Abstract:
A positive displacement pump design that allows optical analysis of the fluids being pumped, mixed or sorted, via optical detection within the pump itself. Various embodiments of the device are disclosed, one employing a glass rod as a piston that gives the ability to convey optical light into the pump cylinder and collect light back out. Another employs a piston rod that encapsulates one or more optical fibers coupled to a gradient index lens at the distal end of the piston rod. A third embodiment comprises an optical fiber that serves directly as a piston actuator rod inserted through the capillary channel of a ceramic ferrule that slidably seats and aligns the optical fiber/piston actuator rod. In all embodiments the pump and detection system can be controlled and synchronized by a microprocessor, and optical detection can be based on fluorescence, scattered light, absorbance, or both.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     The present application derives priority from U.S. Provisional Patent Application No. 60/699,644 filed: 18 Jul. 2005. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to flow analysis in pumps and, in more particularly, to an optical analysis system for digital incremental flow analysis in positive displacement pumps.  
         [0004]     2. Description of the Background  
         [0005]     Conventional positive displacement pumps pump liquids in and out of a pumping chamber by changing the volume of the chamber and controlling the valving of at least one inlet and one outlet port.  
         [0006]     For example, U.S. Pat. No. 6,739,478 to Bach et al. issued May 25, 2004 shows a precision fluid dispensing system with a two-piece positive displacement pump and a precision closed loop controller drive system that addresses the small volume precision dispensing requirements of bioscience applications. A micro-controller with closed loop feedback provides exact linear positioning and motion of the pump piston as well as optional control of a nozzle to provide exact micro-dispensing of fluids. Similarly, U.S. Patent Application 2005036692 by Bach further describes a two piston, two cylinder pump that can have multiple inlet and outlet ports on either diameter. These multiple port dual diameter pumps can have ports for dispensing a common fluid through several outlet ports or can be used to bring different reagents into the pump though multiple inlet ports. The use of different inlet ports for sequential reagent input to the pump allows for pump mixing of reagents and the dispensing of a common mixed solution.  
         [0007]     The conventional displacement (pumping) range for the above-described and other positive displacement pumps is approximately 500 ml to 5 ul, or smaller volumes if coupled to an active nozzle as described in patent U.S. Pat. No. 6,739,478. Smaller precision fluid pumps can be accomplished by using small piston and cylinders coupled to a magnetostrictive, piezoelectric or solenoid actuator. Magnetostrictive fluid pumps rely on expanding rods that serve as actuators. The rods are made of magnetostrictive material that changes dimensions in the presence of a magnetic field. Thus, the rods move in and out of a pumping chamber like a solenoid, thereby changing the volume of the chamber. The rods may be moved within a range of several tens of microns. There are no moving parts at all, and so magnetostrictive pumps can run reliably over a long period of time. For example, U.S. patent application Ser. No. 11/273,583 by Bach et al. employs magnetostrictive actuator(s) to accomplish the functions of precision fluid dispensing, reagent mixing, and microarray dispensing. U.S. patent application Ser. No. 10/688,331 by Bach et al. shows a magnetostrictive actuator valve used for removing small volumes of fluid or fluid containing cells in a flowing stream or incremental flowing stream.  
         [0008]     There is a large demand for cost effective cell sorting of stem and other cell types. Sorted isolated cell populations are used for transplantation into myeloablated cancer patients. There are currently about 100,000 such transplantations a year in the US. Automated cell sorting techniques are becoming indispensable for both research and clinical applications. These devices detect the properties of cells, and implement the physical separation of cells of interest at high speed. The detection of cells are done using optical techniques such as fluorescence and light scattering, but the optics are typically interfaced to a sample chamber downstream of the pump, followed by separation of the cells of interest using electrostatic or other physical separation methods. The sample chamber and sorting relies on an open fluid flow system that creates a high potential for contamination.  
         [0009]     It would be greatly advantageous to provide a positive displacement pump design that allows for precision dispensing and mixing of fluids by assist of an optical system that interfaces directly with the pump itself and a precision closed loop controller drive system that addresses the small volume precision dispensing requirements of bioscience applications. Such a system would allow closure of the fluid flow system, reduces moving parts, and reduces the potential for contamination  
       SUMMARY OF THE INVENTION  
       [0010]     Accordingly, it is an object of the present invention to provide a positive displacement pump design for precision dispensing and mixing of fluids by assist of an optical system that interfaces the pump chamber directly to a precision closed loop controller drive system (utilizing feedback) for optical analysis thereof, especially for small volume precision dispensing requirements of bioscience applications.  
         [0011]     It is another object to provide a positive displacement pump design with direct optical analysis of the pump chamber which is nevertheless a closed fluid flow system, with few moving parts, and reduced potential for contamination  
         [0012]     It is another object to provide a positive displacement pump design as described above that has particular utility in bioscience applications such as a cell sorter.  
         [0013]     According to the present invention, the above-described and other objects are accomplished by providing a positive displacement pump design that allows an optical analysis of the fluids being pumped, mixed or sorted, via optical detection within the pump itself as opposed to downstream there from. According to an embodiment of the present invention, the pump incorporates a glass rod as a piston that gives the ability to convey optical light into the pump cylinder and collect light back out of the piston to optical detectors. As an alternative to a glass piston, a positive displacement rod may encapsulate one or more optical fibers coupled to a gradient index lens at the distal end of the piston rid. A gradient index lens employs a gradually varying index of refraction within the lens material itself, allowing light rays to be redirected towards a point of focus. Thus, for example, a GRIN lens such as an EndoGRIN™ or Selfoc™ lens may be carried at the distal end of the piston rod and optically coupled directly to an optical fiber embedded in the positive displacement piston (or the optical fiber or bundle may itself serve as the pump piston). The gradient index lens serves as the optical focusing element and allows optical interrogation within the chamber of the positive displacement pump. The incorporation of optical detection within the confines of a positive displacement pump chamber has great utility, especially as the internal analysis volume decreases. For example, pistons in accordance with the present invention allow the detection in the pump to approach femto-liter volumes. The pump and detection system can be controlled and synchronized by a microprocessor. Optical detection can be based on fluorescence, scattered light or both. Other detection techniques such as absorbance are also included in this application.  
         [0014]     It is also understood that the use of a piston and cylinder incorporating optical detection in accordance with the invention can be used as a Precision Dispensing (or “Pick and Place”) type of pump. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     Other objects, features, and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiment and certain modifications thereof when taken together with the accompanying drawings in which:  
         [0016]      FIG. 1  shows a preferred embodiment of a positive displacement pump  2  with pump-integrated optical analysis system according to a first embodiment of the invention.  
         [0017]      FIG. 2  shows a dual-diameter positive displacement pump  120  with pump-integrated optical analysis system according to an alternate embodiment of the invention.  
         [0018]      FIG. 3  shows a positive displacement pump  220  with pump-integrated optical analysis system according to another embodiment of the invention for small volume precision dispensing requirements of bioscience applications.  
         [0019]      FIG. 4 (A-C) is a sequential view of a ‘pick and place” precision fluid pump with pump-integrated optical analysis system according to another alternate embodiment of the invention, while  FIG. 4D  illustrates an enlarged cross-section of the pick and place pump.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]     The present invention is a positive displacement pump mechanism that allows for precision dispensing and mixing of fluids by an optical system coupled directly to the pump chamber for small volume precision dispensing requirements of bioscience and other applications. The novel concept of the present invention is a positive displacement pump having an optically-transmissive piston coupled to an optical system including an optical detector and light source, at least the detector being connected to a closed loop controller drive system (e.g., a “pump integrated optical analysis system”). In general operation, the light source emits light that is transmitted through the transmissive piston, which transmits the light into an analysis section within the confines of the pump chamber. The light may be reflected back from the analysis section back through the piston to the detector for sensing, or alternatively through the pump chamber to a detector mounted opposite the piston on the interior cylinder head. Either way, any optical change in the analysis region can be observed via the reflected light and used as feedback to control the pump drive system. The concept lens itself to various positive displacement pump embodiments including: 1) a glass piston embodiment in which the piston is formed entirely of glass or has an embedded glass core; 2) a fiber-optic or fiber bundle piston embodiment in which the piston comprises an optical fiber or has an optical fiber embedded lengthwise therein; and 3) a GRIN lens (described below) configuration in which a GRIN lens is mounted on the piston and is optically coupled through the piston (as per 1 &amp; 2 above) to form an optical analysis cell between the piston an cylinder bottom.  
         [0021]      FIG. 1  shows a preferred embodiment of a positive displacement pump  2  with pump-integrated optical analysis system according to a first embodiment of the invention.  
         [0022]     The positive displacement pump  2  generally comprises an optically-transmissive piston actuator rod  12  that may be formed entirely of light-transmissive optical glass, polymeric material, an optical fiber, fiber bundle, or alternatively having an embedded glass/polymeric rod or optical fiber therein. The piston actuator rod  12  is formed with a flat, convex or concave reflective lens  14  at its distal end. The piston actuator rod  12  is slidably mounted in a cylinder  16 , seated at its lower end at a piston movement coupling point  22  that serves to drive the piston rod  12  axially under control of a pump drive controller  40  to provide volumetric displacement in the cylinder  16 . The piston movement coupling point  22  may be any of a variety of commercially-available electromechanical or magnetic piston drive mechanisms that serve to drive the cylinder axially under control of a pump drive controller  40 , which is in turn under the control of a processor CPU  60 . The CPU  60  may be any of a variety of commercially available programmable logic controllers or a fully-equipped computer. Likewise, the drive controller  40  may be any of a variety of digital-to-analog pump drive control modules for controlling the displacement of piston rod  12 . U.S. Pat. No. 6,739,478 describes a stepper motor drive system where the piston is digitally adjusted to provide a precise distance between the end of the piston and bottom of the cylinder. Other drive systems are commercially available, including those used in syringe pumps by manufacturers such as Cavro and Hamilton, servo systems such as used in the Bausch &amp; Strobel filling equipment for two piece pumps, or Bosch Packaging where steppers or servos are used with three piece piston cylinder pumps. Manual systems can also be used, such as those in the Ranin hand held pipetting devices. One or more rotary valve inlet and outlet ports  20  are in communication with the cylinder  16  for induction and expulsion of fluid there from. The piston actuator rod  12  is optically coupled to an optical system that includes a beam splitter  32 , optical detector  34 , and optical light source  36 . In operation, the light source  36  emits light through the beam splitter  32  into the glass piston actuator rod  12 , which transmits the light into an analysis section  18  between the lens  14  and cylinder  16  head. The light is reflected back from the fluid in the analysis section  18  back through the piston actuator rod  12  to the beam splitter  32 . The beam splitter may be a conventional prism with dichroic element for separating the source light from reflected light. The reflected light is diverted to the optical detector  34  for sensing. A converter  50  such as a conventional analog-to-digital (A/D) converter converts the raw signal from detector  34  into a digital equivalent, which is in turn transmitted to a controller CPU  60  for interpretation and processing. The signal is analyzed to generate feedback as necessary to control or modify the pump drive control signals emitted from the CPU  50  to the pump drive controller  40  to thereby control the displacement of piston rod  12 . Thus, any optical change in the analysis region  18  can be observed via the reflected light and used as feedback in controlling displacement of the piston rod  12 .  
         [0023]     As an alternative to a flat, convex or concave refractive lens  14 , a GRIN lens or graded fiber may be used. GRIN is short for graded-index or gradient index, which is an optical element having a varying refractive index. More specifically, a GRIN lens is a lens whose material refractive index varies continuously as a function of the spatial coordinates in the material. Similarly, a graded-index fiber is an optical fiber having a core refractive index that decreases radially outward toward the cladding. There are two basic types of GRIN lenses: radial or axial (or RGRIN and AGRIN, respectively). The present embodiment preferably employs an RGRIN lens having a flat frontal surface capable of focusing light just as a normal lens with curved surfaces does. Thus, the RGRIN lens is effectively used as a high quality image relay. There are a variety of suitable commercially-available GRIN lenses that will suffice, including EndoGRIN lenses™ from Gradient Lens Corporation or Selfoc™ lens from NSG, Inc. In either case, the lens  14  is optically coupled directly to the piston actuator rod  12 . Also, it is not necessary that the entire piston actuator rod  12  be optically transmissive. The same goal can be accomplished with an optical fiber, or glass/polymeric rod embedded axially in the piston actuator rod  12 , or an optical fiber may itself serve as the pump piston rod  12 . Optical polymers may be any from among the class of acrylates, polyimides, polycarbonates, and olefins (e.g., cyclobutene).  
         [0024]     It should also be understood that the use of a piston and cylinder incorporating optical detection in accordance with the invention can be used as a Precision Alignment Dispensing or “Pick and Place” type of pump. This type of pump aspirates fluid into the end of the cylinder (or an extension pipette tip coupled to the cylinder), as the piston is moved upward causing the fluid to move into the pipette tip or pump.  
         [0025]      FIG. 2  shows a dual-diameter positive displacement pump  120  with pump-integrated optical analysis system according to an alternate embodiment of the invention, in which like components are numbered as show in  FIG. 1 . Here fluid is aspirated into the cylinder head  17  via an inlet port  19 A coupled to the cylinder  16 . The aspiration occurs as the valve  17  is aligned with the inlet port  19 A then the piston  16  is moved downward causing the fluid to move into the cylinder  16 . The valve  17  is then rotated to the dispensing port  19 B. The piston  14  is moved to a second location (the piston  14  and valve  17  move as a set for enhanced precison dispensing to take place),where piston  14  is again moved to dispense the fluid through the outlet port  19 B. The foregoing is a conventional dispensing approach such as used Bosch Packaging and other existing companies. The use of optics in this type of pump, if used in the manner shown and described with regard to  FIG. 1 , provides for an analysis of the effectiveness of the fluid transfer.  
         [0026]      FIG. 3  shows a positive displacement pump  220  with pump-integrated optical analysis system according to another embodiment of the invention for small volume precision dispensing requirements of bioscience applications. The positive displacement pump  220  generally comprises a combined optical fiber/piston actuator rod  212  inserted through the capillary channel of a ceramic ferrule  214 . The ceramic ferrule  214  is a high-performance, multimode optical connector approximately 2.5 mm in diameter and with an approximate 127 um internal channel for slidably seating and aligning the optical fiber/piston actuator rod  212 . The ceramic ferrule  214  is coupled (or integrally joined) to a cylindrical pump chamber  216  for volumetric displacement therein. One or more rotary valve inlet and outlet ports  222  are in communication with the pump chamber  216  for induction and expulsion of fluid there from. The optical fiber/piston actuator rod may be coupled (at left) to an optical system as in  FIG. 1 , including a beam splitter  32 , optical detector  34 , and optical light source  36 . In operation, the light source emits light through the beam splitter into the optical fiber/piston actuator rod, which transmits the light into the fluid in the pump chamber  216 . The light is reflected back from the fluid in the pump chamber  216  back through the optical fiber/piston actuator rod to the beam splitter. The reflected light is diverted to the optical detector for sensing. Thus, any optical change in the pump chamber  216  can be observed via the reflected light.  
         [0027]     While the illustrated embodiments show the piston as source and/or detector, the cylinder can be the also a source and/or detector by embedding a light transmissive element therein.  
         [0028]      FIG. 4 (A-D) is a sequence views of a ‘pick and place” precision fluid pump with pump-integrated optical analysis system according to another alternate embodiment of the invention. In a pick-and-place pump no valving is required because fluid never enters the pump. Rather, a small quantity it is inducted into the cylinder (pipette) tip and is then dispensed there from. The use of optical detection in a pick-and-place pump configuration is also a novel contribution. The pick and place pump generally comprises a piston rod  12  having an optical fiber bundle  29  embedded therein, the fibers of bundle  29  terminating at the face of the piston rod  12 . The piston actuator rod  12  is slidably mounted in a cylinder  17 . In this Precision Alignment Dispensing or “Pick and Place” type of pump, the distal end of the cylinder  17  is introduced into fluid (as at A), and fluid  27  is aspirated into the end of the cylinder  17  (or an extension pipette tip coupled to the cylinder  17 ) as the piston  14  is moved upward, causing an amount of fluid  27  to move into the pipette tip or pump cylinder  17 . As seen at C the pipette tip or pump cylinder  17  is then moved to a dispensing position with the fluid  27  still in the cylinder  17 . The piston  14  is moved downward (as at B) and the fluid is “Touched Off” allowing small dispensing of fluid quantities. In this embodiment optical fiber bundle  29  is a randomized bifurcated fiber optic bundle  29  embedded inside the piston  14  and exposed on the underside of piston  14 . A light source (as at  36  of  FIG. 1 ) is coupled to one fiber (or set of fibers) and a detector (as at  34  of  FIG. 1 ) is coupled to the other. As seen in the enlarged sectional view of the piston  14  end at  FIG. 4D , any residual fluid left over in the cylinder  17  after a touch off of the piston  14  in a fluid transfer would result in fluid bridging of the source and sensor fibers  29 . Thus, the amount of backscatter sensed by the detector is reduced by the residual. Consequently the detector provides an indication as to the effectiveness of the fluid transfer. Similarly, if fluid is present and bridging the source and sensor fibers  29  an optical reflective signal can be detected. If the fluid is not present little to no optical reflective signal is detected. Again, one skilled in the art should understand that other piston configurations may be suitable and the use of glass rods, fibers, GRIN lenses, etc. are considered to be within the scope of the invention.  
         [0029]     It should now be apparent that the above-described positive displacement pump design by virtue of its combination optical fiber/piston actuator rod offers a high-throughput and high-accuracy filling and dispensing solution for various applications, with particular utility for small volume precision dispensing requirements of bioscience applications such as cell sorting. In this case the piston pump can make an optical analysis on a discrete volume located within the pump. This analysis can be a “scouting test” and if further results are needed further analysis can be accomplished before the discrete fluid volume is move forward. If this type of discrete pump and cell sorting gating device is synchronized selected volumes can be cut from the discrete fluid dispensing system.  
         [0030]     Having now fully set forth the preferred embodiments and certain modifications of the concept underlying the present invention, various other embodiments as well as certain variations and modifications of the embodiments herein shown and described will obviously occur to those skilled in the art upon becoming familiar with said underlying concept. It is to be understood, therefore, that the invention may be practiced otherwise than as specifically set forth in the appended claims.