Patent Publication Number: US-2010108621-A1

Title: Self-contained particle separator device

Description:
RELATED APPLICATIONS 
     This application claims priority benefit of U.S. Provisional Application Ser. No. 61/085,954 filed Aug. 4, 2008; the contents of which are hereby incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention in general relates to a self-contained device for concentrating particulate dissolved or suspended in a liquid on a device surface as a function of particle size and/or flexibility and in particular to a device that spontaneously draws liquid away from the concentrating particles on the device surface with an equilibrium interaction of capillary draw and air equilibrium to provide a controlled and reproducible rate of concentration. 
     BACKGROUND OF THE INVENTION 
     There are numerous instances when detection of particulate within a liquid would be of considerable value in fields as far ranging as medical diagnosis, water quality, and material characterization. Unfortunately, concentration of particulate from a liquid has practically been difficult to perform without resort to laboratory facilities. While syringe luer filters provide for the prospect of field concentration of particulate from a liquid onto a filter cartridge, subsequent resolvation and use of the concentrated particles from such a syringe filter requires appreciable equipment and a degree of technical skill. Additionally, syringe filters exert dynamic and uncontrollable pressure on the liquid sample to force the same through the syringe filter and in the process potentially compromising both the quality of the concentration and the morphology of delicate particles. 
     Separating particles from a liquid such as malformed erythrocytes from blood or finding parasites within water is labor intensive as a result of the need to pipette aliquots of the liquid and subsequent separation associated with amino chemistry, chromatography, sedimentation rates or other conventional separation techniques. These problems are compounded in instances where the particle of interest is found at low concentrations such that only a single such particle or a few such particles is likely to be found in any given aliquot. The effort and equipment typically required to perform a conventional such separation precludes field use of such separation thereby making field testing problematic. 
     Thus, there exists a need for a particle concentrator device that is simple to use and therefore amenable for field operation as well as providing a controlled and reproducible concentration process that leaves concentrated particles amenable to collection and subsequent use. 
     SUMMARY OF THE INVENTION 
     A concentrator of particles dissolved or suspended in a liquid includes a top surface having a hole array therethrough and a bottom surface fused to the top surface to define an intermediate volume accessed only through the hole array. A concentrator of particles dissolved or suspended in a liquid is also provided that has an inner channel and an exterior surface and a tube having a hole array providing liquid communication between the inner channel and the exterior surface. A liquid-impermeable sheath surrounds the hole array and forms a seal to the exterior surface to define a volume between said sheath and the exterior surface. A process for concentrating particles from a liquid with these concentrators is also provided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an inventive concentrator; 
         FIG. 2A  is a longitudinal cross section of the concentrator of  FIG. 1  along the plane  2 - 2 ; 
         FIG. 2B  depicts the addition of a liquid droplet to an inventive concentrator as depicted in  FIG. 2A ; 
         FIG. 2C  depicts the concentration of particles from within the liquid droplet and the disposition of the droplet liquid after concentration has occurred on the inventive concentrator as depicted in  FIG. 2A ; 
         FIG. 3A  is a longitudinal cross section of an alternative embodiment of an inventive concentrator; 
         FIG. 3B  depicts the addition of a liquid droplet to an inventive concentrator as depicted in  FIG. 3A ; 
         FIG. 3C  depicts the concentration of particles from within the liquid droplet and the disposition of the droplet liquid after concentration has occurred on the inventive concentrator as depicted in  FIG. 3A ; 
         FIG. 4A  is a longitudinal cross-sectional view of a tube form of an inventive concentrator; 
         FIG. 4B  is a transverse cross-sectional view of a tube form of an inventive concentrator of  FIG. 4A  along plane A-A; 
         FIG. 4C  is a longitudinal cross-sectional view of a tube form of an inventive concentrator through the liquid-impervious sheath of  FIG. 4A ; 
         FIGS. 5A-5E  depict sequential steps in concentration of a large reservoir volume of dilute suspension with the concentrator of  FIGS. 4A-4C ; 
         FIGS. 6A-6E  depict sequential steps in operation of an inventive self-contained particle separator device based on an inventive concentrator of  FIG. 1 , while  FIGS. 6F and 6G  represent alternate separation results obtained for no target and a target substance respectively; 
         FIG. 7A  is an exploded view of an inventive device of  FIGS. 6A-6E  within a housing providing for measured and sequential step performance; 
         FIG. 7B  is a cross-sectional view of an inventive device of  FIGS. 6A-6E  depicted in transverse cross section within an exemplary housing; 
         FIGS. 8A-8E  depict sequential steps in operation of an inventive self-contained particle separator device based on an inventive concentrator as detailed with respect to the preceding figures within the housing depicted in  FIGS. 7A and 7B , while  FIGS. 8F and 8G  represent separation results obtained for no target and a target substance, respectively; and 
         FIG. 9  is a perspective view of an alternate housing for measured and sequential step performance to that depicted in  FIG. 7A . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention has utility as a simple and passively operated particle concentrator operating on the principle of size exclusion. An inventive concentrator is operative to separate particulate of a limitless variety as a function of particle size and/or flexibility, such particles illustratively including eukaryotic cells, prokaryotes, cellular agglomerates, organic debris, and inorganic debris. The liquid in which the particles are dissolved or suspended is also nearly limitless with the proviso that the liquid be compatible with the concentrator materials. The present invention operates with capillary action drawing liquid into an inventive concentrator with the pressure generated internal to the concentrator acting as an equilibrating counterforce. This reliance on force equilibrium between capillary action and internal concentrator pressure provides for only a preselected quantity of liquid being drawn into a concentrator and at a preselected rate. 
     Referring now to  FIGS. 1 and 2 , an inventive concentrator is shown generally at  10 . The concentrator  10  has an interior volume  12  isolated from the exterior of the concentrator  10  save for a hole array  14 . It is appreciated that the volume  12  assumes any number of shapes and dimensions beyond the rectilinear plate form depicted in the accompanying figures. The hole array  14  is provided with holes dimensioned to exclude particle desired to be concentrated from passing therethrough. 
     The top surface  16  is formed from a variety of materials illustratively including glass, metal, and polymers. A hole array  14  extends to communicate with volume  12 . The hole array  14  has a first array mean hole area on the top surface  16 . The holes that make up the hole array  14  are each provided in a variety of shapes as measured at the top surface  16 , these shapes illustratively including circular, square, hexagonal, as well as an etched or porous region allowing a liquid placed in contact therewith to percolate from top surface  16  to volume  12 . Additionally, it is appreciated that each of the holes making up the hole array  14  need not have the same hole area at top surface  16  as at the boundary  28  of volume  12 . By way of example, a given hole of the hole array  14  can taper to a larger or smaller area while traversing from the top surface  16  to the boundary  28  of volume  12 . It is appreciated that a tapering hole particularly well suited for excluding components of a liquid from entering one of the holes of the hole array  14  the component has a size greater than the hole area top surface  16  while a hole of the hole array  14  that tapers smaller area as the hole traverses from top surface  16  to boundary  28  of volume  12  is operative to trap liquid components of intermediate size between hole area at top surface  16  and hole area at boundary  28  of volume  12 . It is appreciated that a hole array  14  is readily formed by mechanical boring, laser boring, lithographic etching, or insertion of an insert into a complementary sized cutout formed in the plate  10 . The insert illustratively includes a mesh, a porous membrane, or a porous gel. 
     The hole array  14  is formed to include a small area portion of top surface  16  having at least two holes therethrough to communicate with volume  12 . The holes of array  14  are preferably segregated to an area of the top surface  16  in relationship with each other. Preferably, the holes are uniform in area with the understanding that formation inevitably leads to variation in hole area. The hole area of each hole of array  14  is preselected to preclude passage of a desired particle from the liquid and ranges from 100 nanometers to 100 microns. The hole array  14  is intended to be overlaid by a droplet D of a given liquid containing suspended or dissolved particles to be concentrated. 
     An inventive concentrator  10  is readily formed by blow molding glass of a polymeric material to the approximate shape of an inventive concentrator and inserting a capillary draw agent  18  to the volume  12  in instances when the dimensions of the volume  12  are too great to effectively induce capillary draw for a given liquid through contact with the opposing boundaries  28  and  22  that define the volume  12  and thereafter sealing the opening associated with the blow molding process to hermetically seal the volume  12  of the concentrator. Hole array  14  is then bored in the first surface  16  to yield the inventive concentrator  10 . Alternatively, a sheet material mentioned as top surface  16  having a hole array preformed or formed after formation of concentrator  10  is then edge adhered in a spaced apart relationship with a bottom surface  24  0.1-1.0 mm thickness dimension defines wall  22  so as to in turn define the volume  12 . Again, the volume  12  is filled with a capillary draw inducing agent  18  as needed. Conventional techniques of edge bonding the first surface  16  to second surface  24  illustratively include the use of contact adhesives, sonic welding, and thermal fusion. It is appreciated that an edge spacer  26  placed between first surface  16  and second surface  24  readily defines the vertical separation bounds of the volume  12 . 
     In the event that the volume  12  has the lateral separation between walls  22  and  28  of greater than 3 millimeters, inventive concentrator  10  is unable to efficiently provide capillary flow for an aqueous based solution or suspension of particles; and a separation of greater than 2.5 millimeters is inefficient for supporting capillary draw of polar organic solvents while a separation of greater than 2 millimeters is ineffective at supporting efficient capillary draw of apolar organic solvents. In instances where the dimensions of the volume  12  are themselves too large to support efficient and reliable capillary draw of a liquid into the volume  12 , a capillary draw agent  18  is provided within the volume  12  and underlying the hole array  16 . A capillary draw agent  18  operative herein is effective to wick liquid from a droplet applied onto the top surface  16  overlying the hole array  14 . Capillary draw agent operative herein illustratively includes nonwoven fiber mat such as cellulosic based papers; liquid swellable polymers such as in the case of water or polar organic solvents polyacrylic acids, gelatin, and polyalkylene, polystyrene granules are particularly well suited to wick away nonpolar organic solvents; closed packed spheres of glass, inorganic materials and polymers; and packed organic or inorganic granules wet by the liquid in which the particles are suspended or dissolved so as to wick the liquid through the hole array  14 . Owing to the ease of processing, the capillary draw agent  18  is preferably a piece of filter paper inserted therebetween and the edges of top surface  14  and bottom surface  22  being fused together to hermetically seal the filter paper as a capillary draw agent  18  within the volume  12 . The hole array  14  typically has from tens to thousands of like sized holes formed in pattern to be covered by a drop containing particles to be excluded from passing through the hole array  14 . 
     An alternative embodiment of an inventive concentrator is depicted generally at  30  with reference to  FIGS. 3A-3C , where like numerals correspond to those used with respect to FIGS.  1  and  2 A- 2 C. The concentrator  30  varies from the concentrator  10  in having an aperture  32  adapted to receive a pipette or other liquid delivery device P. It is an aspect of the present invention that the surface tension of a drop D applied to a hole array  14  can preclude capillary draw through the hole array  14  and into the volume  12  absent an external stimulus such as a surfactant to reduce drop surface tension, physical deformation of the drop D, or prewetting the hole array  14 . This attribute is exploited herein to incubate a drop on top of hole array  14  for a preselected amount of time as shown in  FIG. 3A . The incubation may involve reaction of the particles in the drop with a reagent to illustratively create a chemical transformation, agglomeration, or replication of a viral or cellular particle. By way of example particles decorated with antibodies binding a substance within a drop D agglomerate to form a precipitate too large to traverse the hole array  14  and remain on the top of the hole array  14 . In contrast, a particle with surface exposed antibodies that is not agglomerated by a target substance passes through the hole array  14 . After a preselected incubation time per  FIG. 3A , an aliquot of liquid  33  is introduced to the volume  12  ( FIG. 3B ) to wet the underside of the hole array  14  to induce capillary draw of the drop D through array  14  and directionally away from aperture  32  until the air bubble  34  exerts a counterbalancing pressure relative to capillary draw forces, as shown in  FIG. 3C . Particles that are either too large or too rigid to transit hole array  14  are isolated on the surface  16  above the array  14 . In instances when the drop D is colored and that color interferes with subsequent evaluation, a bleaching agent is optionally added to the liquid  33 . Other additives to the liquid  33  illustratively including antimicrobials, disinfectants, indicator reagents as to a particular substance being present, and combinations thereof. 
     A tubular embodiment of an inventive concentrator is depicted generally at  50  with reference to  FIGS. 4A-4C , where like numerals correspond to those used with respect to the aforementioned figures. The concentrator  50  has a tube  52  defining an internal channel  54 . While the tube  52  is depicted in  FIGS. 4A-4C  as having a square cross section, it is appreciated that other cross-sectional shapes are operative herein illustratively including circular, triangular, and other regular polygonal and irregular polygonal shapes. A hole array  14  provides communication between the exterior  56  of the tube  52  and the internal channel  54 . As with the aforementioned concentrators  10  and  30 , the hole array  14  in addition to being a series of holes can also include a piece of mesh, porous membrane, or porous gel overlying a nonexclusionary larger cutout in the tube  52 . Liquid-impermeable sheath  58  surrounds the hole array and forms a seal to the exterior surface  56  to define a volume between the sheath  58  and the exterior surface  56 . The volume  60  is dimensioned to induce capillary flow of a liquid exiting the internal channel  54  by way of hole array  14  and into contact with sheath  58 . Optionally, the volume  60  is filled with capillary draw inducing agent  18  as needed. As the volume  60  is sealed other than openings defined by hole array  14 , only a predetermined amount of liquid is drawn into the volume  60  before the dimensions of the volume  60  capable of inducing capillary draw without resort to a capillary draw agent  18  those detailed with respect to volume  12 . After a finite quantity of liquid has entered the volume  60 , a counterbalancing air pressure develops as liquid exits the hole array  14  and enters the volume  60  thereby trapping a volume of air beneath the hole array and liquid. As a result, the preselected amount of concentration enhancement is exacted on a liquid. 
       FIGS. 5A and 5B  depict the operation of an inventive concentrator  50  in contact with a fluid reservoir R containing a large volume of liquid, as shown in  FIG. 5A . By creating a partial vacuum on the mouth  62  of the concentrator  50  as denoted by the arrow, liquid is drawn from the reservoir R into the internal channel  54  into contact with the hole array  14 , as shown in  FIG. 5B . The partial vacuum drawn on the mouth  62  is provided by way of a bulb, pipette, pump or other conventional mild vacuum source. With the liquid drawn into the internal channel  54  and into contact with the hole array  14 , capillary draw pulls the liquid from the internal channel  54  and into the volume  60 . Preferably, the volume  60  is sized such that a preselected amount of liquid within the internal channel  54  is accommodated within the volume  60 . As shown in  FIG. 5C , volume  60  is wet with the liquid that previously was in reservoir R in  FIG. 5A . The remaining liquid within the internal channel  54 , as shown in  FIG. 5C , contains particulate size excluded from passing through the hole array  14 . With the liquid draw completed, a positive pressure is exerted on the mouth  62  as denoted by the downward arrow in  FIG. 5D  to urge the now concentrated size-excluded particles and a predefined volume of liquid down the internal channel  54 . With continued positive pressure application in the mouth  62 , a concentrated volume of liquid containing the size-excluded particles exits the second end  64  of the concentrator  50 . 
       FIGS. 6A-6G  depict components of an inventive device for rapid and self-contained detection of a substance by way of size exclusion within an inventive device depicted generally at  70 , where like numerals correspond to those used with respect to the preceding figures. It is appreciated that while  FIGS. 6A-6G  depict the use of a concentrator  10 , one of ordinary skill in the art would readily appreciate that a similar self-contained device is readily formed with resort to the concentrators  30  or  50 . As shown in  FIG. 6A , a needle  72  containing a quantity of a target substance dissolved or suspended in a liquid S is divided. The needle  72  lances a preselected volume of a solution T. The container  74  is defined by a circumferential ring  76  with the solution T bounded within spatially separated septa  78   a  and  78   b.  A ring spacer  79  optionally is included to provide a spatial separation between septum  78   b  and the hole array  14 . The ring  76  is readily formed of a variety of materials nonreactive towards solution T for sample S and illustratively includes thermoplastics, thermosets, glass, and metal. The septa  78   a  and  78   b  are readily formed of conventional thermoplastics, elastomerics, and metal foils. The solution T provides a known amount of dilution for a sample S and is chosen based on the nature of sample S and the substance to be size excluded therefrom. By way of example, if sample S is blood containing malaria deformed red blood cells, then the solution T is by way of example a malaria parasite propagation solution. For the size exclusion of particularly small substances such as proteins or separation of a specific type of substance such as a bacteria from other like sized bacteria, the solution T includes particles that are surface decorated with antibodies binding a target substance within sample S so as to agglomerate to form a precipitate too large to reverse the holes of a concentrator  10  and thus remain on the top of the hole array  14  of the concentrator  10 . In contrast, such particles with surface exposed antibodies that are not agglomerated by contact with a target substance in the sample S pass through the hole array  14  and into the volume of the concentrator  10 . 
       FIG. 6B  shows sequentially that the needle  72  punctures the upper septum  78   a  of container  74  to introduce the sample S into the solution T. Sample S is incubated in the solution T within container  74  for an amount of time to allow mixing therethrough and a desired reaction to induce propagation or agglomeration or other like process to occur. It is appreciated that in an incubation stage as depicted in  FIG. 6C , physical conditions such as temperature, pressure and incident light exposure are optionally modified to promote a desired reaction between a target substance within sample S and the solution T. Subsequent to the incubation stage depicted in  FIG. 6C , the needle  72  is driven through second septum  78   b.  As depicted in  FIG. 6E , the liquid contents contained within the container  74  are then conveyed by the needle  72  or a hole formed in septum  78   b  by the needle  72  to the top of hole array  14  of the concentrator  10 . As the solution contacts a capillary draw agent  18 , the contents of container  74  are drawn into the volume of the concentrator  10 . As shown in  FIG. 6F , when none of the target substance is present in the sample S, the top of hole array  14  remains uncovered and all of the content of container  74  is now within the volume  12  of the concentrator  10 . In contrast, if the sample S contained a target substance, for example malaria infected blood cells of low deformability, such cells are found decorating the top of hole array  14  while the liquid contents originally in container  74  have passed into the volume  12  of the concentrator  10 . While  FIGS. 6A-6G  depict a single substance separation, it is appreciated that an array of containers  74  and concentrators  10  are readily provided to allow for parallel size exclusion detection of multiple substances within a sample S with variations between the nature of the solution T, characteristics of hole array  14 , or combinations thereof. 
       FIG. 7A  depicts separation of an inventive device  70  as shown with respect to  FIGS. 6A-6G  within a housing and provides excessive controlled movement of a needle  72  through a container  74 , where like numerals correspond to those used with respect to the preceding figures. Optionally the needle  72  has a base  83  to facilitate positioning.  FIG. 7A  depicts inventive device  70  as an exploded view within an exemplary housing  82 . The housing  82  has a first portion  84  sized to retain a concentrator  10  in overlying alignment with a container  74  and an intermediate spacer  79  therebetween. The first portion  84  affords a barrier against the leakage of sample S or solution T therefrom. The housing  82  also has a second portion  86  adapted to receive the needle  72  such that when the first portion  84  and second portion  86  are joined, the needle  72  is in overlying alignment with the septa  78   a  and  78   b,  as depicted in  FIG. 7B . A connector  88  retains the first portion  84  and the second portion  86  in a connected manner. The housing  82  is also characterized by prescored spacer flanges  90  and  92  CM the first portion  84  and the second portion  86 , respectively. 
     The operation of the housing  82  to provide sequential and controlled movement of the needle  72  relative to container  74  and concentrator  10  as detailed with respect to  FIGS. 6A-6G  is shown schematically in  FIGS. 8A-8G .  FIG. 8A  is identical to  FIG. 7A  with the proviso that the needle  72  has been loaded with a sample S. In  FIG. 8B , closed housing  82 , as depicted in  FIG. 7B , has had spacer flange  92  removed from the second housing portion  86  to allow the needle  72  to pierce the first septum  78   a.  An incubation phase is depicted in  FIG. 8C  with this spatial separation between device components. In  FIG. 8D , spacer flange  90  is removed allowing needle  72  to pierce the second septum  78   b.  In  FIG. 8E , the contents of container  74  are observed to pass through the spacer region  79  and into the concentrator  10  with the results for no target substance being found depicted in  FIG. 8F  while size excluded target substance is seen in  FIG. 8G . It is appreciated that the instances when the needle base  83  and the housing surface  87  are transparent, visual detection as to the presence of a target substance on top of the hole array  14  occurs without the need to open the housing  82 . 
     In addition to the use of spacer flanges  90  and  92  to provide sequential and controlled collapse of the housing  82  to perform the function of an inventive device  70 , a similar result is performed with resort to complementary threaded first and second housing portions  102  and  104  that correspond in function to housing portions  86  and  84 , respectively. Thread engagement stops  106  and  108  as depicted in  FIG. 9  are sequentially removable and correspond to the spatial separations depicted in  FIGS. 8B and 8D , respectively. Optionally, a transparent surface  110  affords visual observation of the top of a hole array within the housing  100  without a need to open the same and risk exposure to fluid contained therein. 
     EXAMPLE 1 
     A sheet of Mylar having a thickness of 100 microns is subjected to laser boring to produce a close packed array of 300 holes, each having a diameter of 5 microns with the entire hole array covering a circular central area on the sheet of 3 millimeters. A duplicate sheet of 
     Mylar cut to the same dimensions of 1 centimeter by 3 centimeters and a slightly undersized piece of blank filter paper providing a margin of 3 millimeters there around is sandwiched between the Mylar films and the edges of the Mylar films fused to form a sealed pocket containing the filter paper. A drop of blood from a subject suspected of harboring malaria plasmodium is applied over the hole array and the blood components inclusive of normal erythrocytes are wicked into the filter paper through capillary draw under controlled rate conditions until such point as the air pressure within the housing exerts a countervailing force on blood component capillary draw into the filter paper thereby assuring the sampling of a preselected quantity of liquid, as depicted in  FIGS. 2A-2C . Erythrocytes infected with malaria causing parasites are too rigid to enter holes of the hole array and are concentrated on the top surface for subsequent study or incubation by conventional techniques. The rigidity of such infected cells is known to the art. PNAS Dec. 3, 2003, 100(25), 14618-14622. 
     EXAMPLE 2 
     The procedure of Example 1 is repeated with a drop of blood from a subject suspected of suffering from the hereditary disease sickle cell anemia with comparable isolation of abnormal erythrocytes on the top surface of an inventive concentrator overlying the hole array. 
     EXAMPLE 3 
     The process of Example 1 is repeated with a sample of water having been incubated with an antibody specific to giardia. An agglomerate of giardia and such antibodies is collected from the top surface overlying the hole array after a droplet of the incubated water has been applied thereto.