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Phys. Rev. Lett. 98, 248001 (2007) [4 pages]

Measuring the Coordination Number and Entropy of a 3D Jammed Emulsion Packing by Confocal Microscopy

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Jasna Brujić
Department of Physics and Center for Soft Matter Research, New York University, New York, New York 10003, USA

Chaoming Song, Ping Wang, Christopher Briscoe, Guillaume Marty, and Hernán A. Makse
Department of Physics and Levich Institute, City College of New York, New York, New York 10031, USA

Received 14 April 2006; revised 26 November 2006; published 15 June 2007

Jammed matter is by definition impenetrable to light, such that little is known about the geometry of jammed systems. Using confocal microscopy to image an emulsion in 3D, we first explain the origin of the enhanced fluorescence at the droplet contacts and then determine the contact network inside the model frictionless system. This enables the experimental determination of the average coordination number Z which agrees with the isostatic predicted value of Z⟩≈6. Furthermore, we calculate the entropy of the packing from the network of contacts.

© 2007 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.98.248001
DOI:
10.1103/PhysRevLett.98.248001
PACS:
45.70.Cc, 87.64.Tt