US Patent 8158083 Precision liquid dispensing system

A system for dispensing microdrops of reagent in small, precisely metered quantities maintains the fluid reagent to be dispensed in a reservoir under a controlled pressure. The reagent is dispensed through multiple nozzles connected to solenoid-actuated valves that control the flow of the reagent from the reservoir to the nozzles. Each valve is connected to one of the nozzles and electrical pulses are supplied separately to each of the valves to separately control the opening and closing of each valve to dispense predetermined quantities of the reagent through each nozzle at predetermined times.