Technology Bulletin

By: 
November 16, 1998

Universal substrate builds better lasers/thin-film devices

The race to build lasers and other optoelectronic devices on a compliant universal substrate appears to be over. Since 1996, when the concept was first proposed by scientists at Cornell University, research groups around the world burned candles into the night in an attempt to be the first to find a better way to make high performance semiconductor devices. A joint research team from the University of Houston (UH), Applied Optoelectronics Inc. (AOI), and Cornell University won. The new technique for creating epitaxial thin-film devices, recently unveiled at the North American Molecular Beam Epitaxy Conference, "will allow us to create lasers and optoelectronic devices with better performance and lower costs by relieving a lot of the materials constraints," says Steven Pei, associate director for research at the Space Vacuum Epitaxy Center (SVEC), the NASA Commercial Space Center at UH. Epitaxy grows single crystal materials on a base or substrate with atomic precision. A combination of layers might produce a laser, while another combination could result in a high-efficiency solar cell. Traditional epitaxy requires that the substrate's crystalline structure matches the material being placed on top. Currently, only a few substrate materials are available, fewer still are affordable. The "compliant universal substrate" resembles a grid printed on a piece of rubber loosely bonded to a conventional substrate. It expands or contracts to match the grid of the epitaxy thin film grown on top of it. By eliminating concerns about matching the grids on the underlying conventional substrate, the universally compliant substrate could dramatically increase the choices of epitaxy thin films/substrate combinations for optoelectronic applications. It may even lead to less expensive base/substrate materials, say the researchers. The NSF, Air Force, and Ballistic Missile Defense Organization are funding the research to develop semiconductor mid-infrared lasers for environmental monitoring and jamming of heat-seeking missiles. E-mail: Smart@uh.edu.

Secure your computer against hackers with a 'real' lock

Researchers at Sandia National Labs (Albuquerque, NM) dealt a severe blow to potential computer hackers when they debuted the Recodable Locking Device. Made with microelectromechanical systems (MEMS) technology, the lock consists of a series of tiny notched gears that move to the unlocked position only when the owner enters the right code. Dubbed the "world's smallest combination lock," the device may be the first mechanical hardware designed to keep unwanted guests from breaking codes and illegally entering computer and other secure systems, say researchers. The device consists of six code wheels, each less than 300 microns in diameter, driven by electrostatic comb drives that turn electrical impulses into mechanical motion. The lock owner sets a combination to any value from one to one million. The entire mechanism, about the size of a button, measures 9.4 mm @ 4.7 mm. The lock has a secure side and a user side. To unlock the device, the user must enter a code that identically matches the code stored in the code wheels. After one failed try, the device mechanically shuts down and cannot be reset except by the owner on the secure side. Sandia demonstrated prototypes in July and expects a finished lock in about two years. Phone: Larry Dalton, (505) 844-2520, or e-mail lidalto@sandia.gov.

It's all in the hand

Warwick Mfg. Group, part of the University of Warwick (Coventry, UK), joined forces with Umbro International to create a technologically advanced goalkeeping glove for England's Arsenal goalkeeper, David Seaman. Researchers on the glove project, led by Vinesh Raja, principal research fellow at Warwick Mfg. Group, worked with a team from Umbro to create a process that streamlines the way gloves can be made and how they will perform on the pitch. The design begins with a Wicks and Wilson optical scanning device, which captures data needed to produce a 3D computer model of the hand. This image is processed using a reverse engineering technique that analyses the millions of data points quicker and more accurately than ever before, say the researchers. Warwick Mfg. Group's speedy software results in "gloves that exactly fit the hand." Phone: Tom Goodwin +44 (203) 522962.

Goat's milk + spider proteins = light bullet-proof fiber

Jeffrey Turner, president of Nexia Biotechnologies (Montreal, Canada), plans to make a light fabric that is strong enough to stop bullets, but will biograde. The ingredients: goat's milk and synthesized spider proteins. The new material, dubbed "biosteel," could become an alternative to the high-strength plastics used to package shampoos, make commercial fishing nets, even build spacecraft. Tests on natural silk show that it can be stronger and more elastic than high-tensile steel or the Kevlar(R) found in body armor. But the very properties that make silk proteins strong also make them difficult to produce. Turner and his colleagues will mimic the spider's own method of production by using goat mammary cells. The way mammals produce milk proteins and how spiders make silk proteins are similar. Both are produced in skin-like epithelial cells, then held in a space, or lumen, minimizing shear stresses on the protein. FAX: (514) 457-6151.

Long-wavelength laser speeds communications

W.L. Gore & Assoc. (Lompoc, CA) made a breakthrough in long-wavelength Vertical Cavity Surface Emitting Laser (VCSEL) technology. Scientists at Gore say they demonstrated the first long-wavelength VCSELs that meet the performance requirement for many high-speed data communication applications. They did this by overcoming the two largest barriers to producing this type of laser--temperature performance and operating voltage. The Gore laser has a wavelength of 1,300 nm, with useful output power from 0 to 70C and 2.5V operating voltages. It also offers 5-mA threshold currents and can be modulated at data rates greater than a gigabit per second. When successfully commercialized, long-wavelength VCSELs should enable greater bandwidth and distance in multimode fiber and lower-cost light sources for single-mode fiber applications. FAX: (512) 458-4724.

The Three Little Pigs should try this straw material

Particle board made from wheat by-products will help address declining forest reserves, exploding world populations, and the rising need for alternative building materials. HARVESTBOARDTM, a non-toxic, formaldehyde-free panel, is made from the straw left over after the wheat harvesting. Typically, farmers till this straw into the soil or burn it off to prepare for the next planting. Harvest Board International (HBI, Kansas City, MO) recently broke ground for the first of three "agrifiber" particle board plants. HBI says that HARVESTBOARD will be up to 20% lighter than traditional wood-based particle board, with improved water-resistance and greater strength. Initially, the wheat-based particle board will be sold and distributed to end-product manufacturers, with a limited amount sold in sheets to retail outlets. Phone: Emily Heath at (816) 474-9407.

Amusement rides of the future?

Looking for a new thriller at your local amusement park? How about the "Pinballs of Steel," where passengers are slammed around in an oversized pinball machine while strapped inside a clear, fiberglass ball? Invented by Joseph Ciavattone and classmates at Carleton Middle School (Sterling Heights, MI), the ball bounces and twists against bumpers, flippers and walls, while powerful magnets keep the riders inches from danger. The "Lunchroom Nightmare," designed by Grace Shin of I.S. 25 (Flushing, NY), puts riders in cars shaped like cheese, vegetables, macaroni, and other lunchroom specialties, then flings them with enormous spoons and forks along a railing between large "lunch tables" that serve as the start and finishing points. Or there is the "Helical Horror," invented by Justin Irby and Tony Champagne from McMain High School (New Orleans) that spins passengers along a strand of DNA-shaped track cushioned by the same kind of electrodynamic suspension used in magnetic levitation trains. Or how about "Mind Twister" by Ceasar Borja at I.S. 25 (Flushing, NY) that uses virtual reality glasses to create the sensation of being in a real twister. Surround sound technology helps to ensure the ride delivers "15 minutes of sheer terror." These and seven other entries were winners of the Science World challenge. The magazine asked its readers to invent a brand new amusement park ride in its "Ride to the Future Challenge" during last year's National Engineers Week. The rides had to combine engineering technology with constructability. The 10 inventors recently received $100 and a free subscription to Science World for their school libraries. Another challenge will be announced during National Engineers Week, February 21-27, 1999. Phone: (212) 967-8200.

Chainbar configures into multiple shapes

Ever have problems storing those long, straight pieces that come with fold-up, hide-away furniture? "Chainbar" may be the answer. As the name implies, the device consists of a series of links that may either be kept flexible as a chain or locked to form a rigid bar. This simple but useful mechanical device, developed by Mhohm Co. (MCO, Brooklyn, NY), comes in all sizes. The links, hinged together by their ends, form a flexible chain of any length. Each hinge joins the ends of two links to allow movement between the links. If the chain passes through a tube less than one-link long, the movement between links is restricted, to create a strong, rigid pole. Because chainbars can be flexible and rigid within the same structure, there is a wide range of possible applications for the device, such as robotics, artificial limbs, folding ladders, table tops, shelves, tripods, or luggage carriers. After use, the "rigid" bars pack easily away into small containers. Phone (718) 680-8504

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