System and method for dispensing fluid droplets of known volume and generating very low fluid flow rates

摘要

A system and method for dispensing fluid droplets of a known volume uses a control system using inner and outer control loops. The inner control loop includes a pump which pressurizes a fluid against an aperture, causing fluid to pass through the aperture and to a dispensing tip at a particular flow rate. The pressure of the fluid upstream of the aperture is measured and fed back to a controller, which also receives a setpoint input representative of desired dispensed volume. The outer control loop uses a droplet volume measuring system which determines the volume of the droplet that forms at the outlet of the dispensing tip as a result of the applied pressure, the value of which is also fed to the controller. The controller is arranged to maintain the pressure against the aperture (using the inner control loop) as needed to produce a flow rate which will quickly produce a droplet of the desired volume (as determined using the outer control loop), at which time the pressure is reduced to zero and the droplet dispensed