You might not recognize the assembly lines of the future. In fact, you might not even be able to see them without a microscope.
In June, researchers at the University of Texas at Austin (UT) announced that organic viruses can produce microscopically small and uniform semiconducting building blocks for components that eventually could be used to build computers, pagers and other electronic devices. The process used by UT scientists combines proteins from viruses with inorganic elements often used as semiconductors. This results in a hybrid called electronic biocomposite materials. Natural biocomposite material includes bone and shells.
Angela Belcher, UT’s lead scientist for the project, said that once the proteins bind to specific inorganic particles, they are capable of assembling a desired molecular pattern.
The UT scientists went through 100 million viruses before determining which worked best with particular materials. Only proteins that bound themselves tightly to the inorganic material were cloned. Belcher compares it to rounding up 100 million people who try to unlock the same door until they find the one with the right key.
The key already exists in nature. Take the simple but rugged abalone shell, a natural biocomposite product of 2 per cent organic and 98 per cent inorganic materials. Constructed of calcium carbonate crystals that are siphoned from seawater and held together with a mortar of proteins and complex sugars, abalone shells are as strong or stronger than advanced synthetic ceramics.
Mammals produce biocomposite materials such as bone and cartilage. Non-vertebrate sea creatures surround themselves with shells made of biocomposites. Whales’ teeth are made of baleen, a product that strongly resembles plastic and was once used for whalebone corsets. Human bones, teeth, fingernails and hair are biocomposites as well.
These materials are now the starting point for modern scientists. The initial goal is to “control crystal growth and placement and assembly of nanoparticles using tools from nature,” Belcher said. Nanos is the Greek word for dwarf and refers to the construction of highly miniaturized devices.
According to Belcher, “Nature makes materials that are both strong and tough and that display exceptional nanostructure regularity.”
Living systems form organic-inorganic structures by processes that are responsive to local stimuli, are self-correcting and involve disassembly and reassembly. “By understanding the processes by which nature makes materials, new materials can be designed with some of these desired features,” Belcher said.
Researchers have already identified proteins at the ends of viruses that differentiate between semiconductor alloys and bind to specific ones. Selective specificity is critical, said Evelyn Hu, a professor of electrical engineering at the University of California at Santa Barbara and also a member of the UT team.
“This sounds like science fiction, and we are years away from doing this, but selective specificity means you could dump all the components into a virtual vat and assemble fairly complex and sophisticated products,” Hu said. “The instructions would be in the building blocks themselves, rather than in a master builder that would order the process.”
Scientists could use viruses to “grow” electronic building blocks for transistors, wires, connectors, sensors and chips significantly smaller than anything currently manufactured. The components would be so tiny that scientists would have to use atomic force and electron microscopes to see them.
That’s great news for the electronics industry, which experts claim is fast approaching the current limits of miniaturization. In electronics, smaller is faster, cheaper and more convenient – so much so that the federal government has declared nanotechnology a national research priority.
Researchers also are working to enlist other proteins as biological assistants. Cockroach cuticle, which contains a springy protein that doesn’t swell when it meets organic solvents, is perhaps the future source of rubber gloves.
A hybrid of silkworm protein and fibronectin – a blood protein that promotes cell adhesion – forms an ideal medium for growing cells in the laboratory. The protein elastin could be the base of a material that can be made into tubes that feel like real blood vessels. Some day, petroleum-based products might be replaced by materials produced by proteins synthesized by organisms.
The commercialization of such biomimicry is years away. But with each step, biologically-based microscopic components draw closer.
