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Developments that will trigger a boom in the business of printed electronics

Developments that will trigger a boom in the business of printed electronics

Printed electronics is one of the most important new enabling technologies. Printed electronics subsumes electrics such as lighting, batteries, solar cells and heaters, not just electronics. Printed electronics will have a major impact on most business activities from publishing and security printing to healthcare, automotive, military and consumer packaged goods sectors. One enabling technology for printed and flexible electronics devices is the use of a special silver nanoparticle ink that allows the patterning of silver microelectrodes by omnidirectional printing. As per, researchers at the University of Illinois at Urbana-Champaign (UI) have earlier used this ink for the conformal printing of 3D electrically small antennas.Taking an important step towards enabling desktop manufacturing – or personal fabrication – using very low cost, ubiquitous printing tools, the UI team now demonstrated a pen-on-paper approach as a low-cost, portable fabrication route for printed electronic and optoelectronic devices. Paper has emerged as a focus area for researchers developing innovative techniques for printed basic electronics components. Imagine combining this basic tool with modern electronics. Reporting their findings in the June 20, 2011 online edition of Advanced Materials, the team demonstrates the fabrication of electronic art, flexible displays, conductive text, and radio frequency antennas with their technique. The printed features can withstand repeated bending and folding while maintaining high conductivity. The work was led by Jennifer Lewis, the Hans Thurnauer Professor of Materials Science and Engineering, Willett Faculty Scholar of Engineering, and Director, F. Seitz Materials Research Laboratory at UI, and Jennifer Bernhard, a professor in the Department of Electrical and Computer Engineering at UI."Inks developed for pen-on-paper printing exhibit a lower conductivity than a bulk silver – however, our method allows one to conformally pattern conductive features onto rough substrates, such as paper, under ambient conditions," Lewis tells Nanowerk. "A key advantage is that the costly printers and printheads typically required for inkjet or other printing approaches are replaced with an inexpensive, hand held writing tool. Pen-based printing allows one to construct electronic devices 'on-the-fly'." The pen-on-paper paradigm offers a unique approach to fabricating flexible devices by using a patterning instrument that is itself as ubiquitous and portable as the paper substrate," says Bernhard. "Central to the flexible electronics pen-on-paper approach – as with conventional writing on paper – is a silver ink that readily flows through the rollerball pen tip during writing, does not leak from, dry out, or coagulate within the pen, and is conductive upon printing under ambient conditions. The nanosilver ink synthesized by the UI team meets these attributes. The ink design strategy described above is quite general. Lewis says that, with little effort, it can be extended to other particle-based inks, including those based on oxide, semiconductor, and carbon building blocks."We therefore envision that our pen-on-paper approach could be implemented for paper-based batteries, medical diagnostics and other functional devices."

Do-it-yourself electronics manufacturing may soon be possible with your desktop printer, say the designers of a new system that directly prints electronic circuits onto ordinary paper. National Geographic News reports that Jing Liu, of the Chinese Academy of Sciences in Beijing, team's advance - published in the journal Scientific Reports - could be a leap forward in the booming business of printed electronics. "This brand-new technique offers a vital opportunity to realize rapid fabrication of inexpensive, disposable, conveniently portable circuits and functional components," he said, adding that the process could help "pave the way toward personal printed electronics." This, and similar technologies could be used to create customized electronic devices including electronic greeting cards, video game controls, touch-sensitive mobile phone cases, or solar cell arrays. Jing and colleagues developed a new metal-based ink that could work at room temperatures. Their initial formula caused the ink to ball up into droplets, which made it difficult to apply and adhere to the paper. So the team modified the ink by injecting the liquid metal alloy with oxygen, making it more suitable for printing on the kind of paper used for book covers, labels, and advertising stock. A newly developed brush - like a porous pinhead - was also developed to deliver the slow-flowing ink that would clog more conventional printers. While most electronic inks solidify after printing, the one employed by the researchers remains liquid and is encapsulated by a second coating of silicone rubber - this creates a channel to hold the ink. "The fabricated circuits cannot be broken off easily even under frequent bending, showing an attractive and distinguished mechanical flexibility which is a critical advantage in fabricating flexible electronics," the authors write. Because the electronic inks are encased in rubber they can also be stacked in layers without altering their electrical functionality. This would allow users to build electromechanical functions into the body of 3-D printed objects. "Most of the currently available 3-D printers are only capable of making mechanical objects without electronics features inside," Jing said, such as custom items like mobile phone cases or jewelry. Jing's team successfully printed circuits and functional components on paper including conductive wires, inductance coils, and flexible antennas - the building blocks of personalized electronic devices. The machine Jing and his team developed is still expensive for everyday use, but the group is striving to make it affordable for the average desktop.

Researchers at the Palo Alto Research Center (PARC) have been taking significant strides in developing a new technology that makes it possible to print electronic components like sensors, transistors, light-emitters, smart tags, flexible batteries, memory, smart labels, and more. PARC's work can also bring a new element to 3D printing: adding electronic, sensing or optical functionalities to parts. Printing electronics shares one major trait with that very hot technology: It is additive rather than subtractive. That means, said Janos Veres, PARC's program manager for printed electronics, that rather than etching the components out of other materials, the new system uses specially concocted inks to generate the electronics from scratch. Those inks may be composed of molecules, nanomaterials, and even tiny suspended silicon chips. PARC is working in conjunction with private companies and academic institutions to try to break new ground in the field of printable, functional electronics. Ultimately, it is looking for partners with groundbreaking ideas on how to use the technology for functional products or prototypes. At the core of Veres' work is a blending of material science and printing technologies. And that means developing a series of special inks that incorporate the desired functionality, be it sensing, light-emitting, or even chips. "You make inks and print with those inks," Veres explained. "And you only put it where you need it." A prototype electronics printer in Veres' lab is like others that are being developed in the field, this one features different print heads, each of which is used for making a different component. The idea is to be able to print an entire electronics assembly at once, with each head doing a different part of the job. But while one method for printing electronics employs traditional InkJet print heads, other methods, such as gravure, and flexo, are being used as well. One big advantage of printable electronics is that they can be made using large, wide transparent or flexible areas. That's where traditional roll-to-roll printers, often used for things like printing newspapers, can come in handy. Those machines are built to churn out nearly endless copies at hundreds of feet a minute. Instead of the daily news, they could now be useful for turning out large numbers of simple transistors or other components. And this type of printed electronics would be ideal for a wide range of wearable devices. Health tracking is an obvious application, given how conforming thin plastic sheets can be, and how they can be molded into many different shapes, each with a potential different function. But there are plenty of applications outside health care that make sense for the technology. One example is a label with a built-in temperature sensor that's capable of, say, issuing an alert when the package of fish it's attached to rises above a desired temperature. The goal is to be able to incorporate these types of functional sensors directly into packaging. PARC and its partners at universities like Clemson and companies like Thinfilm are developing libraries of functional printed electronics. Over time, as those libraries expand, more partners will likely discover ways to incorporate them. Gradually, these libraries will form the basis for a printed electronics platform.

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