 closely engaging around the cylindrical member 54 and having a bottom axial end plate or flange 60 soldered or otherwise connected thereto. The end plate 60 engages the axial end of the cylindrical member 54, being tightly disposed upon the formation 56. There is a coaxially arranged interior tubular cylindrical member 62 also of metal closely engaged within the bore of the tubular member 54 and having a conically tapered bottom formation or flange 64 that closely follows the tapered formation 56. The tapered formation 56 has a suitable disc-like cavity 66 formed therein, and the wafer 52 is disposed in this cavity with the tip of the tapered conical formation 64 overlying the top of the wafer 52. A tapered countersunk conical recess 68 is formed in the bottom plate 60 and this recess opens at the wafer 52 so that the tip of resulting formation 70 overlies the bottom of the wafer From the above description, it will be seen that the metallic members 58 and 62 have the portions 70 and 64, respectively, which come very close to the aperture 72 of the wafer 52, as taught in connection with the tube 10.
The upper end of the tube 50 has structure to enable the chamber 74 within the inner cylindrical member 62 to be connected into a closed liquid system. It also has structure to enable the two metal tubular cylindrical 58 and 62 to be connected into a detection circuit so that they may function as electrodes.
At its upper end the central metal tubular member 62 has a reduced diameter portion 76 providing a shoulder 78 upon which is secured a disc 80 made out of low loss plastic. A central grommet 82, also of some insulating material such as low loss plastic is tightly secured to the upper end of the chamber 74 and a hollow fitting 84 is engaged therein, as for example by screw-threading. A metal plate or disc 86 engages the top of the disc 80 and clamps the same to the tubular members 58 and 62, also engaging the axial upper end of the central plastic tubular member 54. A conventional electrical connector 88 is set into the upper end plate 86 with its outer ferrule 90 screw-threaded into the plate 86 and its central conductor 92 insulated by the bushing 94 and engaging the end of the tubular member 58 as shown at 96. In this manner, the ferrule 90 is in electrical connection with the interior metal tubular member 62 and the central conductor 92 is in electrical connection with the outer metal tubular member 58. All joints of the tube are made liquid-tight, either by precision fitting or the use of sealants such as adhesive or by both.
The tube 50 is shown with its lower end immersed in a beaker 98 of some insulating material, this beaker having the sample suspension 100 carried therein. The interior chamber 74 is filled with electrolyte to provide the interior body 102 of fluid required in accordance with the Coulter principle. The fitting 84 connects to a T-joint 104 through the conduit 106, one branch 108 leading to the manometer or mercury syphon of U.S. Pat. No. 2,869,078 and the other branch 110 leading to a source of vacuum through the stopcock 112. The operation of this closed system is well-known and does not require further description. The conductor 92 and the ferrule 90 are connected to the Coulter particle analyzing device 114 through the lead 116 and ground 118, respectively. The circuitry will include a current source which provides the high frequency aperture current intended with this form of aperture tube.
It will be noted in FIGS. 2 to 5 that the wall of the inner plastic tubular member 54 is relatively thick so that capacitance would be expected to be less than that of a thin-walled glass vessel. In such case, the member 54 is the equivalent of the wall 14 of the tube 10. For better results, an air space could be provided within the wall by having two spaced partitions or layers, as taught in said U.S. Pat. No. 3,539,919. Such a structure is shown in FIGS. 6 and 7.
In FIGS. 6 and 7 the aperture tube 120 has an inner wall or partition 122 of insulating material such as glass, an outer wall or partition 124 of similar insulating material and a tapered formation where the two walls or partitions join to form the lower tip 126. A wafer 128 having a central aperture 130 is mounted in the tip 126 axially of the tube 120. The walls 122 and 124 also join at their upper ends at 132 so that a cylindrical inner space is provided by the chamber 134. The space is preferably air, since the dielectric constant does not differ materially from that of a vacuum. There is an interior chamber 136 which is intended to form a part of the liquid flow system of the apparatus. The outer wall 124 has its outer surface coated by a layer 138 of conductive material, and a similar layer 140 is provided on the interior surface of the interior wall 122.
The aperture tube is mounted in a vessel 142. The inner coating or layer is connected through the upper wall 178 to the Coulter apparatus 180 by the electrical line 182 to function as the inner electrode means for the Coulter arrangement. The outer layer 138 comes up to just above the top of vessel 142 and is connected by line 184 to the Coulter apparatus 180. Both layers or coatings come very close to the aperture 130, overlying the wafer 128 in this respect as shown at 186 and 188. This gives the benefits of the invention mentioned above. The added benefits of low capacitance between the inner and outer electrodes are achieved by the double wall or partition construction. The Coulter apparatus 180 provides number and size information concerning the particles that pass through the aperture 130. The block shown will also include the source of aperture current which will be a high frequency current for the maximum benefits of the invention. Such source may provide aperture current having more than one different frequency whereby to obtain additional benefits. Under such circumstances, the block 180 will have circuits for discriminating between the signals produced in the aperture at the different frequencies classifying and counting means, etc.
The aperture tubes of the invention are shown to have considerable versatility in construction and use. Thus, it should be noted that considerable variation in details may be made without departing from the spirit or scope of the invention as defined in the appended claims.
What it is desired to secure by Letters Patent of the United States is:
1. An aperture tube particularly adapted for use in a Coulter particle analyzing device and comprising a vessel having a wall of electrically insulative material, a substantially closed bottom end portion with a minute aperture extending therethrough and coverings of electrically conductive material on the inner and outer respective surfaces of said bottom end portion of said vessel, each covering surrounding said aperture and being spaced from said aperture by a few diameters of said aperture.
2. The aperture tube according to claim 1 wherein said tube has a tip at said bottom end portion thereof and said aperture is situated in said tip.
3. The aperture tube according to claim 1 wherein said aperture tube narrows to said bottom end portion.
4. The aperture tube according to claim 1 wherein said wall comprises inner and outer partitions spaced apart, with said inner covering on the interior surface of said inner partition and said outer covering on the exterior surface of said outer partition, said partitions being joined at the location of said aperture.
5. The aperture tube according to claim I wherein said coverings of electrically conductive material on the inner and outer wall surfaces of said vessel are disposed over a substantial portion of said surfaces and form electrodes.
6. The aperture tube according to claim 1 wherein at least one of said coverings is metal.
7. The aperture tube according to claim 1 wherein said vessel is made of a synthetic resin.
8. The aperture tube according to claim 1 wherein said bottom end portion has a cavity therein, a wafer having said aperture therein is disposed in said cavity, and said coverings extend over a portion of said wafer and engage said wafer on the upper and lower surfaces thereof to hold said wafer in said cavity.
9. The aperture tube according to claim 1 wherein at least one of said coverings is a coating.
10. The aperture tube according to claim 1 wherein said vessel comprises an elongate tubular cylindrical member of electrical insulating material having a narrowed part at its bottom end, said inner and outer coverings comprise metallic tubular cylinders coaxially arranged in intimate engagement with the respective interior and exterior surfaces of said insulating tubular cylindrical member and each of said metallic cylinders has an annular radially inwardly extending flange at the bottom end thereof engaged with said narrowed part on its upper and lower surfaces but for a small central location, there being a wafer of electrically non-conductive material disposed at said central location and having a passageway therethrough which defines said aperture, said passageway extending. generally in an axial direction with respect to said cylindrical member and each of said flanges respectively surrounding one end of said passageway.
11. The aperture tube according to claim 10 wherein a cavity is formed in said narrowed part at said central location, said wafer is disposed in said cavity, and said flanges engage said wafer on the upper and lower surfaces thereof.
12. A particle analyzing device of the Coulter type comprising an aperture tube including a vessel having a wall of electrically insulative material, a substantially closed bottom end portion with a minute aperture extending therethrough, and coverings of electrically conductive material on the inner and outer respective surfaces of said bottom end portion of said vessel, each covering surrounding said aperture and being spaced from said aperture by a few diameters of said aperture,
a body of electrolyte in said aperture tube, the lower portion of which is immersed in a second body of electrolyte, one of said bodies having particles therein, means for causing a flow of fluid containing particles in suspension from one of said bodies of electrolyte through said aperture, conductors connected respectively with said coverings, and alternating current generating means for generating a high frequency electric current and for applying same to said conductors for causing said high frequency current to flow through said aperture simultaneously with said particles.
13. A particle analyzing device in which a suspension of particles is passed through an aperture from a body of fluid carrying particles in suspension, said device comprising an aperture tube including a vessel having a wall of electrically insulative material, a substantially closedbottom end portion with a minute aperture extending therethrough and coverings of electrically conductive material on the inner and outer respective surfaces of said bottom end portion of said vessel, each covering surrounding said aperture and being spaced from said aperture by a few diameters of said aperture,
moving means for moving fluid through said aperture, and an electrical circuit including detecting means for detecting changes in the impedance of the aperture contents, said aperture having an entrance on one wall surface of said tube and an exit on the opposite wall surface of said tube, said conductive coverings forming electrodes at opposite ends of said aperture, one electrode being in intimate contact with said body of the fluid and the other electrode being in intimate contact with at least the stream of fluid emerging from said aperture exit, said electrodes being connected in said electrical circuit for providing an electric current flow through said aperture in the fluid traversing said aperture, said moving means being operable to physically move fluid through said aperture simultaneously with the flow of electric current therethrough and said detecting means being operable to detect changes in the impedance of the aperture contents caused by the passage of particles through said aperture.
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