Chileans in the lab, February 2013

Camilo Ulloa Camilo is working on a new way to cut a drop of fluid in two in the lab of physics Prof. William Irvine. Combinatorial chemistry and automated chemical analysis often require separating and combining small volumes of fluid.  One way to do it is to trap the fluid in holes in two plates, and then slide the plates apart.  The goal is to avoid uncontrolled motion at the moment when the fluid breaks apart. Camilo figured out how to make the holes and the plates and how to make the faces hydrophobic so that water would be trapped in the holes.  Then he was able to see the water divide in two as the top plate is shifted horizontally.  Left: Camilo explains his setup with a side view of the apparatus circled at right.  Right: closeup side view of the real drop at the point of scissoring, with the remaining connecting link circled.  Top half of picture shows top view. ---TW 12 March 2013,

Sergio Correa Sergio, working with Justin Burton in the lab of Prof. Douglas MacAyeal in the Geophysical sciences department is studying how glaciers break into icebergs. As a glacier slides down a mountainside and into the ocean, vertical slabs break off and twist into a horizontal position.  This twisting causes violent water currents that can induce further breaking.  To follow this process in detail, the group probes a model glacier slab made out of a 10 kg slab of Teflon plastic.  The current project is to measure the pressure field in the water as the slab twists, using a sensitive pressure probe.  The main effects of the breakoff event are transmitted through this presssure.  Sergio designed the protocol for the measurements and analyzed the data from many runs.  Now there is a full data set that can be stringently compared with computer simulations.  Left: Sergio shows where slab is initially positioned.   Top right, diagram of the slab tipping sideways.  Bottom right, shows the tipping slab a half second after release.  Black wire at top lead to the pressure sensor with its front submersed in the water..    ----TW 5 March 2013

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