Parts | Days | Selection | Search | Updates | Downloads | Help
CPP: Fachverband Chemische Physik und Polymerphysik
CPP 30: Friction and Rheology
CPP 30.4: Talk
Tuesday, March 13, 2018, 12:45–13:00, C 264
Microliter viscometry using a bright-field microscope: η-DDM — Manuel A. Escobedo-Sanchez1, Juan-Pablo Segovia-Gutierrez1, Angel B. Zuccolotto-Bernez2, Jan Hansen1, Caroline-C. Marciniak1, Katrin Sachowsky1, •Florian Platten1, and Stefan U. Egelhaaf1 — 1Condensed Matter Physics Laboratory, Heinrich Heine University, Düsseldorf, Germany — 2Departamento de Física, CINVESTAV-IPN, México D.F, Mexico
Passive microrheology can be considered as the counterpart of bulk small amplitude oscillatory shear measurements at the microscale. Microrheology exploits the Brownian motion of colloidal tracer particles. The mean-squared displacement (MSD) of the tracers is related to the rheological and viscometric properties of the suspension. It is commonly determined by particle tracking, which requires a careful selection of tracer trajectories. In contrast, Differential Dynamic Microscopy (DDM) avoids particle tracking and hence its limitations while still allowing for microliter-sized samples. DDM exploits the spatial Fourier transform of image differences which provides access to the MSD via the intermediate scattering function that is commonly acquired in dynamic light scattering experiments. We propose to combine DDM with the empirical Cox-Merz rule to estimate the steady shear viscosity of biological and soft matter systems. This technique even is applicable when reliable steady shear measurements are hard to achieve due to the torque resolution limit. Hence, an optical microscope can be used as a convenient and reliable microliter viscometer.