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updated 7/29/2013 5:19:31 PM ET 2013-07-29T21:19:31

3D printing is still a niche industry, largely due to the costs associated with the machines and materials. But as those costs decrease, 3D printers are being used for a form of production that designers call "mass customization."

3D printers can quickly produce large amounts of products that have all been tweaked or modified in unique ways. For example, 500 people might order a certain kind of doll, but some may want black eyes and some may want purple, while others want may desire a certain nose or mouth. Because 3D printers build directly from the digital model instead of using a mold, end products can offer that kind of nuance at no additional cost to manufacturers or consumers.

But with mass customization, there comes a new challenge: How is it possible to keep track of all those objects, each one the tiniest bit different?

[See also: 3D Printing Shop Makes a Big Move ]

Researchers at Microsoft have developed an answer: a new method of marking objects without leaving a visual trace.

The method involves creating objects with various internal gaps, or bubbles, within its body that form predetermined patterns. These patterns can then be observed using a Terahertz scanner, a device that has been used in airport security since 2007.

Terahertz,  or THz, radiation is a type of electromagnetic light that is not visible to the human eye and also doesn't harm organic matter like nuclear radiation does. It can also pass through most plastics, fabric, wood and organic material, making it ideal for imaging the insides of objects. By analyzing the rate at which the Terahertz radiation beams pass through the object, the scanner can locate the gaps that make up the pattern and interpret the gaps' meaning.

Microsoft calls this type of tag an InfraStruct. It's similar to a barcode or a QR code, but the mark is structural, not visual, and therefore doesn't have to be on the outside of an object. Unlike radio-frequency identification tags, or RFIDs, tags such as InfraStructs don't require any kind of electricity to exist; they're just a part of the object's architectural makeup.

This method is particularly easy to implement with 3D-printed objects, as the printers work by creating an object layer by layer, so adding the pattern is a relatively simple modification.

3D printers capable of printing in multiple materials, such as different types of polymers or even metal, could easily create a different type of InfraStruct. If you were to make one of those layers a different material than the rest, a Terahertz scanner would detect it because the radiation would pass through that layer at a different rate than the rest.

This technique could be used to create encoded messages, said Karl Willis, a doctoral graduate from Carnegie Mellon who worked with Microsoft on the InfraStructs research.

"We're either punching holes in that [different layer] or changing materials, so it returns a different type of [Terahertz] reflection," he told us.

InfraStructs answer a need that 3D printers will soon have to address as the practice become more common.

"As 3D printing factories really scale up and you see companies like Shapeways getting up to huge volumes [of] tiny objects that all look very, very similar, how do they deal with the logistics of … figuring out how one object is different than the next?"  Willis told us.

[See also: What Doesn't Make Sense to 3D Print? ]

InfraStructs have other applications aside from keeping track of inventory. Willis describes them as a means of "link[ing] objects to the digital world." For example, a digital game could track the location of physical game pieces such as pawns or toy swords via their InfraStructs. Robots could interact more easily and seemingly intuitively with InfraStruct-marked objects by reading and interpreting the data embedded within them.

Willis also pointed out that this technology could be used in forensic studies to trace a specific device much the same way that detectives can trace a bullet back to the specific gun that fired it.

Terahertz radiation scanning is still a relatively new field, though its ability to provide noninvasive images of an object's interior has a number of practical applications. For example, NASA used Terahertz scanners to analyze the space shuttle Discovery for structural flaws after its fuel compartment sprung a leak in 2010.

However, even though the process of implementing InfraStructs doesn't pose an additional cost, according to the researchers, Terahertz scanning technology is still expensive: The technique requires superfast lasers, and is also fairly specialized and therefore not mass-produced. Willis expressed a hope that, were InfraStructs to become popular, the demand would "give the market an excuse to push the volume up" and lower the cost of Terahertz technology.

Email  jscharr@technewsdaily.com  or follow her@JillScharr. Follow us@TechNewsDaily, onFacebookor on Google+.

© 2012 TechNewsDaily

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