What Are Printers?

Printers are output devices that produce a physical copy of digital or electronically generated content on paper, film, or other media. The term encompasses a broad range of technologies distinguished by the mechanism used to transfer marks onto the substrate: some deposit ink or toner, others use heat, pressure, or light exposure, and still others build three-dimensional structures layer by layer. Printers connect to computing systems through standardized interfaces and communicate using page description languages such as PostScript or PCL, which specify the layout of text, graphics, and images independently of the output device. The engineering challenges in printer design span fluid dynamics, optics, electrostatics, materials science, and precision mechanical control.

The history of electronic printing began with impact technologies adapted from typewriters and telegraphs, progressed through laser and inkjet systems that defined the desktop computing era, and now extends to industrial and additive manufacturing applications. IEEE has recognized several milestone contributions to printer technology, including the development of the laser printer at Xerox Corporation in the early 1970s, as documented on the IEEE Milestones wiki for the laser printer.

Laser and Inkjet Printing

The two dominant non-impact technologies for office and desktop printing are laser and inkjet. Laser printers use a photoconductive drum charged with static electricity; a modulated laser beam selectively discharges areas corresponding to the printed image, which then attracts and fuses toner particles to paper under heat and pressure. The electrophotographic process allows speeds of hundreds of pages per minute in production systems. Inkjet printers fire microscopic droplets of liquid ink through arrays of nozzles directly onto the receiving medium. Two competing mechanisms drive droplet ejection: thermal inkjet uses a resistive heater to flash-vaporize ink and push out a droplet, while piezoelectric systems use voltage-deformed crystals to mechanically displace ink. As reported by IEEE Spectrum on the history of inkjet printing, modern commercial inkjet printheads contain up to 21,000 nozzles producing droplets approximately 14 micrometers in diameter.

Thermal Printers

Thermal printing produces marks by selectively applying heat to a thermally sensitive medium or to a ribbon that transfers colorant to plain paper. Direct thermal printing, used in point-of-sale receipt printers and shipping label systems, requires no ink or toner because the paper itself darkens when heated. Thermal transfer printing uses a heat-activated ribbon to deposit wax or resin ink onto a variety of substrates, including labels, tags, and textiles. Both formats benefit from mechanical simplicity: without toner cartridges or ink tanks, thermal printers achieve high reliability in high-volume automated environments. Dye-sublimation printing, a variant of thermal transfer, drives dye from a solid ribbon into the receiving substrate using controlled heat, producing continuous-tone photographic-quality output used in photo kiosks and medical imaging.

Specialty and Industrial Printing Systems

Beyond office applications, specialized printers serve manufacturing, science, and healthcare. Large-format inkjet systems produce technical drawings, banners, and fine-art reproduction prints at widths exceeding three meters. UV-curable inkjet printers deposit inks that polymerize immediately under ultraviolet illumination, enabling printing on rigid and non-porous substrates. Bioprinters, which adapt inkjet and extrusion mechanisms to deposit living cells in defined patterns, are studied for tissue engineering and pharmaceutical screening. The Progress and Trends in Ink-jet Printing Technology resource from the Society for Imaging Science and Technology documents the extension of inkjet into DNA array synthesis and electronic device fabrication.

Applications

Printers have applications across a wide range of industries and contexts, including:

• Office document production and graphics reproduction
• Point-of-sale receipt and label printing in retail and logistics
• Medical imaging output including radiographs and patient records
• Large-format technical and artistic printing
• Additive manufacturing and 3D prototyping