liquids but possess some properties of solid crystals. They also have their own unique properties not found in either solids or liquids. Thermochromic liquid crystals (below), or TLCs, are liquid crystals that react to changes in temperature by changing color. Most TLC mixtures turn from colorless to red at a low temperature, then pass through the colors of the visible spectrum as temperatures rise. The color change permits their use as temperature indicators in such applications as digital thermometers, hot/cold warning indicators, disease diagnosis tools, thermal imagers, and chemical and gas detectors. Hallcrest, a company in Glenview, Illinois, has been a leader in TLC technology since the industry's birth in 1973. In the mid-1980s, Hallcrest collaborated with NASA's Langley Research Center on a research effort to improve aerodynamic testing methods. The result was a new way to visualize boundary layer transition in flight and wind tunnel testing of aircraft wing and body surfaces. The boundary layer is the layer of air adjacent to the aircraft skin. In flight, when the boundary layer is smooth, it produces very low skin friction drag; but when it becomes turbulent with increased speed, drag increases. In aerodynamics research, it is important to determine exactly where the boundary layer transition from smooth to turbulent flow occurs on an aircraft. A As air turbulence increases skin friction, it also raises the boundary layer temperature, which can be detected with a TLC. A liquid crystal solution formulated by Hallcrest was applied like paint over the surfaces of a test aircraft. Researchers then photographed color changes as the plane changed altitudes during flight. The TLCS successfully indicated the transition points and the test results correlated closely with transitions indicated by other more costly and time-consuming methods. This work enabled Hallcrest to establish a new market for TLC products in government/industrial aeronautical research and flow visualization/heat transfer studies. Hallcrest also supplies training kits designed to educate potential TLC users in the new technique, which is finding wide acceptance. Hallcrest continues to develop temperature-indicating devices for industrial uses such as nondestructive testing and flaw detection in electric/electronic systems; medical diagnostic systems; and food, refrigerator, baby bath, and aquarium thermometers. A specific example is the Duracell battery (above), which comes with a liquid crystal battery tester that changes color to indicate the battery's condition. Scratch-Resistant Sunglass Coating glass is its brittleness, so eyeglass manufacturers turned to plastics. Plastic lenses offered resistance to shattering, lower manufacturing costs, excellent optics, and far better absorption of ultraviolet radiation. In addition, they were lightweight and easier to shape to facial contours. The one disadvantage was that, unlike glass, plastics were highly susceptible to scratching. Foster Grant Corporation, Leominster, Massachusetts, devoted a decade of research to the search for a coating that would give plastic lenses glass-like scratch resistance without compromising any of plastic's attributes. The answer was a highly abrasion-resistant coating and deposition process developed at NASA's Ames Research Center by researcher Dr. Ted Wydeven (at top). Initially intended to protect the plastic surfaces of aerospace equipment in harsh environments, the coating increases lens hardness and, thereby, scratch resistance. Foster Grant acquired an exclusive license for the process from NASA and began manufacturing sunglasses. Their scratch-resistant lenses lasted, with normal wear, ten times longer than the most widelyused plastic optical lenses, surpassing even glass (shown at left). Today, the majority of sunglass, corrective, and safety lenses sold in the United States are made of plastic. In 1991, Fosta-Tek assumed the license for the NASA process from Foster Grant and currently uses it on eyewear, industrial face shields, and flat-sheet plastic for industrial applications. The coating is one of the most pervasive space technology spinoffs. Athletic Shoes The Compression ChamberTM midsole was subjected to stresses equivalent to 400 miles of running and showed no visible signs of wear or structural fatigue Athletic shoe manufacturers spend millions annually searching for innovations that will give them an edge in a lucrative and extremely competitive industry. One company, AVIA Group International, Inc., Portland, Oregon, a subsidiary of Reebok International, Ltd., applied space technology in a major shoe advancement known as the AVIA Compression midsole, intro duced to the market in October 1990. In the late 1980s, AVIA began a project to eliminate the unwanted compression or breakdown that causes loss of cushioning in athletic shoes. The company contracted with Alexander L. "Al" Gross of Lunar Tech, Inc., Aspen, Colorado, to design an advanced shoe that would retain its shock absorption, stability, and flexibility properties over a longer lifetime. Al Gross, an aerospace engineer who has won several awards for his work in space suit design, turned to NASA technology. His basic approach to the shoe design was to eliminate foam materials from the midsole because they are subject to cushioning loss from the repeated vertical force of body weight and as a result become rigid. A task force led by Gross chose a "rigid, flexible" system similar to that in a space suit. Being pressurized, the space suit is rigid but permits astronaut mobility with the "convolute system," a series of bellows in the joint areas that expand and contract with every motion. By layering or combining materials and varying the shape, size, and number of bellows, space suit designers can vary joint flexibility. For the AVIA shoe project, the task force created an external pressurized shell with horizontal bellows for cushioning and vertical columns for stability. By varying the shape, number, and thicknesses of shell materials and the styling lines within the shell, the designers were able to "tune" the stiffness and National Basketball Association star Clyde Drexler puts AVIA Compression Chamber shoes through a workout. The shoe, designed to retain its performance properties over a longer life span, is an adaptation of NASA space suit technology. cushioning properties of the midsole. Creating a stress-free environment to ensure durability demanded a single part without weld lines or cement seams. To meet that requirement, AVIA and Gross adopted another NASA technology-a stressfree "blow molding" process originally employed to get superior impact resistance for the Apollo lunar helmet and visor. Blow molding, never before used in the footwear industry, allows AVIA to reconfigure the Compression Chamber for different sports. In durability tests at Penn State Center, the Compression Chamber midsole was subjected to stresses equivalent to 400 miles of running and showed no visible signs of wear or structural fatigue. The midsole, AVIA officials say, is the "first step" towards a completely foamless, non-fatiguing midsole that will not wear out. treated water but also inhibits the growth of bacteria within the filtering unit. It was developed by Ionics, Inc., Bridgeville, Pennsylvania, manufacturer of water treatment equipment for municipal, industrial, and consumer use. The IQ's ability to arrest bacterial growth is based on NASA silver ion technology developed to purify water aboard the space shuttle. In space use, an electrolytic water filter generates silver ions in concentrations of 50 to 100 parts per billion into the water flow. The silver serves as an effective bactericide/deodorizer. The NASA innovation has been applied in several water purification products, among them a line of home and portable water filters developed by Ray Ward, president of Ambassador Marketing, National City, California. Ward was assisted in his equipment design by Ionics, which helped him make the most efficient use of silver-impregnated carbon. Activated carbon helps remove objectionable tastes and odors caused by the addition of chlorine and other chemicals to municipal water supplies. Ionics vice president Walter J. Poulens later learned that some European countries were considering a ban on water softeners that breed bacteria. It occurred to Poulens that the silver ion technology he had |