* NEWS*WELCOME TO THE INK-JET AGE
* NEWS*WELCOME TO THE INK-JET AGE
2006-01-09 at 10:28:00 am #13407
Welcome to the ink-jet age
Mention the term ink jet and most people will probably think of printers. Indeed there can be few computer owners who have not possessed one, and although the cartridges can be rather expensive, the printers themselves are cheap and give a high quality full colour print out.
However, when the engineers at HP Laboratories first developed the ink jet back in 1979 printing was far from being their number one application for the new technology. These engineers had visions of using the device in applications as wide ranging as medicine and materials science, but, as so often happens it was the marketing department that decided upon the application, printing would yield bigger profits and take far less development.
So it has come about that ink jet technology is now firmly associated in the minds of most people with printing. But the vision that those engineers had back in 1979, of ink jets being used for a wide range of other applications, was not forgotten.
Innovators are increasingly realising that although an ink jet is a deceptively simple technology – an array of nozzles that moves back and forth depositing tiny droplets of ink onto a sheet of paper – it is the fact that those ink droplets are so precisely measured and placed which means that the range of such a device extends far beyond merely printing on paper.
“Inkjet technology is no longer just being harnessed to print coloured fluid inks, but also functional fluids, for applications such as electronic circuits, displays, fuel cells, RFID tags, live tissue engineering and rapid manufacture.” says Rob Harvey, business development manager of inkjet manufacturer Xaar. “Inkjet, and Xaar’s solution enables manufacturer’s to take a ‘product’ concept, which utilises functional fluids, and build it rapidly from prototype to one-off manufacture through to quite large volumes, economically and with greatly reduced development time.”
To understand why this is so, we need to look at the basics of ink jet technology. The secret of the ink jet’s versatility lies in the ability of manufacturers to drill an array of very small nozzles, just a few micrometers in diameter, in a silicon or composite printhead. The size of the nozzle determines the size of the droplets that can be produced.
Behind each nozzle in the printhead lies a small ink chamber with a connecting channel that allows it to be filled from an ink reservoir. At the other end of the ink chamber from the nozzle lies a piezoelectric crystal that is connected to the ink jet control circuitry. When an electric current bends this piezoelectric crystal it forces the liquid ink down the nozzle at high velocity, and as it comes out of the nozzle it forms a small droplet travelling at speed. Each droplet produced is exactly the same size and travelling at exactly the same velocity.
The ink jet should not therefore be though of as a printer but is a general purpose tool for creating very small precisely measured droplets of liquid.
Over the last twenty years ink jet technology has been greatly refined, the number of nozzles in a head has increased from just 12 to over 3,000 in some industrial devices. Droplet sizes have been reduced to just a couple of micrometers in diameter and the number of droplets that can be produced per second has increased considerably.
What innovators are realising is that the ink jet allows the engineer to precisely place an exactly measured minute quantity of liquid onto a surface. In a printer the liquid is coloured ink, but it could be anything that comes as a liquid or is suspended within a liquid medium – from suspensions of metal particles to living cells. Similarly in a printer the head is simply moved from side to side and the paper gradually inched up, however, the printhead could equally well be mounted on a mechanism that allows a minute drop of liquid to be precisely positioned in three dimensions.
It is the development over the last decade of a wide range of substances that can be used as ‘inks’ in ink jet print heads, together with developments in printhead positioning and control systems that has made possible the developments that are now starting to come onto the market.
One of the first applications to use the unique capabilities of ink jet technology has been in the electronics industry where special industrial printers are being used to print the very high density multi-layer circuit boards that are increasingly required by the electronic equipment that we now take for granted.
Printed circuit board
This technique involves printing very fine lines in a conductive ink made from very fine silver or copper particles onto a rigid or flexible substrate. By using an insulating ink in another print head it is possible for the printer to quickly and accurately lay out a printed circuit board with conductors just a few micrometers wide.
This manufacturing technique not only provides the next step in miniaturisation – Seiko Epson of Japan recently demonstrated a 20 layer ink jet printed board that was just 200µm thick – it also helps to reduce the amount of pollution produced by the electronics industry. Existing circuit board manufacturing techniques rely upon the use of photomasks and acid etching, neither of which are required by ink jet printers which produce circuit boards using an additive process.
“Manufacturers have already recognised ink jet as a key, enabling technology with the potential of becoming the deposition method of choice,” says John Attard, a business development manager with Xaar. “Inkjet is ideal for applications where the material to be deposited is expensive; management of waste fluid is an issue; manufacturing simplicity, yield and cost effectiveness is key; and where variable patterns are required, particularly on short runs.”
A big advantage of this manufacturing technique is the flexibility that it offers manufacturers and designers. Changes to the design can be made by simply changing the CAD file that drives the printer, with no need to create new photomasks. This makes design and development quicker, it makes it possible to economically produce very short runs, even one-offs. In fact the combination of all these advantages means that many in the electronics industry expect ink jet printed circuit boards to be the norm by 2007.
The techniques for printing circuit boards using ink jet printers and conductive ink are giving rise to a whole new industry for manufacturing devices using printed electronics. These devices include RFID tags – used for wireless identification of everything from clothes to automotive components – as well as pharmaceuticals and event tickets. With printed electronics such tags can be produced on a continuous roll-to-roll basis at extremely low cost, a technology that is being pioneered in Germany in a partnership between BASF Future Business and Lucent Technologies’ Bell Labs.
RFID tags are not the only product from the printed electronics industry that is set to revolutionise the world, an even more significant product is the flexible e-paper display. Within three years people may well be routinely reading newspapers, magazines and books on light weight flexible screens many of which the user will simple roll up and slip into a pocket when not in use.
Such flexible displays are built using advanced ink jet printers with inks made from special organic electronic polymers. Today dozens of companies around the world are racing to commercialise.the technology of flexible plastic screens, in the full knowledge that such displays will probably be the key component of the next generation of mobile electronic gadgets.
One such company is Philips, which is using a four-head industrial inkjet printer with 256 piezoelectric nozzles to print the fine arrays of organic light emitting diodes that will be used on paper thin computer and television screens. In Korea Samsung have already announced that they will be in volume production of 15.5inch OLED displays by May 2006, and Epson have said that they will be launching a 40inch OLED screen at about the same time. Other companies working in the same area include Toppan Printing of Japan, Cambridge Display Technology of the UK, and Universal Display Corporation of the US.
In another approach to the construction of flexible plastic displays, HP engineers in Bristol are using inkjets to print arrays of tiny liquid-crystal cells onto a flexible plastic substrate, an array of electrodes printed onto the flexible plastic turn the LCD cells on and off. The result is a full-colour display manufactured entirely using ink jet technology that the researchers believe could, around 2010, rival the printed page in flexibility, lightness of weight, colour and resolution.
Organic electronic circuits
Meanwhile in Cambridge, Plastic Logic have just demonstrated the first engineering samples of a flexible display that uses an organic electronic active matrix backplane and electrophoretic frontplane. The company expect such displays to be in commercial use in e-publication readers by 2007. Once again the ink jet is a crucial technology in their manufacture, industrial ink jets from Xaar and Litrex are used in Plastic Logic’s production line to print the matrix of very small organic electronic circuits directly onto a flexible plastic substrate. When bonded to the flexible frontplane the result is a thin, light, flexible display that can be viewed, like paper, from all angles and in any type of light.
Sensors are another area where printed electronics and the ink jet are opening up new markets. In Austria a new factory is being built by Nanoident Organic to produce organic photo-detectors using ink jet printers. This new generation chip factory will use intelligent, highly efficient manufacturing technologies.
In the light of these developments researchers around the world are now asking the question – if ink jet printers can be used to create electronic circuitry, why not do away with conventional assembly and build complete devices using an ink jet printer? At the University of California at Berkeley engineering professor John Canny is experimenting with ways of doing just this using a concept he calls flexonics. Research which could soon lead to a 3D ink jet being used to print out complete devices, including the case, electronics, battery, and all mechanical components such as switches and plugs.
High-resolution 3D ink jet printers from companies like 3D Systems, Z Corporation and Stratasys are in fact already being used to ‘print out’ prototypes of a wide range of manufactured products. Hundreds of companies around the world are now using them, Motorola used one to produce prototypes of the casing for its latest mobile phone, and Hyundai have used a 3D printer to make prototype vehicle dashboards.
Some companies in Europe and the US are even using them as ’3D data faxes’ to send design prototypes between their design and marketing departments and their Asian manufacturing facilities. “Communication is so much more effective when you can get a physical product into a customers hands rather than a drawing or text,” says Marina Hatsopoulos.
A typical 3D printer costs about $30,000 and uses a 448-nozzle print head to deposit a pattern of bonding glue onto a layer of powder dusted onto an aluminium plate in microscopically thin layers, the glue bonds the powder and forms the object, whilst the un-bonded powder acts as a physical support for the object as it is built. By dusting and printing layer after layer the machine slowly builds up the object using data provided by the CAD software running on the attached computer.
Once the printing process has finished, which typically takes about an hour, the supporting powder is dusted off leaving a hard finished plastic object at an average cost of about $10. This can then be further machined, painted, or used as a mould or pattern for casting plastic or metal objects.
“Time to market is extremely important it is no good just having a good idea it is how quickly you can get that to idea to market otherwise somebody beats you to it, you can try ten different designs with 3D printing allowing you to quickly get customer reaction,” says Dr Walter Bornhost, chairman Z corporation comments.
Stereolithography rapid prototyping systems, as 3D printers were known when first developed back in 1986, have advanced enormously. The rather rough jagged products of early machines have given way to smooth surfaced products of almost commercial quality. The machines in use today are desktop devices that can be used in any office environment says Motorola’s global prototyping manager Mike Jahnke. “It is so quiet and its so simple anyone can use it.”
Today with several competing companies fighting for market share commercial 3D printer prices are rapidly dropping and could soon hit a level that most businesses can afford. There are even rumours of a sub-$1000 home model.
Build living organs
As the price of ink jet based 3D printers drops and the quality of the objects produced improves, the latest generation can even produce multicoloured objects, so the range of applications for such printers grows. Architects are using them to build models of their designs, geologists are using them to build models of geological structures, and surgeons are using them to plan complex surgical operations by producing plastic replicas of the patient’s internal organs using data derived from 3D CAT scans. Some biomedical researchers are even using 3D printers to build living organs from an ‘ink’ of live cells.
Rather than build small plastic models of buildings, an engineer at the University of Southern California’s Contour Crafting Centre, Behrokh Khoshnevis, is using a giant 3D ink jet printer to print entire buildings straight from the electronic blueprints using an ink of quick setting liquid concrete. The university has partnered with architects, and construction companies to help Khoshnevis develop this concept. This system he believes will, within a couple of years, be capable of constructing a 200m² building in a single day, including all walls, roof, and conduits for electricity and plumbing. This is an innovation that could completely change the construction industry.
The ink jet is thus rapidly becoming an important manufacturing tool from nanotechnology to construction, and one that will be increasingly important in an era of manufacturing flexibility and product personalisation. It is also a tool that further increases the productivity of manufacturers by facilitating greater automation of the manufacturing process.
Above all, however, the ink jet is a tool which is changing the fundamental process of manufacturing away from the reductive process of cutting an object from a solid block or sheet – whether this is a silicon circuit board or the cylinder block of a car engine – to an additive process where material is added in small quantities to build up an object. It is a change that will not only shake the manufacturing sector to its core, but will also make manufacturing far less polluting and far more responsive to consumer needs.