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arXiv · 1701.07070

Direct measurement of the ballistic motion of a freely floating colloid in Newtonian and viscoelastic fluids

Andrew P. Hammond·Eric I. Corwin
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Abstract

A thermal colloid suspended in a liquid will transition from a short time ballistic motion to a long time diffusive motion. However, the transition between ballistic and diffusive motion is highly dependent on the properties and structure of the particular liquid. We directly observe a free floating tracer particle's ballistic motion and its transition to the long time regime in both a Newtonian fluid and a viscoelastic Maxwell fluid. We examine the motion of the free particle in a Newtonian fluid and demonstrate a high degree of agreement with the accepted Clercx-Schram model for motion in a dense fluid. Measurements of the functional form of the ballistic-to-diffusive transition provide direct measurements of the temperature, viscosity, and tracer radius. We likewise measure the motion in a viscoelastic Maxwell fluid and find a significant disagreement between the theoretical asymptotic behavior and our measured values of the microscopic properties of the fluid. We observe a greatly increased effective mass for a freely moving particle and a decreased plateau modulus.

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Andrew P. Hammond, Eric I. Corwin. 2017-10-02. Direct measurement of the ballistic motion of a freely floating colloid in Newtonian and viscoelastic fluids. https://doi.org/10.1103/physreve.96.042606

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