Flexible sorting decision and droplet charging control electronic circuitry for flow cytometer‐cell sorters

We describe sorting decision and droplet charging control electronic circuitry for a flow cytometer-cell sorter. The circuitry can handle up to five independent input signals and can sort in up to four directions. A sixth input channel is used to determine the presence or absence of an event requiring analysis. Sorting decisions are stored in a read-only memory semiconductor device. All the input signals for a given event are reexpressed as either 0 or 1 and are used to define an address in this memory which contains the desired sorting outcome for the event. A set of switches enables one to choose between many different procedures for relating input cell pulses to sorting outcomes by switching to different blocks of the memory. The circuitry has been found capable of purity of cell separation to the level permitted by "deadtime" in the preceding analog stages. It is in regular use with the Ontario Cancer Institute flow cytometer-cell sorter.