‘Paper labels’ can now harvest energy from your smartphone signals and reply back

Printed Diodes – Researchers demonstrate an e-label that harvests energy from the smartphone's signal, and used it to illuminate a small display. Bridging gap between 'internet of things' and mobile networks.

Imagine these scenarios

1. A T-shirt, a magazine, or even an orange with electronic labels—flexible, printed electronics that can draw power from their environments and use it to dispense useful information about the object.
2. A security code on a banknote - a smartphone held close to the banknote would be able to identify the e-label, which might hold information about the origin of the note and should be difficult to counterfeit.

A research team based in Sweden and the UK has now created the first printed e-label than can communicate with a smartphone.

As a proof of principle, the device harvests energy from the smartphone's signal, and uses it to illuminate a small display. The device was unveiled in the Proceedings of the National Academy of Sciencesof the United States of America.

Smartphones typically transmit and receive signals in the ultra-high frequency (UHF) band, spanning 300 MHz to about 3 GHz, and previous e-labels have struggled to pick up those frequencies. Organic semiconductors, for example, can be printed onto flexible substrates to make components such as diodes and transistors, but in most of them charge moves sluggishly—reducing their operating frequencies. Laying down the organic semiconductor films under high vacuum can improve charge carrier mobility, but it makes the labels much more expensive to mass-produce. Nanoparticle semiconductor inks, in contrast, are more suitable for high-frequency work, but most require extreme heat treatments that would destroy flexible plastic or paper backing.

The solution is a printable Schottky diode that combines the best aspects of both technologies to pick up higher frequencies. "This is the first time anyone has done anything like this in the gigahertz region," says Göran Gustafsson, a materials scientist at the Norrköping branch of the Acreo Swedish ICT research institution. "This is the starting point of having paper connected to the internet."

Excerpt Courtesy: ieee.org

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All-printed e-tag activated by placing a call from a mobile phone. Credit: Linköping University and Acreo Swedish ICT

Read more at: http://phys.org/news/2014-07-bridging-gap-internet-mobile-networks.html#jCp