Professor Harold Craighead (rear) looks on as graduate student Stephen Turner adds a DNA sample to a laboratory setup for testing an experimental biochip. Turner described his research on an artificial gel at the APS meeting. Robert Barker/University Photography
It could be a scene from amovie: A doctor puts a drop of blood intoa small hand-held device and instantlyreads out a complete DNA analysis. But itwould have to be a science fiction movie,because in real life machines thatanalyze DNA are about the size of arefrigerator. And hundreds of them,working for the past 10 years, haven'tbeen able to map the equivalent of oneperson's DNA.
But Cornell researchers areworking on a "biochip" -- an "artificialgel" made of silicon -- that might be astep toward the science fiction dream.Stephen Turner, a graduate studentworking under Harold Craighead, Cornellprofessor of applied and engineeringphysics, described his biochip research at the American Physical Society meeting in Atlanta.
The global scientific community has set itself the goal of sequencing all ofthe DNA in the human genome. But to date only about 10 percent of the totalhas been mapped. Largely, Cornell researchers say, this is because theprocess being used, gel electrophoresis, is cumbersome and time-consuming.
Electrophoresis gels consist of a maze of interlockingpolymer molecules that leave many tiny openings through which moving DNAmolecules must navigate. Using the same techniques used to make electroniccircuits, tiny passageways can be carved on a silicon chip.Turner's artificial gels are forests of vertical pillars with sizes down to100 nanometers (nm) thick and 100 nm apart. (A nanometer is one billionth ofa meter.)
They are smaller, Craighead believes, than earlier versions ofartificial sieves, an achievement made possible by using the CornellNanofabrication Facility's electron-beam lithography tools, which can layout features much smaller than those used so far in commercial integratedcircuits. Turner used a new technique in which the channel is filledwith a "sacrificial layer" that can be etched out after a covering layer is deposited. This allows much more precise control of the height of thechannel, he explained.
The artificial gel could lead to faster and cheaper methods forsequencing DNA.
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