Authors: M. Hosseini, M.M. Yazdanapanah, S. Siddique, R.W. Cohn
Affilation: University of Louisville, United States
Pages: 413 - 416
Keywords: viscosity, drag force, AFM, rheology, polymer, nanowire, nanofluidics
We recently demonstrated that long metal nanoneedles grown on atomic force microscope (AFM) probes can give very clear measurements of the surface tension, evaporation rate and viscosity of simple liquids. However, in the case of concentrated polymeric solutions, measured by the Q damping method, the viscosity measured with a nanoneedle-tipped probe was found to be orders of magnitude lower than with macroscopic viscometer measurements. Increasing the amplitude of cantilever deflection by 10X leads to some increase in viscosity, but far from the expected macroscopic value. Viscosity also increases with adsorption of monolayers of PEO. While the source of these discrepancies requires additional investigation, it is still possible to observe drag forces corresponding to macroscopic viscosity when the needle is displaced microns of distance and velocities of at least 10 microns/s. These investigations are directed at understanding if Q damping measurements are capable of sensing the dynamics of short range random polymer chain interactions at distances less than the entanglement length.
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