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University of Vermont: Building the Electron Superhighway: Scientists Invent New Approach in quest for Organic Solar Panels and Flexible Electronics

genesisnanotech.wordpress.com – But the basic science of how to get electrons to move quickly and easily in these organic materials remains murky. To help, Furis and a team of UVM materials scientists have invented a new way to c…

Hong Kong Polytechnic U: Novel Efficient and Low-Cost Semitransparent Solar Cells

genesisnanotech.wordpress.com – Solar energy is an important source of renewable energy, in which solar cell will be used to convert light energy directly into electricity by photovoltaic effect. The first generation crystalline …

Canadians need to hear politicians’ plans for a resilient economy

theglobeandmail.com – Jim Dewald is dean of the Haskayne School of Business at the University of Calgary. Adam Legge is president and CEO of the Calgary Chamber of Commerce. The Globe and Mail is hosting a debate on the…

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University of Vermont: Building the Electron Superhighway: Scientists Invent New Approach in quest for Organic Solar Panels and Flexible Electronics


Israeli 0422 flexible-screen-811x497TV screens that roll up. Roofing tiles that double as solar panels. Sun-powered cell phone chargers woven into the fabric of backpacks. A new generation of organic semiconductors may allow these kinds of flexible electronics to be manufactured at low cost, says University of Vermont physicist and materials scientist Madalina Furis.

But the basic science of how to get electrons to move quickly and easily in these organic materials remains murky.

To help, Furis and a team of UVM materials scientists have invented a new way to create what they are calling “an electron superhighway” in one of these materials — a low-cost blue dye called phthalocyanine — that promises to allow electrons to flow faster and farther in organic semiconductors.

Their discovery, reported Sept. 14 in the journal Nature Communications, will aid in the hunt for alternatives to traditional silicon-based electronics.

U of VT 150914220524_1_540x360

University of Vermont scientists have invented a new way to create what they are calling an electron superhighway in an organic semiconductor that promises to allow electrons to flow faster and farther — aiding the hunt for flexible electronics, organic solar cells, and other low-cost alternatives to silicon. To explore these organic materials, UVM graduate students (from left) Naveen Rawat and Lane Manning, and professors Randy Headrick and Madalina Furis, deployed this table-top scanning laser microscope. Their latest finding is reported in the journal Nature Communications — and may, someday not too far off, let you roll up your computer like a piece of paper.
Credit: Joshua Brown, UVM

Hills and Potholes

Many of these types of flexible electronic devices will rely on thin films of organic materials that catch sunlight and convert the light into electric current using excited states in the material called “excitons.” Roughly speaking, an exciton is a displaced electron bound together with the hole it left behind. Increasing the distance these excitons can diffuse — before they reach a juncture where they’re broken apart to produce electrical current — is essential to improving the efficiency of organic semiconductors.

Using a new imaging technique, the UVM team was able to observe nanoscale defects and boundaries in the crystal grains in the thin films of phthalocyanine — roadblocks in the electron highway. “We have discovered that we have hills that electrons have to go over and potholes that they need to avoid,” Furis explains.

To find these defects, the UVM team — with support from the National Science Foundation — built a scanning laser microscope, “as big as a table” Furis says. The instrument combines a specialized form of linearly polarized light and photoluminescence to optically probe the molecular structure of the phthalocyanine crystals.

“Marrying these two techniques together is new; it’s never been reported anywhere,” says Lane Manning ’08 a doctoral student in Furis’ lab and co-author on the new study.

The new technique allows the scientists a deeper understanding of how the arrangement of molecules and the boundaries in the crystals influence the movement of excitons. It’s these boundaries that form a “barrier for exciton diffusion,” the team writes.

And then, with this enhanced view, “this energy barrier can be entirely eliminated,” the team writes. The trick: very carefully controlling how the thin films are deposited. Using a novel “pen-writing” technique with a hollow capillary, the team worked in the lab of UVM physics and materials science professor Randy Headrick to successfully form films with jumbo-sized crystal grains and “small angle boundaries.” Think of these as easy-on ramps onto a highway — instead of an awkward stop sign at the top of a hill — that allow excitons to move far and fast.

Better Solar Cells

Though the Nature Communications study focused on just one organic material, phthalocyanine, the new research provides a powerful way to explore many other types of organic materials, too — with particular promise for improved solar cells. A recent U.S. Department of Energy report identified one of the fundamental bottlenecks to improved solar power technologies as “determining the mechanisms by which the absorbed energy (exciton) migrates through the system prior to splitting into charges that are converted to electricity.”

The new UVM study — led by two of Furis’ students, Zhenwen Pan G’12, and Naveen Rawat G’15 — opens a window to view how increasing “long-range order” in the organic semiconductor films is a key mechanism that allows excitons to migrate farther. “The molecules are stacked like dishes in a dish rack,” Furis explains, “these stacked molecules — this dish rack — is the electron superhighway.”

Though excitons are neutrally charged — and can’t be pushed by voltage like the electrons flowing in a light bulb — they can, in a sense, bounce from one of these tightly stacked molecules to the next. This allows organic thin films to carry energy along this molecular highway with relative ease, though no net electrical charge is transported.

“One of today’s big challenges is how to make better photovoltaics and solar technologies,” says Furis, who directs UVM’s program in materials science, “and to do that we need a deeper understanding of exciton diffusion. That’s what this research is about.”


Story Source:

The above post is reprinted from materials provided by University of Vermont. Note: Materials may be edited for content and length.


Journal Reference:

  1. Z. Pan, N. Rawat, I. Cour, L. Manning, R. L. Headrick, M. Furis. Polarization-resolved spectroscopy imaging of grain boundaries and optical excitations in crystalline organic thin films. Nature Communications, 2015; 6: 8201 DOI: 10.1038/ncomms9201

KAIST Lab team develops Hyper-stretchable Elastic-Composite Energy Harvester: Applications: Flexible Electronics


Elastic Energy 041415 akaistresearA research team led by Professor Keon Jae Lee of the Department of Materials Science and Engineering at the Korea Advanced Institute of Science and Technology (KAIST) has developed a hyper-stretchable elastic-composite energy harvesting device called a nanogenerator.

Flexible electronics have come into the market and are enabling new technologies like flexible displays in mobile phone, , and the Internet of Things (IoTs). However, is the degree of flexibility enough for most applications? For many flexible devices, elasticity is a very important issue. For example, wearable/biomedical devices and electronic skins (e-skins) should stretch to conform to arbitrarily curved surfaces and moving body parts such as joints, diaphragms, and tendons. They must be able to withstand the repeated and prolonged mechanical stresses of stretching. In particular, the development of elastic energy devices is regarded as critical to establish power supplies in stretchable applications.

Although several researchers have explored diverse stretchable electronics, due to the absence of the appropriate device structures and correspondingly electrodes, researchers have not developed ultra-stretchable and fully-reversible energy conversion devices properly.

Recently, researchers from KAIST and Seoul National University (SNU) have collaborated and demonstrated a facile methodology to obtain a high-performance and hyper-stretchable elastic-composite generator (SEG) using very long silver nanowire-based stretchable electrodes. Their stretchable piezoelectric generator can harvest mechanical energy to produce high power output (~4 V) with large elasticity (~250%) and excellent durability (over 104 cycles). These noteworthy results were achieved by the non-destructive stress- relaxation ability of the unique electrodes as well as the good piezoelectricity of the device components. The new SEG can be applied to a wide-variety of wearable energy-harvesters to transduce biomechanical-stretching energy from the body (or machines) to electrical .

Elastic Energy 041415 akaistresear

Top row shows schematics of hyper-stretchable elastic-composite generator (SEG) enabled by very long silver nanowire-based stretchable electrodes. The bottom row shows the SEG energy harvester stretched by human hands over 200% strain. Credit: KAIST 

Professor Lee said, “This exciting approach introduces an ultra-stretchable piezoelectric generator. It can open avenues for power supplies in universal wearable and biomedical applications as well as self-powered ultra-stretchable electronics.”

This result was published online in the March issue of Advanced Materials, which is entitled “A Hyper-Stretchable Elastic-Composite Energy Harvester.”

Explore further: Nanoengineers develop basis for electronics that stretch at the molecular level

Stretchable Silicon for Flexible Electronics? Video


1-KAUST 04d5b1fProf. Muhammad Mustafa Hussain, Associate Professor of Electrical Engineering at KAUST, and his group, have developed an innovative type of ultra-stretchable silicon (up to 10 times its original length) for flexible electronics. This “smart skin” represents and important advance in the future development of foldable electronics and photovoltaics.

The flexibility required when fabricating flexible electronic components has led to the use of plastic substrates, carbon nanomaterials, and different transfer techniques to fabricate flexible devices. One of the biggest obstacles to mass adoption of flexible electronics has been the incompatibility of most of these solutions with industry’s state-of-the-art silicon-based CMOS processes – which still produce about 90% of today’s electronics. Researchers have now demonstrated ultra-stretchability in monolithic single-crystal silicon. The design is based on an all silicon-based network of hexagonal islands connected through spiral springs. “With this structure, we have been able to achieve a remarkable stretch ratio of about 1000% using a brittle material such as silicon,” Muhammad Mustafa Hussain, an Associate Professor of Electrical Engineering at King Abdullah University of Science and Technology (KAUST), tells Nanowerk. Hussain and his team have published their findings in Applied Physics Letters (“Design and characterization of ultra-stretchable monolithic silicon fabric”). The fabrication process is based on conventional microfabrication techniques consisting on five basic steps: Starting with a silicon-on-insulator wafer (50 µm), 1) a gold hard mask is first deposited on silicon-on-insulator and then patterned using 2) photolithography and 3) reactive ion etching (RIE). Next, 4) the silicon is deeply, anisotropically etched (DRIE) until the buried oxide layer is reached and then the hard mask is removed. Finally, 5) the silicon structure is release with vapor hydrofluoric acid, which removes the underlying oxide layer.

microfabrication process for stretchable siliconSummarized fabrication process flow with digital photographs of final designs. (a) Hard mask deposition. (b) Photolithography step. (c) Hard mask’s patterning. (d) Silicon DRIE and hard mask removal. (e) Release of silicon structures with VHF. (f) Digital photographs and zoom-ins of an array of 800 µm-side-hexagons interconnected by single 5 µm-arm spirals (scale bar is 2mm long, 1mm for the first zoom-in and 0.5mm for the spiral zoom-in). (g) Digital photographs and zoom-ins of an array of 800 µm-sidehexagons interconnected by double 2 µm-arm spirals (scale bar is 2mm long, 0.5mm for the first zoom-in and 0.2mm for the spiral zoom-in). (© AIP) Hussain points out that device implementation can be achieved through CMOS-compatible fabrication previous to the 5-step release process described above. The resulting single-spiral structures can be stretched to a ratio more than 1000%, while remaining below a 1.2% strain. Moreover, these network structures have demonstrated area expansions as high as 30 folds in arrays.

This video shows the manual stretching of a single 5 µm-arm silicon spiral for 8 cycles, which demonstrates mechanical robustness and reliability. (Video: Integrated Nanotechnology Laboratory, KAUST)

“While handling still remains a challenge, our method can provide ultra-stretchable and adaptable electronic systems for distributed network of high-performance macro-electronics especially useful for wearable electronics and bio-integrated devices,” says Hussain. The researchers are currently working to demonstrate electronic devices implemented on top of their hexagon islands and interconnected through the spiral springs to form stretchable sensor networks with outstanding electrical performance and mechanical robustness.

Printing Ultrafast Graphene Chips for Flexible Electronics


Futurists are always talking about how flexible electronics will change our lives in amazing ways, but we’ve yet to see anything mind-blowing come to market. A team of scientists from the University of Texas in Austin, however, think they’ve found the key to changing that: ultrafast graphene transistors printed on flexible plastic.

Graphene is amazing. Or at least, it could be. Made from a layer of carbon one-atom thick, it’s the strongest material in the world, it’s… Read…

   9 Incredible Uses for Graphene

Graphene is amazing stuff for a lot different reasons. One reason is that it’s the perfect material for chip-making, and conventional graphene chips have broken several electronic speed records. In the past, however, attempts to put graphene transistors on flexible materials have caused that speed to take a dive. Not with this new method.

Indeed, the chips from Texas clock in at a record-breaking 25-gigahertz. The MIT Technology Review explains the manufacturing process:

To make the transistors, the researchers first fabricate all the non-graphene-containing structures—the electrodes and gates that will be used to switch the transistors on and off—on sheets of plastic. Separately, they grow large sheets of graphene on metal, then peel it off and transfer it to complete the devices. …

The graphene transistors are not only speedy but robust. The devices still work after being soaked in water, and they’re flexible enough to be folded up.

And things are only getting better. Earlier this week we learned about a cutting edge technique for making graphene chips developed by a team of researchers from the University of California.

All we need now is a company to take the plunge and start bringing some of this next level technology to market. And you thought Liquidmetal was cool !!     [Technology Review]

READ MORE …

Scientists Just Figured Out How to Make Lightning-Fast Graphene CPUs

Graphene has the power to change computing forever by making the fastest transistors ever. In theory. We just haven’t figured out how yet. Sound familiar? Fortunately, scientists have just taken a big step closer to making graphene transistors work for real.

Graphene transistors aren’t just fast; they’re lightning fast. The speediest one to date clocked in at some 427 GHz. That’s orders of magnitude more than what you can tease out of today’s processors.  The problem with graphene transistors, though, is that they aren’t particularly good at turning off. They don’t turn off at all actually, which makes it hard to use them as switches.

http://gizmodo.com/scientists-just-figured-out-how-to-make-lightning-fast-1177727488

Advances in R2R barrier technologies to Help Plastic Electronics Continuous Production


201306047919620A number of promising barrier technologies that could be used in the industrial production of plastic electronics are being developed for continuous production processes.

Roth & Rau's PECVD tool is used by the Holst Centre for barrier/encapsulation technology developmentFlexible barrier and encapsulation technologies improve the shelf life of devices such as flexible OLED lighting and OPVs from moisture ingress particularly, which tend to cause the technology to degrade.

Requirements for plastic electronics are higher than other technologies as some devices will need a shelf life of several years, while the level of protection can also depend heavily on the application – barrier and encapsulation requirements for a flexible OPV device, used to power an indoor sensor system, will be different to a flexible OLED lighting product, which will differ to an outdoor building- integrated PV (BIPV) application for an OPV panel. In addition high barrier technologies for plastic electronics have to be manufactured cost-effectively.

Plastic electronics R&D clusters in Europe are beginning to make headway in this area. In 2010 plasma-enhanced chemical vapour deposition (PECVD) technology equipment supplier Roth & Rau Microsystems joined the Holst Centre‘s large area flexible electronics programme, specifically to work on roll-to-roll (R2R) deposition tools for transparent high barrier layers.

Progress

OLED lighting devices using the batch-processed thin film flexible barrier technology have been validated in accelerated lifetime tests, while Roth & Rau Microsystems continue to scale the process for R2R.

The Holst Centre’s PECVD barrier technology is also being used in the Solliance project, of which Holst Centre is a founding R&D partner, as a baseline process, for flexible solution processable OPVs, though other barrier technologies and processes that have the potential to be more cost-effective are also being investigated.

In the UK, the Centre for Process Innovation (CPI) is working closely with atomic layer deposition (ALD) tool supplier Beneq. The partners will, together, develop an industry-ready transparent high-barrier/encapsulation process that can be applied using an R2R ALD tool that the CPI has bought from Beneq.

In future, might this mean that the CPI and Beneq are able to collaboratively offer barrier technologies to the plastic electronics industry – Beneq the production tool and CPI the know-how – which may differ depending on devices and applications for devices. Potentially barriers can be applied in several ways, including supplied as a standalone transparent film product that can be laminated onto a device, applied directly onto a device, or applied as a layer on to a film/foil substrate that devices are made on. Investigation and development of these will be done by the CPI.

There Are Endless Electronics We Could Build With This New Stretchy Material


stretchy-electronics-4Flexible electronics are the gateway to a new generation of phones, brain  implants, artificial limbs, solar cells, and limitless other devices that  benefit from the ability to bend, fold, and rollup.

 

 

 

 

The problem is figuring out how to make them.

Stretchability and conductivity are difficult properties to combine.  Materials that are good conductors do not stretch well and materials that do  stretch well are not good conductors.

This happens because the stretching of solid material lengthens chemical  bonds, changing the distance between atoms, and in turn, decreasing  conductivity. Alternatively, the crystalline structures of metals, which makes  them good conductors of heat and electricity, are hard to mold since their  internal bonds are not very forgiving.

“This is the story throughout the entire family of stretchable conductors,”  said study researcher Nicholas Kotov, a professor of engineering at the University of  Michigan, who may have developed the best stretchy conductor yet.

The new material is made from gold nanoparticles that are embedded in a  flexible synthetic material called polyurethane. The bendy film, described in a  paper published in Nature on  Wednesday, July 17, can conduct electricity even when stretched to more than  twice its original length.

Scientists used electron microscope images to see what happened when the  material was stretched. It turns out that the gold nanoparticles aligned into  chains when pulled — instead of becoming disorganized — creating a good  conducting pathway. Importantly, the nanoparticles rearranged themselves when  the strain was released, meaning the process is reversible.

Stretchy Electronics

Michigan  Engineering

The gold nanoparticles are produced in the lab, represented  by this deep purple substance.

 The secret lies in the gold nanoparticles, which were made in the lab so that  they they would have a very thin shells on their surface. The thin shells are  much better than thicker traditional shells.

“This is important because the shell stabilizes the particles and typically  prevents the transfer of electrons from one nanoparticle to the other,” Kotov  told Business Insider.

Without a thick shell, the electrons can hop from one nanoparticle to another  more easily and are able to conduct electricity very well.

The practical applications of elastic metal are far-reaching, but  Kotov is particularly interested in how his material can be used to improve  medical devices.

There are a number of implantable devices for the brain, heart, and muscles.  The problem with these rigid electrodes is that the human tissue easily  recognizes them as foreign materials and generates scar tissue as a response,  explains Kotov. The scar tissue reduces the performance of implantable devices.  A pliable material that is more akin to our soft tissue is key to longer-term  implants.

The search for a material that has the unusual combination of stretchability  and electrical conductivity is ongoing, but this is a critical step forward.

Read more:  http://www.businessinsider.com/highly-conductive-stretchable-material-flexible-electronics-2013-7#ixzz2ZLEssnA8

Flexible and printed electronics: Approaching the tipping point


201306047919620(Nanowerk News) FlexTech Alliance announced that the 2014 Flexible and Printed Electronics Conference &  Exhibition (2014FLEX) returns to the Phoenix Convention Center February 3-6,  2014 with the Renaissance Hotel in downtown Phoenix, Arizona, as the  headquarters for several of the networking functions. This conference and  exhibit is the most comprehensive North American event exploring technology and  markets in flexible and printed devices and its supply chain. Industry analysts  contend that this sector is steadily approaching an inflection point moving from  technology push into market pull.
Organized by FlexTech Alliance, a membership-driven industry  association which represents companies in the flexible and printed electronics  sector, 2014FLEX leverages the association’s educational programs, worldwide  connections, and management of R&D projects.
Three industry leaders have committed to chair the conference  and share their experience in this emerging field of electronics: Ross Bringans,  vice president at PARC, A Xerox Company (Palo Alto Research Center), Michael  Idacavage, vice president of business development at Esstech, Inc., and Robert  Miller, senior business manager at EMD Chemicals.
“The Flex Conference has built a well-deserved reputation for  excellent technical content and as a very effective place to meet partners,  discover new approaches, and to be inspired in our research and development of  new offerings,” states Bringans.
“As an 8+ year veteran of this event, I look forward to helping  2014FLEX maintain its position as the most innovative and most rewarding event  of its kind,” adds Idacavage.
Miller notes, “Advancements made in equipment, materials and  processes that have been introduced at the Flex Conference have helped to enable  the touch revolution, large scale conformable displays, flexible power  generation, just to name a few. As presenters, exhibitors or attendees, we know  our time and effort has excellent return on our investment at this, the original  conference in the field of flexible electronics.”
“Insightful business perspectives and top technical  presentations are the hallmarks of the Flex Conference,” comments Michael  Ciesinski, FlexTech Alliance’s chief executive officer. “We draw subject matter  experts from the global industry and provide a platform for the technical and  business development community to accomplish all of their professional and  corporate objectives.”
One of the first activities for the leaders was to identify a  theme for the conference, this year tagged as “Approaching the Tipping Point”,  conveying the industry’s perception that wide-scale adoption of flexible and  printed electronics is imminent. Growth in the sector has been steady and  technological advances continue to enhance existing products.
The conference chairs are supported by 28 distinguished members  of the program committee who will identify and invite leading business  professionals and researchers around the world to present a paper or give a  short course at 2014FLEX. Their first activity was to create a list of topics  for the newly-released Call for Papers. This list and details on presenting at  the conference has been carefully created to attract those working on the  cutting edge and ready to present their work to an audience of peers, potential  customers and potential suppliers.
Source:  FlexTech Alliance

Read more: http://www.nanowerk.com/news2/newsid=31230.php#ixzz2YdaXpFR5

Flexible electronics could transform the way we make and use electronic devices


Flexible electronics open the door to foldaway smartphone displays, solar cells on a roll of plastic and advanced medical devices — if we can figure out how to make them.

QDOTS imagesCAKXSY1K 8Nearly everyone knows what the inside of a computer or a mobile phone looks like: A stiff circuit board, usually green, crammed with chips, resistors, capacitors and sockets, interconnected by a suburban sprawl of printed wiring.

But what if our printed circuit board was not stiff, but flexible enough to bend or even fold?

It may sound like an interesting laboratory curiosity, but not to Enrique Gomez, an assistant professor of chemical engineering at Penn State. “It could transform the way we make and use electronic devices,” he says.

Gomez is one of many scientists investigating flexible electronics at the University’s Materials Research Institute. Others are doing the same at universities and corporations around the world.

Flexible electronics are in vogue for two reasons.

First, they promise an entirely new design tool. Imagine, for example, tiny smartphones that wrap around our wrists, and flexible displays that fold out as large as a television. Or photovoltaic cells and reconfigurable antennas that conform to the roofs and trunks of our cars. Or flexible implants that can monitor and treat cancer or help paraplegics walk again.

Penn State’s interest in flexible and printed electronics is not just theoretical. In October 2011, the University began a multi-year research project with Dow Chemical Corporation. Learn more about the partnership.

Second, flexible electronics might cost less to make. Conventional semiconductors require complex processes and multi-billion dollar foundries. Researchers hope to print flexible electronics on plastic film the same way we print ink on newspapers.

“If we could make flexible electronics cheap enough, you could have throwaway electronics. You could wear your phone on your clothing, or run a bioassay to assess your health simply by wiping your nose with a tissue,” Gomez says.

Before any of this happens, though, researchers have to rethink what they know about electronics.

Victim of Success

That means understanding why conventional electronics are victims of their own success, says Tom Jackson, Kirby Chair Professor of Electrical Engineering. Jackson should know, because he helped make them successful. Before joining Penn State in 1992, he worked on IBM‘s industry-leading laptop displays. At Penn State, he pioneered the use of organic molecules to make transistors and electronic devices.

Modern silicon processors integrate billions of transistors, the semiconductor version of an electrical switch on tiny slivers of crystalline silicon.

Squeezing so many transistors in a common location enables them to handle complex problems. As they shrink in size, not only can we fit more transistors on a chip, but the chip gets less expensive to manufacture.

“It is hard to overstate how important this has been,” Jackson explains.

“Remember when we paid for long-distance phone calls by the minute? High-speed switching drove those costs way down. In some cases, we can think of computation as free. You can buy an inexpensive calculator at a store for $1, and the chip doesn’t even dominate the cost. The power you get is amazing.”

That, says Jackson, is the problem. Semiconductor processors are so good and so cheap, we fall into the trap of thinking they can solve every problem.

Sometimes, it takes more flexibility to succeed.

Electronics-research-001

Consider surgery to remove a tumor from a patient’s liver. Even after following up with radiation or chemotherapy, the surgeon is never sure if the treatment was successful.

“But suppose I could apply a flexible circuit to the liver and image the tissue. If we see a new malignancy, it could release a drug directly onto that spot, or heat up a section of the circuit to kill the malignant cells. And when we were done, the body would resorb the material,” Jackson says.

“What I want,” he says, “is something that matches the flexibility and thermal conductivity of the body.” Conventional silicon technology is too stiff and thermally conductive to work.

Similarly, large, flexible sensors could monitor vibrations on a bridge or windmill blade and warn when they needed maintenance.

“If you want to spread 100 or 1,000 sensors over a large area, you have to ask whether you want to place all the chips you need to do that, or use low-cost flexible electronics that I can apply as a single printed sheet,” Jackson says.

None of the flexible electronics now under development would match the billions of transistors that now fit on silicon chips, or their billions of on-off cycles per second. They would not have to. After all, even today’s fastest televisions refresh their displays only 240 times per second. That is more than fast enough to image cancer in the body, reconfigure an antenna, or assess the stability of a bridge.

So how, exactly, do we make flexible electronics, and what kind of materials do we make them from?

Printing

To explain what draws researchers to printing flexible electronics, Jackson walks through the production of flat panel displays in a $2-3 billion factory.

The process starts with a 100-square-foot plate of glass. To apply wires, the factory coats the entire plate with metal, then covers it with a photosensitive material called a resist. An extremely bright light flashes the pattern of the wires onto the coating, hardening the resist. In a series of steps, the factory removes the unhardened resist and metal under it. Then, in another series of steps, it removes the hardened resist, leaving behind the patterned metal wires.

Factories repeat some variant of this process four or five times as they add light-emitting diodes (LEDs), transistors and other components. With each step, they coat the entire plate and wash away unused materials. While the cost of a display is 70 percent that of a finished device, most of those materials get thrown away.

None of the flexible electronics now under development would match the billions of transistors that now fit on silicon chips, or their billions of on-off cycles per second. They would not have to.

“So it’s worth thinking about whether we can do this by putting materials where we need them, and reduce the cost of chemicals and disposal. It is a really simple idea and really hard to do,” Jackson says.

An ideal way to do that, most researchers agree, would be to print the electronics on long plastic sheets as they move through a factory. A printer would do this by applying different inks onto the film. As the inks dried, they would turn into wires, transistors, capacitors, LEDs and all the other things needed to make displays and circuits.

That, at least, is the theory. The problem, as anyone who ever looked at a blurry newspaper photograph knows, is that printing is not always precise. Poor alignment would scuttle any electronic device. Some workarounds include vaporizing or energetically blasting materials onto a flexible sheet, though this complicates processing.

And then, of course, there are the materials. Can we print them? How do we form the precise structures we need? And how do we do dry and process them at temperatures low enough to keep from melting the plastic film?

Material World

Fortunately, there are many possible materials from which to choose. These range from organic materials, like polymers and small carbon-based molecules, to metals and even ceramics.

At first glance, flexible ceramics seem like a stretch. Metals bend, and researchers can often apply them as zigzags so they deform more easily.

Try flexing a thick ceramic, though, and it cracks. Yet that has not deterred Susan Trolier-McKinstry, a professor of ceramic science and engineering and director of Penn State’s W.M. Keck Smart Materials Integration Laboratory.

Ceramics, she explains, are critical ingredients in capacitors, which can be used to regulate voltage in electronic circuits. In many applications, transistors use capacitors to provide instantaneous power rather than waiting for power from a distant source.

Industry makes capacitors from ultrafine powders. The tiniest layer thicknesses are 500 nanometers, 40 times smaller than a decade or two ago. Even so, there is scant room for them on today’s overcrowded circuit boards, especially in smartphones. Furthermore, there is a question about how long industry can continue to scale the thickness in multilayer ceramic capacitors.

Trolier-McKinstry thinks she can deposit smaller capacitors directly onto flexible sheets of plastic, and sandwich these in flexible circuit board. That way, the capacitors do not hog valuable surface area.

One approach is to deposit a precursor to the capacitor from a solution onto a plastic film and spot heat each capacitor with a laser to remove the organics and crystallize the ceramic into a capacitor. Another approach is to use a high-energy laser beam to sand blast molecules off a solid ceramic and onto a plastic substrate.

As long as she can keep capacitor thicknesses small, Trolier-McKinstry need not worry too much about capacitor flexibility. Previous researchers have demonstrated that it is possible to bend some electroceramic films around the radius of a Sharpie pen without damage.

Of course, not every element placed on a flexible substrate will be small. So what happens if your transistors need to bend?

One way to solve that problem is to make electronics from organic materials like plastics. These are the ultimate flexible materials. While most organics are insulators, a few are conductive.

“Organic molecules have tremendous chemical versatility,” Gomez explains. “My group’s goal is to turn these molecules into transistors and photovoltaic cells.” Easier said than done. The almost infinite number of possibilities available in organic chemistry, he says, make it challenging to find the right combination of structure, properties and function to create an effective device.

Molecules may not be picky about their neighbors, but they still need to form the right type of structures to act as switches or turn light into electricity. Gomez attacks the problem by using a technique called self-assembly. It starts with block copolymers, combinations of two molecules with different properties bound together in the middle.

Trolier-McKinstry thinks she can deposit smaller capacitors directly onto flexible sheets of plastic, and sandwich these in flexible circuit boards. That way, the capacitors do not hog valuable surface area.

“Think of them as a dog and a cat tied together by their tails,” Gomez explains. “Ordinarily, they want to run away from each other, but now they can’t. Then we throw them into a room with other tied dogs and cats. What happens is that all the cats wind up on one side of the room and the dogs on the other, so they don’t have to look at each other.”

Gomez believes this process could enable him to build molecules programmed to self-assemble into electronic structures at very low cost.

“The overarching problem,” Gomez continues, “is figuring out how to design the molecule and then tickle it with pressure, temperature and electrical fields to form useful structures. We don’t really understand enough to do that yet.”

Despite the challenge, flexible electronics promise changes that go beyond folding displays, inexpensive solar cells, antennas and sensors. They could veer off in some unexpected directions, such as helping paraplegics walk again.

Mimicking Jell-O

That is the goal of Bruce Gluckman, associate director of Penn State’s Center for Neural Engineering. To get there, he must learn how the brain’s neurons collaborate.

“Computations happen at the level of single neurons that connect to other neurons. Half the brain is made up of the wiring for these connections, and any cell can connect to a cell next to it or to a cell across the brain. It’s not local in any sense,” he explains.

Scientists measure the electrical activity of neurons by implanting silicon electrodes into the brain. Unfortunately, Gluckman says, the brain is as spongy as Jell-O and the electrode is as stiff as a knife.

Plunging the electrode into the brain causes damage immediately. Every time the subject moves its head, the brain pulls away from the electrode on one side and makes better contact on the other. It takes racks of electronics to separate the signal from the noise of such inconsistent output.

“This is why we need something other than silicon,” Gluckman says.

Despite the challenge, flexible electronics promise changes that go beyond folding displays, inexpensive solar cells, antennas and sensors. They could veer off in some unexpected directions, such as helping paraplegics walk again.

Flexible electronics would better match the brain’s springiness. While some researchers are looking at all-organic electrodes, Gluckman believes they are too large and too slow to achieve the resolution he needs. Instead, he has teamed with Jackson to develop a flexible electrode based on zinc oxide, a faster semiconductor that can be deposited on plastic at low temperatures.

The work is still in its early stages, but Gluckman believes they can develop a reliable electrode that lasts for years and produces stronger, clearer signals.

Researchers have already demonstrated that humans can control computer cursors, robotic arms and even artificial voice boxes with today’s problematic electrodes. Yet the results are often short-lived.

“No one is going to let you operate on their brain twice,” Gluckman says. “If you want to directly animate limbs with an implant, the implant has to last the life of the patient. If we can do that, we can enable paraplegics to get around on their own.”

As Jackson notes, computers and smartphones may have powered silicon’s development, but the results are visible in everything from cars and digital thermometers to toys and even greeting cards.

Displays and solar cells are likely to power the new generation of flexible electronics, but brain implants are just one of the many unexpected directions they may take.

Enrique Gomez is assistant professor of chemical engineering, edg12@psu.edu. Thomas N. Jackson is Kirby Chair Professor of Electrical Engineering, tnj1@psu.edu. Susan Trolier-McKinstry is professor of ceramic science and engineering and director of the W.M. Keck Smart Materials Integration Laboratory, STMcKinstry@psu.edu. Bruce Gluckman is associate director of Penn State’s Center for Neural Engineering, bjg18@psu.edu.

Flexible Electronics Help Create Multi Sensing Cardiac Ablation Catheter


by GENE OSTROVSKY on Nov 16, 2012

flexible cardiac ablation catheter Flexible Electronics Help Create Multi Sensing Cardiac Ablation CatheterFlexible electronics are a fairly new advancement with the promise of radically transforming certain aspects of medicine. Unlike many technologies that take years to reach practical implementation, flexible electronics are already being embedded to significantly improve the functionality of existing devices. As an early example that was just announced, an international team of researchers built and tested a balloon ablation catheter capable of measuring intracardiac pressure, EKG, and local temperature around the device tip. All this data can be monitored in real time by the physician during ablation without having to switch devices.

The technology behind the flexible electronics is being developed by MC10, a company we’ve been following for the last couple of years as they rush to bring new capabilities to medical devices.

From Northwestern University:

Central to the design is a section of catheter that is printed with a thin layer of stretchable electronics. The catheter’s exterior protects the electronics during its trip through the bloodstream; once inside the heart, the catheter is inflated like a balloon, exposing the electronics to a larger surface area inside the heart.

With the catheter is in place, the individual devices within can perform their specific tasks. A pressure sensor determines the pressure on the heart; an EKG sensor monitors the heart’s condition during the procedure; and a temperature sensor controls the temperature so as not to damage surrounding tissue. The temperature can also be controlled during the procedure without removing the catheter.

These devices can deliver critical, high-quality information — such as temperature, mechanical force, and blood flow — to the surgeon in real time, and the system is designed to operate reliably without any changes in properties as the balloon inflates and deflates.

Flexible electronics flashbacks on Medgadget

Northwesten press release: Simplifying Heart Surgery with Stretchable Electronic Devices

More from MC10: MC10′s Latest Research on Cardiac Webs and Instrumented Catheters in the Proceedings of the National Academy of Sciences (PNAS)

Study abstract in PNASElectronic sensor and actuator webs for large-area complex geometry cardiac mapping and therapy

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