Labor and manufacturing processes will be severely reduced, but daunting barriers remain.
Many electronics industry veterans have heard about, but have limited understanding of, a breed of materials science called printed electronics. This field involves thin films, coatings and inks that perform electrical functions (conducting, semiconducting, insulating, etc.) similar to silicon electronics, with one exception: They are applied in a continuous and often soluble process across a variety of substrates (glass, paper, flexible and special polymers, etc.), as opposed to via a rigid and brittle silicon deposition process that yields products in batch and on a massive scale.
Why would such a technology represent a threat to a sector that has grown to be over a trillion dollars in size? The answer seems to be in the upside potential that printed electronics represents that concern printable (that is, configurable-on-demand) electronics circuits with integral qualities and capabilities involving multiple components such as sensors, amplifiers, antennas, battery, audio, display and wireless communications that today are manufactured and assembled as discrete components.
To appreciate printed electronics’ potential, it’s important to understand how it works technically. Consider traditional printing processes: flexography, gravure, inkjet, offset printing, screen printing, and thermal transfer. It is clear these methods have been developed to solve unique printing applications (newspapers, magazines, business documents, various other forms of mass printing), yet they also can be applied in electronics if the correct materials (organic and inorganic) can be produced to perform electrically functional applications. It turns out, this is what’s happening.
Printed electronic products are printable at different levels of resolution, conductivity (material blends), layers, sensitivity, size and speed. This can vary according to the particular kind of print technology being used: continuous, high-speed throughput, wide format, or simply low cost. As such, new products are being engendered that work outside the current paradigm of semiconductor and circuit board technology.
New Organic Electronics
Organic conductors are lighter, more flexible and less expensive than inorganic conductors. This makes them a desirable alternative in many applications, provided high performance is not essential. (While conductive, they are not as fast or efficient as inorganic materials such as silicon or copper.) But this difference creates the possibility of new applications, such as electronic paper or smart/flexible windows, which would be impossible using traditional technologies. Additionally, organic conductive polymers are expected to play an important role in the emerging science of molecular computing.
Until now, circuits built with organic materials have permitted only one type of charge to move through them. The latest research provides for charges that flow both ways by positive and negative charges. Over the past 30 years, researchers have been working to make organic electronics by layering two complicated patterns on top of one another: one that transports electrons and another that transports the positive holes. Recently, polymers have been created with a donor and an acceptor part that can transport both positive and negative charges in one material. The material would permit organic transistors and other information-processing devices to be built more simply, in a way that is more similar to how inorganic circuits are now made.
Yet, printed materials and conductive inks have begun to penetrate many established products and extend them in new ways. Kovio was the first company to make an entirely printed transistor-based RFID device with nanosilicon on stainless steel foil, and PolyIC on its website is promising kits of transistor RFID in 2010. To this end, antennae have been printed on certain RFID tags by companies such as Hyan Label (China), which can print directly on paper adhesive labels using reel-to-reel transfer.The number of transistors on these tags is small, therefore so is the performance, but potentially the cost is low if done in volume.
The primary goal of making organic transistors and integrated devices is to create circuits that are functional, inexpensive and printable on-demand. Organic thin-film circuits can take the place of silicon circuits in applications that require short turnaround times, flexibility and configurable performance. Moreover, organic materials can be rendered into a liquid form and applied at room temperature and atmospheric pressure, and thus are ideal for printable formats. Thus, this emerging breed of low-cost electronics can easily and quickly be applied via conventional ink-jet technologies at minimal cost.
By combining different print and production techniques, these polymer electronics can be engineered in conductor paths of any desired length, with print layers of 1/1,000 mm thick. As the process technology evolves, polymer electronics will be able to integrate hybrid designs so that transistors, diodes, memory, and displays can be provided in a continuous and mass-printed form. To date, polymer electronics have produced touch-sensitive sensors (keys), digital memory (16 to 96 bits, depending on the available surface area on the substrate), processor logic, photovoltaic batteries and color displays. Yet printable inorganic materials and composites are being developed that form a class of conductors with vastly better conductance and cost, ideal for producing superior printed laminar batteries, large electrophoretic, electroluminescent and electrochromic displays and solar cells. Moreover, inorganic materials have been applied to quantum dot devices and for transistor semiconductors such as logic and memory (zinc oxide) devices with 10 times the frequency and mobility of organic devices, in addition to greater stability.
Composites include oxides, amorphous mixtures and alloys. Increasingly, organic devices such as OLEDs employ a variety of inorganic materials such as boron, aluminum, titanium oxides and nitrides as barrier layers against water and oxygen. Similarly, aluminum, copper, silver and indium tin oxide are used as conductors, while calcium or magnesium can be developed as cathodes, cobalt-iron as nanodots, and iridium and europium in light-emitting layers on displays.
In 2009, inorganic semiconductors were being sold by companies such as Kovio for RFID tags due to much higher mobilities versus what is found in organic semiconductors. Similarly, companies such as Pelikon and elumin8 have applied inorganic materials to flexible electroluminescent displays that involve six to eight layers, including a copper-doped phosphor. These displays can be deposited on plastic or other film substrates that can cover meters of square area and are capable of emitting a range of colors.
Printed electronic circuits eliminate the required traditional subtractive wet process used today, which includes etching, stripping, metallization and copper plating. Without the costly process finishing, significant savings occur in labor, equipment and water consumption. These savings are further extended by way of wastewater treatment and sewer user fees, which involve the use of formaldehyde, chelators, ammonia, heavy metals and acids. Electric and gas consumptions see a notable reduction by eliminating the need to heat most of the wet processes, multilayer presses, and the large plant-wide demand for compressed air. HVAC reductions also are experienced due to greatly reduced exhaust requirements.
With the reduced amount of the many complex chemical processes to monitor, high overhead labor is eliminated. Printed electronic circuits (PEC) are expected to use 20% of the current labor requirement with the same square foot output. A printed circuit line of conductive silver and ceramic dielectric inks allows for a circuit to nearly equal the resistance properties of etched copper by controlling both the thickness and the width of the conductor, and therefore the overall resistance of the trace. Moreover, PEC permits the interconnection to be accomplished using highly conductive nano-inks without the need to drill holes or solder components. By eliminating the drilled via hole, printed circuits increase the interconnect reliability because the vias are 100% filled with silver ink and have equal resistance to a drilled plated via.
The special conductive inks permit a drilled hole to be filled with silver and re-drilled smaller to create a very strong conductive through-hole, if desired.
PEC gets particularly interesting when considering flexible surfaces or when active functions are required such as contamination detection or time/date sensitivity. Adidas, for example, has striking innovations involving smart clothing and fabrics that measure body data to help better manage health or achieve optimal athletic performance. The application that has made the most inroads in PEC can be found in “plastic” electronics, in which carbon compounds have created a new class of electrophoretic display used in today’s popular e-readers, such as the Kindle and Nook. Organic light-emitting diodes (OLEDs) can now be printed on a variety of flexible surfaces and open new applications in displays, signage and packaging.
Printed electronics will emerge in some of the most mundane and unobvious sectors. For example, PEC will have an enormous impact on the consumer sector, giving products special appeal by combining unique displays and signs, producing sounds and information on a product’s packaging. Cosmetics that rely on color shapes will be enhanced with unique lighting and audio features on the display shelf. Another application is foods or pharmaceutical packages that are time-sensitive for freshness, safety and potency, not to mention detection monitoring for toxins or efficacy. Perhaps more exciting, printed electronics is a precursor to many nanotechnology innovations, including engineering bionic limbs that integrate carbon nanotubes with human nerves, and artificial implanted hairs that detect pressure/temperature sensing, yet are dispersed in a flexible polymer composite skin. This stuff is now emerging and preeminent.
Barriers to Growth
The market for printed electronics has become reality, albeit not at the rate that many have predicted. The barrier to exponential growth seems to be the inability of suppliers to lower costs so that mass production can be adopted and demand generated. This is the classical economic dilemma with disruptive technologies when highly competitive and traditional alternatives exist that continue to innovate at similar rates and thus are difficult to displace.
NVR is now completing its second edition of its syndicated market research report titled The Worldwide Printed Electronics Market. This study looks at this technology, what it replaces and the opportunities it presents, but also the challenges that printed electronics faces. The results are disruptive, to say the least, and while the market potential is profound, just when and how is this expected to emerge? It turns out there are significant barriers to printed electronics’ ascendancy in the near future.
In the near future, printed applications concerning RFID and OLED displays will come, manufactured using OTFT (organic thin film transistor) technology. These technologies are penetrating a wide number of products, but not at the rate nor with the impact to displace traditional technologies. As costs decline and performance improves, customers will be justified to switch, and in many cases, entirely new design solutions will be created. For example, photovoltaic thin films are beginning to emerge along with battery storage technologies that could soon exceed the electrical efficiency of competing technologies and at lower costs. However, these solutions often involve tradeoffs such as a greater area to produce the same cost per watt, and so cannot be ubiquitous. Table 1 summarizes the worldwide market for printed electronics by product application in 2009.
Over the next 10 years, printed electronics will have direct impact in the RFID market, where low-cost printed tags with embed codes and biometric data can displace traditional barcode products by integral wireless technology in active devices. The implications are profound, including embedding ID information in passports, smart cards, transportation and freight, healthcare, manufacturing, prisons and agricultural tracking devices. Printable OLED displays will compete with tradition TFT devices in the areas of sub-displays, mobile phones, cameras, video, car audio and games where configuration, form-factor and power consumption are determining issues. Finally, printed PV thin films will gradually replace traditional poly-silicon technologies that so dominate the solar panel market today. Table 2 summarizes the worldwide market for printed electronics by product application in 2019.
The critical business distinction for printed electronics becomes one of scale, volume and cost/performance, whereby printed electronics will often be at a disadvantage to traditional electronics. Yet we have seen disruptions such as the demise of CRT televisions by more expensive flat screen TVs because of better performance and functionality. Why should printed electronics not displace certain semiconductor logic and memory components that integrate transistor circuits with display, antenna and audio technology in a single device?
The nexus lies in the R&D investment that exists within the semiconductor and flat panel industry that vastly exceeds any being made by printed electronics. Yet much of the breakthrough work is borne out of the national labs, government research agencies and corporate R&D departments, among such companies as 3M, Applied Materials, Fujitsu, HP, Intel, Samgsung, Sharp, Xerox and a host of more exciting lesser-knowns such as E-Ink, elumin8, Kovio, Nanoink, Plastic Logic, PolyIC, T-Ink, and Thin Film Electronics. These companies are incrementally producing breakthrough technologies that potentially will be the cornerstones of paradigm-shifting products that could make parts of the semiconductor industry obsolete and noncompetitive.
We live in a time when innovation is constantly evolving. While it is always difficult to predict the growth curve for disruptive technology, printed electronics stands to take the electronics industry in a new direction. What better time is there for those on the cutting-edge to make their value-proposition fresh and compelling? We look forward to monitoring these new innovations and measuring their cross-impact over the next several years. CA