Keeping your balance while standing upright can be tricky, particularly for older people. That is because standing steady is partly a result of slight adjustments to posture that are ordered by the brain in response to sensory information from the feet. But as people age, they become less sensitive to touch and send their brains fewer signals.

Now James J. Collins, a professor of biomedical engineering at Boston University, and his colleagues have found a way to use random signals to increase the sensory data coming from the feet. In a series of experiments, healthy 75-year-olds stood on a platform that transmitted randomly varying vibrations to the soles of their feet. With these good vibrations, the subjects reflexively adjusted their balance until they swayed about the same amount as 25-year-olds who did not receive the random signals. Younger people who used the vibrating system also swayed less.

Collins, who led the research group, attributed the improvement to stochastic resonance, a well-known phenomenon in which random noise enhances the detection of weak signals. In this case, the noise made the nerves in the feet more sensitive and better able to detect the kinds of pressure changes that occur when the body goes slightly out of balance and puts more pressure on one part of the foot. "It's a foot massager with a twist," Collins says of the research setup. The vibrations are not soothing because the motion is below a detectable level, but they do make people more stable.

In the world of signal detection, noise is traditionally viewed as a prime nuisance. Electromagnetic noise creates snow on TV sets; acoustic noise makes conversation impossible in some restaurants. But in Collins's experiments, as in those of other researchers who have investigated stochastic resonance, certain kinds of noise is helpful.

"For electrical signals, the low levels of noise essentially tickle the membranes of the neurons," he says, making them more likely to fire when there is a physical stimulus of some amplitude. For mechanical signals, noise serves to boost weak stimuli. "The experiment is a good example of how noise lets a neuron fire in the company of a signal that it is normally unable to detect," he says.

Although the principle of stochastic resonance has been investigated for more than a decade, Collins says, these experiments were the first in which it was shown to improve balance. The effect, described in a paper to appear in the journal Physical Review Letters, may be sufficient to offset age-related declines in balance control, he says.

The platform used in the study has hundreds of small holes; a small plastic rod protrudes slightly through each of them so that it contacts the bottom of the test subject's foot. The rods are hooked up to motors that cause them to vibrate at random frequencies generated by a computer while the test subject is standing quietly. "They couldn't feel the random vibrations," Collins says. "We set the noise up at too small an amplitude for them to detect it."

Attila Priplata, a student of Collins's and lead author of the paper, designed gel-based shoe insoles that contain small vibrating devices designed to produce the same effect. When the researchers repeated the study with people using the insoles, Collins says, they found even stronger effects. It is important that the signals be random because neurons quickly get used to regular signals.

John Milton, a neuroscientist at the University of Chicago, says that Collins's bionic inserts might one day prove to be an inexpensive remedy for legions of aging baby boomers who have grown less steady on their feet. "These noisy sneakers could save a lot of money if they were used for treatment," Milton says. "And there are no side effects I can imagine from wearing noisy sneakers."

Collins has written a series of research papers on ways to use stochastic resonance to improve health. An earlier paper, for instance, discussed the use of noise to improve the sensitivity of touch in older adults who suffered diabetes or the effects of a stroke. But he is well aware of more frivolous applications, particularly for sports equipment. "I could imagine having noise introduced into the handles of golf clubs or tennis rackets," he says.

Vibrating shoes might be something like an electronic version of flubber, the magic substance that turned a so-so basketball player into a superstar in the old Walt Disney movie and recent remake. But Collins was quick to point out the superiority of his discovery over flubber. "The energy source in flubber is the material itself," he says. "Here we are taking advantage of the natural senses-the sensory neurons' shifting their detection thresholds to a lower value."

Kurt Weisenfeld, a professor of physics at Georgia Tech who did some of the early defining work in stochastic resonance, says that Collins's experiments were a striking example of thinking creatively about possible applications of the phenomenon. "This is a practical idea that could help people maintain their balance," he says.

He particularly admired Collins's solution because it is relatively simple. "For someone with sensory problems, the high-tech answer might be a bionic ankle," he says. "But maybe instead they'll just slip into a pair of bionic socks. Those are a whole lot cheaper."

-Anne Eisenberg, New York Times, November 14, 2003.

In 1999, more than 72,000 people in the United States alone waited for organ transplants-6,100 died before an organ was available. While tissue engineering and the development of artificial implantable hearts have had considerable success in recent years, large-scale use of such technologies is still in the distant future.

For people with hearts weakened by congestive heart failure, however, help in the form of a microheart-a penny-sized liquid pump on a silicon chip-may be closer at hand.

This technology, now being developed by Xin Zhang, an assistant professor of manufacturing engineering at the College of Engineering, with support from a SPRInG grant, builds upon recent advances in Power MEMS-miniature devices that integrate mechanical pumps, electrical motors, chemical reactors, valves, and other components onto a single silicon chip.

Zhang's design, fabricated on a single 1.5-centimeter-square silicon chip, would use an 8-millimeter diameter rotor capable of pumping up to 5 liters of blood per minute. Encased in an ultrathin layer of biocompatible artificial tissue, the micro-heart would work with the left ventricle of a weakened heart to pump blood throughout the body, allowing the damaged organ to rest and, perhaps, to heal.

Since they are so small, the Power MEMS devices can be implanted using minimally invasive state-of-the-art surgical techniques, which consist of integrated robotic laparoscopic micromanipulators, a three-dimensional endoscopic viewing system, and a computerized control system, allowing delicate surgery to be performed through centimeter-sized incisions.

Because of their efficiency and small size, Power MEMS have enormous potential for other important medical applications, including delivery of localized precision doses of programmed drug mixtures based on feedback from integrated biochemical sensors. Such a device might deliver insulin to a patient with diabetes or a custom drug cocktail to a patient with an immune deficiency.

According to Zhang, over the longer term, microbioreactors that generate new chemicals or cells within the body may even be possible.

- Joan Schwartz

Selim Unlu (left), an ENG associate professor in electrical and computer engineering, and Bernard Goldberg, a CAS professor of physics in their shared lab in the Photonics Center.

For young Benjamin Braddock in the 1967 film The Graduate, the future was neatly summarized in one word: plastics. If Mike Nichols had directed the film 30 years later, that word may well have been nano.

Nanoscale science and technology are expected to change virtually every human-made object in the next century. The essence of nanoscience involves manipulating atoms and molecules to build structures with new and improved properties. In the 1980s, when researchers first started working at the nanoscale (a nanometer is one billionth of a meter, or about 1,000 times smaller than the diameter of a single human hair), they were surprised to find that small groups of atoms or molecules often have unexpected properties, such as increased strength, electrical resistance, and optical absorption, that are significantly different from the properties of the same matter when it is a single molecule or part of a vast array of connected molecules.

Over the past three years, BU researchers have been pursuing several ambitious nanoscience projects. But until now, says Bennett Goldberg, a CAS professor of physics, these disparate efforts have been limited by their lack of collaboration. In the first step toward building an intercollege working group of engineers, physicists, biologists, and chemists, Goldberg and Selim Unlu, an associate professor of electrical and computer engineering, have received funding from the National Science Foundation (NSF) and the National Institutes of Health (NIH) to begin two interdisciplinary projects in the field of nano-optics, which strives to see tiny objects in ever-finer detail.

Nano-optics is an important starting point because to fully make use of the potential of nanotechnology, researchers need to see what they're working with. With a $1.3 million grant from the NSF, Unlu and Goldberg will develop tools and methods for seeing objects 10 to 20 nanometers wide. The project is one of several NSF grants to support nanoscale interdisciplinary research teams (NIRTs) at universities across the United States. BU's NIRT team includes Todd Murray and Kamil Ekinci, both ENG assistant professors of aerospace and mechanical engineering, and Raj Mohanty, a CAS assistant professor of physics.

The team's initial goal is to get around a fundamental limit of nature. For 300 years, optical microscopes have been limited by the way light behaves. It's impossible for even the most powerful lenses to see things smaller than about one half the wavelength of light, the so-called diffraction limit. A decade ago, Unlu and Goldberg pioneered a technique called near-field optics to get around this limit. Now they're developing an even better technique called solid immersion microscopy. The idea is to shorten the wavelength of the light by passing it through a substance with a very high index of refraction. The higher the index, the slower the speed of light in that medium and the shorter the wavelength.

In a separate project, Goldberg and Unlu have received $1.7 million from the NIH to apply a different sort of nano-optics to observe the subcellular structures of Shigella bacteria. With Anna Swan, an ENG research assistant professor of electrical and computer engineering, Unlu and Goldberg will refine a new technique called self-interference fluorescence microscopy. One of the main tools for probing biological systems, fluorescence microscopy involves injecting a fluorescent molecule into the specimen and tracking its position with a microscope. Currently, researchers can use this technique to see things as small as 400 nanometers, but Unlu and Goldberg's team wants to better that by a factor of 50 using their patented technique.

Other instruments, such as electron microscopes, can already render images of biological features at a much higher resolution. But the problem with this technique, explains Goldberg, is that it requires killing the cell, freezing it, and slicing it thinly before bombarding it with high-energy electrons, which damage the sample as they bounce off it. The goal is to develop an instrument that can locate, in real time and three-dimensional space, the precise position of certain proteins in living bacteria and viruses.

For Goldberg, the NIH-funded project illustrates the importance of interdisciplinary work in nanoscience. "The real breakthroughs and advances in nanoscience are going to happen at the boundaries between disciplines," he says. "It's pretty unusual for me, a condensed-matter physicist, to have an NIH grant to do biological imaging. As we understand more about the physical processes of things at the nanoscale, then the great application is to match them to the natural biological systems at the same scale."