Microrheology

Diffusing Wave Spectroscopy and particle tracking based microrheology

Analyzing the passive or driven motion of a colloidal probe particle immersed in a complex environment, provides unique insights into the local mechanical properties of materials. We have made contributions to this field since 2000 both on the technological side as well on the study of the physics and material properties. Since a few years we have added advanced particle tracking and manipulation to our portfolio based on new microscopy equipment purchased in 2011. In 2015 we demonstrated diffuse light induced attractive forces between micron sized particles (Nat. Comm. 2015). More recently we have expanded our research to non-linear optical microrheology in emulsion glasses. We monitor the trajectories of the probe and measure displacements and their probability distributions. Our experiments reveal intermittent dynamics and bimodal van Hove distribution functions around a depinning transition at a threshold force. This work in carried out in collaboration with our colleagues at UC Los Angeles, University of Konstanz and Seoul National University.

· Yoon, J., Cardinaux, F., Lapointe, C., Zhang, C., Mason, T. G., Ahn, K. H., & Scheffold, F. Brownian dynamics of colloidal microspheres with tunable elastic properties from soft to hard. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 546, 360-365 (2018).

· C. Zhang, G. Brügger and F. Scheffold, Tracking of colloids close to contact, Opt. Express 23 (17), 22579 (2015)

· G. Brügger, L. S. Froufe-Pérez, F. Scheffold, and J. J. Saenz, Controlling dispersion forces between small particles with artificially created random light fields, Nat. Comm. 6, 7460 (2015)

· P. Domínguez-García, F. Cardinaux, E. Bertseva, L. Forró, F. Scheffold, S. Jeney, Accounting for inertia effects to access the high-frequency microrheology of viscoelastic fluids, Phys. Rev. E 90, 060301 (R) (2014)