Nanotech -- the science of building and manipulating structures at the molecular level -- promises fresh perspectives on and unexpected solutions to a wide range of existing problems in semiconductors, optics, sensing, and biotechnology. Many of this year's TR100 honorees, determined to make new breakthroughs, are turning to nanotechnology to gain an unprecedented level of precision, control, and flexibility in creating new materials and devices. The nanomaterials invented by this elite group promise everything from faster and smaller electronics to more effective and targeted therapies. "When you get to the nano length scales, you can get unique properties," says Yi Cui of the University of California, Berkeley. The TR100's Nanotech+ category includes a broad range of innovations and research in materials science and energy. But it is on the scale of the ultrasmall that many of this year's TR100 are making their biggest contributions.

Much of the action is in biomedicine. That's because nanomaterials are just the right size to interact with important biological actors, such as proteins, DNA molecules, and viruses. Applying nanotech to biomedical problems "is a natural fit," says Darrell Irvine, a biomedical-engineering professor at MIT.

Irvine is helping to build better vaccines against diseases such as malaria and cancer by designing nanoparticles of a synthetic polymer. The nanoparticles, which carry specific stimulating molecules and antigens, are taken up by immune cells, triggering an immune response. Because of their tiny size, the nanoparticles can deliver the molecules with a high level of precision to specific receptors inside cells. That means better control of the strength and type of the resulting immune response, which should make for more effective vaccines. Irvine has recently begun working with medical researchers at Harvard University to investigate materials that could be used to deliver an HIV vaccine.

Albena Ivanisevic, a chemistry professor at Purdue University, is employing a technique called dip-pen nanolithography to help solve a central problem for tissue engineers hoping to repair damaged body parts: controlling the precise growth of cells at specific locations. Ivanisevic coats microscopic tips with cell-nourishing peptide molecules; the tips then deposit the peptides onto a surface. The ability to arrange those peptide molecules with nanoscale precision gives Ivanisevic greater control over how and where cells will grow on the surface -- ultimately forming new tissue for the body.

Nanotech also opens up new possibilities for those working to more effectively exploit or manipulate light. As anyone who has ever had to change a light bulb might suspect, conventional incandescent lighting is based on a 150-year-old technology, and researchers are eagerly looking for new ways to extend the lifetimes and boost the efficiencies of light-emitting materials. One of the favorite toys of researchers in the field is quantum dots -- nanoparticles of semiconductor material that give off different colors of light depending on their size. And Vladimir Bulovic, a professor of electrical engineering at MIT, is using these hardy, brightly colored nano dots to reinvent the light bulb. From quantum dots, Bulovic has built novel light-emitting diodes that can be incorporated into flexible materials like plastic and should last much longer than typical light bulbs. While others, including Bulovic himself, have already developed organic light-emitting diodes, Bulovic says quantum dots can extend their effective lifetime, making them more widely usable. He's hoping to produce a highly efficient and long-lasting light-emitting flexible material in the next one to two years.

Marcel Bruchez, lead product development scientist at Quantum Dot of Hayward, CA, is also enlisting the glowing nanoparticles, but for biological imaging and the development of diagnostics. Quantum dots emit light for much longer than the conventional dyes used to track activity inside living cells, and their varied colors mean that researchers can simultaneously image multiple events and gain greater insight into the inner workings of cells. For Bruchez, the benefit of working with nanomaterials is that they open up whole new ways of thinking about problems. "It gives you greater flexibility in manipulating the materials and in putting them where you want them to go," says Bruchez.

Electronics researchers pursuing ever smaller and faster circuits are also making strides with the help of nanotech. "The silicon industry is already in the nano regime," points out Kinneret Keren, a researcher at Stanford University. "Now they're trying more for the molecular regime." That means using molecules such as carbon nanotubes to build next-generation electrical circuits. While other researchers have already made transistors out of individual semiconducting nanotubes, Keren decided to address the process of assembling such transistors. Her trick was to attach complementary pieces of DNA to a nanotube and to a silicon wafer; because the two pieces of DNA naturally bound to each other, they did the work of bringing the nanotube and the wafer together so as to produce a transistor. While Keren's process remains a laboratory feat, it could eventually offer a new method of efficiently manufacturing tiny circuits in which each transistor is a single molecule.

While researchers like Keren recruit biomolecules to help fabricate electronics, Mayank Bulsara is sticking with traditional silicon -- but manipulating it in new ways. Bulsara, cofounder and chief technology officer of AmberWave Systems of Salem, NH, is developing a new form of silicon that promises to make computer chips 20 percent faster while lowering power consumption by 30 to 40 percent. The key is to stretch a silicon crystal by pulling its atoms apart just a few thousandths of a nanometer -- "like a rubber band," says Bulsara. This stretching alters the properties of the material so that the electrons racing through it are less likely to collide with silicon atoms, scatter, and slow down. Bulsara hopes to have chips containing the stretched silicon on the market in major quantities by the end of next year.

This year's TR100 are just beginning to demonstrate the results of nanotech's forays into exciting new territories, but taking their work out into the real world poses its own problems. "The greatest challenge is coming up with ways of producing nanomaterials over large enough areas," says Bulovic. But when that challenge is finally met, don't be surprised if the rising stars you'll read about in the next few pages were among those who helped point the way.