8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

P9.22Tue 611:23-14:00A non-Brownian suspension with switchable attractiveinteractionsChristoph Goegelein 11 Max-Planck-Institute for Dynamics and Self-Organization, MPI-DS, Am Fassberg 1737077, Goettingen, GermanyWe study the fluidization and sedimentation process of micrometer-sized spheres in a binary liquidmixture. For this purpose, a fluidized bed setup has been designed to control the temperature ofthe flow cell very accurately. The non-Brownian particles are immersed in a mixture of waterand lutidine which exhibits a well studied lower critical point slightly above ambient temperature,i.e. the mixture starts to phase separate upon heating. Since the water-rich phase wets thehydrophilic glass spheres, capillary bridges are formed between adjacent particles [1]. If thesystem is cooled below the demixing temperature, the bridges disappear within a few seconds byintermolecular diffusion. Thus, this systems offers the opportunity to switch the capillary bridges(i.e. an attractive interaction) on and off by altering the temperature. The effect of these attractiveinteractions on sphere packings with different volume fractions is study in the present work.[1] C. Gögelein, M. Brinkmann, M. Schröter, and S. Herminghaus, Langmuir 26 (2010)22, 17184.Acknowledgement: This project is generously subsidized by the Explore program of BP.22