Experimental Soft Condensed Matter Group Harvard University, Prof. D. A. Weitz Cool Picture of Summer 1998

This is from an oil and water emulsion (with SDS) prepared by Mike Popchuk. The image was produced using differential interference contrast microscopy by Eric Weeks. The image is about 25 microns across. This pattern only occured in one place on the slide, and the rest of the slide was extremely disordered. Another snapshot below shows the lower corner of this structure, along with some nearby droplets that are more typical of what was on the slide.

Note: for those unfamiliar with DIC microscopy, you should be aware that the three-dimensional appearance of the image is an illusion.

Some guesses how this formed:

• Several people have suggested gravitational forces. If these droplets were by themselves in a spherical puddle of water, the large heavy ones would push their way into the center, leaving the smaller lighter ones crowded to the outside. This assumes the puddle of water is lowest in the center, that is, that it has some sort of curvature.
• Randy Kamien suggested a bubble collapsing, which would smoosh the droplets onto the plate (with more room for the larger droplets at the central, highest point of the collapsing bubble). If there was a uniform pattern of droplets on the original bubble surface, they might be forced to coalesce into this five-fold symmetric pattern. (Imagine projecting a soccer ball onto a plan, you would see the original five-fold symmetry of the soccer ball pattern.)

Later, we found this image. We don't understand this image either, although we'd like to point out that it is an M. C. Escher work (C) Cordon Art, Baarn, the Netherlands. All rights reserved. We don't want to be sued.

Other cool pictures of the month/season

• March 1998
• April 1998
• Fall 1998
• December 1998
• Winter '99
• Fall '99
• Winter 99/00
• Spring '00
• late Spring '00