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(June 5, 2007) SAN DIEGO — Since carbon nanotubes (CNTs) tend to grow with erratic kinks and bends in the tube structure, a group of engineers from Stanford University has devised circuit-simulation algorithms that eliminate bad connections caused by errant CNTs. The work, which involves fine grids rather that direct interconnects, is being presented at the Design Automation Conference (DAC), June 4–8 in San Diego.
Subhasish Mitra, assistant professor of electrical engineering and computer science; H.-S. Philip Wong, electrical engineering professor; Chongwu Zhou, chemistry professor at the University of Southern California; and Nishant Patil and Jie Deng, graduate students, initially devised a single-circuit element — a NAND gate — immune to the misconnections CNTs can create. They then abstracted and generalized the fundamental mathematics of this circuit to create an algorithm that produces working circuit designs with twisted or misaligned CNTs. Simulations suggest that the algorithm is valid, so the Stanford team will use simulated designs to build and test real circuit elements based on the algorithm's output. The Mircroelectronics Advanced Research Corporation supported the research.
The algorithm breaks each circuit element into a fine grid, which can be analyzed mathematically. Engineers determine which grid squares CNTs must pass through, and those that CNTs cannot traverse, to create a working circuit design. CNTs in "illegal" or unwanted connection areas can be chemically etched away or rendered electrically irrelevant. This algorithm determines "legal" and "illegal" connection regions automatically, rendering circuits capable of a certain function. As yet, the researchers are not able to guarantee that CNTs will make the desired interconnect, but they can automatically prevent bad connections.
For more information on the research, visit Stanford's website. For more on the DAC conference, see DAC Hosts Range of Design Presentations and DAC Approaching in June.
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