fantastic plastic

Takeo Someya and coworkers at the University of Tokyo have created a flexible sheet comprising organic TFTs that inductively charges electronic gadgets placed on its surface.

According to this Technology Review article, the

system is designed in a way that overcomes the limitations of common induction schemes. Traditional induction systems can only spread small amounts of power over a relatively large area, and fairly large amounts of power can only be supplied to precise locations (such as a toothbrush mount). Someya’s power sheets, in contrast, can be large, and they can still supply a large amount of power to gadgets placed near them.

This new capability, he says, is enabled by a novel design and by advances in the fabrication of flexible electronics. The power system actually consists of two types of sheets: one sheet senses the position of an object, and the other sheet supplies power to the object’s point of contact, but not to the rest of the sheet. “In this way, the system selectively feeds power as high as 30 watts to electronic objects placed upon it,” Someya says.

The position-sensing sheet relies on two types of flexible electronics. Using a technique similar to silk screening, the researchers printed an array of copper coils 10 millimeters in diameter. In addition, they used a modified inkjet printer to print an array of organic transistors. Both devices are thin and flexible enough to bend with a sheet of plastic.

Gadgets would need to be equipped with a coil and special power-harvesting circuitry to use the power pad. As the gadget gets closer to the pad, the electrical resistance of the pad’s coils decreases. The array of transistors detects the exact position of the change in resistance and effectively directs the subsequent power flow, which is provided by devices on the second sheet of plastic.

This second power-supplying sheet has an array of switches and copper coils. The switches, made of silver and plastic, turn the electric current on and off, mediating its flow to the adjacent copper coil.

Instead of the usual rubbed polyimide alignment layers,

they use the in-situ photopolymerization of alkyl acrylate monomers in the presence of nematic liquid crystals to provide a cellular matrix of liquid crystalline droplets in which the chemical structure of the encapsulating polymer controls the liquid crystal alignment.

“Small changes in the chemical nature of the polymer will change the alignment of the molecules at surfaces,” said Mohan Srinivasarao, a professor in Georgia Tech’s School of Polymer, Textile and Fiber Engineering. “It turns out that this can be done over a fairly large area, and it is reproducible.[…]”

Srinivasarao described the self-aligning of liquid crystals Sept 14 at the 232nd national meeting of the American Chemical Society in San Francisco.

Apart from eliminating the rubbing step (a potential yield killer) the technique offers the following advantages over standard standard LCs for Ds:

• resulting displays are less sensitive to mechanical deformations (rigidity provided by the liquid crystals), and thus more suitable for flexible displays

• completely dark ‘off’ state (made possible by the vertical alignment of the liquid crystals)

Srinivasarao and collaborators Jung Ok Park and Jian Zhou have used the technique and a nematic material with negative dielectric anisotropy to fabricate highly flexible liquid crystal devices that have high contrast and fast response times – without using an alignment layer. Control is obtained by variation of the alkyl side chains and through copolymerization of two dissimilar monofunctional acrylates.

Bi-stable metal sheets might be useful as substrates for rollable screens (e.g. electronic newspaper). The ‘dimpled’ copper-alloy structures are apparently cheap to produce from a single sheet of metal.
BBC article
Smart structures group at the Department of Engineering (Cambridge)

George Malliaras and coworkers at Cornell created a novel type of organic diode with an “ionic junction” by laminating together layers of

an anthracene derivative containing free positive ions and a ruthenium, complex containing negative ions. When the two are joined, ions diffuse across the junction creating a difference in energy levels that facilitates rectification, electroluminiscence and photovoltaic response.

The technique is potentially suitable for low-cost fabrication of flexible photovoltaics and LEDs.

The work is described in the Sept. 7 issue of the journal Science in a paper by Cornell graduate researchers Daniel Bernards and Samuel Flores-Torres, Héctor Abruña, the E. M. Chamot Professor of Chemistry and Chemical Biology at Cornell, and Malliaras.

Gizmag is reporting on SiPix and SmartDisplayer’s recently announced payment card with a flexible electrophoretic display, which

enables cardholders to generate and display a dynamic passcode for one-time use.

The application subsequently landed the companies the Display Application of the Year Award from the Society for Information Display (SID). […]
SiPix Microcup Electronic Paper is the key enabler for the DisplayCard solution, specifically designed for the application’s requirements – flexibility, impact resistance, extreme thinness, and ultra-low power consumption. The result is a flexible, 0.25-mm thin e-paper display […].
To meet demand by merchant banks, SiPix will complete expansion of its automated high-volume module production line before the end of 2006.

The Cambridge Evening News is reporting that

Amazon, the world’s biggest bookseller, is in talks with Cambridge company, Plastic Logic, about the end of books as we know them. […]
News of the Amazon/Plastic Logic link was given to a Cambridge audience on Thursday night when Hermann Hauser delivered the RSA Lecture at Magdalene College. […]
“The reason why Amazon doesn’t sell e-books at the moment is because people don’t like reading on a screen, but now they can curl
up with an e-book,” Dr Hauser said.

This past week, Plastic Logic has been showing off its new product concepts at a trade show in San Francisco, under the heading ‘Life is Flexible‘.

NE Asia is reporting on iSuppli market predictions for flexible displays.

Note that according to their prediction, flat or formed displays (not bent during use) will take the lion’s share, while

True flexibility/rollability will appear in displays with small shipments in 2008, and will become a US$59 million market in 2013 […].

Challenges for the flexible display industry are listed as:
- the OLED industry’s promised shift to flexible has still not happened
- large investments are required in manufacturing infrastructure *
- new, unknown market

* [While this is certainly true for new deposition/patterning methods (e.g. inkjet printing) the hurdle is much lower for companies using traditional lithography.]

 

 

NanoMarkets predictions for the OLED and e-paper, smart packaging, and thin-film photovoltaics industries:

Markets for OLED and Paper-Like Displays to Total $10.2 Billion by 2011:

• combined sales of OLED displays and paper-like displays will reach $10.2 billion by 2011 and then go on to reach $14.7 billion by 2013.
• shelf-edge displays will be the biggest opportunity for the paper-like display business in the next few years, generating $1.2 billion in annual revenues by 2011.
• OLED televisions will reach $2.2 billion in revenues in 2011
• by 2011, flexible displays will account for $1.7 billion in revenues.

Smart Packaging Market to Reach $4.8 billion by 2011:

• The global smart packaging market will grow to $4.8 billion in 2011 and reach $14.1 billion in 2013
• Smart packaging will account for over $1.1 billion in printable electronics components by 2011 growing to $4.2 billion in 2013
• Smart packaging will also consume $1.1 billion in printable and chip-based RFID tags by 2011

Thin Film and Organic Photovoltaic Market To Reach $2.3 Billion ($US) in 2011:

• Integrated building and construction products such as PV enabled roofing and window materials are projected to be the largest market opportunity measuring $800 million ($US) in 2011 with large project and consumer electronic products the second and third largest market opportunities.
• On the materials front, amorphous silicon, the best established of the various thin-film PV materials, will represent an $800 million ($US) opportunity followed by organic and hybrid organic/inorganic materials and then CIS/CIGS.
• Thin film/organic PV is also generating buzz in the industry and several companies have received large VC rounds. Major multinationals are also supporting this technology as Honda has announced it will soon start full-scale production of thin film PV and Shell has just sold off its conventional PV business to focus on thin film. On the other hand, NanoMarkets points out that thin film and organic PV is also a technology space that has received its fair share of hype and controversy with competing claims by different manufacturers on where and how it can be applied and disputes over conversion efficiencies and costs per watt.

A centre for printed organic electronics, printronics, has been formed around printed systems, a leading player in the field. Four other companies (3D Micromac, GEMAC, GETT Gerätetechnik, KSG Leiterplatten) and two research institutes (Multi Device Integration group at the Chemnitz branch of the Frauenhofer Institute and the Institute for Print and Media Technology at the Technical University Chemnitz) are part of the printronics centre, which receives 5.3 million euros of regional government funding.
Under the motto “printed electronics everywhere”, printronics’ goal is to establish a knowledge and production center for printed electronics and become the world leading supplier of mass-printed electronic products within 10 years.
[press release in German]

A while ago a group at Philips research presented (’Video-speed electronic paper based on electrowetting‘, Nature Vol. 425, pp. 383-385, 25 September 2003; link to pdf reprint) a novel display type based on the principle of electrowetting.
Liquavista, a spin-out with New Venture Partners as main investor and Philips remaining a shareholder, is now commercialising this technology (press release).

Some of the benefits compared to other display technologies are:

• video speed
• low power consumption
  (less need for supplimentary illumination)
• indoor & outdoor usability
• no inherent limit on viewing angle

Regarding the manufacturing process, Liquavista is building on existing LCD technoloy:

To contemplate the development and promotion of a new technology, without considering accessibility of large scale manufacturing resource would challenge the benefits of even the most exciting of technologies. That is why, from the outset, Liquavista has developed electrowetting display technology to be almost entirely compatible with existing display manufacturing techniques and processes. […]
A proprietary low cost, scalable fill process, performed at the bipane level, and patented by Liquavista, improves further on the standard LCD manufacturing cycle.

More background information here.

Quantum Paper Inc. (nothing on their website yet) appears to be a relatively new player in the electronic paper business.

According to PrintWeek, the company claims it has created the “first production quantities”:

The US firm said its paper features an electronic display that can be printed on ordinary paper, board or plastic. […]
President Michael Feldman said: […] “The technology is prototype, but we hope to roll out licences for printers to make electronic paper-based displays later this year. “It is made on paper by standard printing presses, with no need for specialised gear.”
Chief technology officer Dr William Ray said: “It is one of the most important developments in printing in more than 10 years. “The paper is a unique marriage between the relative simplicity and low cost of printing and the high technology of pixel-based electronic displays.” He claimed it had the potential to replace mobile phone and computer screens, interactive billboards and high-definition TVs at a “fraction of today’s cost”.

Unfortunately no technical information yet, but some more PR at package printing:

“This technology has the potential to transform printing as we know it,” says Dr. William J. Ray, the principal inventor and Quantum Paper’s chief technology officer. “It is no exaggeration to call Quantum Paper’s electronic paper as one of the most important developments in the printing industry in more than 100 years.”
The technology can also be used to create the equivalent of television on paper. Quantum Paper has fully addressable, high-quality dynamic color displays under development with the potential of replacing conventional cell phone and PDA screens, computer monitors, interactive billboards, electronic wallpaper, and high-definition televisions at a fraction of today’s cost.
“Quantum Paper’s electronic paper is a unique marriage between the relative simplicity and low cost of conventional printing and the high technology of pixel-based electronic displays,” said Ray. “The performance of our displays meets or exceeds that of competing technologies but our electronic paper can be manufactured at such a low cost as to be considered disposable.”

[via MobileRead]

The Princeton Institute for the Science and Technology of Materials (PRISM) has been awarded a $1.7M R&D contract by the U.S. Display Consortium (USDC)

to develop the process technology and know-how to produce amorphous silicon thin film transistors (a-Si TFTs) on a clear, high temperature-capable polymer foil substrate.

[…] organic substrates cannot withstand typical TFT semiconductor on glass processing temperatures of >300°C. The Princeton program is based on a new type of clear, flexible polymer substrate that is capable of use at these “glass-like” processing temperatures.

The two-year program has several important milestones. For example, by the end of Year 1, a best effort will be made to demonstrate an electrophoretic test array and an OLED test array on the plastic substrate. […]
The principal investigators, Wagner and PRISM director Dr. James Sturm, have been working on experimental substrates for some time and have made a-Si TFTs at 280° C with performance nearly identical to typical TFTs made on glass. Applied Materials’ subsidiary, AKT, will collaborate to investigate the scale up of these materials using industry-standard fabrication tools.

Thin Film Electronics and Xaar have presented the first printed polymer memory device at the IPEX ‘06. From the presentation (available online; 12 MB PDF file):

A 100 bit non-volatile re-writable cross-point array memory device was presented, in which all layers were printed.
- top & bottom electrodes: conducting polymer Baytron P Jet HC (220um linewidth)
- dielectric layer: ferroelectric polymer
- substrate: PET foil
- contact pads: silver nano-particle ink

[previous post on Thin Film Electronics]

According to their press release

Toppan Printing Co., Ltd. has developed an amorphous oxide semiconductor thin film transistor (TFT) array and succeeded in driving an electrophoretic E Ink front panel laminate to fabricate a prototype flexible electronic paper display.

Apparently the amorphous InGaZnO semiconductor used here has a higher charge carrier mobility (> 5cm^2/Vs) than a-Si and can be deposited at room temperature. Flexible TFTs based on a-InGaZnO were first demonstrated by Professor Hosono and coworkers at Tokyo Institute of Technology (Nomura et al, Nature 432, 488 (2004)).
All layers of the 2 inch diagonal (80 x 60 pixels) display were deposited onto the flexible PEN substrate by sputtering, but Toppan plans to deposit and pattern some of the layers by printing.

Toppan plans to develop flexible TFTs with goals to commercialize thin, lightweight and flexible displays such as electronic paper, starting with a practical prototype display in fiscal 2008. In parallel, we aim to introduce printing methods into the fabrication process of flexible TFTs for simplification and cost reduction.

Note: This research was reported at IDW’05 as EP2-4L (International Display Workshop, Dec.6-9, 2005, Takamatsu, Japan)

Acreo, in collaboration with Linköping University, are developing low-cost electronics printed on paper. Their focus is on electrochemical devices, such as electrochromic displays. The change between bright and dark state is based on the difference in absorbtion of a polymer, e.g. PEDOT:PSS, in the oxidised versus the reduced state. Switching occurs at low voltages (0.6 to 0.9V), but is inherently slow (~1s).
The difference in conductivity of polymers, such as PEDOT:PSS, PANI, Polypyrrole and Polyhexylthiophene, between different redox states can be used to fabricate electrochemical transistors.

Other applications exploiting a change in material properties upon oxidation/reduction are a wettability switch and and a switchable polariser.

Acreo is using different printing techniques (e.g. screen- and offset-printing) to deposit layers such as the conducting polymer and polymer electrolyte layers.