Ling, J. (2009), "Day 2", Microelectronics International, Vol. 26 No. 3. https://doi.org/10.1108/mi.2009.21826cac.004
Emerald Group Publishing Limited
Copyright © 2009, Emerald Group Publishing Limited
Article Type: Conferences and exhibitions From: Microelectronics International, Volume 26, Issue 3
Dr Zvi Yaniv is the President of Applied Nanotech Inc. A versatile company working in various fields, they have developed copper inks for direct writing, which are ink jettable, using copper nanoclusters of more than ten atoms. Surface volume ratios are important, said Dr Yaniv, and UV radiation will reduce copper oxides to metallic copper. Dr Yaniv touched upon many of the problems of formulating a copper ink for ink jet printing, and he made mention of the Optomec aerosol inkjet printer giving 30 μm lines and spaces with good track structure.
Frank Louwet of Orgacon Electronic Materials had new developments as his topic. PEDOT is a transparent conducting electrode and was described, and Orgacon also produce conductive inks and films. Key properties include low surface resistance with good VLT; and good stability to temperature, relative humidity and light (T, 85°C; RH, 85 per cent); direct patterning needs inks with low curing temperature, which can be screen printed, and which are flexible, formable and stretchable. Frank went on to describe how Orgacon inks could replace the indium tin oxide (ITO) in an OLED structure. The SER/VLT ratio is closing the gap with ITO.
Charge injection barriers at realistic metal/organic interfaces was the topic of Mandy Grobosch who came from IFW in Dresden to talk to the physicists amongst us about their work on barriers. Molecules respond to the presence of interfaces and she showed the effect of metal surface contamination. The photoelectric effect was illustrated, and she showed how UHV conditions can affect the surfaces resistivity of PES. They have an impressive photoemission spectroscope in their laboratories, which can determine interface properties, and study chemical reactions, charge transfer, the charge neutrality level and interfaces states. The work done at IFW provides a new insight into the energy level alignment at realistic organic/metal interfaces can help in the future to better design and optimise organic devices.
Dr Vipin Varma is the Director of Development at Vorbeck Materials, and informed us about Graphene. Graphene is a sheet of carbon, a single atom in thickness; it has exceptional strength and stability, with some unique electrical and thermal properties. Graphene has been proven to be the strongest known material, and in sheet format can be bent, shaped and folded. Think, therefore, of durable, foldable, portable printed electronics. Vor-X Graphene sheets are less than a nanometer thick, but you can control sheet thickness, which is important for printing properties. His company has put graphene into an ink, and this gives sinter-free processing, exceptional conductivity, can be applied to a wide range of substrates, has an eco-friendly formulation and gives robust DFT with excellent flexibility. Surface resistance is 1 Ω−2 resistivity at 1 mil, with abrasion resistance of 2-3H. Rub resistance is high, 5-8 per cent loss after ten rubs, and flex resistance is 13-15 per cent loss after 100 flexes. The product lends itself to use in the UHF and capacitive RFID fields, with very fine resolution, and may be formulated for thick-film supplications, for roll to roll processing, and a formulation for spray painting complex 3D shapes. An interesting paper.
HTWK University in Leipzig had sent along Professor Dr Ulrike Herzau-Gerhardt to talk about their work on printing functional layers using flexography. They use rotary flexo presses with rubber plates, using low-viscosity inks, which are of variable speed. Resolution of 20 μm has been achieved, and they are also printing on glass sheets with a glass anilox roller. They have printed ITO as a dispersion, which has many advantages, and have formulated it into a printing ink with a viscosity of about 100 m Pa s, and a surface resistivity of less than 200 Ω−2 They have tested different solvents with ITO, have improved the homogeneity and avoided pinholes. Thus, far, they have printed negative lines of 50 μm, and positive lines of 100 μm. Evenness of the of the layer is a problem, but in general, flexo can be used to transfer ITO dispersions as a printed layer but they now need to optimise the process.
Dr David Müller of Merck Chemicals in the UK spoke about advances in material and formulation development for printed organic electronics. They are working in the organic sector down at Chilworth, with applications including LCD, printing, OPV and flex display. Lisicon® is their trade mark, and this covers products for organic semiconductors and organic printed electronics. Performance, stability and processability have to be combined in one formulation to meet the market requirements for organic semiconductors. Control of the morphology of the crystals is important, and the selection of optimum solvent systems, additive systems all contribute to level films. For bottom gate devices, they now have good processability good shelf lie, whereas top gate OSC dielectric is more stable once the GTT is increased. Their polymeric formulations appear sound and are available for several different printing processes, especially flexo.
Professor Emil List is the Scientific Director at the NanoTec Centre at the Technical University of Graz in Austria. Novel concepts for organic and inorganic sensors were illustrated. Happily, organic semiconductors are sensitive to almost everything and therefore make then ideal candidates for sensor research. The main issues are however oxygen, water, temperature, etc. and naturally sensor requirements are many. To meet these requirements, there is a project called ISOTEC which comes under the EU-funded programme SEMOFS, and the professor described the work being done in considerable technical detail. Amongst the novel concepts discussed were ink-jet printed nanocrystal photodetectors; a sub-ppm ammoniac detector by means of a printed conducting polymer resin; and an integrated optical oxygen probe, realised using an OLED device.
Mrs Christl Lauterbach is the CEO of Future-Shape in Germany and presented a paper on smart textiles. Her company make SensFloor® a large area sensor system based on printed textiles. This very clever flooring detects when someone walks across it using proximity sensors, and this information can be used to open doors for example, or close them too. SensFloor operates with a flexible RF module. Produced on a roll-to-roll process, it has a 50 cm pattern grid with 32 sensor plates per metre, and the copper nickel plated lines on a flexible PCB give a sheet resistance of 10 Ω−2. The system detects the direction a person is taking, and will operate the door if it detects that the person is headed towards it. It is clever enough for one to distinguish normal use from forced entry. Calling it intelligent room surveillance is apt. If a person gets out of bed, the lights could come on automatically. Domestic items left on can be switched off automatically. If a person falls, and does not get up again, then this is detected and help can be provided. Clever textiles, and of great application in care for the elderly. Cost? About 500-1,000 €/m2, but for volume demand this could drop down to 150 €/m2.
Mr Geoff Boyd looks after new business development for NXT Technology in the USA. He looked at the interface between the human being and printed electronics. Geoff is involved with sound, and it was the human ear that he was interested in. Bending Wave Haptic is interesting, and uses printed electronics as a spin-off from the NXT experience with flat-panel speakers where normal loudspeakers cannot be accommodated. NXT began life as Wharfedale speakers, so they know about distributed mode loudspeaker technology, and have a strong IP base.
Geoff handed round various examples of products from licensees, such as Hallmark, with greetings cards containing music which plays once the card is opened. Qinetiq is working with NMX, and Nissha printing, printing touch panels. Haptics? Haptics are the bending of waves in touch panels to create sounds.
Printed electronics are supposed to deliver low-cost interactive high information content for smart packaging by now, but it has not happened. Working with various companies, NXT is producing invisible sound for printed electronics, with applications inc smart packaging, smart labels, self-authentication; ID cards, greetings card; and novelties such as magazine, newspapers and book inserts. The scope for application is huge, but progress so far has not been exactly brisk.
Rutgers had a paper on Graphene-based thin films for transparent and flexible electronics given by Professor Manish Chhowalla. Graphene vs Graphite was illustrated, and graphene is a zero gap semiconductor, whereas graphite is a semi-metal; graphene has linear dispersion, graphite had a parabolic dispersion. Graphene has good conductivity, good optical transmittance, and it is an interesting material for conversion into everyday objects if we can make a transparent conductor of it. Indium has increased in price dramatically, whereas graphite is available in large quantities and is cheap; cheap, flexible, chemically stable and with uniform transmission. Graphene has many potential applications but it is not ready (yet) for technological implementation. There is no viable deposition method, no control over deposition areas, no control over the substrate, and no control of the number of graphene layers. But with graphene inks many things are possible. Graphene-based composites thin films are also possible, the optoelectronic properties of graphene thin films can be tuned by controlling film thickness and the degree of reduction.
Graphene-based composites offer a route to the solution of processsable field emitters.
Dr Sven Murano from Novaled in Germany spoke on high-efficiency OLEDS for lighting applications. Novaled is a spin off from technical university here in Dresden and specialise in OLED technology. OLED displays are readable from all angles and have an integrated reflector so no fixture or luminaire is required. Challenges include existing lighting systems, as OLED requires really good encapsulation to protect against air, moisture, etc. Novaled have spin-coated HDL layers with very good hole injection which helps towards this goal. A roadmap was shown in which whitestacked OLED without coupling gave 38 lm/w, with 85 lumens possible later.
Thin Film Electronics had Dr Nicklas Johansson come from Sweden to talk about printed memories. This company have entered into the production of printed memories will bring the unit price down to where it is wanted. Thin film memory is non-volatile, is rewritable, is solution processsable, that there is no active circuitry in memory cells allows for stand alone applications. Printing on roll to roll has been carried out in InkTec factory in South Korea, five printed layers, using silver ink, and in a class 10,000 clean room, the process uses direct gravure, rotary screen printing, flexo printing and microgravure coating. There is 12 m, five zone oven for drying, and the line runs at 10 m/m. There is a yield of 94 per cent and the printed memories pass all test procedures including environmental testing, thermal cycling, and passivation. The many applications include game cards, interactive toys, brand protection, counterfeit prevention, and of course, printed RFID. So, roll-to-roll printing of memories is now a commercial reality, with yields up to 98 per cent and opens the door for other applications.
Dr Torsten Thieme of memsfab in Germany regaled the delegates with an interesting take on how they have been working closely with DB Schenker and KSW Microtec in Germany on the field trialling of shipment monitoring by smart RFID. They have been using sensors applied to packing cases which can detect tilt and shock, as well as RFID tags to facilitate routing and handling. It is possible to tell where any incident happened. RFID is a very useful addition in the whole logistics system, it is innovative, offers a real-time statement of procedures and cargo streams and improves security and localisation of sensitive cargo by linking it to GPS.
PolyIC Germany has Dr Wolfgang Clemens as the Head of Applications. His company prints electronics, roll to roll, and is a JV with Siemens and Kurz. They make printed electronics thin, flexible inexpensive and simple, pervasive and disposable. Printed electronics does not compete with silicon, but opens up a new world of possibility; being present everywhere at low cost. RFID enables contactless transmission of information via radio frequency waves. Printed on polyester films, RFID tags are cheap to produce. What they are doing now is producing a 13.56 MHz printed roll-to-roll manufactured RFID chip in commercial production, and are offering printed Smart Objects as well. Electronic ticketing, electronic vouchers, electronic counting of participants at a conference, all contributes to the safety and security of and for the consumer.
VTT Technical Research Centre of Finland has Mr Hanu Helistö as their Chief Research Scientist. He told us about Printed Electronic Coding. This is an ultra low-cost ultra near field communication system based on printed electronics. The coding system is composed of special inks, low-cost readers, and a code database server with secure encrypted communication. Codes are printed by standard printing technology but with special Nicanti inks which are slightly conductive. Codes are read and decrypted with the reader by sweeping over the code. Memory is presently 32-96 bits, sufficient for individual item coding, and these codes can be hidden under text or images or made invisible with special inks. Many different printing processes can be used; substrate may be paper, plastic, glass, textile and even metal. Serial printing is possible (changing codes for every item/label) and printing on two sides is possible as well. Tag yield is about 100 per cent. It is suitable for mass production, is of a small size, simple and robust. Tags are completely recyclable just like newsprint. The potential for use is huge – documents, payment devices, fashion goods, industrial products, spare parts, luxury consumer goods, low-cost consumer goods. It is a totally secure system, and exciting to boot.
TNO Science and Industry of The Netherlands has Mr Anton Kaasjagar as a Project Leader who spoke about printing conductive structures on textiles and membranes. TNO is an R&D company in Holland undertaking contract research and they are active in all kinds of areas, employing some 4,500 people. His project under discussion was making conductive tracks in textiles, with connectors, and shielding.
They have to bring those elements together within the textile, either for warming, or cooling. Interest from military authorities is keen. Early experiments with palladium were unsatisfactory, but then they tried inkjet printing and matters became altogether easier. They decided that the conductive element should come in earlier, integrated it into the dying and finishing stage. Anton moved onto conductive membranes, where they have used seven different materials (PE, PU, etc.) and APTMS as a hydrophobic agent, and then wetting out untreated areas. Vaporised APTMS is a very good way to treat the surface and control the deposition as well as make images using a mask. Washing, sweating, all have been assessed, and as the metallised part should be non-allergic, copper has been ruled out and electroless palladium is altogether better. Much yet to be done including two-sided metallisation, shielding, etc. but he sees interesting applications for integrated electronics.
This review is by no means comprehensive; with three parallel sessions, there is no coverage of photovoltaics, flexible batteries, e-readers, digital printing, to name but a few. But it may serve as an insight into a world somewhat removed from that of pure circuitry and microelectronics, but only somewhat. It is a world that expands exponentially at an incredible rate, and is an interesting one to visit.
In 2010, Printed Electronics Europe will be held once again in Dresden at the Maritim Conference Centre on 12-15 April.
John LingAssociate Editor