Peter Andersson Ersman
Labels for verification of security documents and other documents of value. The aim of the project is to develop such systems, by reel-to-reel processes.
In a long term development project carried out in collaboration with De La Rue International Ltd, Acreo has taken ideas of printing semiconductors from the stage of testing novel material combinations in the laboratory to the refinement of industrial printing processes for these materials.
The system consists of three components: antenna, rectifier and display. It should be powered by energy harvested from sources radiating at radio frequencies; therefore an antenna optimized for the frequency of the radiating source is needed. The rectifier, not necessarily a perfect diode, delivers a net offset voltage sufficient to update the display. The key development challenge for the system has proven to be the rectifier performance at high frequencies.
Diodes have been made using commercial printing techniques, e.g. screen-, flexo- and/or inkjet printing. All these printing techniques are available for true large volume manufacturing in reel-to-reel processes. Even though the component not shows perfect diode characteristics, a difference in current throughput of several orders of magnitude have been observed when comparing the forward and reverse voltage sweeps. Such rectification is sufficient to enable switching of the printed electrochromic display system.
What at first was intended as a novel and hard to copy system for authenticity and verification of security documents has lately gained interest as an enabler for the hype “Internet of things”. One of the major obstacles for getting small things connected to each other and communicating over the Internet is how to solve the power supply issue. With this low cost and all-printed energy harvesting system it will be possible to power up communication systems without onboard power sources and without wired connections.