New Colloid Structures
Using tiny rods (viruses) and spheres (tiny polystyrene balls),
researchers at Brandeis University have observed several colloid
structures never seen before. Found in many types of biological systems, colloids are small objects
suspended in a continuous substance such as a gas or liquid.
The figures show micrographs,
which do not quite reveal individual particles, and drawings
depicting the arrangement of rods and spheres. (a) Planes of stacked rods
separated by sheets of spheres plus additional columns of spheres.
(b) Rods separated by planes of spheres.
(c) and (d) Rods and spheres in yet more mixed phases.
Although the spheres and rods are essentially noninteracting,
they assembled themselves into these structures,
illustrating the notion that entropy (the tendency towards greater disorder)
can lead to a sort of localized order, at least in parts of a system.
(Courtesy, Seth Fraden, Brandeis.)
