How Piezoelectric Inkjet Printing Works

A 1970 patent describing how to print images by using electrical pulses to bend a tiny crystal plate, squeezing individual ink drops out of a nozzle on demand.

What it covers

This patent describes a drop-on-demand inkjet printing mechanism. Instead of spraying a continuous stream of ink, it ejects individual droplets only when needed. The system features a fluid chamber connected to a constant ink supply and a nozzle orifice. One wall of the chamber contains a piezoelectric actuator made of two plates bonded together. When an electrical pulse is applied, these plates expand in opposite directions, causing the actuator to bend inward. This sudden volume reduction squeezes exactly one droplet of ink out of the nozzle at a rate of 100 to 3,000 drops per second.

What it doesn't cover

• —Does not cover continuous inkjet printing where a constant stream of droplets is electrostatically deflected.
• —Does not cover thermal inkjet printing, which uses heat resistors to vaporize ink and create a bubble to eject drops.
• —Does not cover printing rates outside the claimed range of 100 to 3,000 droplets per second.
• —Does not cover single-layer piezoelectric actuators that do not use two transversely expanding plates secured together to bend.

The clever bit

Using a bimorph piezoelectric actuator—two plates that expand in opposite directions when electrified—to act as a tiny, solid-state pump. This bending motion creates a highly controllable, rapid physical displacement without moving parts like gears or pistons.

Why it matters

This patent is a foundational document for drop-on-demand piezoelectric inkjet printing. This technology eventually enabled high-resolution color home printing, industrial textile printing, and modern 3D bioprinting. It avoided the messy ink-recirculation systems required by earlier continuous inkjet printers.

Real-world examples

• 1.Epson Micro Piezo printheads
• 2.Brother desktop inkjet printers
• 3.Industrial wide-format UV flatbed printers
• 4.Piezoelectric 3D bioprinters