Light lets microswimmers switch between bacteria-like and algae-like propulsion

This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Physicists at Leipzig University and Charles University in Prague have developed a method for changing the swimming style of tiny artificial microswimmers in real time. They can make a single microscopic particle switch at will between modes of swimming inspired by bacteria and algae.

The researchers have thus turned a property that was previously fixed during production into a programmable parameter. They believe their findings pave the way for an evolutionary approach to the development of synthetic active matter. Their study has now been published in Nature Communications.

Microswimmers are objects generally only a few micrometers in size that move through fluids. They include both living microorganisms, such as bacteria and algae, and synthetically produced particles. The latter serve as physical models for understanding the complex interactions between biological microorganisms.

Until now, it has not been possible to alter the swimming style of artificial microswimmers. However, researchers led by professor Frank Cichos have now found a way to use light to switch the artificial particles between the swimming styles of bacteria and algae at will. Bacteria such as E. coli propel themselves using flagella at their rear, pushing themselves forward.

Algae such as Chlamydomonas beat flagella at their front, pulling themselves through the fluid. Bacteria swim with what might be described as rear-wheel drive, while algae use front-wheel drive. The two generate entirely different flow fields in the process.

"Our work helps us understand what an 'optimal' swimmer actually means in reality. We show that the physical constraints of the swimming mechanism can prevent a swimmer from achieving the theoretical optimum," explains doctoral researcher Lisa Rohde, first author of the study. According to Rohde, the same constraints also exist in nature.