Spatially-resolved rotational microrheology with an optically-trapped sphere

• DOI: 10.1038/srep01759
• Publication Date: 2013-05-02T14:38:21Z
• Authors: James S. Bennett; Lachlan J. Gibson; Rory M. Kelly; Emmanuel Brousse; Bastian Baudisch; Daryl Preece; Timo A. Nieminen; Timothy Nicholson; Norman R. Heckenberg; Halina Rubinsztei...
• Keywords: Fluids; Science & Technology; Tweezers; 01 natural sciences; Article; Multidisciplinary Sciences; DIFFUSING-WAVE SPECTROSCOPY; 1000 General; 0103 physical sciences; Science & Technology - Other Topics; Rheology; TWEEZERS

We have developed a microrheometer, based on optical tweezers, in which hydrodynamic coupling between the probe and fluid boundaries is dramatically reduced relative to existing microrheometers. Rotational Brownian motion of a birefringent microsphere within an angular optical trap is observed by measuring the polarisation shifts of transmitted light. Data gathered in this manner, in the strongly viscoelastic fluid Celluvisc, quantitatively agree with the results of conventional (bulk) rheometry. Our technique will significantly reduce the smallest sample volumes which may be reliably probed, further extending the study of rare, difficult to obtain or highly nonhomogeneous fluids.