Monday, February 11, 2013

'Living crystals' reported in Science

Living Crystals of Light-Activated Colloidal Surfers is a recent publication in Science. It presents a study of the dynamics of interacting particles that are propelled by a light-catalyzed reaction between hematite (located on the surface of the colloidal particles) and hydrogen peroxide. These particles experience a nonequilibrium driving force from the reaction, repulsive forces between one another due in part to SDS surfactant present in the solvent, and attractive phoretic forces towards other particles. They observe that when the system is illuminated with blue light and the hydrogen peroxide reaction is catalyzed, the particles form crystalline arrangements that dynamically grow, shrink, merge and split. This is a form of self-organization and is fueled by the energy delivered to the system in the form of light.

Importantly, the attractive pair forces and and driving forces are not present when the light is off, which demonstrates that the formation of the crystals occurs under nonequilibrium conditions.

This rather elegant work demonstrates how complex behavior in systems can emerge from interactions between the parts of the system.

A PopSci article summarizes the work, though I think it focuses too much on the properties of life that the crystals satisfy.