Mechanics of Interfacial Composite Materials

[Under construction -- Nick Schade (fall 2009)]

Figure 1. Stable support of different anisotropic "armored interfaces" with various particle sizes and bubble sizes. (a) Ellipsoidal bubble obtained by fusing two spherical armored bubbles. (b) Extremely high aspect-ratio gas bubbles such as these mm-length spherocylinders can be formed by several successive coalescence events. (c) A membranelike solid created by partially evacuating an armored bubble that was originally spherical. (d) One can even generate a permanent stable change in topology of an air bubble by introducing a hole to create a toroid.

Experiments have shown that if a fluid/fluid interface is covered with particles that are sterically jammed, the interface can exist in stable non-spherical shapes. The jammed particles thus allow the interface to behave in some ways like a solid. In this article, the authors examine the effects of small homogeneous and inhomogeneous stresses on this granular medium, or "armored bubble". They characterize the armored interface as an interfacial composite material because the interfacially trapped particles retain their individual characteristics.

General Information

Keywords:

Authors: Anand Bala Subramaniam, Manouk Abkarian, L. Mahadevan, and Howard Stone.

Date: May 24, 2006

Division of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA.

Langmuir 2006, Vol. 22, No. 24, 10204-10208. [1]

Summary

Armored interfaces are fluid/fluid interfaces covered with rigid particles typically larger than a micron in diameter. Various recent studies have shown that armored interfaces are capable of supporting bubbles or droplets with various nonspherical geometries, as shown in Figure 1. It can be shown that armored interfaces have the attributes of composite materials, because the system exhibits collective mechanical properties distinct from the properties of the constituent particles and fluid/fluid interface.