TIME: Almanac 1993/TIME Almanac 1993.iso/time/123091/1230300.000

Text File | 1992-08-28 | 8.8 KB | 193 lines

                                                                                SCIENCE, Page 75

Adventures in Lilliput


Extraordinary new laser tools and microscopes are enabling
researchers to observe and manipulate a breathtaking microworld

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.