Patent Publication Number: US-2005118074-A1

Title: Methods and devices for storing and dispensing liquids

Description:
RELATED APPLICATION  
      This application is a continuation of U.S. application Ser. No. 09/827,570, filed Apr. 5, 2001, which claims priority to U.S. application Ser. 60/194,586, filed Apr. 5, 2000, which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION  
      1. Field of the Present Invention  
      The present invention generally relates to devices and methods for storing and dispensing quantities of liquids. More specifically, the present invention uses a macro/micro interface and a microelectro mechanical system to store and dispense chemical and biological liquids in minute quantities.  
      2. Description of the Related Art  
      Until the relatively recent advent of combinatorial chemistry and genetic research spawned the need for high-throughput analyzing and screening techniques, researchers performed such assays using vials, tubes and beakers. However, with ever more substances available via synthesis or via combinatorial techniques for testing, the need has arisen to test the possible role of thousands, or even millions of substances, in comparable numbers of possible reactions. Miniaturization has been identified as a promising path to more efficient, e.g. less expensive, chemical, and in particular, drug, analysis and screening. Discussions of various aspects of such analysis and screening techniques are found in J. D. Devlin, ed., High Throughput Screening: The Discovery of Bioactive Substances (Marcel Dekker, Inc., New York, 1997); which is incorporated herein by reference to more fully describe the state of the art to which the present invention pertains.  
      A minaturization apparatus may be broadly classified into at least two categories. A first category deals with micro-chemistry and involves the placement of chemical substances in small amounts in sites formed on glass or a similar substance. These small amounts generally range between picoliter and microliter aliquots. Such amounts shorten reaction times significantly over those conducted in reaction vessels holding on the order a fraction of a milliliter, as currently achievable by a lab technician working “by hand”. In addition to microchemical testing, levels of gene expression and protein levels can be tested on a large scale using micro-chemistry.  
      An example of this first category is the development of microplate technology in which a substrate (e.g. plastic) may include site densities of up to about many thousand (e.g. 96 to about 10,000) sites. This technology generally includes the use of complex micro-robotics or the adaptation of ink-jet technology to apply chemical and biochemical substances to chosen sites on the substrates. Frequently, at least one of the reactants in a chemical assay to be performed is chemically linked to or otherwise immobilized at the reaction site, so that fluids may be added to and removed from the reaction site without removing an intermediate or end product of the reaction, since it is desirable that the intermediate or end product(s) is (are) to be retained at the reaction site, so that the outcome of the chemical assay may thereby be determined.  
      Currently, credit-card sized chips (e.g. glass chips) with greater than many thousand (e.g. 10,000) sites are in development (See Leach, 1997, Drug Discovery Today, 2:253). Each site may cover an area of 100 square microns and may contain much less than 1 microliter in volume. The chip is a glass sandwich formed from individual glass layers, which are glued together to form tubes to move substances between sites. The tubes are generally formed by cutting (e.g. etching), trenches or grooves in a first glass layer and then sandwiching the trenches under a second glass layer.  
      A second category of miniaturization apparatus (e.g. “lab on a chip”) employs silicon or glass as some functional modality in some functional (e.g. electrical or mechanical) modality as a substrate, and chemicals then are tested on the substrate. This category of apparatus may include the use of electrokinetic motive forces. Micro-robotics or micro-chemistry, or both, may be employed with such substrates, including the use of micro-fluidic pumps (pumps having no moving parts) to move substances between sites, the use of electrophoresis or electrokinetic pressure pumping (a combination of electrophoresis and electro-osmosis) as motive agents to analyze chemical reactions acting over the surface of the silicon substrate (for about e.g. 25 reaction sites).  
      Currently, to achieve high-throughput analyzing and screening techniques for chemical and biochemical reactions, complex operations using combinations of films and substrates or complex robotics for the precise placement of fluids carrying chemical compositions, or both are required. Such complex systems are subject to failure due to their inherent complexity and are expensive to manufacture and maintain.  
      Moreover, current methods and systems for liquid sample processing consume large amounts of expensive, toxic and specialty reagents. This is especially true in the pharmaceutical arts when throughput rates for a singe lab can be up to 100,000 samples per day, where each sample includes a volume on the order of 2-20 microliters.  
      Accordingly, it is desirable to be able to process hundreds or thousands of liquid samples concurrently at a volume in the pico to micro liter range.  
     SUMMARY OF THE INVENTION  
      The devices and methods according to the present invention possess new capacities and capabilities in liquid handling, storage, and dispensing. The present invention enables the storing of liquid samples in any format (including a conventional 96 sample format) for a period of time, and also allows for the dispensing of the liquid samples in minute volumes. These volumes preferably range from picoliters to microliters.  
      Accordingly, the present invention provides a liquid handling device and method for storing and dispensing liquid samples in high density formats using liquid volumes with a range of several orders of magnitude.  
      The present invention also provides liquid handling devices and methods using a macro to micro interface and a new microelectro mechanical system for real-time re-arraying of combichem and biochemical libraries and other liquid samples, as well as a means for compound storage, compound indexing, and compound dispensing.  
      The liquid handling devices and methods according to the present invention is particularly suited for re-arraying combichem and biochemical libraries existing in 96 well formats into higher density formats, e.g. 384 or 1536 well formats. Higher density formats (e.g. 500,000, 1,000,000, and 2,000,000 samples) are within the scope of this invention.  
      Accordingly, in one aspect of the present invention, a liquid handling system includes a liquid handling substrate having a plurality of channels for conducting a liquid sample. The channels terminate in a corresponding plurality of exit ports in an outer surface of the substrate for transfer of a quantity of the liquid sample. The liquid handling system also includes a liquid storage and dispensing substrate having a plurality of cartridges corresponding to the channels, where the cartridges terminate in a corresponding plurality of exit ports in an outer surface of the substrate for transfer of a quantity of the liquid sample. Each channel includes a reservoir in communication with a corresponding cartridge which creates an interface between the channel and the cartridge. Each cartridge terminates at a dispensing device. The dispensing device may include a microelectro mechanical system (MEMS) comprising a membrane with an opening, a nozzle positioned adjacent to the opening on a side of the membrane and a piezoelectric element.  
      Liquid is conveyed in the present invention using any one or a combination of means including capillary action, pneumatic means, electroosmotic flow, and a minipump.  
      In another aspect of the present invention, the liquid handling system according to the above aspect may be used in a method having the steps of drawing a liquid sample into the channels either by capillary action, pneumatic means, electoosmotic flow, a minipump or any combination thereof, storing the liquid sample in the cartridges, and dispensing the liquid sample after a period of time.  
      Moreover, the above aspect may include further features including: 
          a liquid detecting means comprising a light emitting diode (LED) and a photo-detector, for detecting a level of a liquid sample in a cartridge;     a monolithic assembly of all cartridges; 
            separable cartridges, which may be separated using a multifunctional head arrayed in either a fountain, roller, conveyor belt or chain geometry;    
            electrical conductor(s) for supplying electrical energy to the liquid detecting means and the liquid storage and dispensing substrate; and     a registration mark and/or indexing mark on the outer surface of the cartridge.        

      For a better understanding of the invention, reference is made to the below referenced drawings and written description following immediately thereafter. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIGS. 1A-1D  are schematic diagrams of one embodiment of the liquid handling system.  
       FIGS. 2A-2B  are schematic diagrams of one embodiment of the cartridge of the liquid storage and dispensing substrate and the MEMS.  
       FIG. 3  is a schematic diagram of one embodiment of the liquid storage and dispensing substrate in which the cartridges are arranged in a monolithic array.  
       FIG. 4  is a schematic diagram of one embodiment of the liquid storage and dispensing substrate in which the separable cartridge are arranged in a fountain geometry.  
       FIG. 5  is a schematic diagram of one embodiment of the liquid storage and dispensing substrate in which the separable cartridges are arranged in a roller geometry.  
       FIG. 6  is a schematic diagram of one embodiment of the liquid storage and dispensing substrate in which the separable cartridges are arranged in a conveyor belt geometry.  
       FIG. 7  is a schematic diagram of one embodiment of the liquid storage and dispensing substrate in which the separable cartridges are arranged in a chain geometry. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      As shown in  FIGS. 1A-1D , a macro interface includes 96 glass (or other comparable material) capillary tubes  1  arrayed in a conventional 96 sample format, fixed in place relative to one another. A corresponding micro interface  11  includes 96 cartridges  12  fixed in place relative to one another by a holder. A liquid sample reservoir  3  is positioned between each capillary tube and corresponding cartridge. The array may be arranged in any number of arrangements for yielding the desired number of tubes and cartridges. Such arrangements are illustrated in  FIG. 1D   20 - 22 .  
      FIGS.  2 A-B, illustrate enlarged views of a cartridge  12  and a micro-electrical, mechanical system (MEMS)  4  positioned on one end of the cartridge. A liquid sample flows from the liquid handling substrate through the reservoir into a lower part of the cartridge. Applying a vacuum to orifice  23  forces liquid to enter the cartridge to “prime” the cartridge. Once the cartridge is primed, the liquid storage and dispensing substrate is inverted and both sides of the cartridge are sealed with an appropriate sealant to prevent evaporation, cross-contamination of the sample, and the introduction of particulate matter therein. A hydrophobic membrane  24  positioned adjacent the orifice  23  allows airflow into and out of the cartridge and prevents the liquid sample from being drawn out of the cartridge at the orifice  23 .  
      A liquid sensing system monitors the liquid sample level in the cartridge. Using an LED  9 , collimated light is sent through a narrow bleed passageway  25  that separates the MEMS  4  from the vacuum orifice  23 . When a liquid sample is present, light is refracted to a photodetector  10  positioned on an opposite side of the bleed passageway  25  from the LED  9 . Light is refracted away from the photodetector  10 , however, when the level of the liquid sample becomes too low after dispensing of the liquid sample or if the device loses its prime and the bleed passageway  25  does not contain liquid.  
      Fluid flows from the lower part of the cartridge through a micro-filter  26  (for removing particulate matter) as shown in  FIG. 2B , so that clogging of a silicon nozzle  7  at an exit orifice  6  is avoided. The exit orifice  6  is defined by a region surrounded by a silicon membrane  5 , which is held in place by a glass substrate  27 . The exit orifice and silicon nozzle are created by micro-etching the silicon membrane. Coating the silicon membrane is a piezoelectric substance  8  that acts as an actuator for dispensing fluid. To dispense a fluid, the silicon nozzle points in a downward direction and electrical energy is supplied to the piezoelectric substance. This causes the silicon membrane to flex and results in droplet ejection from the nozzle.  
      During assaying of the liquid sample, individual cartridges  12  may be separated from other cartridges of the liquid storage and dispensing substrate. However, it is also possible to maintain the cartridges in the same positions relative to one another creating a monolithic dispenser  11 . Accordingly, each cartridge includes registration  18  and indexing marks  19  on the surface of the cartridges so that the cartridge may be easily aligned and identified when the cartridges are separated from one another. The cartridges are then fed in a serial manner into a multifunctional head reader  28 .  
      The multifunctional head reader  28  includes an array of elements having electrical conductors  17  for supplying electrical energy to the cartridge  12  and an array of detectors  29  for determining the chemistry of the dispensed liquid samples. The head device may be designed in any number of geometries as indicated in the examples set forth below.  
     EXAMPLE 1  
     Multifunctional Head Device in a Fountain Geometry  
      As shown in  FIG. 4 , a fountain geometry  13  of individual cartridges  12  are fed down through a set of tracks  30  arrayed across the assay substrate  31  in a spoke-like manner. Each of the tracks may house two belts  32  on either side of a horizontal portion of the track. Cartridges are drawn into the horizontal portion of the track via gravity and then conducted across the surface of the substrate by the two belts on either side. The bottom and tops of the tracks may include air bearings or a material  33  with a low coefficient of friction to ease passage of the cartridges through the tracks. The tracks may also contain electrical conductors  17  that may run the length of the horizontal portion of the track or are split into discrete contact points. To dispense liquid, electrical energy is supplied to the electrical conductors  17  at an appropriate time when the cartridge  12  is positioned over a target. To ensure accurate positioning of the particular cartridge, the tracks may include one or more sensors  37  to detect registration marks  18  and one or more sensors  38  to detect indexing marks  19  provided on the cartridges. Sensors for chemistry detection  29  may also be used and may be positioned on the underside of the tracks or placed on rails between the tracks.  
     EXAMPLE 2  
     Multifunctional Head Device in a Roller Geometry  
      As shown in  FIG. 5 , roller geometry tracks  34  similar to those described in Example 1 are arrayed in a cylindrical manner. Cartridges  12  are positioned into the tracks  34  with the exit orifice  6  of each dispenser facing outwards. Each track includes a row of cartridges which may be staggered relative to one another at a pitch corresponding to reaction sites below or some multiple of the pitch. The cartridges may be locked into each track via a pressure plate applied to the open end to ensure that each cartridge is snuggly positioned adjacent cartridges. This insures proper alignment of the cartridges within the track. Either contiguous or discrete electrical conductors  17  or a combination of the two may be placed along the length of each track to provide electrical energy to dispense liquid from an entire row of cartridges, individual cartridges in the row, or groups of cartridges within a row. Registration marks  18  on the cartridges may also be read via a detector  37  to ensure proper registration of the cartridges with respect to the roller  14  and chemistry substrate  36 . Dispensing is accomplished by rotating the roller  14  so that the appropriate track  34 /cartridge  12  is positioned over the reaction sites  36  and then energized via the electrical conductors  17 . Sensors  29  to detect chemical activity may also be used and positioned between the tracks, in another roller (a detection roller  35 ) or may be part of an overhanging arm positioned adjacent to the dispenser roller arm. In order to increase throughput, multiple rollers may also be used.  
     EXAMPLE 3  
     Multifunctional Head Device in a Conveyor Belt Geometry  
      As shown in  FIG. 6 , in the conveyor belt  15  geometry individual cartridges  12  are affixed to a conveyor belt  15  that transports each cartridge  12  to its appropriate dispensing location. At the point of alignment where the cartridge is horizontal, electrical conductors  17  are in place to transmit electrical energy to actuate the dispenser. Additionally a sensor  37  may be placed adjacent to this point to ensure accurate registration of the dispenser with respect to the reaction site  36  below. A sensor  29  to detect chemical activity may also be placed at this location.  
     EXAMPLE 4  
     Multifunctional Head Device in a Chain Geometry  
      As shown in  FIG. 7 , in the chain geometry  16  individual cartridges  12  are linked male end  39  to female end  40  in a manner similar to that of a bicycle chain. In essence the linked cartridges form a conveyor belt similar to that seen in Example 3, supra. By either using a sprocket and teeth system or a friction drive system the cartridges can be aligned with respect to the reaction sites using a similar geometry and instrumentation to that described supra in Example 3.  
      Having thus presented the present invention in view of the above described embodiments, various alterations, modifications and improvements will readily occur to those skilled in the art. Such alterations, modifications and improvements are intended to be within the scope and spirit of the invention. Accordingly, the foregoing description is by way of example only and is not intended to be limiting. The invention&#39;s limit is defined only in the following claims and the equivalents thereto.