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Capillary Aging of the Contacts between Glass Spheres and a Quartz Resonator Surface

Year: 2006

Journal: PRL 96, 058301 (2006), 20100827

Authors: D’Amour J. N., Stålgren J. J. R., Kanazawa K. K., Frank C.W., Rodahl M., Johannsmann D.

Last authors: D. Johannsmann

Organizations: Department of Chemical Engineering, Stanford University, Stanford, California, 94305, USA Q-Sense AB, SE-426 77 Västra Frölunda, Sweden Institute of Physical Chemistry, Clausthal University of Technology, Arnold-Sommerfeld-Strasse 4, D-38678 Clausthal-Zellerfeld, Germany

Country: Germany

The strength of the contacts between small glass spheres and the surface of a quartz crystal resonator has been probed based on the increase of resonance frequency induced upon sphere contact. The acoustic interaction between the sphere and the plate is modeled as a low-frequency coupled resonance; the dependence of the resonant parameters on overtone order lends support to this model. After exposing the sample to humid air and drying it again, the contact strength increases at least tenfold due to capillary forces--we observe a hysteretic form of the sand-castle effect. Repeated wet-dry cycles reveal logarithmic capillary aging with time. The experiments suggest that the drying of the liquid bridges leads to a contraction of small voids in the contact zone, subsequently increasing cohesion.