Optical particle sensing following fluid ejection

A method, comprising:

• activating a fluid ejector of a particle dispensing system to eject a cell onto a substrate;
• optically detecting the fluid following ejection;
• and
• determining, following ejection and with an optical verification system, whether a desired quantity of cells was ejected during an ejection event.

A particle dispensing system, comprising:

• a port to receive a number of fluid cartridges, each fluid cartridge to hold cells to be ejected individually during an ejection event;
• an optical verification system to, following ejection, verify that a single cell was ejected during the ejection event;
• a controller to selectively activate a number of fluid ejectors to eject the amount of fluid;
• and
• a stage controller to suppress a motion of a stage holding a substrate during optical verification.