There’s a Hero on Your Desktop
To most, it's just a printer. But to tissue engineers, rocket scientists and architects, the good old inkjet is the secret to grand innovation
If you were to toast the most dazzling gadget in your home, you might compose an ode to your plasma TV, recite a limerick about your computer-controlled telescope, or maybe sing the praises of your video conferencing, nose-hair-trimming espresso maker. But the invention most deserving of your adoration, the contraption that will one day
sit in the pantheon of great American machines alongside the telephone and the transistor radio, is something far more prosaic. It is the inkjet printer, and it is much more than a peripheral. Its core technology may seem simple-an array of nozzles that moves back and forth, depositing tiny droplets of ink on paper-but its breadth of uses has turned out to be nothing short of astonishing, so much so that the humble inkjet is driving innovation in disciplines from aerospace engineering to pharmacology.
How does a printer go from spitting out pictures of Uncle Bob to powering jet planes? The secret of the inkjet´s unheralded versatility lies in its print head-a silicon or composite plate a tenth of an inch wide
studded with as many micro-nozzles as a manufacturer can cram onto it. The nozzles fill with ink, and either heat or an electric charge forces out uniform droplets [see â€Inkjet 101,â€ below]. Refined over the past 20 years from heads with 12 nozzles to ones with more than 3,000, the inkjet is the first cheap, mass-produced machine to control minute pearls of fluids-it ultimately jump-started the field of microfluidics. This precise control of ever-smaller droplets (some now a small fraction the size of a pinpoint),
coupled with faster printing speeds has opened up dozens of new and decidedly more glamorous applications: printing cellphones and human livers, delivering drugs more efficiently and without side effects, producing fuels without nasty by-products.
You may marvel at such a notion, but it´s no real surprise to the inkjet´s innovators. They never intended it for the menial task of churning out term papers and memoranda. In fact, when Hewlett-Packard Laboratories engineers developed the first nozzle array in 1979, they kicked around the idea of using the device for medicine and materials science before deciding that the printing biz would net more profits. Their first machine hit the market in 1984, and more than 20 years later-now that the inkjet dominates the industry-big players like HP, Epson and Canon can afford to take a step back and figure out ways to squeeze new uses out of the machine. â€Most people don´t realize how sophisticated the system has become,â€ says Stephen Nigro, vice president of HP´s technology platforms organization. â€Millions of drops a second come from the print head. It´s really an incredible technology.â€
Corporate bosses aren´t the only ones smitten. Piggybacking on industry advances in printing speed and nozzle size, some researchers are using souped-up inkjets to print full-scale homes, others to stamp out skin grafts. In the future, scientists may deliver inkjet-printed nanomachines, targeted cancer treatments and, who knows, maybe even inkjet-printed pets.
So go ahead and worship your shiny new MP3 player, your ionizing hair dryer, your remote-controlled ottoman-whichever machine has you mesmerized this month. But then please take a moment to give props to your workaday inkjet, which has thrived in near anonymity lo these many years. Accolades or no, it´s sure to keep spitting out impressive results with elegant simplicity for decades to come.
The Desktop Organ Factory
Growing replacement body parts in the lab is a grand idea, but researchers haven´t had much luck doing it. For one thing, manually stitching together billions of cells to form a nose or a liver involves labor so tedious that it´s been impossible to finish the job before the cells die. A perfect task for the you-know-what, thought Clemson
University chemical engineer Thomas Boland in 2001 when he scrounged scrap inkjet printers from campus surplus and pressed them into service as cell-spitting robots.
By rewriting software drivers, modifying
the output tray to drop a tiny notch with each pass of the print head to build up 3-D structures, and swapping ink for hamster ovary cells and growth factor, Boland introduced the inkjet to the world of tissue engineering. To date, he´s used his printers to create half of a cat´s heart that beat in
a petri dish and tubes of cells that he hopes to one day coax into viable blood vessels. Constructing the vascular system is a crucial hurdle he´ll have to clear to meet his ultimate goal, which is to print custom organs on demand. In the next decade, Boland says we´ll see the printing of simpler tissues, including bits of cartilage for plastic surgery and cell sheets for skin grafts.
The Santa Claus Machine
Shopping is dead-or at least it will be if 3-D CAD printing catches on
and you´re able to download and print toys, dishes, even cellphone covers right at your desk. Companies such as 3D Systems, Z Corporation and Stratasys already have high-resolution 3-D inkjet printers. The $39,900 InVision printer from Valencia, California´s 3D Systems uses a 448-nozzle print head to deposit photosensitive acrylic and wax onto an aluminum plate in microscopically thin layers, slowly building up whatever its engineers have commanded:
a prototype engine part, direct-mail figurines or a mock-up gadget. Melt off the wax molding, and you´re left with a hard acrylic object. With these and other companies fighting for market share, commercial replicators are closing in on a range that a typical consumer could afford, with rumors of a $1,000 home model on the horizon.
Putting Electronics on the Inkjet Diet
Researchers at the university of California at Berkeley are shooting for more than just plastic tchotchkes. They want to print complete digital devices-MP3 players, PDAs, cellphones-in one fell swoop, rather than assembling a gadget´s body and then adding its electronic components. Engineering professor John Canny is integrating polymers-plastics able to conduct electricity-into a 3-D inkjet that could someday print out electronic devices in one simple step, bypassing the timely fabrication of circuit boards and other components. Meanwhile, engineers at Seiko-Epson in Japan have proved that inkjet-printing at least the guts of a gadget is viable. Last November they printed a 20-layer circuit board only 200 microns thick, the smallest ever, by swapping copper and silicon for conductive and insulating inks, respectively. Instead of building a Dagwood sandwich of bulky materials, they use a piezoelectric print head with microscopic nozzles to lay down conductive silver-infused beads of ink measuring tens of nanometers in diameter alongside strips of a newly developed insulating ink. The lower volume of materials allows for tight patterns with very little dead space. The company estimates that the skinny boards will show up in gadgets by 2007, but competition from Hewlett-Packard and others experimenting with
circuit printing may bring the boards to stores earlier.
The Finest Atomizer, Bar None
Before long, you may find inkjets under the hood of your car or inside the engine of a fighter jet serving as exquisitely controlled fuel injectors. A conventional injector atomizes gasoline or diesel into tiny droplets, much the way a bottle of Windex sprays out a mist of fluid. The more completely the droplets vaporize and mix with air, the more efficiently the hydrocarbons burn. The inkjet (being the inkjet) is best equipped for the job. Researchers at Hewlett-Packard aren´t divulging details, but they say that they´re figuring out how to replace single-injector systems with hundreds of tiny inkjet nozzles, each with its own actuator, as a way to create even tinier drops for increased fuel efficiency.
Microscopic inkjet-based fuel-injection systems are already an indispensable component of the U.S. Navy´s experimental pulse detonation engine (PDE), which is designed to harness the energy of a violent fuel explosion and power a jet aircraft to Mach 3. The detonation depends on atomized droplets of fuel just 50 microns in width, which is why Jim Nabity, a senior researcher at TDA Research, turned to the inkjet nozzle. Its microscopic fuel dots vaporize so fast that they ignite, generating a thrust per pound of fuel comparable to any other supersonic engine, Nabity says.
Dream Homes on Demand
the inkjet is great at micromanaging the small stuff, but with a few steroidal
modifications, it can work wonders on a macroscale too. Engineer Behrokh Khoshnevis of the University of Southern California is experimenting with oversize inkjet printers that, with the press of a button, can build custom housing from electronic blueprints. The automated system, which Khoshnevis calls Contour Crafting, consists of an overhanging carriage on which a nozzle slides back and forth, streaming layers of quick-setting concrete into walls [illustration, right]. â€It´s much like printing on paper,â€ the engineer says of his $30,000 brainchild. â€But unlike an inkjet print head that just moves sideways, our nozzle can move in all directions, like old vector plotters.â€ He is partnering with architects, construction companies and real-estate specialists to create a Contour Crafting center at U.S.C., and he predicts that the system will soon erect a 2,000-square-foot home in a single day, including the roof and conduits for plumbing and electricity. Later this year he plans to demonstrate a prototype capable of putting up 500-square-foot emergency shelters.
Three years from now, when you unroll your e-newspaper from its pencil-case-size tote for the latest headlines or show off your vacation snapshots on a 17-inch high-definition screen that folds up like a yoga mat, you can thank, yes, the inkjet. Dozens of companies worldwide are in a sprint to commercialize the technology of flexible plastic screens. Philips, for instance, is using a four-headed industrial-size inkjet with 256 piezoelectric nozzles to print organic light-emitting diodes-materials that glow when a current is applied-onto computer and television screens.
HP engineers in Bristol, England, are using inkjets to print tiny liquid-crystal dots onto a plastic substrate, where they serve as pixels. Electrodes in the bendable plastic turn the crystals on and off for a full-color display that could finally rival the printed page in resolution. Plastic Logic in Cambridge, England, hopes to release flexible displays by 2007. As an alternative to liquid crystals, the company is using industrial inkjets to print electronic inks on flexible plastic to produce an image that can be viewed from all angles and in any type of light without distortion.
Taking Drugs, the Smart Way
Conventional inhalers tend to spray a sloppy mist of large, uneven drops, and that´s fine for applications like asthma medications, which simply need to be dumped into the lungs. But it´s less than ideal for delivering most other drugs, which need to make it into the bloodstream. That could change when digital aerosols-thermal print heads inside inhalers that squirt tiny, perfectly uniform droplets-hit the market late this year. The aerosol, being developed by the Australian company InJet Digital Aerosols and being licensed to Canon, looks like a battery-powered inhaler. It delivers a mist of droplets between two and 20 microns in diameter, small enough to be absorbed through the lungs and in some cases directly into the bloodstream. InJet expects its inhaler to deliver drugs faster than pills or patches and with less pain than needles. Clinical trials are under way to test nicotine-filled inhalers as smoking-cessation devices.
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