Printed electronics sector takes hard look at the flexible future

The flexible and printed electronics community reports encouraging progress in the materials and process ecosystem needed for commercial production — and an increasingly realistic focus on applications that best capitalize on the technology’s strengths. Best near-term prospects now look to be sturdy light-weight displays, smart sensor systems, and flexible and large area biomedical sensors and imagers.

Improving technology for everything from barrier films to roll-to-roll in-line testing may mean printed or flexible electronics will start to see some more significant commercial applications in the next few years. Judging from the reported status of sturdy lightweight displays, smart-enough sensor tags, and medical sensors and imagers at FlexTech Alliance’s annual conference last week in Phoenix, suppliers are increasingly targeting higher-value applications that can’t easily be made in other ways.

Light-weight, Rugged Displays

“This industry is starting to become reality,” asserted Plastic Logic CEO Indro Mukerjee, “We’ve moved from a science project to an industrial process, and have created a value chain with partners to make the business possible.”  He has moved the flexible display company away from marketing its own e-reader to supplying its electrophoretic display on flexible backplane module to a wide range of new users, now working with partners making outdoor signs, watches, automobiles, smart cards, and industrial indicators. He’s also promoting the company’s flexible TFT backplane for use in other markets, and aggressively pursuing LCD makers to transfer the production process for scaling. “The technology frontier business is not for the faint hearted,” he noted. “We’re going for it at Plastic Logic.” 

Growing into Major Markets: Will Take Time

Flexible and transparent displays will be the next big thing in displays, and will start to see real growth after 2015, to account for 19 percent of the display market by 2020, projected Sweta DashIHS senior director, Display Research and Strategy. She noted that Samsung and LG planned to start production, to some degree at least, of displays on unbreakable substrates this year for smart phones and tablets, targeting lighter weight and better durability.  IDTechEx senior technology analyst Harry Zervos figured only 1 percent of the large OLED display market would be either printed or flexible by 2018, but 12-14 percent would be so within ten years.  Though the same technologies will help the cost and performance of OLED lighting and organic PV, these applications, however, still seem a little further from significant commercial products. In five years, IDTechEx projects OLED lighting to reach a ~$120 million market, with flexible batteries, logic and memory, and solar all in the $50-$60 million range. 

Most of these flexible products still need better flexible barrier films to extend their useful lifetimes, and new transparent conductors to replace brittle ITO. Barrier films appear to remain problematic, but progressing. The sector has big hopes for lower cost ALD films, and Beneq Oy reported progress on cross flow technology for batch processing, with capacity to coat 35 2G-sized sheets with 50nm of Al2O3 in three minutes.  It has also scaled up a roll-to-roll (R2R) system, by separating the precursor gases by space instead of time, for coating several meters per minute. Best results for its 25nm Al2O3 barrier are 10-4g/m2/day. Vitriflex CEO and founder Ravi Prasad said its mixed-oxide thin-film stack with a novel top seal made by low-cost R2R sputtering on polymer film had been tested at independent labs at better than the industry target 10-5 g/m2/d. Sean GarnerCorning Inc. research associate, reported good results from initial runs of common material stacks on its rolls of 50-100nm flexible glass at pilot and research R2R printed electronics facilities. Wire grids and possibly silver nano wires appear to look like the best options for ITO replacement. 

Integrating Components into Flexible Systems

Beyond the display market, the major enabler for other printed applications is the ability to efficiently integrate various separate components into useful systems, and here Thin Film Electronics and its partners now target smart sensor tags, roll-to-roll printed in large volumes. The key market for printed electronics will not be large area devices that need very good yields, but instead simple devices in very large numbers, argued Thin Film CEO Davor Sutija

The company and its partners aim at  the ~$1.4 billion time and temperature sensor market, with tags potentially combining printed memory from Thin Film, organic logic from PARC, a printed thermistor from PST Sensors, and an electrochromic display from Acreo. Thin Film is also partnering with major packaging supplier Bemis to develop and market such smart packaging applications.  A more developed commercial product version of the current proof-of-concept demonstrator is targeted for 2014.

Shippers currently use simple color-changing tags to indicate if perishable shipments have gotten too hot or too cold in transit, but the information is limited and the color doesn’t last long. Simple printed systems of sensors plus memory and some 500-1,000 transistors of logic could be R2R printed at high volumes to record and display more usefully precise information than current alarm tags or data loggers, at lower cost than silicon. Similar simple tags for smart objects to store small amounts of actionable information could also be used for things like dynamic price displays, pharmaceuticals or logistics. Sutija optimistically projects smart sensor tags will be a 60 million unit market by 2014, and reach some 2 billion units by 2016, worth some $300 million — suggesting a ~$0.15 per tag price at those volumes. 

The company’s well established memory technology uses a ferroelectric polymer sandwiched between top and bottom electrodes that changes and maintains its state of capacitance when pulsed.  It has also developed much of the manufacturing infrastructure as well, including a  high-speed R2R step-and-go electrical test system based on a print web handling tool, and a hard scratch UV varnish coating to protect the memory, with a key flexible layer underneath to minimize the mechanical stress. 

Another approach to integrating components into flexible systems is to attach silicon chips to the flexible substrate, which could be easier if the chips were flexible. American Semiconductor and TowerJazz are currently qualifying a commercial foundry process for flexible silicon-on polymer CMOS, which will offer multi-project wafer runs to ease development. American Semiconductor CEO Doug Hackler said characterization of first wafers shows no shift in transistor performance of the flexible wafers, and that in fact removing the handle layer of the SOI wafer appeared to reduce parasitic capacitance and improve performance for RF devices.  It’s currently working on systems using the flexible chips in a smart conformable antenna with the Air Force Research Lab, and a flexible smart card with security card supplier ASI.

Flexible Medical Devices with Hybrid Approaches

Research efforts are targeting medical applications that require flexibility to comfortably wear on the body or wrap around it for measurement, such as MRI coils, or better collect data from inside it, via catheters or endoscopes or pills but that often need to be integrated with silicon-quality processing or communications.  FlexTech announced it was awarded a $5 million grant for a Nano-Bio Manufacturing Consortium, sponsored by the U.S. Air Force Research Lab, to bring together the diversity of players needed for cooperative R&D to develop a common manufacturing platform for microfluidics on flexible substrates for wearable sensors for monitoring human response, integrating wireless communication with hybrid electronics manufacturing.

MC10 is launching its first product, an impact monitoring device developed and marketed with Reebok, for inside a sports helmet to indicate when the wearer has had a high impact to the head, reported R&D VP Kevin Dowling. The company is also testing attaching its flexible sensors to catheter balloons, for interventional devices than can be inflated once inside the body. For example, these could be used to measure atrial fibrillation, to determine if an ablation treatment worked, or to send back a fuller map of electrical data from the beating heart than possible from one or two electrodes.  MC10’s approach is not to print the electronics, but to embed thinned silicon die with flexible wire connections in rugged polymer to make its flexible systems.  The chips are under-etched, released, and then transferred to the mold substrate, using transfer tools for the thinned die the company developed in house.

MC10, and a host of other researchers, with both hybrid systems and fully printed ones, are also working on measuring a wide range of vital signs with flexible skin patches or other units adhered to the skin, for condition monitoring, often sending the data to a smart phone for analysis. Ana Arias of the University of California at Berkeley showed good results with a flexible finger sensor to measure blood oxygenation with red and IR sources and detectors, and also printed MRI coils on flexible substrates that could wrap conformably around different sized people and body parts to get better images more quickly.  GE Global Research’s work on medical monitoring for the U.S. Army aims to print the sensors and conditioning electronics, but then use silicon for the high-speed communications. Electronic systems engineer and PI Jeff Ashe noted that a major challenge was how to efficiently assemble the silicon die with the printed the components, as assembly could account for almost half the total cost of the system. The solution: printing a magnetic layer on the chips and then shaking them over film with a patterned magnetic template underneath, so the chips quickly stick to the desired magnetic sites.

By far the most commercially advanced results were from Body Media, which is extending its sensor patch and armband, and sensor fusion and monitoring software, to more applications. Though the company puts its sensors in a flexible patch for trial purposes, and some need a flexible wire in flexible armbands, the core of the system is more conventional MEMS and other rigid sensors in a watch-like unit to measure activity, heart rate, galvanic skin response, and even ECG from the upper arm. The company has gotten good traction so far for weight loss, thanks in part to enthusiastic publicity from users on “The Biggest Loser” TV show, but CEO Ivo Stivoric sees opportunity in combining the rich activity and stress information from the system with other outside information on, say, glucose levels or cardiac data to aid in better managing other medical conditions. The company is looking for partners with the domain expertise to apply the sensor and software solution to other applications.  

Solution or Vapor Processing? On Flexible or Rigid Substrates? Printed Features or Attached Silicon Die?

All these systems have to navigate a complex system of tradeoffs between potentially disruptive and low-cost solution processing, flexible substrates, and organic materials— and the better performance possible with more established vacuum processes, rigid substrates, and conventional silicon devices.  IDTechEx’s Zervos predicted as much as a $20 billion market for “predominantly printed” electronics in a decade, but only a little over half of that would actually be made on flexible substrates, as developments in laser lift off, other peel-off technologies, and even thinned silicon wafers may allow more easily controlled processing on rigid substrates for making flexible products. 

Though OLED displays are now all vacuum coated on rigid substrates, producers are moving to solution printing the first, hole-side layer that is the thickest and uses expensive materials to save time and cost, and will likely gradually move to eventually printing more or even possibly all of the layers on rigid substrates, but area volumes will never be high enough for roll-to-roll printing on flexible substrate to make sense, argued NOVALED CSO Jan Blochwitz-Nimoth.  For large area OLED displays for TVs, the fine metal masking now used for depositing and patterning the red, green and blue OLED layers will be hard to scale up to 8G-sized substrates, so inkjet or nozzle printing could be the alternative. But that’s a big change to introduce on such a large scale, so producers are also looking at vapor processes like small mask scanning, laser induced thermal imaging, and using white OLED with a color filter instead. OLED lighting, on the other hand, could go to either R2R vacuum coating, or to adding some printed layers on rigid substrates to reduce costs in high-volume production. Blochwitz-Nimoth also noted that improved high deposition rates at low temperature from Aixtron’s new source could mean OLED lighting would not need solution processing after all.  OPV, in contrast, needs the high area volumes that only make sense to do with R2R, either all vacuum as NOVALED is starting pilot testing, or with printed hole-side layers. 

Supposedly low-cost printed electronics may often not actually be the lowest cost solution, argued David Miller from Arizona State University. He estimated that with appropriate performance, printing on flex in current low-volume R&D/pilot-type lines actually costs some $29/cm2, compared to ~$7/cm2 for CMOS and ~$0.05/cmfor displays, though the comparison between research-level and production-level process costs is of course "apples to oranges." Still, for small die, it could make most sense to just attach a rigid or thinned silicon device to the flexible system. At moderate and high area volumes, however, printed TFTs should become significantly cheaper than silicon, so printed technologies may likely have the advantage for large area displays, and large area sensing arrays for things like optical imagers, x-rays and radiation detectors.  High-intensity computation and high-speed communication could then be added by conventional CMOS chips on the periphery.

SEMICON West has become a forum for the latest solutions and technologies for flexible electronics manufacturing of interest to the semiconductor/display world.  Now in its fifth year, the Printed and Plastic Electronics forum, organized by FlexTech, brings together manufacturers, developers, equipment and materials suppliers, and other solution providers.  FlexTech will also offer a workshop on transparent conductor technology developments.

Exhibiting Opportunities Available 

Companies are invited to exhibit at SEMICON West. If you have plastic and printed electronics technologies or solutions, exhibit in the Extreme Electronics zone. Close proximity to the presentation stage plus focused attendee marketing ensures high visibility with visitors focused on and interested in plastic electronics technologies. Great opportunities are still available — learn more about exhibiting at SEMICON West and Extreme Electronics! 

SEMICON West 2013 visitor registration opens March 18.


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