Tag Archives: bendable electronics

Flexible electronics and Inorganic-based Laser Lift-off (ILLO) in Korea

Korean scientists are trying to make the process of creating flexible electronics easier according to a Nov. 25, 2014 news item on ScienceDaily,

Flexible electronics have been touted as the next generation in electronics in various areas, ranging from consumer electronics to bio-integrated medical devices. In spite of their merits, insufficient performance of organic materials arising from inherent material properties and processing limitations in scalability have posed big challenges to developing all-in-one flexible electronics systems in which display, processor, memory, and energy devices are integrated. The high temperature processes, essential for high performance electronic devices, have severely restricted the development of flexible electronics because of the fundamental thermal instabilities of polymer materials.

A research team headed by Professor Keon Jae Lee of the Department of Materials Science and Engineering at KAIST provides an easier methodology to realize high performance flexible electronics by using the Inorganic-based Laser Lift-off (ILLO).

The process is described in a Nov. 26, 2014 KAIST news release on ResearchSEA, which originated the news item (despite the confusion of the date, probably due to timezone differentials), provides more detail about the technique for ILLO,

The ILLO process involves depositing a laser-reactive exfoliation layer on rigid substrates, and then fabricating ultrathin inorganic electronic devices, e.g., high density crossbar memristive memory on top of the exfoliation layer. By laser irradiation through the back of the substrate, only the ultrathin inorganic device layers are exfoliated from the substrate as a result of the reaction between laser and exfoliation layer, and then subsequently transferred onto any kind of receiver substrate such as plastic, paper, and even fabric.

This ILLO process can enable not only nanoscale processes for high density flexible devices but also the high temperature process that was previously difficult to achieve on plastic substrates. The transferred device successfully demonstrates fully-functional random access memory operation on flexible substrates even under severe bending.

Professor Lee said, “By selecting an optimized set of inorganic exfoliation layer and substrate, a nanoscale process at a high temperature of over 1000 °C can be utilized for high performance flexible electronics. The ILLO process can be applied to diverse flexible electronics, such as driving circuits for displays and inorganic-based energy devices such as battery, solar cell, and self-powered devices that require high temperature processes.”

Here’s a link to and a citation for the research paper,

Flexible Crossbar-Structured Resistive Memory Arrays on Plastic Substrates via Inorganic-Based Laser Lift-Off by Seungjun Kim, Jung Hwan Son, Seung Hyun Lee, Byoung Kuk You, Kwi-Il Park, Hwan Keon Lee, Myunghwan Byun and Keon Jae Lee. Advanced Materials Volume 26, Issue 44, pages 7480–7487, November 26, 2014 Article first published online: 8 SEP 2014 DOI: 10.1002/adma.201402472

© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Here’s an image the researchers have made available,

This photo shows the flexible RRAM device on a plastic substrate. Courtesy: KAIST

This photo shows the flexible RRAM device on a plastic substrate. Courtesy: KAIST

Finally, the research paper is behind a paywall.

Stretchable carbon nanotubes as supercapacitors

This Nov. 25, 2013 news item on phys.org was a bit of a walk down memory lane for me,

A mobile telephone display for your jacket sleeve, ECG probes for your workout clothes—wearable electronics are in demand. In order for textiles with built-in electronics to function over longer periods of time, all of the components need to be flexible and stretchable. In the journal Angewandte Chemie, Chinese researchers have now introduced a new type of supercapacitor that fulfills this requirement. Its components are fiber-shaped and based on carbon nanotubes.

The reference to a mobile telephone display on a jacket sleeve brought back memories of Nokia’s proposed Morph device,, from my Aug. 3, 2011 posting,

For anyone who’s not familiar with the Morph, it’s an idea that Nokia and the University of Cambridge’s Nanoscience Centre have been working on for the last few years. Originally announced as a type of flexible phone that you could wrap around your wrist, the Morph is now called a concept.  …

At the time I was writing about exploring the use of graphene to enable the morph (flexible phone). This latest work from China is focused on carbon nanotubes,. The Angewandte Chemie Nov. 25, 2013 press release, which originated the news item on phys.org,  provides more details,

For electronic devices to be incorporated into textiles or plastic films, their components must be stretchable. This is true for LEDS, solar cells, transistors, circuits, and batteries—as well as for the supercapacitors often used for static random access memory (SRAM). SRAM is often used as a cache in processors or for local storage on chips, as well as in devices that must maintain their data over several years with no source of power.

Previous stretchable electronic components have generally been produced in a conventional planar format, which has been an obstacle to their further development for use in small, lightweight, wearable electronics. Initial attempts to produce supercapacitors in the form of wires or fibers produced flexible—but not stretchable—components. However, stretchability is a required feature for a number of applications. For example, electronic textiles would easily tear if they were not stretchable.

A team led by Huisheng Peng at Fudan University has now developed a new family of highly stretchable, fiber-shaped, high-performance supercapacitors. The devices are made by a winding process with an elastic fiber at the core. The fiber is coated with an electrolyte gel and a thin layer of carbon nanotubes is wound around it like a sheet of paper. This is followed by a second layer of electrolyte gel, another layer of carbon nanotube wrap, and a final layer of electrolyte gel.

The delicate “sheets” of carbon nanotubes are produced by chemical vapor deposition and a spinning process. In the sheets this method produces, the tiny tubes are aligned in parallel. These types of layers display a remarkable combination of properties: They are highly flexible, tear-resistant, conductive, and thermally and mechanically stable. In the wound fibers, the two layers of carbon nanotubes act as electrodes. The electrolyte gel separates the electrodes from each other while stabilizing the nanotubes during stretching so that their alignment is maintained. This results in supercapacitor fibers with a high capacity that is maintained after many stretching cycles.

For the curious, here’s a link to and a citation for the paper,

A Highly Stretchable, Fiber-Shaped Supercapacitor by Zhibin Yang, Jue Deng, Xuli Chen, Jing Ren, and Prof. Huisheng Peng. Angewandte Chemie International Edition
Early View (Online Version of Record published before inclusion in an issue)Article first published online: 8 NOV 2013 DOI: 10.1002/anie.201307619

Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This article is behind a paywall.

Bend it, twist it, any way you want to—a foldable lithium-ion battery

Feb. 26, 2013 news item on ScienceDaily features an extraordinary lithium-ion battery,

Northwestern University’s Yonggang Huang and the University of Illinois’ John A. Rogers are the first to demonstrate a stretchable lithium-ion battery — a flexible device capable of powering their innovative stretchable electronics.

No longer needing to be connected by a cord to an electrical outlet, the stretchable electronic devices now could be used anywhere, including inside the human body. The implantable electronics could monitor anything from brain waves to heart activity, succeeding where flat, rigid batteries would fail.

Huang and Rogers have demonstrated a battery that continues to work — powering a commercial light-emitting diode (LED) — even when stretched, folded, twisted and mounted on a human elbow. The battery can work for eight to nine hours before it needs recharging, which can be done wirelessly.

The researchers at Northwestern have produced a video where they demonstrate the battery’s ‘stretchability’,

The Northwestern University Feb. 26, 2013 news release by Megan Fellman, which originated the news item, offers this detail,

“We start with a lot of battery components side by side in a very small space, and we connect them with tightly packed, long wavy lines,” said Huang, a corresponding author of the paper. “These wires provide the flexibility. When we stretch the battery, the wavy interconnecting lines unfurl, much like yarn unspooling. And we can stretch the device a great deal and still have a working battery.”

The power and voltage of the stretchable battery are similar to a conventional lithium-ion battery of the same size, but the flexible battery can stretch up to 300 percent of its original size and still function.

Huang and Rogers have been working together for the last six years on stretchable electronics, and designing a cordless power supply has been a major challenge. Now they have solved the problem with their clever “space filling technique,” which delivers a small, high-powered battery.

For their stretchable electronic circuits, the two developed “pop-up” technology that allows circuits to bend, stretch and twist. They created an array of tiny circuit elements connected by metal wire “pop-up bridges.” When the array is stretched, the wires — not the rigid circuits — pop up.

This approach works for circuits but not for a stretchable battery. A lot of space is needed in between components for the “pop-up” interconnect to work. Circuits can be spaced out enough in an array, but battery components must be packed tightly to produce a powerful but small battery. There is not enough space between battery components for the “pop-up” technology to work.

Huang’s design solution is to use metal wire interconnects that are long, wavy lines, filling the small space between battery components. (The power travels through the interconnects.)

The unique mechanism is a “spring within a spring”: The line connecting the components is a large “S” shape and within that “S” are many smaller “S’s.” When the battery is stretched, the large “S” first stretches out and disappears, leaving a line of small squiggles. The stretching continues, with the small squiggles disappearing as the interconnect between electrodes becomes taut.

“We call this ordered unraveling,” Huang said. “And this is how we can produce a battery that stretches up to 300 percent of its original size.”

The stretching process is reversible, and the battery can be recharged wirelessly. The battery’s design allows for the integration of stretchable, inductive coils to enable charging through an external source but without the need for a physical connection.

Huang, Rogers and their teams found the battery capable of 20 cycles of recharging with little loss in capacity. The system they report in the paper consists of a square array of 100 electrode disks, electrically connected in parallel.

I’d like to see this battery actually powering a device even though the stretching is quite alluring in its way. For those who are interested here’s a citation and a link to the research paper,

Stretchable batteries with self-similar serpentine interconnects and integrated wireless recharging systems by Sheng Xu, Yihui Zhang, Jiung Cho, Juhwan Lee, Xian Huang, Lin Jia, Jonathan A. Fan, Yewang Su, Jessica Su, Huigang Zhang, Huanyu Cheng, Bingwei Lu,           Cunjiang Yu, Chi Chuang, Tae-il Kim, Taeseup Song, Kazuyo Shigeta, Sen Kang, Canan Dagdeviren, Ivan Petrov  et al.   Nature Communications 4, Article number: 1543 doi: 10.1038/ncomms2553  Published 26 February 2013

The article is behind a paywall.

Transparent image sensor has no electronics or internal components

This shows the world's first flexible and completely transparent image sensor. The plastic film is coated with fluorescent particles. Credit: Optics Express.

This shows the world’s first flexible and completely transparent image sensor. The plastic film is coated with fluorescent particles. Credit: Optics Express.

Stunning isn’t it? The work is from researchers at the Johannes Kepler University Linz in Austria and is featured in an article being published in Optics Express. From the Feb. 20, 2013 news release about the Optics Express article on EurekAlert,

Digital cameras, medical scanners, and other imaging technologies have advanced considerably during the past decade. Continuing this pace of innovation, an Austrian research team has developed an entirely new way of capturing images based on a flat, flexible, transparent, and potentially disposable polymer sheet. The team describes their new device and its possible applications in a paper published today in the Optical Society’s (OSA) open-access journal Optics Express.

The new imager, which resembles a flexible plastic film, uses fluorescent particles to capture incoming light and channel a portion of it to an array of sensors framing the sheet. With no electronics or internal components, the imager’s elegant design makes it ideal for a new breed of imaging technologies, including user interface devices that can respond not to a touch, but merely to a simple gesture.

The news release goes on to describe the technology,

The sensor is based on a polymer film known as a luminescent concentrator (LC), which is suffused with tiny fluorescent particles that absorb a very specific wavelength (blue light for example) and then reemit it at a longer wavelength (green light for example). Some of the reemitted fluorescent light is scattered out of the imager, but a portion of it travels throughout the interior of the film to the outer edges, where arrays of optical sensors (similar to 1-D pinhole cameras) capture the light. A computer then combines the signals to create a gray-scale image. “With fluorescence, a portion of the light that is reemitted actually stays inside the film,” says Bimber. [Oliver Bimber of the Johannes Kepler University Linz in Austria, co-author of the Optics Express paper] “This is the basic principle of our sensor.”

For the luminescent concentrator to work as an imager, Bimber and his colleagues had to determine precisely where light was falling across the entire surface of the film. This was the major technical challenge because the polymer sheet cannot be divided into individual pixels like the CCD camera inside a smartphone. Instead, fluorescent light from all points across its surface travels to all the edge sensors. Calculating where each bit of light entered the imager would be like determining where along a subway line a passenger got on after the train reached its final destination and all the passengers exited at once.

The solution came from the phenomenon of light attenuation, or dimming, as it travels through the polymer. The longer it travels, the dimmer it becomes. So by measuring the relative brightness of light reaching the sensor array, it was possible to calculate where the light entered the film. This same principle has already been employed in an input device that tracks the location of a single laser point on a screen.

The researchers were able to scale up this basic principle by measuring how much light arrives from every direction at each position on the image sensor at the film’s edge. They could then reconstruct the image by using a technique similar to X-ray computed tomography, more commonly known as a CT scan.

“In CT technology, it’s impossible to reconstruct an image from a single measurement of X-ray attenuation along one scanning direction alone,” says Bimber. “With a multiple of these measurements taken at different positions and directions, however, this becomes possible. Our system works in the same way, but where CT uses X-rays, our technique uses visible light.”

Currently, the resolution from this image sensor is low (32×32 pixels with the first prototypes). The main reason for this is the limited signal-to-noise ratio of the low-cost photodiodes being used. The researchers are planning better prototypes that cool the photodiodes to achieve a higher signal-to-noise ratio.

By applying advanced sampling techniques, the researchers can already enhance the resolution by reconstructing multiple images at different positions on the film. These positions differ by less than a single pixel (as determined by the final image, not the polymer itself). By having multiple of these slightly different images reconstructed, it’s possible to create a higher resolution image. “This does not require better photodiodes,” notes Bimber, “and does not make the sensor significantly slower. The more images we combine, the higher the final resolution is, up to a certain limit.”

The researchers discuss applications,

The main application the researchers envision for this new technology is in touch-free, transparent user interfaces that could seamlessly overlay a television or other display technology. This would give computer operators or video-game players full gesture control without the need for cameras or other external motion-tracking devices. The polymer sheet could also be wrapped around objects to provide them with sensor capabilities. Since the material is transparent, it’s also possible to use multiple layers that each fluoresce at different wavelengths to capture color images.

The researchers also are considering attaching their new sensor in front of a regular, high-resolution CCD sensor. This would allow recording of two images at the same time at two different exposures. “Combining both would give us a high-resolution image with less overexposed or underexposed regions if scenes with a high dynamic range or contrast are captured,” Bimber speculates. He also notes that the polymer sheet portion of the device is relatively inexpensive and therefore disposable. “I think there are many applications for this sensor that we are not yet aware of,” he concludes.

Here’s a citation and a link,

“Towards a transparent, flexible, scalable and disposable image sensor using thin-film luminescent concentrators,” A. Koppelhuber and O. Bimber, Optics Express, Vol. 21, Issue 4, pp. 4796-4810 (2013) (link: http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-21-4-4796).

Canada’s Queen’s University strikes again with its ‘paper’ devices

Roel Vertegaal at Queen’s University (Ontario, Canada) has released a ‘paper’ tablet. Like the bendable, flexible ‘paper’ phone he presented at the CHI 2011 meeting in Vancouver, Canada (my May 12, 2011 posting), this tablet offers some intriguing possibilities but is tethered. The Jan. 9, 2013 news item on phys.org provides more information about the new ‘paper’ device (Note: Links have been removed),

Watch out tablet lovers – a flexible paper computer developed at Queen’s University in collaboration with Plastic Logic and Intel Labs will revolutionize the way people work with tablets and computers.

The PaperTab tablet looks and feels just like a sheet of paper. However, it is fully interactive with a flexible, high-resolution 10.7-inch plastic display developed by Plastic Logic and a flexible touchscreen. It is powered by the second generation I5 Core processor developed by Intel.

Vertegaal and his team have produced a video demonstrating their ‘paper’ tablet/computer:

The Jan. 8, 2013 Queen’s University news release, which originated the news item, provides descriptions (for those who don’t have time to watch the video),

“Using several PaperTabs makes it much easier to work with multiple documents,” says Roel Vertegaal, Director of Queen’s University’s Human Media Lab. “Within five to ten years, most computers, from ultra-notebooks to tablets, will look and feel just like these sheets of printed color paper.”

“We are actively exploring disruptive user experiences. The ‘PaperTab’ project, developed by the Human Media Lab at Queen’s University and Plastic Logic, demonstrates novel interactions powered by Intel processors that could potentially delight tablet users in the future,” says Intel’s Experience Design Lead Research Scientist, Ryan Brotman.

PaperTab’s intuitive interface allows users to create a larger drawing or display surface by placing two or more PaperTabs side by side. PaperTab emulates the natural handling of multiple sheets of paper. It can file and display thousands of paper documents, replacing the need for a computer monitor and stacks of papers or printouts.

Unlike traditional tablets, PaperTabs keep track of their location relative to each other, and to the user, providing a seamless experience across all apps, as if they were physical computer windows.

“Plastic Logic’s flexible plastic displays allow a natural human interaction with electronic paper, being lighter, thinner and more robust compared with today’s standard glass-based displays. This is just one example of the innovative revolutionary design approaches enabled by flexible displays,” explains Indro Mukerjee, CEO of Plastic Logic.

The partners are saying that ‘paper’ tablets may be on the market in foreseeable future  according to Emma Wollacott’s Jan. 8, 2013 article for TG Daily,

The bendy tablet has been coming for quite a while now, but a version to be shown off today at CES [Consumer Electronics Show] could be ready for the market within three years, say its creators.

You can find out more about the Human Media Lab at Queen’s University here, Plastic Logic here, and Intel Core I5 Processors here.

Crowdfunding Qii, a foldable, soft keyboard made of a carbon nanotube/fullerene hybrid

Canatu Ltd. is a Finnish company that’s trying to crowdfund its foldable, soft keyboard, Qii, on indiegogo. Here’s more about Canatu’s keyboard project from the Nov. 24, 2012 news item on Nanowerk,

Canatu Ltd., a developer of a new class of versatile carbon nanomaterial based custom films and sensors for flexible and formable touch devices, is launching Qii – the world’s first, truly mobile, rollable touch accessory.

The company appears to be creating a new class of product under the Qii brand name. From the indiegogo campaign description,

With Qii, your smartphone and your imagination, any surface can be effectively turned into a touch surface and any “dumb” object can be turned into a “smart” object. Nanotechnology and organic electronics make it possible. The idea is simple, but the applications are endless.

As our first Qii product, we’re offering a full QWERTY computer keyboard, including a number pad and function keys, wirelessly connected to your smartphone. Because its ultra thin and flexible, Qii is both full sized and pocket sized, so you’ll be able to effortlessly type and surf anywhere you go, be it in a café, the woods, or a car, train, bus or plane. It has an anti fingerprint coating to keep it clean and a textured surface for easy touch typing. It’s dirt and water resistant, so you don’t have to worry about spilling and it’s easily washable with soap and water. And, since Qii’s rollable electronics are printed, it’s tough.

Qii’s case is also a touchpad, allowing you to point, tap and scroll for easy surfing and graphical editing. You can use Qii on most any surface, so you can check your email on your friend’s belly, update your Facebook on your pet, or write your next novel on your pillow.

Some keyboards claim to be rollable, but you can’t roll them up and fit them in your pocket. We use a new kind of flexible transparent electronic film together with a new kind of touch sensing technology that can sense both position and force to create a compact and portable and programmable touch surface.

Qii will work with iPhone, iPod, iPad, Android, iPhone, Blackberry, Windows Phone, and Palm phones according to each platform’s available QWERTY keyboard and pointer standards.

Intriguing, non? You might want to watch this video for a demonstration,

There is a very brief description of the technology in the campaign material,

Our team has been working for years with our partners to bring Qii to life. Together we have developed new carbon based nanomaterials, new dry printing manufacturing techniques and now new, ultra-high transparency, flexible, bendable, stretchable, rollable and foldable touch technologies and unique touch algorithms to make Qii possible. It starts with our flexible, transparent, electrically conductive film made with a new carbon nanomaterial connected to state-of-the art sensing electronics to make a flexible, transparent touch sensing surface that determines both your finger’s position and force.

We’ll introduce the Qii in pliable hard coated plastic, but, in the future, the sensor can be printed on most anything, even paper, rubber or fabric.

I took a look at the Canatu website and found this information about a material they’ve developed and named, NanoBuds® and which I believe forms the basis for the company’s proposed Qii keyboard,

Canatu has developed a new material, the Carbon NanoBud®, which is a hybrid of Carbon Nanotubes and fullerenes. The hybridization is achieved directly in the material synthesis process and the resulting material combines the best features of both fullerenes and nanotubes.

Canatu’s first products focus on taking advantage of the high conductivity, high aspect ratio, low work function, chemical stability and mechanical flexibility of NanoBuds® to make the world’s highest performance carbon based transparent conductive film for transparent conductors in touch, haptics, displays and photovoltaics. These films, consisting of randomly oriented deposits of NanoBuds on polymer or glass substrates, are flexible, bendable, stretchable and have excellent transparency conductivity performance as shown below. [emphasis mine]

David Brown, the company’s Chief Technical Officer (CTO) originally announced the crowdfunding Qii campaign would take place on Kickstarter in Dan Rogers’s Oct. 10, 2012 article for Plastic Electronics,

An accessory using a novel nanomaterial touchscreen will be launched via the Kickstarter project in the coming weeks, according to nanotechnology developer Canatu.

Based in Finland, Canatu supplies carbon NanoBuds that can be used as a conductive layer alternative to indium tin oxide, which is considered too brittle for flexible electronics.

I’m not sure what happened with the ‘Kickstarter’ plans but the indiegogo campaign has 41 days left as Canatu tries to raise $1,850,000 by Jan. 6, 2013. The company must raise the entire amount requested or it receives nothing.

Good luck to the folks at Canatu. Qii looks like a product which would make moving around much easier. Imagine not having to lug your laptop or tablet around while enjoying the benefits of a full size keyboard.