Method And Apparatus For Compensating For Variations In Particle Trajectories In Electrostatic Sorter For Flowcell Cytometer

For use with a flow cytometer, wherein a carrier fluid containing particles to be sorted flows through a particle fluid transport chamber having an output orifice coupled to a droplet generator that controls a point at which droplets are charged and break off from said carrier fluid leaving said output orifice, and a droplet sorter that is operative to cause selected droplets to be deflected and thereby sorted along a sorted droplet deflection path, separate from an unsorted droplet path along which a stream of unsorted droplets travel, a cytometer subsystem for controlling the point at which droplets are controllably charged and break off from said carrier fluid, said subsystem comprising:

• a particle sensor which is operative to monitor a prescribed zone within said particle fluid transport chamber for the presence of a particle traveling therethrough, and to produce an output pulse having a width that is representative of the length of time that said particle is within said prescribed zone as it travels through said particle fluid transport chamber;
• a signal processor, which is coupled to receive said output pulse from said particle sensor, and is operative to calculate a composite time delay in accordance with geometry parameters of said particle fluid transport chamber, between the time that said particle is sensed as being present in said prescribed zone and the time at which a droplet containing said particle will break off from said carrier fluid;
• and
• a droplet charger that is operative to controllably charge a droplet containing said particle at the termination of said composite time delay as calculated by said signal processor.

For use with a flow cytometer, wherein a carrier fluid containing particles to be sorted flows through a particle fluid transport chamber having an output orifice that is coupled to a droplet generator that controls a point at which droplets are controllably charged and break off from said carrier fluid leaving said output orifice, and a droplet sorter that is operative to cause selected droplets to be deflected and thereby sorted along a sorted droplet deflection path, separate from an unsorted droplet path along which a stream of unsorted droplets travel, a method of controlling the point at which droplets are controllably charged and break off from said carrier fluid, said method comprising the steps of:

• (a) calculating travel times of a particle to be sorted through successive zones of said particle fluid transport chamber through which said particle travels in the course of its transit to the point at which a droplet containing said particle is to be charged and break off from said carrier fluid;
• (b) calculating a composite time delay in accordance with said travel times calculated in step (a);
• and
• (c) using said composite time delay calculated in step (b) to controllably charge said particle as said particle breaks off from said carrier fluid.