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FLEXO Magazine : May 2010
Industry Indicators with stretchable silicon technology from Professor John Rog- ers’ laboratory. The venture-backed startup is currently developing processes and applications that enable high performance electronics to be placed in novel environments and form fac- tors. MC10’s approach transforms traditionally rigid, brittle semiconductors into flexible, stretchable electronics while retaining excellent electrical performance. Stretchable silicon allows for a degree of design freedom capable of expand- ing the functionality of existing products whilst providing a platform on which new microelectronic-enabled applications can be developed. Surgery In a completely different approach, the electroactive devices of Micromuscle AB in Sweden, with stretchable printed electrodes, make surgeons’ tools snake through the human body. Researchers at Purdue University have cre- ated a magnetic ferropaper that might be used to make low-cost micromotors for surgical instruments, tiny tweezers to study cells and miniature speakers. Control and monitor- ing electronics and electrics can be printed onto this new smart paper. The material is made by impregnating ordinary paper—even newsprint—with a mixture of mineral oil and magnetic nanoparticles of iron oxide. The nanoparticle-laden paper can then be moved using a magnetic field. “Paper is a porous matrix, so you can load a lot of this ma- terial into it,” said Babak Ziaie, a Purdue professor of electri- cal and computer engineering and biomedical engineering. The new technique represents a low-cost way to make small stereo speakers, miniature robots or motors for a vari- ety of potential applications, including tweezers to manipulate cells and flexible fingers for minimally invasive surgery. “Because paper is very soft it won’t damage cells or tissue,” Ziaie said. “ It is very inexpensive to make. You put a droplet on a piece of paper, and that is your actuator, or motor.” cPaPer Kimberley Clark is one of the latest to announce a smart substrate suitable for printed electronics. Its cPaperTM is pa- per impregnated with carbon rather than the more expensive carbon nanotubes and it can be used as heating elements, electrodes in printed supercapacitors and supercabatteries and in many other applications. Organic imPregnated cOnductive PaPer In a different approach, the University of Uppsala in Sweden may be on the way to improved printed batteries. It is developing a novel nanostructured high-surface area electrode material for energy storage applications composed of cellulose fibers of algal origin individually coated with a 50nm thin layer of polypyrrole. Results show the hitherto high- est reported charge capacities and charging rates for an all polymer paper-based battery. The composite conductive paper material is shown to have a specific surface area of 80m2g−1 and batteries based on this material can be charged with currents as high as 600mAcm−2 with only 6 percent loss in capacity over 100 subsequent charge and discharge cycles. The aqueous- based batteries, which are entirely based on cellulose and polypyrrole and exhibit charge capacities between 25 and 33mAhg−1 or 38 to 50mAhg−1 per weight of the active mate- rial, open up new possibilities for the production of environ- mentally friendly, cost efficient, up-scalable and lightweight energy storage systems. PaPer-e Also newly arrived is the Paper-e of the New University of Lisbon, which is an inspired way of printing transistor circuits by making the gate of the transistor the paper substrate itself. Interestingly, these transistors, made with the superior, new zinc oxide based printed semiconductors, have much better characteristics than one would expect at first sight and the physics of this is currently being clarified. Needless to say, all the above smart papers for printed electronics can be envi- ronmental and biodegradable. Printed Smart Shelf Plastic Electronic GmbH in Austria specializes in capacitive printed electronic structures. For example, its smart shelf con- sists of polymer film that deforms when things are placed on it and the crossbar conductive patterns on both sides monitor the change in capacitance and thus the position and relative weight of what is on the shelf. Now NTERA Inc., a leader in all-printed, flexible, color change display technologies, and plastic electronic GmbH, have entered into a license agree- ment to develop advanced printed electronics products using NTERA’s flexible printed electrochromic displays. PiezO flagS and eelS Polyvinylidene difluoride (PVDF) and its derivatives are made into ferroelectric ink, which is used to print non-volatile rewritable random access memory on flexible film. It can also form a film itself that becomes a smart substrate for printed electronics. Some examples would be electret microphones, energy harvesting flags and, under the water, eels. Smart BarrierS Barrier layers to protect delicate printed organic photovol- taic and OLED displays are receiving close attention. Hugely improved barrier layer substrate film was recently announced by DNP and 3M Display and Graphics Business Lab, as well as companies such as DELO, which are developing barrier adhesives and inks to go over the patterns printed on these barrier films and to seal encapsulation. ediBle and tranSParent electrOnicS Edible printed electronics from Eastman Kodak Co. and Somark Innovations was initially intended to be applied directly to food, pharmaceutical tablets and meat. However, edible substrates will also be needed, preferably leveraging the electronic functions. Then there is the new discipline of transparent electronics being pursued by Hewlett Packard, Cambridge University in the UK and Fraunhofer ISC in Ger- many, for example. n ABOUT THE AUTHOR: Dr. Peter Harrop FIEE has degrees in physics. He is full-time chairman of IDTechEx, the consultancy, publisher and conference organizer in printed electronics and RFID that he founded eight years ago. It is headquartered Boston, MA , with offices in the UK, Germany and New Zea- land. Harrop was previously chief executive of Mars Electron- ics, which he grew from start-up to $260 million and he has been chairman of 15 high-tech companies over the years. He travels extensively and has written technical and marketing reports for the Financial Times, John Wiley and IDTechEx. 18 FLEXO may 2010 www.flexography.org FLX_May10_sec1.indd 18 4/17/10 11:04 PM