With viruses serving as construction crews and DNA as the blueprint, biotechnology may hold the key to postlithography ICs
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.
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.
In 2001, Belcher and UCSB's Evelyn Hu founded Semzyme (Cambridge, MA), a company that will exploit biological self-assembly to make electronic materials as well as more biotechnology-specific applications, such as long-term storage of DNA. The company is set to begin operations this year and is choosing a first product to bring to market.
Big, established companies are taking this research seriously, too. The Army's Institute for Collaborative Biotechnologies has attracted sponsorship from Aerospace Corp., Applied Biosystems, Genencor, IBM, SAIC, and Becton Dickinson.
Genencor, in particular, took an early interest in bioengineering viruses, forming a $35 million partnership with silicon materials giant Dow Corning in 2001. In the short term, the two firms are merging peptides with silicon-based chemicals to make fabric treatment and cosmetic products. Sensors and other electronics elements are future targets.
DuPont, too, is tinkering with bioevolved peptides. According to Tim Gierke, the company has identified one short-term application: purifying carbon nanotubes. Recently, these hollow pipes just a few nanometers wide have been turned into experimental logic circuits and other devices. Depending on the nanotube's structure, it acts as either a semiconductor or a metal. Unfortunately, current methods generate tubes of both types along with a messy soup of soot, and there's no good way of sorting anything out.
So DuPont evolved peptides that selectively grab the nanotubes and ignore other forms of carbon. To separate the semiconductors from the metallics, the company turned to another important biomolecule--DNA. DuPont scientists discovered that when a particular form of DNA and carbon nanotubes bind, metallic and semiconducting tubes can, to a degree, be separated using a common laboratory trick.