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The Future Is Flexible and Printed

Friday, March 4th, 2016


By Jeff Dorsch, Contributing Editor

Automotive electronics, the Internet of Things, wearable gadgets, and other emerging chip markets are also expected to provide growth for flexible electronics, which often share manufacturing processes and materials with semiconductors.

Such applications were the talk of this week’s 2016FLEX Conference & Exhibition in Monterey, Calif. Printed and hybrid electronics were also on offer in the technical presentations and the compact exhibition area on the mezzanine level of the Monterey Marriott, where the conference was held while the Monterey Conference Center across Del Monte Avenue undergoes a year-long reconstruction project.

The Monterey Marriott and the Monterey Conference Center. (Credit: Jeff Dorsch)

Autonomous vehicles, connected cars, and the IoT are driving demand and innovation in flexible, hybrid, and printed electronics, according to Harry Zervos, principal analyst and business development manager for North America at IDTechEx, the market research, business intelligence, consulting, and events firm.

These new forms provide the capability to “add electronics to more and more mundane things,” he noted.

IDTechEx estimates the printed, flexible, and organic electronics market was worth a total of $24.5 billion in 2015. Organic light-emitting diode displays accounted for the lion’s share, at $15.3 billion. While OLEDs typically are not printed electronics, they stand to lead to flexible displays in the future, according to IDTechEx.

Sensors, mostly glucose test strips, represented $6.6 billion in revenue last year, while conductive inks provided $2.3 billion during 2015.

The market research firm forecasts printed electronics will increase from $8.8 billion in 2015 to $14.9 billion in 2025. Products made on flexible substrates are projected to grow from $6.4 billion last year to $23.5 billion in the next decade.

Market researchers have predicted “billions of sensors” will be sold in the next few years, including sensors for smartphones, Zervos said.  Smartphones will be “becoming flexible, more robust, foldable,” he added.

He is looking ahead to a time of flexible sensors and perhaps flexible microelectromechanical system devices to enable those flexible phones.

Flexible, hybrid, and printed electronics will provide “innovation in form factors, allowing designers to come up with new ideas on what devices could look like,” Zervos said in an interview. Such innovation will lead to “more excitement, higher profit margins,” he added.

This will depend on “an interoperable ecosystem” between the mature semiconductor industry and the nascent flexible electronics industry, Zervos said.

Molex was among the exhibitors at this week’s conference. The company was acquired in late 2013 for $7.2 billion by Koch Industries. Nearly a year ago, Molex acquired certain assets of Silogie, a supplier of flexible and printed electronics for consumer goods, industrial, lighting, medical, and military applications.

During the technical program on Wednesday afternoon, John Heitzinger — Molex’s general manager of printed electronics — described products the company has developed for the structural health monitoring of advanced ammunition, building monitoring systems, and physiological monitoring, the last on behalf of the U.S. Air Force. In working on functionalized carbon nanotubes for detecting and sensing lactate, Molex collaborated with American Semiconductor, Brewer Science, and Northeastern University, he said.

Neil Morrison of Applied Materials WEB Coating presented Wednesday morning on “’Packaging’ of Moisture Sensitive Materials Used in New Form Factor Display Products.” He is manager of research and development in Energy & Environmental Solutions for the Applied Materials unit, based in Alzenau, Germany.

Applied has a 40-year history is supplying chemical vapor deposition equipment for semiconductor manufacturing, he noted, and now offers plasma-enhanced CVD for displays and roll-to-roll CVD for advanced flexible electronics.

For quantum dots and wearables, “you need a barrier solution,” especially multilayer barrier stacks, Morrison said.

He recommended PECVD for manufacturing with silicon nitride, and critical roll-to-roll CVD requirements for high-performance barrier films.

For high-volume manufacturing of roll-to-roll barriers, “process monitoring and control is key,” Morrison said.

Flexible, hybrid, and printed electronics are clearly becoming a big and growing market. How companies take advantage of this market opportunity may be critical to their future.

Conference features the latest in flexible display technology

Thursday, June 4th, 2015


By Jeff Dorsch, Contributing Editor

At Display Week 2015, bigger is better. Smaller is better. And flexible may be best of all, for the era of wearable electronics.

There are some huge screens on display, so to speak, throughout the conference’s exhibition floor, such as BOE Technology Group’s 110-inch 8K Ultra High Definition television or LG Display’s curved 77-inch 4K UHD TV. There are also very small displays, such as E Ink’s smallest electronic shelf labels.

Many new developments can be viewed in the rows of exhibits, such as displays made with quantum dots. Of the 74 sessions in the technical program, at least eight are devoted to flexible displays (including one on electronic paper) or wearable displays.

A seminar on Monday, June 1, titled “Major Issues of AMOLED Displays: Challenges of Flexible OLED Displays and OLED TV” and given by Professor Jun Souk of Hanyang University, Seoul, South Korea, attracted a standing-room-only audience. Thursday, June 4, will see a day-long Market Focus Conference on Wearable-Flexible, with presentations by ARM Holdings, Google, Intel, and other companies.

Sri Peruvemba, chief executive officer of Marketer International, said Tuesday, June 2, that flexible, foldable, and even rollable displays are among the top trends this year at the Society for Information Display conference. The tantalizing prospect of flexible displays has been around for some years, and “I hope it will happen before I retire,” he said.

While E Ink gets most of its revenue from displays for electronic readers, such as the Amazon Kindle, it is active in flexible displays, too, for such applications as smartwatches, according to Giovanni Mancini, the company’s senior director and head of global marketing. For larger form factors, E Ink offers its Mobius active-matrix, thin-film transistor displays, developed in conjunction with Sony. Mobius displays weigh less than half of comparably-sized glass-based electronic paper displays, according to E Ink.

C3nano, a venture-funded startup based in Hayward, California, is completing its emergence from stealth mode with a booth at the SID conference. The company is touting the use of silver nanowires in flexible materials as an alternative to utilizing indium tin oxide. CEO Cliff Morris said C3nano chose silver nanowire technology, based on work from Professor Zhenan Bao’s chemical engineering laboratory at Stanford University, to produce transparent conductive transfer films and inks in its Activegrid line. The company on Monday announced a joint development partnership with Hitachi Chemical.

“Non-ITO transparent conductors are not only replacing ITO, but also provide functions that ITO cannot,” Jennifer Colegrove, CEO and principal analyst at Touch Display Research, said in a statement.

Morris said carbon nanotube nanowires are stronger than silver nanowires, yet don’t offer the clarity and transparency of their silver counterparts. And silver is easily available as a source material, he noted.

Corning had a number of product introductions at the show, including its new Lotus NXT Glass for high-performance displays. The company was also exhibiting its flexible Willow Glass, which can be mounted on a carrier glass with its proprietary bonding solution to provide curved displays for cellphones and other mobile devices.

Flexible displays – they could be coming to your smartphone, laptop, or tablet computer in the near future.

Solid State Watch: March 27-April 2, 2015

Friday, April 3rd, 2015
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Research Alert: October 14, 2014

Tuesday, October 14th, 2014

Revving up fluorescence for superfast LEDs

Duke University researchers have made fluorescent molecules emit photons of light 1,000 times faster than normal — setting a speed record and making an important step toward realizing superfast light emitting diodes (LEDs) and quantum cryptography.

This year’s Nobel Prize in physics was awarded for the discovery of how to make blue LEDs, allowing everything from more efficient light bulbs to video screens. While the discovery has had an enormous impact on lighting and displays, the slow speed with which LEDs can be turned on and off has limited their use as a light source in light-based telecommunications.

In an LED, atoms can be forced to emit roughly 10 million photons in the blink of an eye. Modern telecommunications systems, however, operate nearly a thousand times faster. To make future light-based communications using LEDs practical, researchers must get photon-emitting materials up to speed.

In a new study, engineers from Duke increased the photon emission rate of fluorescent molecules to record levels by sandwiching them between metal nanocubes and a gold film.

“One of the applications we’re targeting with this research is ultrafast LEDs,” said Maiken Mikkelsen, an assistant professor of electrical and computer engineering and physics at Duke. “While future devices might not use this exact approach, the underlying physics will be crucial.”

Mikkelsen specializes in plasmonics, which studies the interaction between electromagnetic fields and free electrons in metal. In the experiment, her group manufactured 75nm silver nanocubes and trapped light between them, greatly increasing the light’s intensity.

When fluorescent molecules are placed near intensified light, the molecules emit photons at a faster rate through an effect called Purcell enhancement. The researchers found they could achieve a significant speed improvement by placing fluorescent molecules in a gap between the nanocubes and a thin film of gold.

To attain the greatest effect, Mikkelsen’s team needed to tune the gap’s resonant frequency to match the color of light that the molecules respond to. With the help of co-author David R. Smith, the James B. Duke Professor and Chair of Electrical and Computer Engineering at Duke, they used computer simulations to determine the exact size of the gap needed between the nanocubes and gold film to optimize the setup.

That gap turned out to be just 20 atoms wide. But that wasn’t a problem for the researchers.

“We can select cubes with just the right size and make the gaps literally with nanometer precision,” said Gleb Akselrod, a postdoc in Mikkelsen’s lab and first author on the study. “When we have the cube size and gap perfectly calibrated to the molecule, that’s when we see the record 1,000-fold increase in fluorescence speed.”

Because the experiment used many randomly aligned molecules, the researchers believe they can do even better. They plan to design a system with individual fluorescent molecule placed precisely underneath a single nanocube. According to Akselrod, they can achieve even higher fluorescence rates by standing the molecules up on edge at the corners of the cube.

“If we can precisely place molecules like this, it could be used in many more applications than just fast LEDs,” said Akselrod. “We could also make fast sources of single photons that could be used for quantum cryptography. This technology would allow secure communication that could not be hacked — at least not without breaking the laws of physics.”

Smallest world record has ‘endless possibilities’ for bio-nanotechnology

Scientists from the University of Leeds have taken a crucial step forward in bio-nanotechnology, a field that uses biology to develop new tools for science, technology and medicine.

The new study, published in print today in the journal Nano Letters, demonstrates how stable “lipid membranes” – the thin “skin” that surrounds all biological cells – can be applied to synthetic surfaces.

Importantly, the new technique can use these lipid membranes to “draw” – akin to using them like a biological ink – with a resolution of 6 nanometres (6 billionths of a meter), which is much smaller than scientists had previously thought was possible.

“This is smaller than the active elements of the most advanced silicon chips and promises the ability to position functional biological molecules – such as those involved in taste, smell, and other sensory roles – with high precision, to create novel hybrid bio-electronic devices,” said Professor Steve Evans, from the School of Physics and Astronomy at the University of Leeds and a co-author of the paper.

In the study, the researchers used something called Atomic Force Microscopy (AFM), which is an imaging process that has a resolution down to only a fraction of a nanometer and works by scanning an object with a miniscule mechanical probe. AFM, however, is more than just an imaging tool and can be used to manipulate materials in order to create nanostructures and to “draw” substances onto nano-sized regions. The latter is called “nano-lithography” and was the technique used by Professor Evans and his team in this research.

The ability to controllably “write” and “position” lipid membrane fragments with such high precision was achieved by Mr George Heath, a PhD student from the School of Physics and Astronomy at the University of Leeds and the lead author of the research paper.

Mr Heath said: “The method is much like the inking of a pen. However, instead of writing with fluid ink, we allow the lipid molecules – the ink – to dry on the tip first. This allows us to then write underwater, which is the natural environment for lipid membranes. Previously, other research teams have focused on writing with lipids in air and they have only been able to achieve a resolution of microns, which is a thousand times larger than what we have demonstrated.”

The research is of fundamental importance in helping scientists understand the structure of proteins that are found in lipid membranes, which are called “membrane proteins.” These proteins act to control what can be let into our cells, to remove unwanted materials, and a variety of other important functions.

For example, we smell things because of membrane proteins called “olfactory receptors,” which convert the detection of small molecules into electrical signals to stimulate our sense of smell. And many drugs work by targeting specific membrane proteins.

“Currently, scientists only know the structure of a small handful of membrane proteins. Our research paves the way to understand the structure of the thousands of different types of membrane proteins to allow the development of many new drugs and to aid our understanding of a range of diseases,” explained Professor Evans.

Aside from biological applications, this area of research could revolutionise renewable energy production.

Working in collaboration with researchers at the University of Sheffield, Professor Evans and his team have all of the membrane proteins required to construct a fully working mimic of the way plants capture sunlight. Eventually, the researchers will be able to arbitrarily swap out the biological units and replace them with synthetic components to create a new generation of solar cells.

Professor Evans concludes: “This is part of the emerging field of synthetic biology, whereby engineering principles are being applied to biological parts – whether it is for energy capture, or to create artificial noses for the early detection of disease or simply to advise you that the milk in your fridge has gone off.

“The possibilities are endless.”

Printing in the hobby room: Paper-thin and touch-sensitive displays on various materials

Until now, if you want to print a greeting card for a loved one, you can use colorful graphics, fancy typefaces or special paper to enhance it. But what if you could integrate paper-thin displays into the cards, which could be printed at home and which would be able to depict self-created symbols or even react to touch? Those only some of the options computer scientists in Saarbrücken can offer.

They developed an approach that in the future will enable laypeople to print displays in any desired shape on various materials and therefore could change everyday life completely.

For example: A postcard depicts an antique car. If you press a button, the back axle and the steering wheel rim light up in the same color. Two segments on a flexible display, which have the same shape as those parts of the car, can realize this effect. Computer scientists working with Jürgen Steimle printed the post card using an off-the-shelf inkjet printer. It is electro-luminescent: If it is connected to electric voltage, it emits light. This effect is also used to light car dashboards at night.

Steimle is leader of the research group “Embodied Interaction” at the Cluster of Excellence “Multimodal Computing and Interaction”. Simon Olberding is one of his researchers. “Until now, this was not possible”, explains Olberding. “Displays were mass-produced, they were inflexible, they always had a rectangular shape.” Olberding and Steimle want to change that. The process they developed works as follows: The user designs a digital template with programs like Microsoft Word or Powerpoint for the display he wants to create. By using the methods the computer scientists from Saarbrücken developed, called “Screen Printing” and “Conductive Inkjet Printing”, the user can print those templates. Both approaches have strengths and weaknesses, but a single person can use them within either a few minutes or two to four hours. The printing results are relatively high-resolution displays with a thickness of only 0.1 millimeters. It costs around €20 to print on a DIN A4 page; the most expensive part is the special ink. Since the method can be used to print on materials like paper, synthetic material, leather, pottery, stone, metal and even wood, two-dimensional and even three-dimensional shapes can be realized. Their depiction can either consist of one segment (surface, shape, pattern, raster graphics), several segments or variously built-up matrixes. “We can even print touch-sensitive displays”, says Olberding.

The possibilities for the user are various: displays can be integrated into almost every object in daily life – users can print not only on paper objects, but also on furniture or decorative accessories, bags or wearable items. For example, the strap of a wristwatch could be upgraded so that it lights up if a text message is received. “If we combine our approach with 3D printing, we can print three-dimensional objects that display information and are touch-sensitive”, explains Steimle.

Research Alert: September 3, 2014

Wednesday, September 3rd, 2014

A new, tunable device for spintronics

Spin-charge converters are important devices in spintronics, an electronic which is not only based on the charge of electrons but also on their spin and the spin-related magnetism. Spin-charge converters enable the transformation of electric into magnetic signals and vice versa. Recently, the research group of Professor Jairo Sinova from the Institute of Physics at Johannes Gutenberg University Mainz in collaboration with researchers from the UK, Prague, and Japan, has for the first time realized a new, efficient spin-charge converter based on the common semiconductor material GaAs.

Comparable efficiencies had so far only been observed in platinum, a heavy metal. In addition, the physicists demonstrated that the creation or detection efficiency of spin currents is electrically tunable in a certain regime. This is important when it comes to real devices. The underlying mechanism, that was revealed by theoretical works of the Sinova group, opens up a new approach in searching and engineering spintronic materials. These results have recently been published in the journal Nature Materials.

Making use of electron spin for information transmission and storage, enables the development of electronic devices with new functionalities and higher efficiency. To make real use of the electron spin, it has to be manipulated precisely: it has to be aligned, transmitted and detected. The work of Sinova and his colleagues shows, that it is possible to do so using electric fields rather than magnetic ones. Thus, the very efficient, simple and precise mechanisms of charge manipulation well established in semiconductor electronics can be transferred to the world of spintronic and thereby combine semiconductor physics with magnetism.

Now, Sinova and his colleagues have shown that gallium-arsenide (GaAs), a very common and widely used semiconductor material, can be an as efficient spin-charge converter as platinum, even at room temperature, which is important for practical applications. Moreover, the physicists have demonstrated for the first time that the efficiency can be tuned continuously by varying the electric field that drives the electrons.

The reason for this – as theoretical calculations of the Sinova group have shown – lies in the existence of certain valleys in the conduction band of the semiconductor material. One can think of the conduction band and its valleys as of a motor highway with different lanes, each one requiring a certain minimum velocity. Applying a higher electric field enables a transition from one lane to the other.

Since the spin-orbit coupling is different in each lane, a transition also affects the strength of the spin-hall effect. By varying the electric field, the scientists can distribute the electron spins on the different lanes, thus varying the efficiency of their spin-charge converter.

By taking into account the valleys in the conduction band, Sinova and his colleagues open up new ways to find and engineer highly efficient materials for spintronics. Especially, since current semiconductor growth technologies are capable of engineering the energy levels of the valleys and the strength of spin-orbit coupling, e.g. by substituting Ga or As with other materials like Aluminum.

Copper shines as flexible conductor

By turning instead to copper, both abundant and cheap, researchers at Monash University and the Melbourne Centre for Nanofabrication have developed a way of making flexible conductors cost-effective enough for commercial application.

“Aerogel monoliths are like kitchen sponges but ours are made of ultra fine copper nanowires, using a fabrication process called freeze drying,” said lead researcher Associate Professor Wenlong Cheng, from Monash University’s Department of Chemical Engineering.

“The copper aerogel monoliths are conductive and could be further embedded into polymeric elastomers – extremely flexible, stretchable materials – to obtain conducting rubbers.”

Despite its conductivity, copper’s tendency to oxidation and the poor mechanical stability of copper nanowire aerogel monoliths mean its potential has been largely unexplored.

The researchers found that adding a trace amount of poly(vinyl alcohol) (PVA) to their aerogels substantially improved their mechanical strength and robustness without impairing their conductivity.

What’s more, once the PVA was included, the aerogels could be used to make electrically conductive rubber materials without the need for any prewiring. Reshaping was also easy.

“The conducting rubbers could be shaped in arbitrary 1D, 2D and 3D shapes simply by cutting, while maintaining the conductivities,” Associate Professor Cheng said.

The versatility extends to the degree of conductivity. “The conductivity can be tuned simply by adjusting the loading of copper nanowires,” he said. “A low loading of nano wires would be appropriate for a pressure sensor whereas a high loading is suitable for a stretchable conductor.”

Affordable versions of these materials open up the potential for use in a range of new-generation concepts: from prosthetic skin to electronic paper, for implantable medical devices, and for flexible displays and touch screens.

They can be used in rubber-like electronic devices that, unlike paper-like electronic devices, can stretch as well as bend. They can also be attached to topologically complex curved surfaces, serving as real skin-like sensing devices, Associate Professor Cheng said.

In their report, published recently in ACS Nano, the researchers noted that devices using their copper-based aerogels were not quite as sensitive as those using gold nanowires, but had many other advantages, most notably their low-cost materials, simpler and more affordable processing, and great versatility.

Competition for graphene

A new argument has just been added to the growing case for graphene being bumped off its pedestal as the next big thing in the high-tech world by the two-dimensional semiconductors known as MX2 materials. An international collaboration of researchers led by a scientist with the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) has reported the first experimental observation of ultrafast charge transfer in photo-excited MX2 materials. The recorded charge transfer time clocked in at under 50 femtoseconds, comparable to the fastest times recorded for organic photovoltaics.

“We’ve demonstrated, for the first time, efficient charge transfer in MX2 heterostructures through combined photoluminescence mapping and transient absorption measurements,” says Feng Wang, a condensed matter physicist with Berkeley Lab’s Materials Sciences Division and the University of California (UC) Berkeley’s Physics Department. “Having quantitatively determined charge transfer time to be less than 50 femtoseconds, our study suggests that MX2 heterostructures, with their remarkable electrical and optical properties and the rapid development of large-area synthesis, hold great promise for future photonic and optoelectronic applications.”

Wang is the corresponding author of a paper in Nature Nanotechnology describing this research. The paper is titled “Ultrafast charge transfer in atomically thin MoS2/WS2 heterostructures.” Co-authors are Xiaoping Hong, Jonghwan Kim, Su-Fei Shi, Yu Zhang, Chenhao Jin, Yinghui Sun, Sefaattin Tongay, Junqiao Wu and Yanfeng Zhang.

MX2 monolayers consist of a single layer of transition metal atoms, such as molybdenum (Mo) or tungsten (W), sandwiched between two layers of chalcogen atoms, such as sulfur (S). The resulting heterostructure is bound by the relatively weak intermolecular attraction known as the van der Waals force. These 2D semiconductors feature the same hexagonal “honeycombed” structure as graphene and superfast electrical conductance, but, unlike graphene, they have natural energy band-gaps. This facilitates their application in transistors and other electronic devices because, unlike graphene, their electrical conductance can be switched off.

“Combining different MX2 layers together allows one to control their physical properties,” says Wang, who is also an investigator with the Kavli Energy NanoSciences Institute (Kavli-ENSI). “For example, the combination of MoS2 and WS2 forms a type-II semiconductor that enables fast charge separation. The separation of photoexcited electrons and holes is essential for driving an electrical current in a photodetector or solar cell.”

In demonstrating the ultrafast charge separation capabilities of atomically thin samples of MoS2/WS2 heterostructures, Wang and his collaborators have opened up potentially rich new avenues, not only for photonics and optoelectronics, but also for photovoltaics.

“MX2 semiconductors have extremely strong optical absorption properties and compared with organic photovoltaic materials, have a crystalline structure and better electrical transport properties,” Wang says. “Factor in a femtosecond charge transfer rate and MX2 semiconductors provide an ideal way to spatially separate electrons and holes for electrical collection and utilization.”

Wang and his colleagues are studying the microscopic origins of  charge transfer in MX2 heterostructures and the variation in charge transfer rates between different MX2 materials.

“We’re also interested in controlling the charge transfer process with external electrical fields as a means of utilizing MX2 heterostructures in photovoltaic devices,” Wang says.

This research was supported by an Early Career Research Award from the DOE Office of Science through UC Berkeley, and by funding agencies in China through the Peking University in Beijing.

Roll over flat panel displays

Tuesday, March 25th, 2014

By Sara Ver-Bruggen, contributing editor

Flexible displays is a technological field that has been in R&D and pre-commercial development for several years, but what needs to happen to make volume production a reality, in areas including substrates, materials and production processes? Semiconductor Manufacturing & Design discussed the issues with Max McDaniel, Director and Chief Marketing Officer, Display Business Group, Applied Materials, Michael Ciesinski, MD of the Flextech Alliance, and Keri Goodwin, Principal Scientist from the Centre for Process Innovation (CPI), in the UK.

SemiMD: Taking a step back and looking at the timeline for flexible display R&D and achievements so far, where is the industry in terms of entering volume production – how close is the industry to resolving those outstanding challenges to volume production, such as cost-effective barrier technologies, for example?

McDaniel: Curved displays are here as evidenced by several curved smartphones and TVs showcased at the Consumer Electronics Show (CES) in January 2014. People are ready for flexible displays, but production volume will take some more time. As the smartphone market matures, brands are embattled in a ‘resolution arms race’. The key challenge for the brand makers is to come up with the next big thing that will differentiate their products and spur new demand from consumers. The display plays a key role in defining the device, and a new form factor – like flexible displays – can bring new opportunities to the market, but the technology is not ready for the mass market because of cost and technology challenges.

Ciesinski: FlexTech initiated its R&D program into flexible displays in 1998 with substantial project funding beginning in 2002 and continuing today. We’ve worked with companies and R&D organizations in the areas of substrates, encapsulation, barrier coating, roll-to-roll (R2R) manufacturing and other key areas. Generally, the supply chain for flexible electronics is adequate but not yet robust, which will occur once large volume production is achieved. In building flat panel displays (FPDs) that industry could build on IC manufacturing strengths and simply scale the equipment. For volume manufacturing on a flexible substrate, many new tools and processes have to be developed from scratch, such as metrology, as experts must build a system to account for a substrate that can shrink or expand depending on temperature, and move in multiple directions. As for barriers, several solutions are available and ready for production. The extreme requirements for OLED thin film barriers have been achieved in production and the main focus now is on cost reduction. The materials industry is quite competitive and ready for volume. In order to obtain better utilization of these materials in production new printing equipment is being developed.

Goodwin: There are still significant challenges to overcome in flexible display volume production. A cost-effective flexible barrier with a very low water transmission vapor rate (WVTR) is still to be developed, this will be required if OLED frontplanes are to be used. Typically these barriers are still multilayer structures with a mix of inorganic and organic coatings to minimize defect levels. While this can be achieved R2R, perhaps via a combination of sputter deposition and solution processing such as slot die, the cost will ultimately be set by the number of multiple coatings required.

An alternative method may be to use R2R atomic layer deposition (ALD), which should yield a significantly lower level of defects, thereby improving the barrier capability of a single layer and reducing, or removing, the need for multiple coatings. However, process scale up is required. CPI envisages that R2R ALD will play important roles in various aspects of flexible printable electronics, where highly conformal nanoscale thin films are required. CPI has been evaluating ALD technology for several years and recently signed an agreement with Beneq to deliver an ALD system to CPI for pilot scale production.

Layer-to-layer registration is another major challenge to overcome in volume production with flexible substrates typically distorting during processing. This issue can be overcome in several ways such as development of lower temperature processes or development of lamination materials to allow sheet-to-sheet (S2S) production without distortion.

And, in terms of commercialization for flexible (as opposed to curved) displays what time frame are we talking?

McDaniel: The approach for early adopters of flexible displays has been a production process that adheres the flexible substrate onto glass, running it through what’s mostly the normal rigid OLED processing, and then delaminating that flexible substrate from the rigid one at the end of processing. What remains is a flexible substrate that has all the transistor structures built onto it. However, this is still a complex process, and due to the cost and complexity involved in manufacturing on a high-volume scale, it is still a ways off from full mass production.

Goodwin: Overall, there are multiple approaches to volume production of flexible displays but all require scale up towards a commercialization solution, therefore it would be expected that the timeline for a product is still five years away. What is important in the short term is to demonstrate controlled processes that can yield products with good lifetime and performance, which then can be scaled up for commercialization.

Ciesinski: Displays in a conformable format have been produced and exhibited; a truly flexible and foldable display is much more than that and there are many approaches to achieving this result in the next few years.

Various flexible display R&D has focused on different substrates, different thin film transistor (TFT) materials and so on. Is there likely to be one approach that will make it to volume production?

Ciesinski: Multiple approaches are currently being considered by the market. For example, plastic substrate films from DuPont Teijin and other suppliers have a strong a presence. Corning’s introduction of flexible glass provides a competitive choice. As for the display technology, LCDs, OLEDs and electrophoretic displays have all been built in a flexible format. Materials will continue to improve and there will be multiple TFT materials for the next few years.

McDaniel: Materials have a key role to play in the R&D efforts for enabling flexible displays. OLED is promising as the rigid glass encapsulation required to protect the organic material from moisture and air can be replaced by thin film. You can make flexible LCD displays but maintaining the required cell gap between the color filter and backplane is very difficult to do. Both OLED and LCD require a TFT backplane. A major challenge for the industry is how to move away from rigid glass while not compromising the operation of the TFT when flexed, folded, or bent.

We have discussed the backplane and encapsulation; but for OLED to get to mass production (especially in large sizes); the industry also has to address challenges in EL evaporation such as lifetime of organic materials, low deposition efficiency, low yield from defects and scalability of evaporation technology which affect the cost of volume production but are not necessarily related to the issues around flexibility. All display technologies, including OLED displays, require very high levels of precision in film uniformity and particle control to maintain yield. There is the potential for OLED display production to become less expensive, and Applied Materials is leveraging its expertise in precision materials engineering to help solve these technology hurdles to reduce the cost and complexity.

Goodwin: It is likely that there will be multiple options for volume production. This will depend on final product requirements, such as limits of flexibility, level of resolution of display and cost of display. For example, metal oxide-based TFT displays already demonstrate high performance in terms of the TFT, and therefore can achieve high resolution displays, but ultimately will be very limited in the flexibility.

Organic electronics show excellent flexibility, but historically have tended to have a lower performance for OLED display backplanes and therefore may not achieve the same level of display resolution as metal oxide in the short term. More recently this gap in performance has been closed substantially making organic TFT backplanes a good candidate for a wide variety of display formats and resolutions. In addition OTFT backplanes may ultimately be a lower cost of production. Overall, it is likely that the different TFT technologies will independently develop the substrate types suitable for their processes, for example metal oxide on high temperature substrates and for organics the substrates are likely to be more flexible and suitable for lower temperature processes.

SemiMD: In terms of production equipment and tool advances, which technologies are most promising for enabling volume production of flexible displays?

Goodwin: Metal oxide is currently deposited via industrially used techniques/tools in the display industry, such as sputter deposition. This makes it a likely candidate for early adoption in the display industry, with moderate investment required to enable scale-up. However, solution-processing of organic based materials is likely to provide a lower cost of manufacture via the route of additive printing and R2R manufacture. CPI is working with a number of SMEs in building scale up capability across a range of printed and plastic electronics technology areas such as OLED, OTFT and barrier encapsulation, to help take forward new research ideas into technology prototypes and then into manufacturing demonstrators.

McDaniel: Flexible and other future bendable form factors in display will require precision engineered materials including thin film technologies that deliver performance with stringent uniformity and defect requirements at lower cost and less power. Advances in CVD and PVD systems for LTPS and metal oxide will play an important role in achieving high resolution but even these processes will require materials modification to support the full promise of flexible displays. One example of a required modification is indium tin oxide (ITO), a mainstay process step in TFT-LCD but as a material may prove to be too brittle in the production of more flexible displays.

Applied is also looking to help display makers mass produce larger scale, more efficient manufacturing processes and advanced materials as a means of gaining economies of scale at the factory.

Ciesinksi: FlexTech has funded and successfully completed projects for key steps in flex display manufacturing, such as lithography and deposition. Clearly various printing technologies and RTR additive manufacturing processes are capable of achieving major advances in flexible display production which will be seen over the next few years.

SemiMD: New display technologies that commercialise successfully have done so because they have enabled new products. The mass volume production of LCDs has helped to initiate smart phones, tablet devices, for example, while e-paper (E-Ink) display technology is largely responsible for e-reader devices such as the ubiquitous Kindle. So what potential new class of consumer/portable electronic device might flexible display technology enable? On the other hand, will the technology, in the nearer term, be more beneficial for enabling rugged/unbreakable display-based electronic devices?

McDaniel: There is a lot of potential. Think about what our phones looked like six or seven years ago. Now we’re seeing HD-quality screens on a device we can slip into our pockets. We could see flexible displays enabling devices that can be rolled up or folded into more compact shapes. Some studies have said that for a tablet, people prefer semi-rigid displays to something that is flopping around, to provide structure while they’re reading it. In the public environment flexible could bring the possibility of more immersive or interactive displays at airports or on billboards, or even on the sides of buildings. There are a lot of possibilities.

Goodwin: Rugged displays are likely to have military applications and so may attract funding support from this sector and therefore this may be a route to the first marketable products. However, the learning from the production of those rugged displays can likely be used within new mainstream product development. Many major display manufacturers are already trying to patent areas of interest such as smart watches and early products may focus on these smaller displays. Ultimately, if volume production is possible and large area displays can be produced then there is a vast range of products that can be envisaged from clothing applications, rollable/foldable phones, large scale advertising hoarding or even replacement of aircraft windows with lightweight displays.

Ciesinski: Technology adopters fall into several categories. For example, early adopters are those with the first cellular phone, the first tablet, etc. These users are willing to sacrifice elegance or product maturity for functionality. Other adopters waited until smart phones became fully functional before consolidating to a primary device from a combination of a PC, cell phone, and pager. Wearable electronics, as a class, represents a game-changing technology. A wearable device – even with limited functionality – is attractive, for example, to competitive athletes if it can help improve performance even modestly. Once wearable technology matures, it can explode into other markets to monitor the chronically ill, aged/infirm, or paediatric patients. Then, it jumps to the packaging or automotive or aerospace markets in the form of sensors.

Once flexible display technologies reach volume production, how fast might the technology establish itself – evolve from niche to mainstream?

Ciesinski: Successful technologies ramp quickly and displace incumbent technologies ruthlessly. Just consider the displacement of CRTs by FPDs or CCFL backlights by LED backlights. FlexTech believes that flexible electronics – of which flexible displays is a subset – will grow rapidly in multiple markets, led by disposable and wearable electronics. Our recent user survey indicated substantial purchases of flexible electronics by key end users within three years; adoption by large contract manufacturers is already taking place due to their customer demands.

Goodwin: This is likely to be dependent on the product uptake. For example the rise of tablets and smart phones drove the development of OLED frontplane and materials development. The same is likely to happen with flexible displays. Early products may have limited flexibility, for example the already available curved display products from LG and Samsung, but later products will need to show the truly flexible nature of these advanced displays. Once market pull is established a range of products are likely to be developed that will aid the flexible display to become a mainstream product. CPI can play a vital role in the move from niche to mainstream by providing the infrastructure and environment for companies to de-risk and scale up their innovative ideas from concept to market.

McDaniel: Five years ago, when display manufacturers wanted to start bending and curving the design, they faced a new set of struggles. Applied Materials had insights on where the market was heading and was already working on technologies to address the challenges. We have seen similar waves of technology with laptops and smartphones, and the acceleration of flexible or curved display devices or other form factors could take off in a similar manner. Display analyst firms are anticipating strong growth for the flexible and curved displays market over the next several years. For instance, Touch Display Research has forecast flexible and curved displays to achieve 16% of the global display revenue market by 2023 compared with 1% in 2013.

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