Researchers Use Oil Droplets To Reveal Bacteria and Other Unicellular Organisms Movements

Despite their relatively basic architecture, bacteria and other unicellular creatures evolved complex strategies to actively explore their surroundings.

Researchers from the Max Planck Institute for Dynamics and Self-Organization (MPI-DS) employed oil droplets as a model for biological microswimmers to uncover these processes.

Corinna Maass, group leader at the MPI-DS and Associate Professor at the University of Twente, and her colleagues investigated microswimmer navigation strategies in several studies, including how they navigate against the current in narrow channels, how they mutually affect their movement, and how they collectively start rotating in order to move.

Movements of bacteria

(Photo : Adrian Lange/Unsplash)

Another study looked at how moving microswimmers impact one other. In their experiment, microscopic oil droplets in a soapy solution move independently by blossoming off little quantities of oil, providing propulsion, as per ScienceDaily.

Microswimmers produce a trace of wasted fuel, similar to how planes leave behind contrails, which can deter others.

Microswimmers can determine if another swimmer has been in the same location recently. "Interestingly, this creates a self-avoiding movement for individual microswimmers, whereas an ensemble of them results in droplets being trapped between the trails of one another," explains Babak Vajdi Hokmabad, the study's primary author.

The repulsive effect of the second droplet on the trajectory of a previously passing one is determined by its approaching angle and the time since the first swimming. T

these experimental findings corroborate prior theoretical work in the subject by Ramin Golestanian, executive director of the MPI-DS.

The study was carried out as part of the Max Planck Center for Complex Fluid Dynamics, a collaboration between the MPI-DS, the MPI for Polymer Research, and the University of Twente.

Finally, the researchers looked at the collective hydrodynamic behavior of many microswimmers.

They discovered that numerous drops may spontaneously form clusters that float like hovercrafts or rise and revolve like small helicopters. T

he cluster's rotation is based on cooperative interaction between individual droplets, which results in coordinated activity - but individual droplets alone do not constitute such movement.

These patterns illustrate another physical concept by which microswimmers may travel without utilizing their minds or muscles.

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Microswimmers

Recent biohybrid microswimmer papers include the utilization of sperm cells, contractive muscle cells, and bacteria as a biological components since they can effectively convert chemical energy into movement and can also execute complex motions depending on environmental variables, as per Frontiers.

In this manner, biohybrid microswimmer systems are made up of two distinct functional components: payload and carrier. The cargo is an element of interest that must be moved (and perhaps released) in a certain manner.

The carrier is the component in charge of the biohybrid's mobility, conveying the necessary payload, which is attached to its surface.

For the conveyance of synthetic cargo for targeted medication administration, the vast majority of these devices rely on biological motile propulsion.

However, because they are not the topic of this analysis, several instances of the reverse case-artificial microswimmers with biological cargo systems will not be discussed in depth here.

The carrier for a biohybrid microswimmer must be capable of producing thrust capable of balancing the viscous drag on the entire assembly and therefore producing directed motion.

Two types of cells can serve as biological carriers: motile substances (such as spermatozoa and bacteria) and muscle cells.

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