Fundamental to the Internet of Things is the idea that objects must be uniquely identifiable. RFID chips are perfect for assigning objects a digital fingerprint, at least so far as traditional manufacturing goes. But with the rise of 3D printing, incorporating an RFID chip into your object means interrupting the printing process. Now, scientists have come up with a way to 3D print a unique tag, called an InfraStruct, inside the object as it's being printed, and it's made possible by the slowly emerging field of terahertz imaging.

Terahertz radiation, which, because of its band of wavelengths also goes by the name of submillimeter radiation, falls between microwave and infrared radiation in the electromagnetic spectrum. Its usefulness is down to the fact that it can penetrate various textiles, papers and plastics without causing harm to living tissue.

Scientists at Carnegie Mellon University and Microsoft Research have demonstrated a range of possible 3D printable InfraStruct tag designs to uniquely identify objects, as well as the terahertz imaging techniques required to make sense of them. Because the tags themselves are built into the object, the cost implications of including them are negligible.

Unfortunately the same cannot be said for reading InfraStructs, as terahertz imaging equipment is still very expensive. NASA Langley Research Center settled on terahertz imaging as the best way to detect defects in the insulating foam used on the Space Shuttle's fuel tanks (after just such a defect caused the Columbia disaster in 2003). NASA turned to a company called Picometrix which released the first commercial terahertz imaging system, the T-Ray 2000, named after the year of its release. NASA asked the company to adapt the technology for its ends.

A series of 3D printed layers created an InfaStruct with a tapir-shaped void (Image: Karl Willis)

The scan of the tapir-shaped void Infrastruct (Image: Karl Willis)

NASA's system was basically looking for cracks, and the same is true of this technology. In a sense it's the negative space within and around the InfraStruct, rather than the InfraStruct itself, which is the key to its detection. The unique ID of the object would be encoded into "bubbles or voids inside the object."

"The ability to embed 3D patterns gives designers new opportunities in creating objects that are meant to be sensed and tracked," said Andy Wilson of Microsoft Research, who worked alongside Karl Willis of Carnegie Mellon. "One idea is to embed a code just under the surface of the object, so that a THz beam can recover its position on the surface, wherever it strikes the object," he added.

Rather than extending the range of possibilities that the Internet of Things entails, InfraStructs instead enrich the options baskets for making those possibilities a reality. Watch this uniquely identifiable space.

The research into InfraStructs is to be presented at SIGGRAPH 2013 on Thursday.

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