Researchers at the University of Arizona are exploring ways to "grow" microchips using proteins from living cells.
Microchips -- those magic devices found in everything from cell phones to automobiles, from computers to clothes dryers -- currently are made by lithography, etching and soldering.
The new biological interconnects would bypass these processes with long strings of proteins called microtubules (MT). They'll connect transistors and other devices in microchips by growing between the device junctions. They're solder-free, don't involve lithography or etching, and are highly uniform. Once the proteins connect devices, they will be coated with metal and turned into microscopic wires.
MTs are common in nature. They help cells carry out mitosis (cell division) and have diameters of about 24 nanometers. That's small. You can pack a million nanometers into a millimeter. MTs also can grow to several microns in length. 1,000 microns make a millimeter.
So MTs can be 1,000 times or more longer than they are wide, which makes them ideal for fabricating incredibly tiny wires. These sizes are difficult to achieve with current lithographic processes and today's microchips have connector widths that are two to three times wider than metalized MT diameters.
MTs will allow designers to pack a lot more circuitry into a smaller package. Because they are uniform in size, have very little process variation and will self-assemble, MTs can be used in low-power circuits to lower energy demands 10 to 100 times below those of conventional circuitry. This energy savings is vital to portable systems, where extending battery life has been a problem.
When MTs are grown on a microchip, they will "know" where to make the proper connections because their ends have different polarities. With the proper chemistry, an MT's polarity can be exploited to cause the proper end to be attracted to the proper connector.
But don't start looking for MTs in devices at your local electronics store any time soon. The research still is in the "basic science" stage, and much remains to be done by scientists and engineers from widely diverse backgrounds.
At the University of Arizona this includes researchers from Electrical and Computer Engineering, Materials Science and Engineering, Biomedical Engineering, Chemical Engineering, Medicine, Chemistry, and Optical Sciences.
Microelectronics is just the first area the UA group is exploring as they study biomaterials, says Materials Science and Engineering Professor Pierre Deymier. He is one of two co-founders of the biomaterials group at UA.
"I can envision in the long term the idea of using biomolecules as building blocks where more traditional materials are used in many applications now," he says. "This is a whole new technology at the interface of biology and engineering, and I can see us creating a new paradigm in device making and a new technology for engineering. It has great potential."
Proteins have been programmed over millions of years to do very specific tasks, he says. Engineers hope to exploit these million-year-old designs and apply them to devices, systems and structures. But they're not limited only to those proteins found in nature. "We could work with biochemists to design proteins for specific tasks," Deymier says. "I can imagine a complete science of protein design for specific non-biological applications."
All this requires an understanding of both biology and engineering and calls for researchers from different academic cultures to work together. "Right now we're doing a cross-cultural kind of thing, trying to bridge those cultures," Deymier says. Biologists who have never seen a circuit are learning about electronics and engineers are finding out about proteins and biological processes. This means learning not only new disciplines, but the jargon specific to each one.
It also requires new ways of thinking about the academic environment. "We're becoming generalists and very task oriented," Deymier says. "Students work on tasks that may require input from various researchers in different disciplines. In this task-oriented approach we no longer have 'our' graduate students, while they have 'their' graduate students. We want to get things done and students move around, working with different faculty as the task requires." - By Ed Stiles
[Contact: Pierre Deymier, James Hoying, Ed Stiles]