MRI-R2: Development of a Correlation Force Spectrometer

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0959228Ducker"This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)."An improved understanding of the nanometer-scale motion of fluids is central to the development of our understanding of complex fluids and biomolecules. The PI proposes to develop an instrument that measures the forces acting during the natural motion of molecules and fluids, with capabilities that exceed all current instruments. This instrument will measure the correlated motion of two antiparallel cantilevers that have atomic force microscope (AFM) tips or colloidal spheres attached to the free ends. The fluid between the tips will couple the two cantilevers such that the correlated motion is sensitive only to the intervening fluid. This antiparallel arrangement will greatly diminish the contribution of the cantilevers compared to conventional AFM. Measurement of the correlated motion results in a large increase in signal-to-noise ratio because the correlation is not sensitive to electronic, optical or mechanical disturbances on individual cantilevers. Moreover, even the thermal noise on the individual cantilever is not part of the correlation signal, so the instrument will have a lower noise floor than is theoretically possible for existing single cantilever AFM techniques. The instrument will be capable of measuring the mechanical properties of individual molecules tethered between the two cantilevers, as well as the viscoelastic properties of complex fluids with nanometer resolution at frequencies up to hundreds of kHz. Also, the simplicity of the mechanical concept provides a relatively easy path for ultimate development of an inexpensive and small instrument.