By now, we’ve all become quite used to seeing QR codes on products, price tags and advertisements – just scan the code with your smartphone’s camera, and it’s converted into readable information. Soon, however, those codes could be facing competition from something called the rectenna. It’s an inexpensive label-like device that transmits data to a near-field communication (NFC)-enabled smartphone, using that phone’s radio waves as its power source.
Any type of rectifying antenna is known as a rectenna, and they've been around in various forms since the 60s. This particular rectenna, however, was developed recently by researchers from Korea’s Sunchon National University, and the Paru Printed Electronics Research Institute. It consists of a flat antenna, printed circuits and a rectifier, which converts alternating current into direct current. A lab prototype was able to generate at least 0.3 watts of power from an alternating current which had a frequency of 13.56 megahertz.
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In the study, batches of the rectennas were printed on plastic foil using five different electronic inks, at a rate of eight meters (26.25 feet) per minute. At that rate of production, they would reportedly cost just one cent per device – less than RFID tags, which perform a similar function.
They can be read by phones utilizing NFC technology. The radio waves emitted by the phone are converted to DC power by the rectifier, which is used by the antenna to transmit information contained within the circuits. A tiny integrated chip could also be used to store that data.
“Our advantage over current technology is lower cost, since we can produce a roll-to-roll printing process with high throughput in an environmentally friendly manner,” said Gyoujin Cho, co-author of a paper on the study. “Furthermore, we can integrate many extra functions without huge extra cost in the printing process.”
Some products already use a similar but more basic technology – the U Grok It object-finding system, for instance, utilizes adhesive-backed flat labels with built-in antennas and chips. When a phone’s radio waves hits one of those labels, they are reflected back in an altered form that conveys a number, used to identify the object bearing the label.
Cho’s paper was published last month, in the journal Nanotechnology.
Source: Institute of Physics