Results published in 2013 in Physical Review Letters
By studying the behaviour of swimming microalgae, the researchers from the laboratory LIPhy have highlighted an interesting photo focusing phenomenon that could serve some applications.
Chlamydomonas reinhardtii is a swimming microalgae sensitive to light intensity. The researchers from the Interdisciplinary Laboratory of Physics in Grenoble have studied the mechanical behaviour of a suspension of these algae in a pipe stream. They showed that the microorganisms will spontaneously migrate and concentrate around the center of the flow when stimulated by a light source placed upstream.
This focusing phenomenon was demonstrated to be due to the interactions between the algae movements towards the light source and the vorticity of the flow.
Considering the important potential of these microorganisms in bio-conversion, this result represents the first step towards new algae separation techniques, a major obstacle in bio-production processes. In an environmental perspective, the presence of certain pollutants was observed to significantly alter the phototaxis of these microswimmers, reducing their self-focusing ability. They could therefore be used in bio-sensors for the accurate detection of water contaminants.
Ref: Garcia X, Rafaï S, Peyla P (2013) Light Control of the Flow of Phototactic Microswimmer Suspensions. Phys. Rev. Lett.