By the time you read this, there's a good chance a virus has built a transistor. Last July, a crowd of microbiologists in New York City heard materials scientist Angela Belcher make a bold prediction: within six months, her laboratory at the Massachusetts Institute of Technology (MIT, Cambridge) would have genetically engineered a virus to coat itself in a crystalline semiconductor sheath and locate and bridge two electrodes--thus forming the critical part of a field-effect transistor, the kind on which most computer chips rely. If Belcher delivers, it will dramatically illustrate biology's promise in furthering nanotechnology, the manufacture of circuits and devices only billionths of a meter in size.
Biological self-assembly, as this field of research is called, has a compelling appeal. Living creatures produce the most complex molecular structures known to science. Crafted over eons by natural selection, these three-dimensional arrangements of atoms manifest a precision and fidelity, not to mention a minuteness, far beyond the capabilities of current technology. Under the direction of genes encoded in DNA, cells construct proteins that put together the fine structures necessary for life. And now that scientists can alter the genetic codes of microbes with increasing ease and accuracy, more and more research is showing that this same mechanism can be forced to construct and assemble materials critical not to nature necessarily, but to future generations of electronics.
Belcher's virus gets its circuit-building power from a coat of proteins that interacts at the molecular level with a material to which it's introduced, such as a semiconductor wafer. In projects now under way, scientists are using proteins and DNA, the molecule that encodes genetic data, to construct nanometer-scale crystals of semiconductor atom by atom, bind to precious metals, distinguish between different nanoparticles by their electrical properties, and otherwise choreograph the arrangement of nanoscale components.
Circuits that assemble themselves may sound like wishful thinking. But Tim Gierke, who leads a growing effort at E. I. du Pont de Nemours and Co. (Wilmington, Del.) to apply biotechnology to electronics, says that after three years of research, his company is convinced that biological self-assembly is within the realm of commercial viability.
And the U.S. Army, one of the original sponsors of this field of research, is such a believer that in August it formed the Institute for Collaborative Biotechnologies, a US $50 million research center comprising the University of California at Santa Barbara, MIT, and the California Institute of Technology, to accelerate the work. The Army and others see a role for biological self-assembly in fabricating future sensors, displays, and magnetic storage devices, as well as in energy production and information processing.
But there is no guarantee that this technology, as promising as it is, will really lead to practical nanometer-scale devices. So far, research has been limited to manipulating materials such as crystals of semiconductor, not constructing complete devices. And there are many nonbiological nanocircuit schemes in the works as well.
Most scientists say the technology will first be used to construct sensors consisting of one or a few nanodevices connected to ordinary silicon circuitry. But that's not what drives the research. Their ultimate ambition is to upend current fabrication methods by genetically engineering microbes to build nanoscale circuits based on codes implanted in their DNA. No more cutting patterns into semiconductor wafers, an increasingly arduous process involving lasers, plasma, exotic gases, and high temperatures in expensive industrial environments. Instead, a room-temperature potion of biomolecules will execute, on cue, a genetically programmed chemical dance that ends in a functioning circuit with nanometer-scale dimensions.
"The goal," says Evelyn L. Hu, professor of electrical engineering at the University of California at Santa Barbara (UCSB) and an IEEE Fellow, "is to see if you can generate the next paradigm shift" in electronics.