Method for dispensing reagent onto a substrate

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 . A method for dispensing a liquid onto a substrate, comprising: 
 metering a predetermined quantity or flow rate of said liquid using positive displacement means;    supplying said metered quantity or flow rate of said liquid to a dispenser to form droplets of a predetermined size and/or quality which are deposited onto said substrate;    providing relative motion between said substrate and said dispenser; and    regulating the metering of said predetermined quantity or flow rate of said liquid and relative motion between said substrate and said dispenser so that the density of said liquid deposited on said substrate is independently controlled in terms of volume per unit length of said substrate.    
     
     
         2 . The method of  claim 1 , wherein said droplets are in the range of about 4 nanoliters to about 1 microliter.  
     
     
         3 . The method of  claim 1 , wherein attainable droplet sizes range in size by a factor of greater than about 250.  
     
     
         4 . The method of  claim 1 , wherein said droplets form an aerosol mist wherein each droplet is smaller than about 1 picoliter.  
     
     
         5 . The method of  claim 1 , wherein said dispenser comprises a valve adapted to be opened and closed at a predetermined frequency and duty cycle and wherein said method further comprises adjusting the frequency of said valve to produce droplets of a desired size for a given flow rate.  
     
     
         6 . The method of  claim 1 , wherein said dispenser comprises a valve adapted to be opened and closed at a predetermined frequency and duty cycle and wherein said method further comprises adjusting the duty cycle of said valve to produce droplets having a desired velocity for a given droplet size and flow rate.