Let's answer your last question about the printhead now: How does it print?

The action starts in the second picture.

The ink inlet fills the chamber with ink (yellow).

The ink is prevented from exiting the nozzle by surface tension.

(Third image) When the printer needs to print, electrical current is applied to the piezo element which expands, creates pressure, and forces a single drop of ink out of the nozzle.

The (microscopic) drop of ink falls on the paper.

The contraction of the piezo element causes the remaining ink in the nozzle opening to be sucked back into the chamber.

Keep in mind that this printer has to control over 240 piezo elements which move over the paper many times in the time it takes to print a single page.