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Fantastic futures atom by atom

Nanotechnology, once considered a field of crackpots, gains mainstream respectability. Physics, chemistry, medical and computer pioneers advance to the once exclusive domain of sci-fi dreamers, envisioning tiniest particles fit into place by human design. Nanotechnology manipulates and builds materials on atomic or molecular levels, producing tools to build objects precise to the last nanometer. Its goal is to create nature from the bottom up, atom by atom, molecule by molecule, with atoms as building blocks. Nature builds complicated molecules precise to the last atom. We seek to do it ourselves. Anything's theoretically possible with atoms and molecules individually controlled. Such an odd world takes getting used to. Venture capitalists, universities and government belie the fact that much passing for nanotech are speculative ideas sounding like late-night movie plots. Any new science has a dark side. Technology churning out miniature computers could also create miniature weapons.

Nanotechnology, defined by goals, lets anyone make anything, jeopardizing understanding of ownership. It's easy to imagine nanotechnologic social and economic chaos. Angel Technologies cofounded a $250,000 Feynman Grand Prize for whoever first produces a mechanical device fitting certain design specifications and small enough to fit in a box 100 nanometers on all sides. How the device is used is beside the point. The need to make good social and political decisions is true about any new technology. Molecular nanotechnology is inevitable whether in 3 or 30 years. Physicist Eric Drexler in his 1986 book Engines of Creation championed nanovisions most famously. Nanotechnology roots trace to the late physics genius Richard Feynman's famous 1959 Caltech talk There's Plenty of Room at the Bottom outlining how all the world's books could be printed on the heads of a handful of pins. Today's dispute is how to do it. Molecular manufacturing already happens, a priority new technology. Proposals before Congress would double federal spending. Future applications are limited only by the imaginations of nanotechnology aficionados:

Computers as big as dust particles. Medical devices as big as bacteria. Hand-carried weapons of mass destruction. On-off switches invisible to the naked eye. Programmable paint changing color on command. Temperature-sensitive cloth. Voice-activated shrink wrap. Nail polish sensors, actuators and computing power painting itself out in stripes or animated scenes. With little done beyond basic research everybody's free to try favorite fantasies, not prevented by any law of physics. Extend an elevator cable into space, suspended in orbit, constructed of braided nanotube ropes thousands of km long. If it broke half of it would fly up, the other half plummeting to Earth. Sensors and actuators built in would keep that from happening. This well-worn fantasy once graced the cover of a popular science magazine. The question is how soon.

A universal assembler, a tiny robot with arms small enough to grab atoms one by one, its first assignment to construct a copy of itself. Given time and cheap raw materials donating atomic bricks and mortar, whole factories could quickly spring up. Experts, even those pioneering the new technology, doubt the first assembler can be built. The fundamental problem is getting the robot's fingers small enough. Despite the fat fingers problem, beguiling computer simulations of atom-sized gears and other machinery are on the Internet. Real-world laboratories clear some of the early hurdles. In 1989 IBM made worldwide headlines using 35 xenon atoms to spell out I B M on a nickel surface, one of the first demonstrations of positional control of atoms. A Cornell grad student built a nanoscale model of a 6-string guitar, each string 100 atoms wide. 20 of these guitars, laid out end to end, would equal the diameter of a single strand of hair. DNA strands become structural scaffolding, locate a single atom of one type hidden among billions of different atoms on a surface and make images of whirring rotary engines visible only to sophisticated measurements of atomic forces. It may even be possible to sculpt the electron clouds buzzing around the nucleus of atoms, using lasers like spatulas on so much subatomic putty.

* NANOTUBES: NANOTECHNOLOGY'S BUILDING BLOCKS
Rice University's nanotechnology center sells elongated buckyballs, or nanotubes, extraordinarily strong wires 50,000 times thinner than a human hair, to conduct electricity or serve as structural elements. The wire-shaped carbon molecules are one of nanotech's more promising design elements. 250 mg of single-walled nanotubes, each 1-billionth of a meter across, swimming in a special solution like noodles in broth, cost $350. Looking like vials of dirt, the tubes are too small to see even with the most powerful microscope. Nanotubes' unique structure gives astonishing characteristics. 200 times stronger than steel they're metallic conductors or semiconductors, depending how they're made. They're already used as fine tips in powerful imaging devices, atomic force microscopes and scanning tunneling microscopes. Nanotubes and other carbon based designs could also create working circuits of a new generation of super-powerful computers, making today's desktops and handhelds seem absurdly big and slow.

Problems
Nanotubes are easily mass-produced in tangled bundles. It takes a long time to straighten them out let alone put them in place one by one. Researchers want to grow nanotubes oriented the same direction like beds of nails. There's little point in things too small to see or detect. Making each machine a molecule at a time takes weeks to make a single working element in a supercomputer needing billions of elements. Making one is easy. Making many and making sure they work is difficult. Arranging rows of nanotubes in special arrays and pushing many tubes around at the same time may make it possible to build something big enough to be useful. Perfected processes to make and control nanotubes would weave super-strong nanotube rope strands, making possible lightweight materials. Car bodies only a few hundred pounds. Superlight space probes with nanotech skin. NASA sees mature nanotechnology used to construct active materials with embedded computing power, like lint. Nanotube actuators built in convert electrical energy to mechanical energy, resulting in materials that sense and repair defects automatically at the atomic scale so things won't have to wear out.

* SMALL SCIENCE - most nanotechnologic things are smaller than even a single skin cell, measured on the scale of nanometers. Special carbon structures called nanotubes for example can be as thin as 1.2 nanometers. A DNA turn is 3.4 nanometers.

* COMPARING SIZES
ATOM Smallest part of any element, its nucleus surrounded by one or more electrons.

NANOMETER 1 billionth of a meter. Nano, Latin for dwarf, means one-billionth. 10 hydrogen atoms = 1 nanometer.

MOLECULE As simple as two atoms or elaborate, relatively large structures. A glucose molecule is 0.9 nanometer. The DNA molecule, one of the most complex, varies in length and is 2.3 nanometers wide.

VIRUSES 10 - 100 nanometers.

BACTERIA 1,000 nanometers, or 1 micrometer.

RED BLOOD CELL 7,000 nanometers.

Human hair = 10,000 nanometers wide.

* EVOLUTION OF NANOTECHNOLOGY - using microscopes to visualize atomic particles. Sophisticated imaging methods view new landscapes. Building blocks are nanotube wires and molecule-sized computer switches. More elaborate nano-devices, such as gears, motors and pistons, have yet to be constructed except in computer simulations. Building nanostructures, scientists:

Feel atoms - microscopes detect atomic forces, examining individual atoms and molecules too small to see with conventional light microscopes. Movable scanning tips feel where particles are located, feeding the information to a computer. Software turns the data into sometimes startling virtual nano-world images, projecting images of atoms onto computer monitors or nanomanipulator workbenches. Computer mice or manipulator arms direct the microscope tips to move particles.

Move atoms - the tip of a scanning tunneling microscope (STM) at the right distance from an atom generates forces between tip and atom. Moving the tip moves the atom. See elaborate nanomanipulation demonstrations at the University of North Carolina.

Make things - some atoms, stickier than others, move more easily to a desired position.

* MOLECULAR SWITCHES
Reversible logic makes computers smaller and more efficient. Hewlett-Packard and UCLA made a rudimentary working on-off computer switch, the basic element of integrated logic circuits, consisting of a single molecule layer suspended between wires, hoping to use the switches and other diminutive components in microscopic nanocomputers billions of times more powerful than today's personal computers. This single-molecule computer component includes single layers of designer rotaxane molecules in its circuits, designed to function on a new generation of chips made through chemical reactions rather than printed circuits. Entire chips produced this way would fit in the intersection of 2 of the tiniest wires now used in computers, the goal not just to make computers the size of dust particles. Dust particles are large by nano-standards. The idea is to make simple computers the size of bacteria, getting something as powerful as today's desktop into a dust particle. Eventually such switches would combine with nanotubes into molecular-scale computer circuits. Hopes are to produce a 16-bit memory cell no larger than a 100 nanometer square.

* COMING Building something one atom or molecule at a time won't produce anything useful in human scale. Takes too long. Chemists can produce billions or trillions of designer particles for large objects. Many would be defective. Chemically assembled nanocomputers would allow for such defects with special software to detect and work around them. DNA scaffolding takes advantage of molecular engineering already evident in nature, possibly with DNA construction materials, capitalizing on DNA's distinctive chemical properties and double helix structure.

Nano-gears: Computer simulations show it possible to combine certain atoms and molecules into useful components of nano-scale machines. None are built yet but all sorts of virtual gears, pistons and rotors are proposed.

Medbots: Sophisticated sensors root out disease in the bloodstream. Programmable brain implants. Tiny instruments repair damage with unimaginable precision, allowing repair of freezing damage in cryonics experiments.

Spray-on computers: Computing power small enough may add smart capabilities to almost anything. Computer-driven sensors and electro-mechanical actuators for example could alter aircraft wings' texture to suit atmospheric conditions.

Sources: IBM, Hewlett-Packard; Cornell, Rice and New York Universities; Foresight Institute, Xerox PARC.

Ultra-small chips

Computer-driven microscopes draw patterns with lines 200-billionths of an inch apart, 15 - 30 nanometers wide, 5 nanometers apart, making possible smaller electronic chips of different materials than those now used. They'll build tiny circuits or store libraries in wafers with 80 million words per square inch and combine quill pens with computer-driven atomic force microscopes to draw lines on a surface. Ink flows down the microscope pen tip onto a surface as ink flows onto paper from the hollow of a dipped quill pen. Water collecting naturally on the microscope tip is a key part of the process, forming a tiny capillary so ink or other materials flow to the surface. At first drawing single lines they draw multiple lines, creating patterns in nanometer proportions. Dip-pen nanolithography transitions from monochrome to 4-color printing on a nanometer scale. Instead of using ink it could assemble useful molecules into pattern lines 30 molecules wide, building circuits of organic materials, the heart of future computers. The next frontier is deciding what kind of molecules to use for circuits. Nanometer drawing might also be used to create DNA arrays to identify genes in blood or other medical specimens, screening for thousands of genes with just one DNA chip.

Nanocomputers. Today's state-of-the art computer chips jam 40 million transistors into a space the size of a postage stamp. If you could build these tiny devices with individual molecules you could pack billions of them into the same area. Devices made from molecules - switches, transistors, diodes - let current flow in only one direction. 5 teams assembled the pieces into circuits that could add numbers and do other computing. Nanoelectronics is rapidly moving from blue-sky research to the beginnings of a technology. Computing will become a property of matter, like color. Molecular computing being feasible doesn't mean it's commercially viable. That will depend on what competing technologies evolve.

Quantum computer in early stages
Billions of molecules suspended in liquid in a test tube doing simple multiplication. Once thought possible only in science fiction, quantum computers could someday zip through calculations taking millions of years on today's fastest models.