Adventures In Lilliput

By J. Madeleine Nash/Chicago

Think small. Now think smaller still. For in the lilliputian wonderland that scientists have begun to explore, a grain of rice looms as large as an asteroid, a droplet of water as wide as an inland sea.

Using powerful new tools, biologists at the University of Chicago have gently sliced through a red blood cell to peer at individual protein molecules clinging to its inner membrane. At the California Institute of Technology, chemists have watched in wonder as a hydrogen atom romances an oxygen away from a carbon dioxide molecule. And at Stanford University, physicist Steven Chu has mastered techniques for levitating millions of sodium atoms inside a stainless-steel canister and releasing them all at once in luminescent fountains. Of late, Chu and his colleagues have amused themselves by stretching a double-stranded DNA molecule as taut as a tent rope. When they ! release one end, the molecule recoils like a miniature rubber band. Boing!

Just as improvements in navigational tools opened the oceans to sailing ships, so a new generation of precision instruments has exposed a breathtaking microworld to scientific exploration. Aided by computers that convert blizzards of data into images on a screen, these instruments are helping scientists see -- and even tinker with -- everything from living cells to individual atoms. "This technology is still pretty crude," marvels Chu. "Who knows what we may be able to do with it in a few years' time."

Among the instruments generating excitement:

FEMTOSECOND LASERS. Like strobes flickering across a submicroscopic dance floor, these devices can freeze the gyrations of atoms and molecules with flashes of light. The lasers are being used to study everything from how sodium joins with other atoms to form salts to how plants convert sunlight into energy through the process of photosynthesis. Physicists from California's Lawrence Berkeley Laboratory reported that they used such a laser to take a "snapshot" of the chemical reaction that is the first step in visual perception. This reaction, triggered when light hits the retina of the eye, had never before been directly observed. And with good reason. The reaction was clocked by the L.B.L. team at 200 femtoseconds, which are millionths of a billionth of a second. How fast is that? Well, in little more than a second, light can travel all the way from the moon to the earth, but in a femtosecond it traverses a distance that is but one hundredth the width of a human hair. "This sort of time scale is almost impossible to imagine," exclaims L.B.L. director Charles Shank, who helped pioneer the technology.

LASER TRAPS. Beams of laser light can also be used to ensnare groups of atoms, which can then be moved around at will. But because atoms at room temperature zoom about at supersonic speed, they first have to be slowed down. In 1985 the invention of "optical molasses" by a research team at AT&T Bell Laboratories provided an ingenious solution to the problem. As its name implies, optical molasses uses light to create enough electromagnetic "drag" to bring wildly careering atoms to a screeching halt. Because the atoms lose virtually all their kinetic energy, they approach the perfect stillness of absolute zero, the frozen state at which motion ceases.

At such supercold temperatures, scientists believe, matter may start to exhibit bizarre and interesting new properties. Certainly, cold atoms can be trapped and manipulated in a variety of cunning ways. The fountains created by Chu, for example, are enabling scientists to observe atoms in free fall and thus measure gravitational force with unprecedented accuracy. Fountains are also helping scientists measure the oscillations of cesium atoms more precisely than ever before, and cesium atoms are to atomic clocks -- the world's most precise timepieces -- what quartz crystals are to wristwatches.

OPTICAL TWEEZERS. With a single beam of infrared laser light, scientists can seize and manipulate everything from DNA molecules to bacteria and yeast without harming them. Among other things, optical tweezers can keep a tiny organism swimming in place while scientists study its paddling flagella under a microscope. Optical tweezers can also reach right through cell membranes to grab specialized structures known as organelles and twirl them around. Currently, researchers are using the technology to measure the mechanical force exerted by a single molecule of myosin, one of the muscle proteins responsible for motion. Scientists are also examining the swimming skill of an individual sperm. "One day," imagines Michael Berns, director of the Beckman Laser Institute and Medical Clinic at the University of California at Irvine, "we may be able to pick up a live sperm and stuff it right into an egg."

SCANNING TUNNELING MICROSCOPES. Invented only 10 years ago, these extraordinary instruments probe surfaces with a metallic tip only a few atoms wide. At very short distances, electrons can traverse the gap between the tip and the surface, a phenomenon known as tunneling. This generates a tiny current that can be used to move atoms and molecules around with pinpoint precision. Thus last year physicists from IBM's Almaden Research Center manipulated 35 xenon atoms on a nickel surface to spell out their company's logo. They have also fashioned seven atoms into a minuscule beaker in which they can observe chemical reactions at an atomic level, and they devised a working version of a single-atom electronic switch that, in theory, could replace the transistor. Though some of the achievements seem whimsical -- constructing a miniature map of the western hemisphere out of gold atoms, for instance -- such stunts demonstrate a technique that may eventually be used to store computer data on unimaginably small devices.

% ATOMIC FORCE MICROSCOPES. Like STMs, these instruments possess an atomically small tip that resembles a phonograph needle. An AFM reads a surface by touching it, tracing the outlines of individual atoms in much the same way a blind person reads Braille. Because the electromagnetic force applied by the tip is so small, an AFM can delicately probe a wide range of surfaces, including the membranes of living cells. Even more astounding, by applying slightly more pressure, scientists can use an AFM tip as a dissecting tool that lets them scrape off the top of cells without destroying their interior structures. Scientists have used an AFM to detail the biochemical cascade that results in blood clotting; to examine the atomic structure of seashells; and to uncover the tiny communication channels that link one cell to another. "We're looking at scales so small," says University of Chicago physiologist Morton Arnsdorf, "they almost defy comprehension."

Without question, these recent additions to the scientific tool kit hold tremendous practical promise. A more accurate atomic clock, for instance, is not just a curiosity. "If we can put better clocks into orbit," notes William Phillips, a physicist at the National Institute of Standards and Technology, "we might improve the global positioning system enough to land airplanes in pea-soup fog." Even now it is not difficult to imagine that STMs might be employed by the semiconductor industry to produce minuscule electronic devices, that optical tweezers might be used by surgeons to correct defects in a single cell or that femtosecond lasers might eventually be harnessed to control, as well as monitor, chemical reactions. Speculates University of Chicago chemical physicist Steven Sibener: "In the future, combinations of these magic wands may become much more powerful than using them one by one."

Such marvels, of course, will not materialize overnight. Cautions IBM physicist Donald Eigler: "The single-atom switch looks small until you realize it took a whole roomful of equipment to make it work." Still, computer chips the size of bacteria and motors as small as molecules of myosin are rapidly moving out of the world of fantasy and into the realm of possibility. "For years, scientists have been taking atoms and molecules apart in order to understand them," says futurist K. Eric Drexler, president of the Foresight Institute in Palo Alto, Calif. "Now it's time to start figuring out how to put them together to make useful things." With such powerful instruments to help them, scientists and engineers may finally be getting ready to do just that.