image: Stabilizing dispersed phases. These schematic representations show how suspensions and emulsions can be stabilized with a third added phase. (A) Dispersed particles forming a pendular state in a primary liquid a (continuous phase, gray). The particles are kept together by pendular menisci of a second, immiscible liquid b (blue). This happens if the contact angle is low and the added liquid wets the particles. (B) Koos and Willenbacher report on a capillary state, in which drops of the secondary liquid form the center of particle agglomerates. In this case, the contact angle is about 90° and the added liquid fails to wet the particles. (C) A similar effect is used to stabilize Pickering emulsions, where colloidal particles prevent droplets in an emulsion from merging into larger droplets. This figure appears in a Perspective paper by Hans-Jürgen Butt of the Max Planck Institute for Polymer Research in Mainz, Germany. The Perspective, titled, "Controlling the Flow of Suspensions," appears in the Feb. 18, 2011, issue of Science. view more
Credit: [P. Huey/<i>Science</i> © 2011 AAAS]