Prototype

Radiograph Revolution

A new method of creating x-rays under development by MXISystems in Nashville, TN, could make this oldest of medical imaging technologies safer and more accurate, improving diagnosis of everything from broken arms to breast cancer. Each pulse from a conventional medical x-ray machine generates radiation at a wide range of frequencies, only a small subset of which are diagnostically useful. Lower frequencies that don’t contribute to the image do yield harmful radiation, and higher frequencies that bounce around inside the body blur radiographs, making the images harder to read. MXISystems’ machine produces x-rays that span an extremely narrow frequency band; its emission can be tuned to the frequency best suited for each specific imaging task-a chest x-ray, say, or a mammogram. The system works by colliding a beam of electrons with an infrared laser beam; their interaction creates x-rays at a frequency that is related to the speed of the electrons, which can be easily adjusted. Based on technology from Vanderbilt University’s W.M. Keck Free-Electron Laser Center, the machine emits less harmful radiation than standard x-ray units. It also produces high-resolution radiographs with sharper contrast between tissues of different densities, making it easier to distinguish tumors from healthy tissue, for example. The company plans to begin trials of the machine for mammography next year.

Communications devices use microwaves, which are tricky to amplify. Vacuum tube hardware weighing hundreds of kilograms is needed to produce the highest-power signals for military radar. Semiconductor devices made of silicon or gallium arsenide work well for the few-kilometer transmissions required by cell phones, but they have too little power to send signals over long distances. A new microwave amplifier built at General Electric’s Global Research Center in Niskayuna, NY, packs the amplifying power of vacuum tubes into a semiconductor package. GE developed techniques for reducing defects in gallium nitride as it is manufactured; the team also built computer models to design devices that work well despite such defects. The result: gallium nitride devices that provide about seven times the power of other semiconductors at certain microwave-communications frequencies. GE is collaborating with Lockheed Martin to deliver high-power radar for lightweight, unmanned military aircraft in five to ten years.

Imagine a wet suit that goes on loose, then snugs down to keep you warm as you descend to icy depths. Thanks to smart-materials developer Mid Technology of Medford, MA, such suits are on the way. To make the suits work, Mid spikes neoprene, the standard wet suit material, with isopropylacrylamide, a “hydrogel” material that swells when it is warmed and contracts as it cools. Mid president Marthinus van Schoor says the hydrogel-neoprene suit, developed for the U.S. Navy Seals, hugs the diver in cold seas, reducing the amount any water trapped inside the suit sloshes across the skin and carries away heat; in tests at 13 C, hydrogel-impregnated suits provided 70 percent more thermal protection than neoprene alone. Santa Cruz, CA-based wet suit manufacturer O’Neill plans to test the Mid technology. If it passes muster, divers won’t be left shivering for much longer.

As microscale devices get smaller and smaller, researchers look for new ways to control movements inside them. A team at the University of Arkansas, led by mechanical engineer Steve Tung and bioengineer Jin-Woo Kim, has developed a way to pump tiny amounts of fluid by harnessing the motions of living cells. Unlike electrical or mechanical systems that rely on high voltages or pressures, the new technique uses harmless bacteria, each of which attaches a leglike appendage to a flat surface and rotates about this anchor point. The rod-shaped bacteria spin “like a merry-go-round,” says Tung, at 10 cycles per second. The trick, he says, is getting the cells to stop, go, or change speed by adjusting their glucose intake. With a few cells lined up in a glass-walled channel, Tung and Kim plan to show that the device can move the 0.25 nanoliters per minute a computer model predicts is possible. Tung says that could lead to biomechanical chips for drug delivery and DNA sequencing in about three years.

Polymer-and-silicon chips lined with tiny structures that act like biological cilia, or hair cells, could provide a new way to position and assemble delicate hardware, says electrical engineer Karl Bhringer at the University of Washington. Activated by heat, the artificial cilia work in groups of four, each group measuring about one millimeter across. Each chip has 256 cilia: Flip the chip upside down, and it can walk on a table. Put a platoon of them on the outside of a space station, and they could grab hold of a small satellite and make minute adjustments to its position as it docks, refuels, and transfers data. In collaboration with Stanford University, Bhringer has shown that an array of four chips can align a mock satellite the size of a tennis ball by nudging it to and fro. But the researchers will need to reduce power consumption by a factor of 10, he says, before the chips will be ready for space. A possible solution: electrostatically activated cilia, which are in development and could be ready for testing within a year.

A simple procedure could make life-saving bone-marrow transplants much easier on patients and increase the number of potential donors. Developed by cancer immunologist Ellen Vitetta and her colleagues at the University of Texas Southwestern Medical Center in Dallas, the process could dramatically lower the risk of a complication known as graft-versus-host disease, in which blood cells made by the donor marrow attack the recipient’s tissues. Vitetta’s solution: eliminate the donor cells that cause the complication and spare those that fight disease. Prior to transplant, doctors mix the donor marrow with the recipient’s blood to activate the “bad” cells. Once activated, these cells display a molecular marker called CD25 on their surfaces. Vitetta then adds a toxin attached to an antibody that targets CD25; the hybrid molecule selectively kills the bad marrow cells, and the rest are then infused into the patient. In an early trial in France, the procedure reduced the incidence of graft-versus-host disease from 70 percent of transplants to 25 percent. Vitetta hopes to begin U.S. clinical trials this spring.

Monitoring the health of bridges requires either drilling out a core sample or embedding boxy sensors that monitor for the intrusion of rust-inducing salt. The first method is labor-intensive; the second relies on wires that can break or degrade. Researchers at SRI International in Menlo Park, CA, are developing an alternative they call a smart pebble. The wireless device, the size of a piece of gravel, can be poured right along with the concrete. The SRI team built the pebble by linking a new type of chloride sensor to an off-the-shelf wireless-communications chip and tucking both into a housing made of cementlike materials. The sensor develops a voltage whose strength is determined by salt concentration. To collect the sensors’ readings, a device mounted on the underside of a van could emit a blast of radio energy as the vehicle drives over a bridge. Each radio query identifies an individual pebble; the code number that bounces back indicates whether salt levels are above or below a certain threshold. SRI is preparing prototype pebbles for the California Department of Transportation, which plans to test them this year.

Able to leap tall buildings in a single bound? Not quite. But a new tool from Quoin International in Ridgecrest, CA, will help you scale a five-story building in about 15 seconds without breaking a sweat. Attach a cable to the top of a wall, cliff, or utility pole, and the portable, two-kilogram winch pulls you up. The key to powering the device, says Quoin CEO Mike Jacobson, is a carefully controlled piston that generates gas at four times the pressure of a conventional turbine compressor. This novel compressor drives a high-speed turbine that produces enough force to lift 100 kilograms steadily. And unlike a conventional turbine, the engine can start and stop frequently without losing efficiency.