Abstract:
The present invention is embodied in a method for precisely dispensing fluid, including treating an orifice of a fluid dispensing apparatus during a fabrication process by applying a low surface energy material layer onto the orifice, adjusting a thickness of the low surface energy material coating to a predetermined threshold and limiting backpressure of a low dead volume fluid delivery system coupled to the orifice to reduce interference or interruptions for precisely dispensing the fluid.

Description:
BACKGROUND 
       [0001]    The dispensing of volumes of solution onto or into fluid receptacles is employed in a wide range of industries and fields such as chemical research, pharmaceutical research titration, biological study and medical research and others. These industries and fields currently employ a number of dispensing methods, for example analog pipetting, acoustics and piezo technologies. The solutions are dispensed in fixed or varying quantities onto or into fluid receptacles, for example glass slides or lab chips or into receptacles, such as test tubes or well plates. Some of these existing technologies used are capable of dispensing volumes in the microliter or nanoliter range. Expensive serial dilution sequence processes are used in some existing technologies because of the large minimum volumes of the solution being dispensed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0002]      FIG. 1  shows a block diagram of an overview of the fluid dispenser with a low surface energy orifice layer for reliable precision dispensing in one embodiment of the present invention. 
           [0003]      FIG. 2  shows an illustration of a structure of a reduced pooling low surface energy orifice layer drop ejector in one embodiment of the present invention. 
           [0004]      FIG. 3  shows a block diagram of an overview of a fabrication process of a low surface energy orifice layer in one embodiment of the present invention. 
           [0005]      FIG. 4  shows a block diagram of a reduced pooling fast reliable disposable low surface energy orifice layer thermal inkjet based printhead in one embodiment of the present invention. 
           [0006]      FIG. 5A  shows a block diagram of a low surface energy orifice layer in thermal inkjet based precision dispensing system operation for a titration process in one embodiment of the present invention. 
           [0007]      FIG. 5B  shows an illustration of a low surface energy orifice layer in thermal inkjet based precision dispensing system operation for a titration process in one embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0008]    In a following description, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration a specific example in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention. 
       General Overview: 
       [0009]    It should be noted that the descriptions that follow, for example, in terms of titration are described for illustrative purposes and the underlying dispensing technology can apply to any precision dispensing operations. In one embodiment of the present invention, clean, reliable and precise fluid dispensing is provided onto test surfaces or into test receptacles. In one embodiment, the fluid dispensing is used in a titration process for varying quantities of fluid to be dispensed. In another embodiment, a series of dispenses or a single dispense is provided for a specified quantity of fluid. 
         [0010]    In general,  FIG. 1  shows a block diagram of an overview of a low surface energy orifice layer for reliable precision dispensing method in one embodiment of the present invention. A fluid dispensing tool  110  includes a thermal inkjet based printhead  120 . The thermal inkjet based printhead  120  is configured with a fluid reservoir  125  on a top area to hold a supply of fluid to be dispensed. The thermal inkjet based printhead  120  is configured with at least one drop ejector  130  or more on a bottom portion of the thermal inkjet based printhead  120 . Each drop ejector  130  is configured with a low surface energy orifice  140  through which fluid is dispensed to a fluid receiving device  150  in one embodiment of the present invention. 
         [0011]    In one embodiment, a new layer is added to the orifice of the drop ejector  130 . The layer is made of low surface energy materials to create a low surface energy orifice  140 , which limits fluid adhesion to surfaces of the low surface energy orifice  140 . Fluid adhesion can cause drooling and pooling of the fluid as it is dispensed. Pooling refers to fluid that unintentionally accumulates on the printhead surface and covers the drop ejectors. Fluid pooling often encompasses the entire surface and affects trajectory, velocity, and drop shape. This can prevent drops from jetting, leading to no fluid being dispensed into a fluid receptacle, for example, a test well of a well plate. Well plates are plastic trays of many mini-test tubes. 
         [0012]    The drop ejector  130  in one embodiment greatly reduces fluid pooling by using the low surface energy orifice  140 , which precisely, efficiently, cost effectively and reliably dispenses clean drops of fluid with minimal drooling and pooling. As such, in one embodiment, the dispensing tool  110  is used for precision dispensing of small quantities of solution for titrating candidate test compounds. 
       Detailed Operation of the Low Surface Energy Layered Orifice: 
       [0013]      FIG. 2  shows an illustration of a structure of the low surface energy orifice layer drop ejector in one embodiment of the present invention. A fluid supply from the fluid reservoir  125  provides at least one drop ejector  130  with a solution or a fluid for dispensing. The solution or fluid flows  215  through a slot  205  at the bottom of the fluid reservoir  125  and continues through a slot  220  extended through a printhead silicon structure and for example a silicon  230  base of the drop ejector, which is configured to reduce pooling. The fluid  215  accumulates in a jetting chamber  217 . Adjacent to a top hat or orifice layer  250  are chamber walls  240  which form a portion of the drop ejector  130  body and form the jetting chamber  217  for fluid  215  before jetting. In one embodiment of the present invention, a low surface energy layer or coating  260  having low surface energy materials is spun onto the top hat or orifice layer  250 . The low surface energy orifice coating  260  can be applied in varying thicknesses. 
         [0014]    In addition, in one embodiment, the low surface energy orifice  140  can be configured with either a bore or counterbore  270 . This is done by patterning the low surface energy orifice coating  260  when applied, for example, to be coincident with the top hat or orifice layer  250  edges (bore pattern) or non-coincident with the top hat or orifice layer  250  edges (counterbore pattern). The bore or counterbore  270  is formed to further reduce pooling and drooling of the fluid  215  during a clean jetting of precision volumed drops  280 . Variations in the configuration of the drop ejector  130  can accommodate different types of fluid  215  for clean jetting of precision volumed drops  280  into or onto fluid receiving device  150  or receptacles in one embodiment of the present invention. 
         [0015]    The reduced pooling drop ejector  130  with the low surface energy orifice  140  can be readily incorporated into for example standard printheads in mass quantities. In one embodiment, the present invention can be configured in a variety of thermal inkjet based precision dispensing printhead fluid delivery systems, making it feasible for use in numerous precision dispensing operations. The reduced pooling drop ejector  130  with the low surface energy orifice  140  can be adjusted to accommodate the various fluid  215  characteristics of different solutions in other embodiments of the present invention. 
       Fabrication Process: 
       [0016]      FIG. 3  shows a block diagram of an overview of an exemplary fabrication process of a low surface energy orifice layer of one embodiment of the present invention. The fabrication process  310  includes the formation of a top hat  250  or orifice layer lamination (step  320 ), creation of a bore or counterbore (step  330 ) that can be incorporated into the tophat or orifice layer  250  of  FIG. 2  prior to spinning the low surface energy coating (step  340 ) onto the top hat  250 . In one embodiment, the bore or counterbore  270  of  FIG. 2  can be varied from thin to thick for different fluids. Next, a low surface energy exposure (step  350 ) can be performed or the layers can be co-exposed in one embodiment of the present invention. 
         [0017]    Applying the low surface energy coating of step  340  prior to when the low surface energy and nozzle develops (step  355 ), allows the pattern of the low surface energy coating  340  to be distinct from the nozzle layer, thereby providing additional design flexibility than if the layers are coincident in one embodiment of the present invention. The unexposed nozzle and low surface energy layers are developed in the same chemistry before fully curing and crosslinking the polymers. Micromachining (step  360 ) is then performed to remove any excess materials. In the fabrication process of  FIG. 3 , several other steps can be included, such as bake and oven cure steps, temporary protective coatings and other steps, which are not shown in  FIG. 3  for brevity. 
       Low Surface Energy Orifice Layer Thermal Inkjet Based Printhead: 
       [0018]      FIG. 4  shows a block diagram of a reduced pooling fast reliable disposable low surface energy orifice layer thermal inkjet based printhead in one embodiment of the present invention. The fluid dispensing tool  110  of  FIG. 1  with the low surface energy orifice  140  layer thermal inkjet based printhead  120  reduces expense and increases efficiency by using a low dead volume fluid delivery system  400 . In one embodiment, the low dead volume fluid delivery system  400  is a slot extender with no backpressure control device or system  410  placed on a top side of the printhead. Backpressure is negative pressure in the drop ejector  130  of  FIG. 1  jetting chamber  217  of  FIG. 2  to retard drooling and pooling. The low dead volume fluid delivery system  400  has no backpressure controlling device or system  410 . 
         [0019]    In one embodiment, a capillary mechanism inherent in the geometry between the drop ejector  130  of  FIG. 1  and fluid reservoir  125  provides a predetermined reduced amount of backpressure at the orifice. The slot extender is a simple plastic reservoir that is used for a portion of the low dead volume fluid delivery system  400  in one embodiment. This acts as the fluid reservoir  125  to hold a large supply of a solution. In one embodiment, a reservoir open to the atmosphere  414  is easily filled, for example, with a pipette manually. 
         [0020]    The solution, through a capillary motion, flows through a slot at the bottom of a reservoir  205  and the slot  220  in the printhead silicon base and the drop ejector  130  of  FIG. 2  with the low surface energy orifice  140 . The slot  220  allows solution to reach one or more drop ejectors  420  at the front of the printhead in one embodiment of the present invention. 
         [0021]    The printhead can have a capacity for numerous reliable reduced pooling drop ejectors  130  of  FIG. 1  with the low surface energy orifice  140  in one embodiment of the present invention. For example, in one embodiment, a thermal inkjet based printhead  120  can have 16 to 32 reduced pooling drop ejectors  130  of  FIG. 1  with the low surface energy orifice  140 . Other embodiments of the present invention can have different numbers and variations of the drop ejector  130  of  FIG. 1  with the low surface energy orifice  140 . 
         [0022]    Efficiency, reliability, and speed are produced in the reduced pooling fast reliable low surface energy orifice layer thermal inkjet based printhead  120  through the use of one or more drop ejectors  420  with reduced pooling low surface energy orifice  140  layer which is placed on the bottom side of the printhead. In one embodiment, clean and precise volumed drops  280  of fluid are dispensed by the printhead  120 . One or more precision volumed drops of solution can be jetted from one or more drop ejectors  420  onto or into a fluid receiving device  150 , such as a test well in a well plate, a glass slide, lab chip or test tube in one embodiment of the present invention. 
         [0023]    Reliability is created by the application of a low surface energy coating  260  of  FIG. 2  to the orifice layer and dispensing surfaces. This limits fluid adhesion and thereby prevents pooling from forming, which limits dispensing failures that may be caused by fluid pooling in a cost effective manner. The reliability in the quality of dispensing is increased because fluid is dispensed with minimal drooling and pooling, which allows faster dispensing speeds in one embodiment of the present invention. 
         [0024]    The low surface energy orifice  140  layer thermal inkjet based printhead  120  also is a cost effective method for using thermal inkjet based dispensing of solution in smaller quantities. This allows a dispensing operation that is faster with higher jetting frequencies, so larger numbers of drop ejectors  130  of  FIG. 1  can be used for large solution fill capacities in one embodiment. 
       Precision Dispensing Operation: 
       [0025]      FIG. 5A  shows a block diagram of a low surface energy orifice layer in thermal inkjet based precision dispensing system operation for a titration process in one embodiment of the present invention.  FIG. 5A  and  FIG. 5B  illustrate an operation of a fluid dispensing tool  110  of  FIG. 1  configured with a low surface energy orifice layer  500  in a thermal inkjet based precision dispensing system. 
         [0026]    An example of a precision dispensing operation using the low surface energy orifice layer fast reliable precision fluid dispensing is a titration  550  process for screening candidate drug compounds. Titration  550  is used in a number of fields and with various dispensing technologies. An example where titration  550  is used extensively is in pharmaceutical drug research in the drug discovery process which uses titration  550  in screening to test very small samples of drug compound concentrations to discover the level needed to effectively attack a target such as a virus. 
         [0027]    The titration  550  process generally employs a method, such as pipetting, to dispense small quantities of various classes of fluids in measured concentrations of the dissolved substance into small receptacle test wells, such as test tubes, which contain a known volume of the test solution. The small receptacle test wells could contain a prior loaded test solution containing for example a buffer, media, markers, enzymes, or cells or other chosen fluid. In this example for illustrative purposes only is a solution of a candidate drug compound  570  (dissolved substance), virus in a solution  580  (test solution) and test wells of well plate  560  (small receptacle test wells). In one embodiment, fluid pooling is reduced, which allows faster speed of reliable dispensing. This faster speed of reliable dispensing benefits high volume titration  550  operations. 
         [0028]    The low surface energy orifice layer  500  varies the amount of the solution of a candidate drug compound  570  being dispensed by clean jetting of precision volumed drops  280  of a highly concentrated solution of a candidate drug compound  570 . The quantity dispensed is from one or more drop ejectors  530  delivering varying numbers of precision volumed drops of a highly concentrated candidate drug compound solution. The quantities dispensed determine the concentration and since the drops are for example picoliter volumed, the range of concentrations delivered can be extensive. 
         [0029]    In one embodiment, a quantity of highly concentrated solution of a candidate drug compound  570  is conveyed using a pipette  505  to fill the reservoir  510 . The tip of the pipette  505  is shown in  FIG. 5B  in the operation to fill the reservoir  510  with a quantity of highly concentrated solution of a candidate drug compound  570 . The fluid reservoir  125  of  FIG. 1  is the slot extender portion of the low dead volume fluid delivery system  400 . Thusly the highly concentrated solution of a candidate drug compound  570  is loaded into the low dead volume fluid delivery system  400  and flows through a disposable thermal inkjet based printhead  520  to each of the drop ejectors with low surface energy orifice  530 . 
         [0030]    The foregoing has described the principles, embodiments and modes of operation of the present invention. However, the invention should not be construed as being limited to the particular embodiments discussed. The above described embodiments should be regarded as illustrative rather than restrictive, and it should be appreciated that variations may be made in those embodiments by workers skilled in the art without departing from the scope of the present invention as defined by the following claims.