TIJ

Thermal inkjet printing, or TIJ, works by heating ink inside microscopic chambers until it forms a vapor bubble. That bubble expands violently and forces a droplet through a nozzle onto the substrate passing below. The process repeats thousands of times per second. Unlike contact printing, TIJ never touches the surface, which means it can print on rough, uneven, or delicate materials where other methods fail.

A TIJ printhead contains dozens or hundreds of firing chambers arranged in a line, each with its own resistive heating element. Ink fills the chamber from a reservoir, and electrical pulses trigger heating and ejection. The droplet size is typically 10 to 50 picoliters, small enough to create crisp text or barcodes. Piezoelectric printheads exist as well, but the thermal type dominates industrial applications because it is simpler and cheaper to manufacture.

Common industrial uses

TIJ equipment appears on high-speed packaging lines, where it prints expiration dates, batch codes, and logos directly onto cardboard, plastic film, or bottles. The substrate moves at speeds between 100 and 500 meters per minute. Food, beverage, pharmaceutical, and cosmetics manufacturers rely on TIJ because the inks dry quickly and the print quality is consistent. Thermal inks are formulated to be volatile; they evaporate in seconds without requiring ultraviolet curing.

The core limitation is that thermal inks must tolerate repeated heating without decomposing. They are typically dye-based aqueous solutions with solvents that boil easily; pigmented inks are rarer because particle suspension becomes unstable when heated. Print resolution rarely exceeds 600 dots per inch because droplet placement accuracy and ink spread on the substrate impose physical limits. Clogging is a persistent problem: ink residue hardens around nozzles, and printheads must be periodically flushed or replaced.

TIJ sits between continuous inkjet technology, which is older and sprays ink at much higher volume, and laser coding, which is slower but produces sharper marks. The trade-off is cost, speed, and maintenance simplicity against resolution. For most industrial marking tasks on moving web, TIJ has become the default choice since the 1990s.