Which method changes the shape of an ink nozzle in response to electrical voltage?

The method that changes the shape of an ink nozzle in response to electrical voltage is piezoelectric technology. In piezoelectric printing, certain materials, typically piezoelectric crystals, create a mechanical deformation when an electrical voltage is applied. This deformation effectively alters the shape of the nozzle, allowing for precision control over the ink droplet size and timing of the ink being ejected.

This technique is advantageous in inkjet printers because it helps achieve finer details and a broader range of droplet sizes, which leads to improved print quality. Piezoelectric printers can produce drops of ink with high accuracy and without heating the ink, which reduces the risk of thermal degradation.

Thermal printing, on the other hand, relies on heating elements to vaporize ink and eject it through a nozzle, but it does not involve changing the nozzle shape actively in response to voltage. Electrostatic methods utilize charged particles for attraction and repulsion but do not directly involve mechanical changes in the nozzle itself. Mechanical methods might change the position of a nozzle or lever but not its shape through electrical means. Thus, among the choices presented, piezoelectric is the only method that specifically aligns with changing the design of an ink nozzle via electrical voltage.