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Nanotech Profiles

Marcel Bruchez
Age: 31 | Cofounder and principal staff scientist | Quantum Dot
Six years ago, Marcel Bruchez, then a graduate student at the University of California, Berkeley, showed that quantum dots – glowing particles just nanometers wide – could be used to tag proteins inside cells. Within months, Bruchez had cofounded Quantum Dot to market the new imaging tool to biologists and drug developers seeking a more detailed picture of molecular events. It is “one of the first commercial applications of nanotechnology,” says Bruchez.

Yi Cui
Age: 28 | Research fellow | University of California, Berkeley
While some nanotech researchers create the basic building blocks of new materials, others, like Yi Cui, play equally important roles in piecing those blocks together and taking the next steps toward practical applications. Cui’s ability to finely control the assembly of nano building blocks has led to new devices that may end up in cancer-screening chips, quantum computers, and solar cells.

As a chemistry PhD student at Harvard University, Cui did pioneering work on nanowires, using a combination of lasers and chemical vapors to cajole silicon to form tiny wires that not only conducted electrons but could also switch a current off and on like a transistor. Cui even fabricated nanowires whose switching depended on the presence of specific proteins, so they could serve as ultrasensitive biosensors in tests for early signs of prostate cancer.

At Berkeley, Cui has continued to master the art of building functional devices on the nanoscale. Most recently, he has found ways to precisely link together new types of nano building blocks called nanotetrapods – dots of material a few nanometers wide, each with four nanorods that radiate out in different directions. While other researchers have previously made nanotetrapods, Cui can link many of them together to create a web of circuitry and finely control their electrical properties. “We can get the nanotetrapods to self-assemble into whatever pattern we need,” including arrays of transistors, says Cui. Because of their small size, these circuits could in theory be several times faster than the circuits in today’s computer chips.

By arranging nanotetrapods into branching networks, Cui has transformed them from a raw ingredient into something that might be built into real devices, such as solar cells. And because the nanotetrapods are small enough to register the presence of individual electrons, they could even take advantage of the weird quantum properties of subatomic particles, forming the basis for new types of computers that will operate thousands of times faster than today’s fastest machines. While that application is many years away, Cui has already demonstrated the possibility of building new structures using the basic ingredients of nanotech.

Leroy Ohlsen
Age: 30 | Founder and chief technology officer | Neah Power Systems
Fuel cells that run on methanol can power cell phones and laptops, but they’re expensive and not very powerful. Leroy Ohlsen, founder of Neah Power Systems of Bothell, WA, replaced the cells’ plastic membranes, which strip electrons out of the methanol to produce electricity, with porous silicon. Not only does the silicon “give us more power,” says Ohlsen, but it could also cut manufacturing costs. Expect the company’s first fuel cells in 2006.

Molly Stevens
Age: 30 | Lecturer | Imperial College London
Materials scientist Molly Stevens believes that when it comes to sensing changes in the environment, nothing beats biological systems. That’s why she’s turning to biological molecules to create “smart” nanomaterials that could lead to new, implantable sensing and drug delivery devices.

Such devices would quickly detect physiological changes in the body, such as a rise in cholesterol, and respond by releasing the appropriate dose of a stored drug. That’s the vision, at least. But realizing it will require new kinds of materials that behave differently under different chemical conditions.

Stevens has recently shown that she can control the behavior of gold nanoparticles by changing the pH of the solution in which they are suspended. She attached the particles to specially designed peptide molecules that, under the right pH conditions, interact with each other to pull the particles together into an organized structure. A change in pH alters the shape of the peptides so that they repel each other, and the particles disperse. “We’re taking the best of nature’s creativity and using it for ourselves,” says Stevens.

The experiment shows that it’s possible to create materials that automatically reshape themselves in response to chemical changes in the body. Such a material could yield implantable drug delivery devices that act as their own biological sensors.

Stevens is tapping into the versatility of peptides for the next stage of her work. She’s now engineering the peptides so that they change shape in subtler and more varied ways. A drug delivery device made using such peptides would be more sensitive to physiological changes and could offer more control over a multitude of different drug dosages. If her new project succeeds, Stevens will have played an instrumental role in making not only nanomaterials but drug delivery far smarter.

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Tagged: Computing, Materials

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