Orateur
Description
The microswimmer Chlamydomonas reinhardtii, a quasi-spheric 10 $\mu$m long microalga, is of particular interest for its ability to swim towards or away from light sources, known as phototaxis. When the C. reinhardtii concentration becomes high enough, bio-convective structures can appear and affect the surrounding fluid [1,2].
This study shows how the phototactic behavior of microalgae can be harnessed to control the transport of passive particles, converting their random motion into directed transport. We enclose micron-sized particles (from 30 $\mu$m to 200 $\mu$m in diameter) in microalgae suspensions within a squared centimetric chamber and use LEDs to drive algae accumulation.
This accumulation generates bio-convective flows, which push denser beads away from algae-dense regions while pulling lighter beads toward them. We can effectively direct the transport of these microparticles and sort them.
[1] J. Dervaux et al., Nature Phys 13, 306–312 (2017)
[2] J. Arrieta et al., PRL 123, 158101 (2019)
