Dispensing apparatus having improved dynamic range

Abstract

A method and apparatus for dispensing precise quantities of reagents is disclosed including a positive displacement syringe pump in series with a dispenser, such as an aerosol dispenser or solenoid valve dispenser. The pump is controlled by a stepper motor or the like to provide an incremental quantity or continuous flow of reagent to the dispenser. The pump and dispenser are operated in cooperation with one another such that the quantity and/or flow rate of liquid dispensed by the dispenser can be precisely metered substantially independently of the particular operating parameters of said dispenser to attain a desired flow rate, droplet size or mist quality, droplet frequency and/or droplet velocity.

What is claimed is:  
     
       1. An apparatus for dispensing predetermined quantities of liquid onto a substrate, comprising: 
       a dispenser having an inlet and an outlet and being adapted to form droplets of said liquid having a size in the range of about 1-4 nanoliters to one microliter which are deposited onto said substrate; and  
       a metering pump hydraulically arranged in series with the inlet of said dispenser for metering predetermined quantities of said liquid to said dispenser;  
       whereby the quantity and/or flow rate of liquid dispensed by said dispenser is metered substantially independently of operating parameters of the dispenser.  
     
     
       2. The apparatus of  claim 1  wherein the quantity and/or flow rate of liquid dispensed by said dispenser is precisely metered substantially independently of the droplet size or quality of said liquid being dispensed. 
     
     
       3. The apparatus of  claim 1  wherein said dispenser comprises an aerosol dispenser having an outlet comprising an air passage terminating in a nozzle and an inlet comprising a liquid passage terminating in a venturi orifice for mixing said liquid with a flow of air to form an aerosol mist proximate said substrate. 
     
     
       4. The apparatus of  claim 3  wherein said aerosol dispenser comprises an adjustable needle valve for adjusting the size of an orifice through which said liquid is dispersed. 
     
     
       5. The apparatus of  claim 1  wherein said dispenser comprises a valve adapted to be opened and closed at a predetermined frequency and duty cycle to form droplets of said liquid which are deposited onto said substrate. 
     
     
       6. The apparatus of  claim 5  wherein said valve is actuated by an electric solenoid. 
     
     
       7. The apparatus of  claim 5  wherein said valve is actuated by a piezoelectric constrictor device. 
     
     
       8. The apparatus of  claim 5  wherein the frequency and duty cycle of said valve can each be adjusted substantially independently for a given quantity or flow rate of liquid to produce droplets of a desired size, frequency and/or exit velocity. 
     
     
       9. The apparatus of  claim 1  in combination with a carriage adapted for X, X-Y or X-Y-Z motion relative to said dispenser for movably transporting said substrate and wherein said dispenser is mounted in juxtaposition with said carriage. 
     
     
       10. The combination of  claim 9  further comprising a controller in communication with said metering pump and said carriage for coordinating the output of said pump with the motion of said carriage so that said liquid may be dispensed in precise quantities of flow per unit length and such flow is precisely metered substantially without being affected by the particular-operating  operating parameters of said dispenser. 
     
     
       11. The combination of  claim 9  further comprising an array of dispensers and metering pumps, the outlets of said dispensers being arranged in a desired pattern suitable for attaining a desired print matrix or dot pattern. 
     
     
       12. The apparatus of  claim 1  wherein said liquid comprises a chemical reagent. 
     
     
       13. The apparatus of  claim 1  wherein said liquid comprises a chemical reagent and said substrate comprises a diagnostic test strip membrane. 
     
     
       14. The apparatus of  claim 1  wherein said metering pump comprises a syringe pump. 
     
     
       15. The apparatus of  claim 14  wherein said syringe pump comprises a syringe housing, a plunger axially displaceable within said syringe housing and plunger shaft having a lead screw formed thereon. 
     
     
       16. The apparatus of  claim 15  wherein said lead screw is sized and positioned such that when said lead screw is rotated, said plunger is displaced axially, causing a predetermined quantity of said liquid to be delivered to said inlet of said dispenser. 
     
     
       17. The apparatus of  claim 15  wherein said syringe housing has a displacement volume of between about 25 microliters about 25 milliliters. 
     
     
       18. The apparatus of  claim 1  wherein said metering pump comprises a stepper motor adapted to cause said pump to dispense predetermined incremental quantities or flow rates of said liquid to said dispenser. 
     
     
       19. The apparatus of  claim 18  wherein said metering pump has an incremental displacement volume of between about 0.42 nanoliters and 2.1 microliters. 
     
     
       20. The apparatus of  claim 18  wherein said metering pump has an incremental displacement volume of less than about 4.2 nanoliters. 
     
     
       21. The apparatus of  claim 18  wherein said metering pump has a resolution of between about 3,000 and 48,000 steps. 
     
     
       22. The apparatus of  claim 18  wherein said metering pump has a resolution of at least about 12,000 steps. 
     
     
       23. The apparatus of  claim 1  further comprising a second metering pump hydraulically coupled to said first metering pump for providing continuous web production capability. 
     
     
       24. The apparatus of  claim 1  wherein said dispenser and metering pump are configured so as to provide a range of selectable droplet sizes attainable for stable operation varying by a factor of greater than about 250. 
     
     
       25. The apparatus of  claim 1  wherein said dispenser and metering pump are configured so as to provide selectable droplet sizes ranging from less than about 4.2 nanoliters to greater than about 1 microliter. 
     
     
       26. An apparatus for dispensing a liquid onto a substrate, comprising: 
       a dispenser having an inlet and an outlet and a valve adapted to be opened and closed at a predetermined frequency and duty cycle to form droplets of said liquid which are deposited onto said substrate; and  
       a positive displacement pump hydraulically arranged in series with the inlet of said dispenser for metering predetermined quantities of said liquid to said dispenser;  
       whereby the quantity and/or flow rate of liquid dispensed by said dispenser can be  is precisely metered substantially independently of the particular  operating parameters of said dispenser. 
     
     
       27. The apparatus of  claim 26  wherein the size, frequency, and velocity of droplets dispensed by said dispenser each is adjusted substantially independently of the quantity and/or flow rate of liquid being dispensed. 
     
     
       28. The apparatus of  claim 26  wherein said valve is actuated by an electric solenoid. 
     
     
       29. The apparatus of  claim 26  wherein said valve is actuated by a piezoelectric constrictor device. 
     
     
       30. The apparatus of  claim 26  wherein the frequency and duty cycle of said valve each is adjusted substantially independently for a given quantity or flow rate of liquid to produce droplets of a desired size, frequency and/or exit velocity. 
     
     
       31. The apparatus of  claim 26  wherein said positive displacement pump comprises a syringe pump. 
     
     
       32. The apparatus of  claim 31  wherein said syringe pump comprises a syringe housing, a plunger axially displaceable within said syringe housing and plunger shaft having a lead screw formed thereon. 
     
     
       33. The apparatus of  claim 32  wherein said lead screw is sized and positioned such that when said lead screw is rotated, said plunger is displaced axially, causing a predetermined quantity of said liquid to be delivered to said inlet of said dispenser. 
     
     
       34. The apparatus of  claim 33  wherein said positive displacement pump further comprises a stepper motor adapted to cause said pump to dispense predetermined incremental quantities or flow rates of said liquid to said dispenser. 
     
     
       35. The apparatus of  claim 26  wherein said dispenser and positive displacement pump are configured so as to provide a range of selectable droplet sizes attainable for stable operation varying by a factor of greater than about 250. 
     
     
       36. The apparatus of  claim 1  wherein said dispenser and metering pump are configured so as to provide selectable droplet sizes in the range of about 0.54 nanoliters. 
     
     
       37. An apparatus for dispensing predetermined quantities of liquid onto a substrate, comprising: 
       a dispenser having an inlet and an outlet and being adapted to form droplets of said liquid having a size in the range of about 1-4 nanoliters to one microliter which are deposited onto said substrate; and  
       a pump hydraulically arranged in series with the inlet of said dispenser for metering predetermined quantities of said liquid to said dispenser;  
       said dispenser and pump being selected and configured so as to provide a range of selectable droplet sizes attainable for stable operation varying by a factor of greater than about 250 and whereby the quantity and/or flow rate of liquid dispensed by said dispenser is metered substantially independently of the  operating parameters of the dispenser.  
     
     
       38. The apparatus of  claim 37  wherein said dispenser comprises a valve adapted to be opened and closed at a predetermined frequency and duty cycle to form droplets of said liquid which are deposited onto said substrate. 
     
     
       39. The apparatus of  claim 38  wherein said valve is actuated by an electric solenoid. 
     
     
       40. The apparatus of  claim 38  wherein said valve is actuated by a piezoelectric constrictor device. 
     
     
       41. The apparatus of  claim 38  wherein the frequency and duty cycle of said valve can each be  each is adjusted substantially independently for a given quantity or flow rate of liquid to produce droplets of a desired size, frequency and/or exit velocity. 
     
     
       42. The apparatus of  claim 37  in combination with a carriage adapted for X, X-Y or X-Y-Z motion relative to said dispenser for movably transporting said substrate and wherein said dispenser is mounted in juxtaposition with said carriage. 
     
     
       43. The combination of  claim 42  further comprising a controller in communication with said pump and said carriage for coordinating the output of said pump with the motion of said carriage so that said liquid may be dispensed in precise quantities of flow per unit length and such flow is precisely metered substantially without being affected by the particular  operating parameters of said dispenser. 
     
     
       44. The combination of  claim 43  further comprising an array of dispensers and pumps, the outlets of said dispensers being arranged in a desired pattern suitable for attaining a desired print matrix or dot pattern. 
     
     
       45. The apparatus of  claim 37  wherein said pump comprises a syringe pump. 
     
     
       46. The apparatus of  claim 45  wherein said syringe pump comprises a syringe housing, a plunger axially displaceable within said syringe housing and plunger shaft having a lead screw formed thereon. 
     
     
       47. The apparatus of  claim 45  wherein said syringe housing has a displacement volume of between about 25 microliters about 25 milliliters. 
     
     
       48. The apparatus of  claim 37  wherein said pump comprises a stepper motor adapted to cause said pump to dispense predetermined incremental quantities or flow rates of said liquid to said dispenser. 
     
     
       49. The apparatus of  claim 48  wherein said pump has an incremental displacement volume of between about 0.42 nanoliters and 2.1 microliters. 
     
     
       50. The apparatus of  claim 48  wherein said pump has an incremental displacement volume of less than about 4.2 nanoliters. 
     
     
       51. The apparatus of  claim 37  wherein said dispenser and pump are configured so as to provide selectable droplet sizes ranging from less than about 4.2 nanoliters to greater than about 1 microliter. 
     
     
       52. The apparatus of  claim 37  wherein said dispenser and pump are configured so as to provide selectable droplet sizes in the range of about 0.54 nanoliters. 
     
     
       53. The apparatus of  claim 1  wherein the dispenser is adapted to form droplets of said liquid having a size of about 0.54 nanoliters.