FACS electrostatic cell sorting depends on the cells characteristics detected in the interrogation point. It is important to set a proper voltage for FSC/SSC. By setting the voltage, you center your cells so that their signals are measurable. Furthermore, you configure a threshold to avoid having false signals of, for instance, dust in your collected data. After interrogation, the stream is partitioned into identically sized droplets that are generated at an extremely fast, stable, and predictable rate, by applying an acoustic wave in the flow chamber.
When a target cell is detected, a charge is applied to the entire connected stream rather than to droplets individually. Then, the stream breaks, forming the droplets in the so-called droplet break-off point.
All of the droplets, charged or uncharged, then pass through an electrical field that is generated by the deflection plates. Charged cells are pulled towards the plates, away from the uncharged cells, and fall into collection tubes, forming side streams, while uncharged cells go into the waste (Figure 1).
Figure 1. FACS electrostatic sorting.