Ilic and colleagues made cantilevers about a micron (millionth of a meter) wide, 5 or 10 microns long and 200 nanometers (billionths of a meter) thick, suspended over an empty space about a micron deep. When energy was pumped in from a laser or by an attached vibrating piezoelectric crystal, the cantilevers vibrated up and down at a resonant frequency that depended on their dimensions and mass.
Then the researchers demonstrated that in-plane motion can be created by hitting the base of the cantilever with a laser pulsed at the resonant frequency of the cantilever's in-plane vibration, which is different from the resonant frequency of its vibration perpendicular to the plane. To measure in-plane motion the researchers shined another laser on the free end of the cantilever and detected the chopping of the beam as the cantilever moved from side to side.
To show that in-plane motion could shake unwanted materials off of biosensors, the researchers distributed polystyrene spheres ranging from half a micron to a micron in diameter onto an array of cantilevers. The spheres, which attached themselves by electrostatic attraction, were removed by in-plane shaking. But when the cantilevers were made to vibrate more intensely up and down -- even so far that they bumped the "floor" below -- the spheres did not budge, nor did they during spinning of the entire chip.
In-plane vibration also could be used to determine how strongly particles are bound to the surface by observing how hard they need to be shaken to come loose, Ilic said. The ability to excite in-plane motion also has applications in making nanoscale gyroscopes, in nano optics and for basic physics experiments, he added. ###
Co-authors with Ilic and Craighead, who is the Charles W. Lake Jr. Professor of Engineering and professor of applied and engineering physics at Cornell, are Slava Krylov, professor in the Department of Solid Mechanics, Materials and Systems at Tel Aviv University, and Marianna Kondratovich, an undergraduate researcher in Cornell's Department of Mechanical and Aerospace Engineering.
Related Information: Craighead Research Group Contact: Press Relations Office pressoffice@cornell.edu 607-255-6074 Cornell University News Service, Bill Steele(607) 255-7164 ws21@cornell.edu
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