Fifteen years ago, a printer was a 40-pound beast that noisily crunched huge piles of perforated paper, and the closest it could come to producing a picture was a dithered black-and-white mesh of brownish dots. Now, a photo-quality printer is within the reach of anybody, and they are in pretty much every home in America. So what’s next?

When most of us still marveled at the first inkjet printers, a small Israeli company named Objet Geometries came up with what will be, someday, a daily part of our lives – 3D printers. Even today, 10 years later, this is still expensive and limited technology, but prices have gone down and you can already go into some print-houses with a USB drive and come out a while later with a 3D model of your choice.

Within a few years – probably less than a decade, this technology could become something like the replicators from Star Trek. Need a nice vase for flowers? No worries – step into the other room, and print one. The kid broke a plate? Piece of cake – hit print, and 2 minutes later you can have a new one. Who knows – someday, we may even be able to print “active” items, like a watch, a cell phone or even some types of food.

The technology behind this is called “polyjet”. The idea is somewhat similar to Inkjet, but instead of ink, the “printer” uses plastic. To make an object that is three-dimensional, the printer prints it in layers – like building a high-riser floor-by-floor. The printer uses a special type of acrylic plastic, known as a “photopolymer”. What’s special about photopolymers is that they are liquid, but when exposed to ultra-violet light, they harder. You may remember how the dentist uses a special “flashlight” that emits blue light and shines it on a tooth after creating the filling? The filling is made out of a photopolymer, and the light causes it to harden, so you can go and grab a sandwich almost immediately after finishing the treatment.

Images via Objet, with text from the author

Photopolymers are not a new invention. Some have been around for many years, though used mostly in industry and not in daily lives. The magic behind photopolymers is a variation on plastic production processes, which are decades-old. All plastics are made of long chains of carbon-based molecules, and these long molecules are what give plastic its strength and durability.

The chemical process of creating plastic is based on using small molecules of carbon, and causing them to bind together and create large molecules. In the case of photopolymers, the liquid is mostly small molecules, but also contains a small amount of an initiator, which is a special molecule that splits into parts when light hits it.

The initiator is usually designed for a very specific wavelength of light, so that the photopolymer doesn’t solidify accidentally. The light causes the initiator to split into two ions, one of which is highly reactive (known as “Radical” in Chemistry). The active ion then binds with some small molecules of Carbon, and starts a chain reaction that causes the entire volume of liquid to solidify quickly. The photopolymer also contains added chemicals that affect the characteristics of the plastic, so the manufacturer can determine how it will look. Adding certain chemicals can make the plastic more or less flexible. Others can make it more or less opaque.

When the user sends a print-job to the 3D printer, the printing software analyzes the object and slices it into very thin layers. Then, it injects tiny droplets of the liquid acrylic onto a print tray just like an inkjet prints a page of text – line by line. After each layer is printed, it’s exposed to Ultra-violet (UV) light, which causes the plastic to harden, and then, the next layer is printed on top of it. After each layer, the print tray moves downward a bit, and so hundreds or thousands of layers are laid on top of each other.

When the process is done, the finished object can be removed from the print chamber, ready for use. At this point, it can also be sanded or painted, if needed. Sometimes, a project requires an object that is larger than the capability of the printer, but an object can be sliced to parts within the printing software, and the final result assembled from printed parts.

Initially, 3D printers were quite limited – they used a very fragile type of plastic that took a while to harden, and even then was still quite fragile. The resolution was also pretty low, so the results were somewhat rough. Today, some of the printers on the market can print “walls” as thin as 0.0006 inches thick and use various types of acrylic polymers that differ in color, rigidity and transparency to create objects – some are even flexible. The latest line can produce items as large as 11.5 x 7.7 x 5.9 inches in size, and there is even a model that’s considered a “desktop” device (It’s actually about as big as an office photocopier). The biggest advantage of the current models is that the hardening process is integrated into the printing, so the objects are ready to use as soon as they are removed from the printing chamber.

Naturally, these machines are still out of reach for a home user, but so were laser printers less than 10 years ago. Currently, entry level devices start at around $45,000, but they are expected to drop below $20,000 within the next year. Within a few years, you might have one of these printers at home or at your school. You could print your own cell-phone cover, key-chains, a globe, toys, dishes, and of course your own sculptures. Just imagine – instead of buying a poster of your favorite movie star, you would soon be able to go online and download a 3D model of him or her, print it and display it proudly, at the comfort of your own home. Wouldn’t that be great?

[Editor's Note: For a different approach to 3D printing, see the technology behind MakerBot Industries, whose founder, Bre Petis, has roots in the Seattle region.]

Erez Ben-Ari, a Seattle-area journalist and technology guru who has worked in the high-tech industry for more than 15 years, for companies including Microsoft and Intel. His written work has been published worldwide in the printed and online media, as well as television and radio. Contact him directly at ohlord@gmail.com.

Previously by Erez Ben-Ari: How 3D works, and why it's back ... The science of electronic books, and the divide in digital reading