For a while, nanotechnology was the latest buzzword. More recently, though, it has moved from the realm of extropian fringe groups, whose members want to freeze their heads when they die, to the less glamorous reality of research and development. Microscopic machines called MEMS (microelectronic mechanical systems) are already on the market, in automobiles and ink-jet printers. Researchers have developed scanning-tunneling and atomic-force microscopes that can visualize single molecules and even move them into specific patterns. Laser beams can be used as "molecular tweezers" so single protein molecules can be studied and manipulated. DNA computers are in the works. Although many people still doubt the feasibility of a future in which true mass-market nanofabrication is standard practice, many researchers have begun to explore the question of what is actually possible.

The Web is an excellent resource for surveying the amazing array of projects and plans currently in the works, or at least in the imaginations of researchers. In fact, one Web search on the term "nanotechnology" turned up over 49,000 matches, an impossible amount of information. Nonetheless, a number of Web sites offer articulate, well-rounded views of nanotechnology (or nanotech) in general, and its applications to biology and medicine.

One good starting point is the Nanotechnology Web site at Xerox PARC, written by Ralph Merkle. It offers an essay on the basic principles of nanotechnology, and lists many useful links, books, and references. Biologists and physicians might also enjoy Merkle's essay called Nanotechnology and Medicine, where he describes a future in which we might "build fleets of computer-controlled molecular tools much smaller than a human cell that . . . could remove obstructions in the circulatory system, kill cancer cells, or take over the function of subcellular organelles."

The Foresight Institute, which describes itself as "a nonprofit organization dedicated to raising public awareness and understanding of nanotechnology," hosts a massive Web site on nanotechnology. One of the founders of the Foresight Institute was nanotech guru K. Eric Drexler, whose book Engines of Creation first developed the future scenario in which disease, poverty, and pollution would be virtually eradicated by nanomachines. The Foresight Institute's site covers nearly everything nanotech, including a vision of the future that is either thought provoking and wondrous or wildly unrealistic and bizarre, depending on your point of view. The site provides extensive essays by Drexler and others, as well as news briefs and numerous links to other sites.

What is possible in the realm of nanotech, and what isn't? One promising approach to exploring this question involves studying the capabilities of living cells. After all, these biological systems have proven that such "nanomachines" as cellular motors and such "nanoassemblers" as DNA polymerase can exist and function without violating known physical laws. So, why not consult the experts?

For example, bacteria use "biosensors" to detect nutrient gradients and then to propel themselves toward the food using flagella. These flagella are true nanoscale motors, as are kinesin and cellular microtubules, and actin and myosin in muscle. A number of Web pages describe how investigators study the ways in which these motors can convert chemical energy from ATP to mechanical energy. These include the pages of Jonathan Howard at the University of Washington, Steven Block at Princeton University, and the Marie Curie Research Institute's Molecular Motors Group. The Curie page posts especially nice visuals, with animated drawings of kinesin "stepper motors," as well as computer-enhanced micrographs of the molecules involved.

In the future, many devices in nanotechnology might mimic another of nature's capabilities - self-replication. Although researchers can now push around single atoms and molecules, it is a slow, painstaking process, and therefore much too expensive for any kind of mass production. Nevertheless, by watching DNA self-replicate, investigators might learn a few tricks. In fact, DNA constitutes almost almost an entire nano-specialty in itself. Ned Seeman, a chemistry professor at New York University, is developing ways to construct three-dimensional objects, including cubes and more complex polyhedra, from synthetic DNA molecules. Such structures could serve as building blocks for new and highly resilient materials made of DNA frameworks, to which other functional molecules could then be attached. One section of this group's site, DNA Technology in Ned Seeman's Laboratory, has some lovely pictures of the structures they have created.

Various laboratories use these forms of microscopy. For example, Jan Hoh's laboratory at Johns Hopkins University School of Medicine uses AFM to address biological problems related to membrane and protein biophysics. A page called the Scanning Probe Microscopy at Ludwig-Maximilians Universität München posts micrographs of chromosomes (whole and cut with AFM) and images of four nucleotides. Each base looks different with STM, and the investigators hope to determine the visual and crystal structures of A,T,G, and C for eventual sequencing applications. Finally, Zyvex, one of the first private molecular nanotechnology development companies, posts STM and AFM micrographs and real-time movies.

Currently, the field of nanotechnology is built more on potential than reality. In many areas, though, it has moved into the realm of "engineering challenge," rather than "visionary pipe dream." Many experts compare the current state of nanotech with that of computer science in the 1950s; investigators don't quite know how they'll get these ideas to work, but they're pretty sure that they can.

Endlinks

NanoMedicine - includes a list of nanomedicine FAQs (frequently asked questions) and links to related sites.

NanoTechnology Magazine - a sort of Popular Mechanics of nanotechnology, covering almost every angle on this field.

Nanotechnology - the Web site for the scholarly journal that covers occasional biology and much engineering and computer science.

Intelligent Micromachine Initiative - includes wonderful movies of micromachines in motion. From Sandia National Laboratories.

The Semiconductor Subway - covers all kinds of semiconductor devices, including MEMS, and includes links to conferences, related newsgroups, and more.