A system for ejecting droplets of a fluid is described. The system includes a substrate having a flow path body that includes a fluid pumping chamber, a descender fluidically connected to the fluid pumping chamber, and a nozzle fluidically connected to the descender. The nozzle is arranged to eject droplets of fluid through an outlet formed in an outer substrate surface. The flow path body also includes a recirculation passage fluidically connected to the descender. The system for ejecting droplets of a fluid also includes a fluid supply tank fluidically connected to the fluid pumping chamber, a fluid return tank fluidically connected to the recirculation passage, and a pump fluidically connecting the fluid return tank and the fluid supply tank. In some implementations, a flow of fluid through the flow path body is at a flow rate sufficient to force air bubbles or contaminants through the flow path body.