Crystal / Liquid Interfaces Seen with Colloids Eric R. Weeks, Emory University, DMR 0239109

1. Crystal / Liquid Interfaces Seen with ColloidsEric R. Weeks, Emory University,DMR 0239109 Interfaces between crystals and liquids govern phenomena such as wetting, lubrication and crystal growth. However, these interfaces are poorly defined at the atomic level – how does an atom “know” if it is in the liquid or the crystal? We use microscopy of micron-sized colloidal particles to study a crystal / liquid interface. The bottom picture shows the analyzed data, revealing that the surface of the crystal (blue) is rough, but that locally there is a sharp boundary between the crystal and the liquid (red). The interface is ambiguous only on the scale of 1-2 particles. This confirms long-standing conjectures that this interface is sharp. Top: Experimental image of crystal / liquid interface. Bottom: Analyzed data showing crystal (blue) and liquid (red). Jessica Hernández-Guzmán & Eric R. Weeks, submitted to Phys. Rev. Lett.

2. Hands-On Science for Students from Developing NationsEric R. Weeks, Emory University, DMR 0239109 The PI (Eric Weeks) and NSF-supported graduate student Kazem Edmond were teachers at the “Hands-on Research in Complex Systems” school at Gandhinagar, India in January 2008. Young scientists and graduate students from developing nations came to this school. Edmond and Weeks developed laboratory activities involving the properties of colloidal pastes (being stirred in the topic picture, and being studied with microscopy in the bottom picture). These lab activities are also used at Emory University in freshman seminar classes on science. Most of the laboratory activities are described in Habdas, Weeks & Lynn, The Physics Teacher 44, 276-279 (2006).