Printed circuits powered by smartphone

Electronic devices "printed" by an inkjet printer and powered by smartphone signals have been announced by scientists in the UK and Sweden.

Imagine waving your smartphone over your shopping basket and the oranges telling you when and where they were picked, the pills in your pharmacy prescription confirm that they are in-date, and even the bank notes you'll use to pay for the shopping can confirm their authenticity.

This is now becoming a reality thanks to a Swedish and UK breakthrough that means it's possible to print electronic circuit components onto paper. The new study, published this week in PNAS, is the result of a collaboration between UK company De La Rue, who manufacture banknotes, and researchers at Linköping University, Sweden.

The original goal of the project was find a way to make currency harder to counterfeit, but in the process the researchers were able to go much further. Using an inkjet printer they were able to spray nanosized silicon particles 1/10,000th of a millimetre across onto a layer of aluminium foil, capping the sandwich off with a protective layer of niobium silicide and a carbon electrode.

The foil acts as an antenna, harvesting stray microwave signals from any nearby mobile phones. These oscillating signals are converted into a DC voltage by the silicon particles, which act as a diode.

A current of about 19 microamps from the current generation of device - is tapped off by the carbon electrode and, in a proof of concept, could be used to drive a small display. This means that ultra-tiny "e-labels", which can be printed onto almost any surface and powered passively by the stray signals from smartphones, are now feasible.

Optimising the devices is the present goal to make them work with even higher-frequency signals emitted by bluetooth and wiFi, and also store energy so that a signal could be sent back to the smartphone, meaning self-authenticating bank-notes and foods that know their own sell-by dates could be around the corner...