Assessing the Potential of
Flexible Electronics
“Flexible electronics” refers to electronic devices that can be bent, rolled, or folded without losing functionality. The term is largely coextensive, albeit not entirely synonymous with terms such as “plastic electronics” (commonly used in the United Kingdom [UK]), “organic electronics,” “OLAE” (organic and large area electronics, a term used in the European Union [EU]), and “printed electronics” and “printed intelligence” (Finland).1
ADVANTAGES OF FLEXIBLE ELECTRONICS
Flexible electronics is an emerging technology offering “completely new product concepts combined with low production costs, low energy consumption and environmentally friendly materials and processes.”2 It is a technology field with revolutionary potential. A blue-ribbon panel of U.S. scientists conducting a 2010 study of flexible electronics programs in Europe under the auspices of the World Technology Evaluation Center, Inc. (WTEC) observed that
[o]rganic/polymeric and inorganic flexible devices integrated in intrinsic and hybridized systems represent a highly promising interdisciplinary area of technology that will provide greatly increased functionality and potential to meet future challenges of scalability, flexibility, low power consumption, light weight,
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1 Although flexible electronics products commonly incorporate “organic” (carbon-based) materials, some of them also contain metals and metal oxides. Although most flexible electronics products are likely to be produced through roll-to-roll printing processes, some are currently being fabricated on conventional liquid crystal display and microelectronics production lines.
2 Valtion Teknillinen Tutkimuskeskus (VTT), Promoting Entrepreneurship in Organic and Large Area Electronics in Europe (2011), 4.
and reduced cost. . . . Application areas impacted by flexible electronics include energy (e.g., photovoltaic energy conversion systems and energy-efficient lighting), consumer electronics (e.g., portable flexible displays, sensors, and actuator), healthcare (e.g., low cost personal health monitoring systems), communications (e.g., radio-frequency identification systems), and national defense (e.g., networked sensing, intelligent and autonomous systems, and enhancement of individual warfighter capabilities). . . . There is excellent promise in all of these applications for reducing costs through manufacturing processes that utilize printing and lithography methodologies and through the combining of multiple functionalities.3
The dramatic potential of flexible electronics technology is widely acknowledged in the global scientific community.4
Functionality
Flexible electronics devices will be able to perform functions that conventional electronic devices cannot, including bending, rolling, folding, and stretching, and may ultimately be more durable. According to one account, an e-paper electronic sign in Japan survived the 2011 earthquake and tsunami and continued to “display emergency contact and note information long after other powered-displays fell dark.”5 Flexible electronics devices have enormous potential for use on and in the human body, not only because they enable stretchability, flexibility, and mechanical softness that cannot be achieved with silicon-based technologies, but also because organic electronics devices are more compatible with biological systems than silicon-based alternatives.6 Printed electronics devices will be able to incorporate multiple functions in a single device that are impossible for silicon devices, such as batteries, microphones and speakers, displays, and solar cells.7
Organic light-emitting diodes (OLEDs) are solid-state devices that emit light and can be mounted on a variety of flexible substrates for applications in displays and lighting. OLEDs have advantages over conventional light-emitting technologies that are leading to their deployment in an increasing number of applications. In the lighting field, conventional light-emitting diodes, the alternative
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3 WTEC Panel Report, European Research and Development on Hybrid Flexible Electronics, July 2010, v, xv. The study was commissioned by the National Science Foundation and the Office of Naval Research. WTEC is a nonprofit research organization originally spun off from Loyola University, Maryland, in 2001. It is the leading organization in the United States conducting international technology assessments through expert review. Its panelists typically are leading scientists in their fields.
4 See Robert H. Reuss, Babu R. Chalamala, et al., “Macroelectronics: Perspectives on Technology Applications,” Proceedings of the IEEE, July 2005.
5 “The Future of Stand-Alone E-Readers,” Flexible Substrate, November 2012.
6 Chemical Sciences and Society Summit, Organic Electronics for a Better Tomorrow: Innovation, Accessibility, Sustainability, September 2012, 14.
7 IDTechEx, Printed, Organic & Flexible Electronics: Forecasts, Players & Opportunities 2011-2021 (2011), 30.
form of solid-state lighting, are small, intensely bright, and operate at high temperatures, whereas OLEDs can be viewed directly, do not require the diffusers used to offset the brightness of LEDs, and operate at lower temperatures, arguably making them more suitable for a variety of lighting applications. With respect to displays, OLEDs offer numerous advantages relative to conventional liquid crystal displays (LCDs), including lower manufacturing and materials cost, ability to operate without a backlight (OLED circuits are light-emissive), lower energy consumption, lighter weight, and higher contrast ratios that enable sharper images.
More Efficient Manufacturing
The prospect that complex electronic devices can be fabricated through a comparatively simple printing process utilizing roll-to-roll (R2R) technology “represents a disruptive manufacturing technology [that] will make it possible to economically generate high value-added technology products at meters-per-minute rates on plastic film, paper or foil, achieving feature dimensions as small as 10 nanometers over areas encompassing billions of identical devices.”8 Most importantly, given the staggering investment costs associated with fabrication of silicon-based microelectronic devices, the prospect that comparable devices could be fabricated with comparatively inexpensive machines and processes intrigues policy makers, scientists, and established companies and entrepreneurs.9 (See Table 2-1.) Kent Displays, for example, an Ohio-based startup making flexible displays for consumer applications, is producing flexible consumer e-writing products using a roll-to-roll process that has minimized investment and production costs. Although a traditional liquid crystal display manufacturing plant requires investments of a billion dollars or more, the Kent Displays facility was built with capital investments of several million dollars.10
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8 Jeffrey D. Morse, Nanofabrication Technologies for Roll-to-Roll Processing: Report from the NIST-NNN Workshop (September 27-28, 2011), 3. Most printing methods available at present are adaptable to flexible electronics production, including inkjet, flexo, offset, and gravure. Printing is an additive process, that is, material is only deposited where it is required, and often there are only two stages between a bare substrate and a functioning layer of circuits on a substrate, a printing stage and a curing stage. By contrast, traditional photolithography, a subtractive process, involves multiple steps, materials, and machines to produce a single functioning layer on a bare substrate and consumes materials not needed in finished devices. “IDTechEx Releases Printed and Thin Film Transistors and Memory Report,” Flexible Substrate, February 2013.
9 Global Foundries’ Fab 8 in Malta, New York, a 300 mm wafer fabrication facility with an eventual capacity of 60,000 wafer starts per month, reportedly involved investments of $8.5 billion. Ajit Monocha, “Keynote Address,” National Research Council symposium, “New York’s Nanotechnology Model: Building the Innovation Economy,” Troy, New York, April 3, 2013.
10 Albert Green, Kent Displays, “Roll to Roll Manufacturing of Flexible Displays,” in National Research Council, Building the Ohio Innovation Economy: Summary of a Symposium (Washington, DC: The National Academies Press, 2013), 123-124. The NRC Committee on Best Practice in National Innovation Programs in Flexible Electronics visited Kent Displays, among other firms in the emerging northeast Ohio flexible electronics cluster, on June 4, 2013.
TABLE 2-1 Comparison of Electronics Processing Techniques
| Conventional | Printed |
| Subtractive batch process (sheet deposition with photolithographic and etched layers) |
|
| Controlled vacuum environment | Ambient temperature and pressure conditions |
| Fixed, long production runs of identical products | Flexible short production runs |
| High equipment, materials costs | Lower equipment and materials cost |
SOURCE: Zella King and Cathy Curling, “Plastic Electronics: Analysis of Competence Matrices for UK and Germany,” UKDL Newsletter, Winter 2008/2009.
Potential Eco-friendliness
Organic electronic products are expected to lead to more energy-efficient displays and other electronic devices, and inexpensive and highly versatile organic photovoltaics will enhance the ability of society to expand the use of renewable forms of energy not reliant on fossil fuels.11 A recent white paper released by the annual Chemical Sciences and Society Summit, which convenes “some of the best minds in chemical research from around the world,” observed that
[a]s chemists continue to study and improve their understanding of the electronic behavior of organic materials, engineers will be able to build devices that last longer and that are recyclable or perhaps even biodegradable.12
Although this prediction may or not be borne out by events, the adoption of organic electronics is likely to reduce E-waste and other environmental problems, such as the current reliance on rare-earth metals such as indium, the extraction of which sometimes results in environmental degradation.13
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11 CS3, Organic Electronics for a Better Tomorrow, 16.
12 CS3, Organic Electronics for a Better Tomorrow, 16.
13 The term “E-waste” embraces discarded information technology and consumer electronics hardware such as mobile phones, computers, printers, televisions, monitors, and other electronic equipment that contains carcinogenic and other toxic substances. The European Union alone generates an estimated 9 million tons of e-waste annually. E-waste contains toxic lead, mercury, cadmium, and other heavy metals, which can cause neurological damage. While the United States and the EU have rules that require recycling and prohibiting export of e-waste to developing countries, these rules are commonly dodged by “itchy-fingered traders, who effectively dodge recycling costs, and illegally export broken goods to developing countries.” “Illegal Trash Trade: E-waste Smuggling Contaminates Developing Countries,” Amman News, August 6, 2013; “Lust for Upgrades Builds a Mountain of e-waste,” Sydney Morning Herald, April 16, 2007; “Toxic Waste Shipped by UK Firm Still Lying at Port,” Kenya Daily Nation Online, August 5, 2013.
Flexible electronics have been cited in connection with an extraordinarily broad range of product applications where bendable and stretchable characteristics offer value.
- Photovoltaics. Photovoltaic panels that conform to curved or otherwise irregular surfaces offer numerous advantages over the heavy and rigid panels that account for most of today’s photovoltaic electricity generation. “Building-integrated photovoltaics” (BIPV) could allow photovoltaic laminates to be applied directly to building surfaces or incorporated in building products such as shingles and siding.14 Dr. Harry Zervos of the consultancy IDTechEx observes that “it will be easy to go to the local DIY shop and buy rolled or folded solar panels and fit them in the average family car to take them home. There will be no need to strengthen the home roof before installing such panels.”15 Current organic photovoltaics (PV) technology has reached conversion efficiency of 10-12 percent, and some researchers believe rates of 15-20 percent will be reached.16
- Lighting. OLEDs can be mounted on curved and bendable surfaces to provide lighting with versatility and energy efficiency superior to conventional forms of lighting. Although OLED lighting has not been widely introduced commercially, “limited release prototypes and commercial products have become available to demonstrate potential and allow interested users to try out OLED technology.”17
- Displays. Flexible displays will be developed that are nonbreakable, waterproof, rugged, and capable of being rolled up or folded for convenience. One much-discussed potential application is the ability to transform smartphones into much better computing platforms by adding a convenient larger display that can be rolled up or folded when not in use.18 Another application is flexible, roll-to-roll produced e-paper, which has already enjoyed some success on a trial basis when used to produce shelf tags for supermarkets. That said, “the flexible display market has not developed commercially as quickly as had been hoped, partially due to industry restructuring and competition from tablet computers.”19
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14 Currently some flexible BIPV products exist based on metal foils that are sufficiently durable for outdoor applications requiring long life. NanoMarkets LC, Flexible Substrate Markets: Special Report for the FlexTech Alliance, April 2012, 5. PELG and ESP KTN, Capability Guide: UK Plastic Electronics, 2012, 4–5.
15 “Flexible Electronics Is the Winner,” Printed Electronics World, March 2, 2011.
16 Chemical Sciences and Society Summit, Organic Electronics for a Better Tomorrow, 11.
17 OE-A, Organic and Printed Electronics, 13.
18 NanoMarkets, Flexible Substrate Markets: Special Report for the FlexTech Alliance, April 2012, 3.
19 OE-A, Organic and Printed Electronics, 14.
- Sensors. Sensors embedded in plastic tags are already being used in radio frequency identification (RFID) applications, and many RFIDs use antennae that are printed on flexible substrates. Sensors embedded in uniforms and other forms of clothing can be used for similar purposes. The firm Mc10, a startup founded by a materials scientist from the University of Illinois at Urbana-Champaign, has entered into a partnership with the sportswear maker Reebok “to develop clothes that can monitor impacts on the body, strains on joints, heart rate, blood pressure, and sweat pH.”20
- Medical devices. Flexible electronics have potential in many important applications, such as wearable health monitoring devices and medical implants. Medical patches and implants utilizing bendable and stretchable sensors can potentially monitor a wide range of biological functions.21
- Smart textiles. Flexible electronics technology may enable the creation of fabrics that can alter their characteristics in response to external stimuli, whether mechanical, thermal, electrical, chemical, or biological. “Currently much of this field is still in the development or prototype stage, with significant work going into areas such as stretchability and hybrid integration.”22
- Defense applications. Flexible electronics devices printed onto uniforms, including electronic readers, displays featuring high-quality photographs, maps, and other information, and communications devices would drastically reduce the loads soldiers carry. Flexible sensors can be placed on aircraft and vehicles to perform multiple functions. Printed photovoltaic devices on tents, buildings, and vehicles could generate local power, reducing the logistical demand for fuel.23 U.S. defense funds are being used to develop the “so-called Dick Tracy wristwatch, a flexible band to be strapped on soldiers’ wrists to provide communication, satellite images and Google Earth-type maps.”24
- Stretchable electronics. Electronic devices that can be stretched as well as bent without losing functionality have many potential applications. The company Mc10 is reportedly commercializing “stretchable skin” developed at the University of Illinois that contains sensors to monitor body functions and provide early warning of heart and brain problems
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20 “Stretchable Electronics: A Shapely Future for Circuits,” The Economist, March 10, 2011.
21 Brian Buntz, “TEDMED Update: Why the Future of Medical Electronics Is Flexible,” Electronic Components, April 12, 2012.
22 OE-A, Organic and Printed Electronics, 19.
23 “Army Researchers Creating Electronic Devices with Flexible Screens,” The Huntsville Times, March 10, 2013.
24 The Dick Tracy device is designed to continue working after being penetrated by a bullet, with the only loss of functionality occurring where the hole is located. “E-fabric Spools Bring Bullet-Proof Watches, Paper-Thin Batteries,” The Christian Science Monitor, April 15, 2011.
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before they occur, enabling real-time intervention by a doctor.25 In the automotive sector, rigid electronics components could be fabricated by stretching them to form during plastic molding, yielding lighter, smaller, and lower cost parts such as overhead lighting systems. Mercedes Benz is reportedly experimenting with stretchable electronic fabrics for use in vehicle interiors that could serve functions such as heating, cooling, and sensing presence.26
- Flexible batteries. Highly flexible batteries would enable the design of a broad range of products freed from the constraints of rigidity and weight that characterize conventional batteries. Flexible batteries could power wearable electronics, including wristbands and clothing, enable the design of slimmer electronics products, and provide a power source for digital smart labels, such as freshness detectors on food packaging.27
Current Commercial Applications
Although flexible electronics technology is still in its developmental stage, numerous applications are already present in the market. Korea’s LG Electronics and Samsung introduced curved OLED 55-inch televisions in 2013, designed to replicate the viewing experience of an IMAX movie.28 The two firms made announcements in 2013 of smartphones with curved displays.29 However, currently available “flexible” displays feature a flexible OLED layer beneath a rigid glass or plastic cover—the “rollable” screen does not yet exist in commercial application.30 Flexible e-paper displays are being used in e-books for e-readers such as Amazon’s Kindle, although sales have declined along with the sales of e-readers.31 Ohio’s Kent Displays reports brisk sales of its electronic e-Writer, a paperless erasable writing tablet known as the “Boogie Board” utilizing flexible liquid crystal display technology.32 Flexible organic photovoltaic solar panels have been commercially available since 2010 and are finding applications in
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25 “MC10 Develops Stretchable Skin to Monitor Health,” Flexible Substrate, November 2012.
26 Peter Harrup, “Stretchable Electronics and Electrics for Electric Vehicles,” Flexible Substrate, January 2013.
27 “Batteries Get Flexible,” Chemical and Engineering News, May 6, 2013; “A New Battery That Could Revolutionize Wearables,” GIGAom, January 8, 2013; “Flexible Battery-Like Films Could Someday Power Your Wearable Device,” GIGAom, April 28, 2014.
28 “LG Throws the OLED Competition a 55-inch Curve,” JoongAng Daily Online, April 30, 2013. “Samsung Unveils Curved OLED TV,” The Korean Times, June 27, 2013.
29 Samsung indicated it would introduce the Galaxy Round, a smartphone with a curved 5.7-inch OLED screen. LG has indicated it will begin mass producing “unbreakable,” bendable displays for smartphones. “Curved, Then Flex . . .” Flexible Substrate, October 2013. HSBC Global Research, Flexible Display: Fantastic Plastic—A Shape Shifting Game Changer, April 2013, 4–5.
30 “Financiers Focus on Flexible Displays,” Flexible Substrate, November 2013.
31 “Printed, Flexible and Organic Technology Sees 15.2% CAGR Over the Next Decade,” Solid State Technology, May 2013.
32 “Production Line Planned,” Akron Beacon Journal, March 2, 2012.
buildings.33 E Ink, a startup based on research originating at MIT, later acquired by a Taiwanese firm, reportedly will go into mass production of Mobius, “a large format (13.3″) digital paper display based on flexible thin-film transistor (TFT) technology developed by Sony.”34
Potential for “User Innovation”
The development of future markets for flexible electronics technologies is likely to be substantially influenced by what MIT’s Eric von Hippel has termed “user innovation”—that is, new products developed by users through improvisations on existing products to meet their particular needs, some of which may have much broader potential application.35 If past experience is a guide, users will innovate new products from existing flexible electronics products along a path that is not presently foreseeable. The process is slow in the early stages because “there aren’t a lot of users.” In that phase, small companies start up, founded by individuals with good user connections, and
then eventually big companies come in because, they say, now we have enough information about this market and we’ll get into it, maybe by acquiring one of those little companies—because new we know there’s a market of sufficient scale for us.36
Forecasting the future size and growth rates of flexible electronics markets is necessarily an inexact exercise. For many anticipated applications of flexible electronics technologies, no commercial products have entered the market or have done so in a very limited manner, so that no meaningful historical sales data exist upon which forecasts can be predicated. Past forecasts in this field have been repeatedly confounded by events.37 That said, a number of surveys have been undertaken that canvass large numbers of knowledgeable individuals, companies, and research organizations, and arguably represent an informed conventional wisdom. These forecasts envision the evolution of robust markets for flexible electronics products over the next 10-15 years.
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33 OE-A, Organic and Printed Electronics, 13–14.
34 “The Glass Is Half Full. . . ,” Flexible Substrate, May 2013.
35 An example of user innovation cited by von Hippel is the skateboard, created by users who pulled apart roller skates and fastened them to boards, creating a new sports/recreational technology. “The User Innovation Revolution,” MIT Sloan Management Review, Fall 2011.
36 Ibid., quoting interview with von Hippel. See generally Eric von Hippel, The Sources of Innovation (New York and Oxford: Oxford University Press, 1988); Eric von Hippel, Democratizing Innovation (Cambridge, MA: The MIT Press, 2005).
37 See essay by industry analyst Chris Williams, “Last Word: Who? Where? When? . . .” Flexible Substrate, December 2013. “Look at 3D TVs—seasoned professionals love the technology, and hype the benefits of it for consumer use, but the consumers themselves have had a look and said ‘no thanks.’”
IDTechEx, an extensively cited consultancy that has covered the field of printed, flexible, and organic electronics since 1999, released a report in mid-2013 that estimated that revenues from flexible electronics products would total about $16 billion in 2013, with most of the income derived from OLED displays, e-paper, flexible photovoltaics, and conductive ink.38 IDTechEx estimates that between 2013 and 2023, the total market for these products would grow to $76.8 billion, or a compound annual growth rate of 15.3 percent.39 Other estimates envision a much higher growth rate.40 For example, Smithers Pira, the global authority on packaging, paper, and print industry supply chains, forecasts that the market for plastic and printed electronics will be $190.0 billion in 2025.41 Looking further ahead, IDTechEx predicts that the market for printed and potentially printed electronics could be “larger than the silicon semiconductor industry, which is not a surprise given that it is applicable to so many things.”42 The consultancy forecasts a market valued at $340.0 billion by 2030. (See Table 2-2.)
Industry observers caution that in addition to the dearth of historical sales data to buttress such forecasts, the market potential for flexible electronics products will be determined, in significant part, by the performance characteristics of the devices themselves in competition with conventional rigid electronics products.43 Cost relative to that of competing conventional devices is currently a major hurdle for flexible electronics consumer applications and may act as a longstanding drag on market growth unless current equipment, process, and yield challenges are surmounted.44
A 2011 study by Germany’s National Academy of Science and Engineering concluded that “organic and large area electronics are forecast to have a global
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38 IDTechEx engages in consultancy in the fields of organic, inorganic, and hybrid electronics, which are manufactured through printing processes or have such potential. It studies related topics such as smart packaging, silicon photovoltaics, and RFID. IDTechEx annually stages the world’s largest conferences on printed electronics topics in North America, Asia, and Europe. It publishes periodic reports on topics and subtopics associated with printed electronics and an online newsletter, Printed Electronics World, <http://www.idtechex.com>.
39 “Printed, Flexible and Organic Electronics Sees 15.3% CAGR,” Printed Electronics World.
40 In 2013, the consultancy IHS Electronics & Media forecast that the global flexible display market alone would reach a value of $67.7 billion by 2023, nearly equivalent to the $76.8 billion forecast by IDTechEx for that year for the entire flexible electronics industry. “Flexible Display Market to Reach $67.7 Billion by 202, Says HIS,” Flexible Substrate, November 2013.
41 Adam Page, Smithers Pira, “Market for Organic and Printed Electronics,” in OE-A, Organic and Printed Electronics, 34.
42 IDTechEx, Printed, Organic & Flexible Electronics, 5.
43 “Flexible displays are going to face a tough challenge if design groups focus on creating devices that use them in applications that already successfully use rigid displays. Unless there is a very compelling reason, people rarely are willing to sacrifice to display performance they are accustomed to viewing. So long as making displays flexible results in diminished visual performance, it’s going to be a tough sell to convince people that a rollability or foldability feature is justification. . . .” Mark Fihn, “Visual Excitement . . . ,” Flexible Substrate (September 2012).
44 “Slim Leap Forward,” South China Morning Post, September 28, 2012; “Flexible AMOLEDs: At the Tipping Point?” The Emitter: Emerging Display Technologies, March 10, 2014.
TABLE 2-2 IDTechEX Market Forecasts for 2030
| Segment | Projected Sales (Billions of Dollars) |
| Logic/memory | 100 |
| OLED display | 100 |
| Photovoltaic | 70 |
| OLED light | 30 |
| Electrophoretic | 14 |
| Sensors | 6 |
| Battery | 5 |
| Conductors (ink only) | 4 |
| Other display | 2 |
| Electroluminescent | .5 |
| Electrochromic | .5 |
| Other | 8 |
| TOTAL | 340 |
SOURCE: IDTechEX, Printed, Organic & Flexible Electronics Forecasts, 7.
market volume of several hundred billion euros in the medium and long term, corresponding about to the economic importance of the current conventional silicon-based electronics.”45
OE-A is a leading international industry association for printed and organic electronics. Although based in Europe, it is comprised of more than 200 companies that include firms based in North America, Asia, and Australia representing various segments of the value chain in the field of flexible electronics.46 OE-A publishes periodic applications “roadmaps,” prepared with the participation of its membership, which forecast what is seen as the likely evolution of the organic and printed electronics industry.47 (See Table 2-3.) Given the breadth and depth of OE-A’s membership, its most recent roadmap, released in June 2013, is likely to reflect current industry views about how the industry’s applications will develop in the coming decade. As the roadmap indicates, although some significant new
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45 acatech, Organic Electronics in Germany: Assessment and Recommendations for Further Development, 2011, 12.
46 OE-A members include 167 organizations in Europe, 11 in Asia, 28 in North America, and 1 in Australia. Andrew Hannah, Building a Global Network for the Printed Electronics Industry, 2013.
47 The 2013 OE-A Roadmap, the fifth in the series, is based on the work of teams of experts in each of five applications clusters, who developed roadmaps for their sectors. These results were presented to and discussed with OE-A members during the association’s meetings. “The resulting roadmap is a synthesis of those results representing common perspectives of these groups.” OE-A, Organic and Printed Electronics, 10.
TABLE 2-3 OE-A Roadmap for Organic and Printed Electronics Applications (2013)
| Theme | 2013 | 2014-2016 | 2017-2020 | 2021 + |
| Organic photovoltaics | Portable chargers | Consumer electronics | Specialized building integration, off grid PV | Building integration, grid-connected PV |
| Flexible displays | Integrated into smart cards, price labels, bendable color displays | Bendable OLEDs, plastic LCD, large area signage, rollable color displays | Rollable OLEDs, transparent rollable displays, flexible consumer electronics | Rollable OLED TVs, telemedicine |
| OLED lighting | Design projects | Transparent and decorative lighting modules | Flexible lighting | General lighting technology |
| Electronics | Single-cell batteries, memory for interactive games, ITO-free transparent conductive films | Rechargeable single-cell batteries, transparent conductors for touch sensors, printed reflective displays | Printed multicell batteries, printed logic chips, integrated flexible multitouch sensors | Directly printed batteries, active and passive devices to smart object |
| Integrated support systems | Garments with integrated sensors, anti-theft, brand protection, printed test strips, physical sensors | Integrated systems on garments, large area physical sensors arrays and mass market smart packaging | Textile sensors on fiber, dynamic price displays, NFC/RFID smart labels, disposable monitoring devices | OLEDs on textiles, fiber electronics, health monitoring systems, smart buildings |
SOURCE: OE-A, Organic and Printed Electronics.
applications are likely to become available commercially in the next 1-3 years, such as “intelligent packaging,” the most dramatic applications, such as rollable televisions and grid-connected organic photovoltaic systems, may be a decade or more away. OE-A comments that organic electronics technology
is still in its early stage; while increasing numbers of products are available and some are in full production, many applications are still in lab-scale development, prototype activities, or early production.48
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48 OE-A, Organic and Printed Electronics, 10.
A basic challenge facing companies seeking to commercialize flexible electronics technologies is the fact that the conventional technologies they are challenging continue to evolve and improve. By the time the UK firm Plastic Logic was ready to announce its e-reader Que, featuring flexible e-paper in early 2010, “Steve Jobs unveiled the iPad and with it effectively blew Plastic Logic out of the water.”49 At a 2011 industry conference on organic photovoltaics (OPV), assumed to be far less costly than silicon and thin-film PV, it was observed that the costs of the latter were falling rapidly and that “by the time we have large scale production of OPV, crystalline silicon PV could be living without subsidies.”50
Flexible electronics are widely acknowledged to have generated “a great deal of hype,” particularly in the years preceding the onset of the global financial crisis in 2008.51 Optimistic forecasts of explosive commercial growth did not materialize.52 New product introductions have been announced but then delayed, usually for technological reasons.53 Lawrence Gasman, founder of the consultancy NanoMarkets LC, commented in early 2013 that “the history of flexible displays over the past decade has already been one of the broken promises, mostly because of technological issues, and in 2012, it became apparent that the supposed ‘killer app’ for flexible displays probably didn’t have as much potential as was once thought.”54 Although the financial crisis was a factor affecting the lower than normal rate of commercialization of flexible electronics products, technological hurdles have proven more daunting than was recognized a decade ago. Kenneth Warner, founder of the consultancy Nutmeg Consultants, specializing in displays, commented in November 2013:
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49 “Why Plastic Logic Failed—Despite the E-book Boom,” GigaOM, May 17, 2012.
50 “Organic PV: Closing the Reality Gap,” Optics.org, September 6, 2011.
51 Adam Page, Smithers Pira, “Market for Organic and Printed Electronics,” in OE-A, Organic and Printed Electronics, 34. The New York Times predicted in 2001 that “thin flexible batteries may soon be plastered on cardboard or plastic surfaces, producing novelty packaging items like cereal boxes that twinkle with light-emitting diodes or containers that advertise their wares by playing brief jingles.” “What’s Next: Batteries Push Paper Into Electronics Age,” The New York Times, May 24, 2001.
52 “Earlier roadmaps for printed electronics have been almost entirely erroneous. It is not primarily about cost reduction, nor is there a trend toward organic versions taking over most applications.” “Printed Electronics—Many New Directions,” Printed Electronics World, February 21, 2011. The principal factor frustrating the realization of the roadmaps has been underestimation of the technological obstacles entailed.
53 UK-based Plastic Logic announced an e-Reader with a flexible display in 2010, but subsequently announced that the commercial release would be delayed indefinitely. In 2011, Korea’s Samsung told industry analysts that it would introduce handsets featuring flexible displays “sometime in 2012, hopefully the earlier part than later,” but a year later reported that the technology was still “under development.” “Samsung’s Courtship of Apple Parts Suppliers May Drive Up Costs,” The Argus, May 16, 2013; “Flex is Next,” San Jose Mercury News, January 17, 2011.
54 Lawrence Gasman, “Notable Developments in Flexible Glass,” Flexible Substrate, January 2013.
What is delaying the introduction of flex-many products? The answer is almost everything. Not only must the display itself (including the backplane and barrier film) be flexible and not deteriorate over many flexing cycles, but so must the other components of the device, including the touch screen, circuit boards and battery. Hard switches and buttons must either be eliminated or designed to work with a flexing substrate and, perhaps, case. None of this is easy, but solving the problems are where the product and investment opportunities lie.55
Encapsulation
Flexible electronic circuits are likely to be made of organic materials that are highly vulnerable to contamination from exposure to oxygen and water vapor. Although rigid electronic devices can be protected by encapsulating them in glass or other hard materials, encapsulation of flexible circuits poses greater challenges. Plastic tends to be permeable and may degrade in demanding environments. Flexible glass may be an alternative but, at present, is expensive, as are other specialized encapsulation alternatives.56 Flexible electronics products such as OLED lighting systems and devices incorporating flexible memory, logic, and battery functions “still need better flexible barrier films to extend their useful lifetimes.”57 OE-A declared in its roadmap that “barrier properties of flexible, low-cost encapsulation need to be strongly improved to enhance the lifetime of the devices.”58
Functional Materials
Conventional electronic devices are fabricated with conductive elements made of metal or metal oxides on rigid substrates, usually processed at high temperatures. The transition to flexible electronics requires the creation of circuits that do not lose functionality when bent, folded, or rolled. The use of flexible plastic substrates precludes fabrication processes involving temperatures so high that they deform the substrate. Identification of materials and processes capable of surmounting these physical limits has proven a universal challenge.
Indium tin oxide is one of the most widely used conductors in conventional electronic devices, with applications in displays, lighting, and photovoltaics.
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55 “Financiers Focus on Flexible Displays,” Flexible Substrate, November 2013.
56 NanoMarkets, Flexible Substrate Markets: Special Report for the FlexTech Alliance, April 2012, 9–10.
57 Several promising efforts to address this challenge have been reported. These include flexible glass developed by Corning and novel coatings being developed by Beneq Oy and Vitriflex. Beneq Oy reports that thin atomic layer deposited (ALD) inorganic coatings “have shown to provide excellent moisture barrier properties on flexible substrates.” “Sealing Up ALD Moisture Barrier Technology,” Flexible Substrate, May 2013. “Printed Electronics Sector Takes a Hard Look at the Flexible Future,” Solid State Technology, March 2013.
58 OE-A, Roadmap for Organic and Printed Electronics, reproduced in OE-A, Organic and Printed Electronics, 28.
However, although ITO circuits can bend slightly without loss of functionality, they are probably too brittle for use in rollable or foldable applications, and ITO has other major disadvantages.59 An alternative is the use of printed metallic conductive inks, but these, too have drawbacks—silver, which is highly conductive, is expensive, and various alloys of aluminum, copper, and nickel (including silver-coated variants) involve trade-offs in workability, conductivity, and reactivity.60
Ordinary forms of carbon are barely conductive compared to silver, although carbon pastes can be blended with silver to reduce cost, adjust conductivities in specialized applications, and inhibit electromigration. However, in terms of performance carbon-based conductive materials are not competitive with silver. Exotic carbon nanoparticles, including graphenes and carbon nanotubes, are highly conductive and have the potential to form flexible circuits, but “the production of carbon nanomaterials is still pretty complicated, at least of the conductive forms.”61 In many respects ranging from energy efficiency to materials resource requirements, flexible electronics promises to be more environmentally friendly than silicon-based electronics. However, “many polymers require carcinogenic solvents, including some not allowed in the EU printing industry because of their toxicity.”62 Although the extent of the problem of toxicity associated with flexible electronics is not clear, given the incipient state of the industry, a general challenge in flexible electronics is developing polymers that are soluble in nontoxic solvents and “rely on more benign methodologies in general.”63
Manufacturing Hurdles
The manufacture of flexible electronics devices offers numerous potential advantages in terms of lower cost and high volume throughput. However, the fabrication of complex flexible electronic devices poses challenges for which solutions have not yet been found and which could delay the widespread commercial introduction of many products. Even the manufacture of flexible displays on conventional thin-film transistor production lines poses an array of technical
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59 China, one of the world’s principal suppliers of indium, has maintained export restrictions on rare earth metals including indium for a decade, driving up its cost and raising concerns about its availability. “S. Korea to Speed Up Overseas Development of Indium,” Yonhap, May 11, 2011; “Scrambling for Raw Materials: EU Plans Measures to Tackle Resource Crunch,” Spiegel Online, November 20, 2010. “ITO, if flexed too much, tends to crack, so for truly flexible displays, ITO cannot be used.” NanoMarkets, Special Report for the FlexTech Alliance: Transparent Conductor Market, December 2012.
60 NanoMarkets, Silver Inks and Pastes Markets: Special Report for the FlexTech Alliance, February 2012, 810.
61 Ibid., 8-9.
62 Royal Society for Chemistry, “Organic Electronics for a Better Tomorrow” September 2012. Access at http:www.rcs.org.
63 NanoMarkets, Silver Inks and Pastes Markets: Special Report for the FlexTech Alliance, op. cit., p. 8-9.
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difficulties.64 In early 2014, the chronically low yield rates in the production of flexible AMOLED (active matrix organic light-emitting diode) displays was cited as the principal factor underlying the huge cost differential between AMOLED and conventional rigid displays.65
Roll-to-roll processing techniques for flexible electronics are widely discussed, but “layer-to-layer registration with a conventional deposition and patterning process remains a formidable challenge when the film is handled in this way.”66 The U.S. Army–supported Flexible Display Center at Arizona State University encountered extreme difficulty in immobilizing plastic substrates sufficiently to enable deposition of amorphous silicon transistor arrays, and overcoming this hurdle was the object of a dozen separate research programs undertaken by the Center and its research partners. A National Institute of Standards and Technology–sponsored workshop in September 2011 convened a group of 30 U.S. experts in roll-to-roll manufacturing to identify the “key barriers to the adoption of nanofabrication processes within R2R manufacturing processes.”67 The workshop concluded that although many U.S. companies are engaged in R2R manufacturing, there was a general lack of standardized infrastructure, most universities did not have R2R fabrication facilities, and data were lacking on what could and could not be achieved using R2R processes. In addition, certain process tools and core capabilities presented “challenges,” and “the supply chain has not been established.”68
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64 Nick Colaneri from the Flexible Display Center at Arizona State University recently noted that the heat sensitivity of polymer films required the development of systems for handling them and process steps to avoid exceeding their temperature limits. The Flexible Display Center has developed potential solutions, and he indicates that the first flexible high-resolution displays to enter the commercial market will utilize “materials handling techniques that have been developed to allow use of this existing film transistor fabrication facility.” However, he notes, “these techniques are still under intensive development, including the evaluation of the relative merits of different design trade-offs.” Nick Colaneri, “Manufacturing Flexible Displays: The Challenges of Handling Plastic,” Solid State Technology, May 1, 2013.
65 “[M]anufacturing costs for flexible AMOLED displays are a multiple of equivalent size rigid panels.” “Flexible AMOLEDs: At the Tipping Point?” The Emmitter: Emerging Display Technologies, March 10, 2014.
66 Colaneri, “Manufacturing Flexible Displays.”
67 InterNano, “Accelerating Progress for Advanced Manufacturing,” June 28, 2012.
68 Equipment and competency challenges identified included large-area, cost-effective, e-beam patterning tools/capabilities; plasma etching tools for large-area, uniform R2R processing; ink jet applicators compatible with wide range ultraviolet monomers; development of high-quality nickel metal electroforming processes for high aspect ratio, large pattern volume structures; high durability, low-cost transparent imprinting of molds, or inexpensive/fast replacement transparent molds; fabrication of seamless cylindrical imprint molds; large area, real-time metrology and process characterization, etc. Jeffrey D. Morse, Nanofabrication Technologies for Roll-to-Roll Processing: Report from the NIST-NNN Workshop, September 27-28, 2011.
Substrates
The use of bendable substrates for electronic devices offers numerous advantages, including the potential for manufacturing on a roll-to-roll basis and applications requiring flexibility. However, although the use of traditional electronic conductive materials requires heating, plastic substrates cannot be processed in high-temperature environments. Moreover, the bendability that makes flexible substrates attractive, as well as surface characteristics, makes it more difficult to ensure the adhesion of inorganic and organic coatings. Paper, sometimes discussed as an alternative to plastic, is rough, porous, dimensionally unstable, and characterized by poor barrier characteristics.69
Device Performance
The consultancy IDTechEx released a report in 2013 indicating that although many types of electronic components are being produced through various printing processes (including batteries, PV devices, interconnects, memories, antennas, and energy harvesters), “in many cases the performance is not as high as their non-printed counterparts and therefore businesses are leveraging their other characteristics, including potential for low cost, large-area coverage and flexibility.”70 Current flexible displays “are almost always compromises on visual performance.”71
The vast preponderance of government financial support for flexible electronics that is catalogued in this report is flowing toward research projects to address these technological challenges, usually through industry-university-governmental collaborations.
Market Uncertainty
Flexible electronics is an emerging field characterized by a multiplicity of potential applications, manufacturing processes, and base materials, and the direction in which the industry or industries will evolve is not at all clear. There are no commonly accepted base materials and methods that characterize most of the semiconductor industry (e.g., complementary metal oxide semiconductor devices fabricated through photolithography). These uncertainties have deterred investment in flexible electronics and will continue to do so in the future, a factor
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69 Department for Business Enterprise and Regulatory Reform, Plastic Electronics in the UK: A Guide to UK Capability, 2008/09, 9.
70 “The performance of printed transistors is also below par today. Their mobility is limited to <0.1 cm2/Vs in most cases. Their lifetime and stability are poor and they often need expensive encapsulation layers. Indeed their performance may not yet be adequate today for the obvious target markets of large-sized display backplanes and RFID tags.” “IDTechEx Releases Printed and Thin Film Transistor and Memory Report,” Flexible Substrate, February 2013.
71 Mark Fihn, “Visual Excitement . . .” Flexible Substrate, September 2012.
underlying the conclusion by the President’s Council of Advisors on Science and Technology (PCAST) that flexible electronics is a sector that may well not develop if left to market forces.72
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72 PCAST, Report to the President on Ensuring American Leadership in Advanced Manufacturing (June 2011), 19–20. Stephen Freilich, Director of Materials Science and Engineering for DuPont Central Research and Development, observes that “[f]rom a materials supplier’s standpoint [in a new technology field] there can be a disincentive to do truly revolutionary work when you see this rapid change in markets and technologies. We can do it, but the investment is so great, and rate of return so dependent on the longevity of the technologies that you’re not going to see the kind of innovation you need.” He indicates that in such situations companies will limit themselves to incremental changes in existing materials and technologies. Steven C. Freilich, “DuPont Reflections on Photovoltaics,” in National Research Council, The Future of Photovoltaic Manufacturing in the United States (Washington, DC: The National Academies Press, 2011), 68.
