Related papers: Controlling cell motion and microscale flow with p…
We use moving light patterns to control the motion of {\it Escherichia coli} bacteria whose motility is photo-activated. Varying the pattern speed controls the magnitude and direction of the bacterial flux, and therefore the accumulation of…
How the cells break symmetry and organize their edge activity to move directionally is a fun- damental question in cell biology. Physical models of cell motility commonly rely on gradients of regulatory factors and/or feedback from the…
A new mechanism for micro-swimmer motion in an aquatic environment, which implies light-induced polarization perturbations as a motivation for its motion, is proposed. The mechanism assumes that natural light leads to an enhancement of the…
We study the velocity distribution of unicellular swimming algae Euglena gracilis using optical microscopy and theory. To characterize a peculiar feature of the experimentally observed distribution at small velocities we use the concept of…
Active matter comprises individually driven units that convert locally stored energy into mechanical motion. Interactions between driven units lead to a variety of non-equilibrium collective phenomena in active matter. One of such phenomena…
We study how simple eukaryotic organisms make decisions in response to competing stimuli in the context of phototaxis by the unicellular alga $Chlamydomonas~reinhardtii$. While negatively phototactic cells swim directly away from a…
Many motile microorganisms react to environmental light cues with a variety of motility responses guiding cells towards better conditions for survival and growth. The use of spatial light modulators could help to elucidate the mechanisms of…
Previously published experimental work by other authors has shown that certain motile marine bacteria are able to track free swimming algae by executing a zigzag path and steering toward the algae at each turn. Here, we propose that the…
Eukaryotic swimming cells such as spermatozoa, algae or protozoa use flagella or cilia to move in viscous fluids. The motion of their flexible appendages in the surrounding fluid induces propulsive forces that balance with the viscous drag…
Suspensions of swimming micro-organisms provide examples of coordinated active dynamics. That has stimulated the study of a phenomenological theory combining synchronization and polar order in active matter. Here, we consider another…
Some micro-algae are sensitive to light intensity gradients. This property is known as phototaxis: the algae swim toward a light source (positive phototaxis). We use this property to control the motion of micro-algae within a Poiseuille…
E. coli bacteria swim following a run and tumble pattern. In the run state all flagella join in a single helical bundle that propels the cell body along approximately straight paths. When one or more flagellar motors reverse direction the…
We study a generic model for the polarisation and motility of self-propelled soft objects, biological cells or biomimetic systems, interacting with a viscous substrate. The active forces generated by the cell on the substrate are modelled…
Active Brownian particles are capable of taking up energy from their environment and converting it into directed motion; examples range from chemotactic cells and bacteria to artificial micro-swimmers. We have recently demonstrated that…
In this fluid dynamics video, we present the first time-resolved measurements of the oscillatory velocity field induced by swimming unicellular microorganisms. Confinement of the green alga C. reinhardtii in stabilized thin liquid films…
Active fluids can develop spontaneous flow instabilities and complex patterns. However, spatio-temporal control of active particles has remained challenging, despite its relevance in biological and applied contexts. Here, we harnessed…
We present the first time-resolved measurements of the oscillatory velocity field induced by swimming unicellular microorganisms. Confinement of the green alga C. reinhardtii in stabilized thin liquid films allows simultaneous tracking of…
Optical tweezers are widely used for the manipulation of cells and their internal structures. However, the degree of manipulation possible is limited by poor control over the orientation of trapped cells. We show that it is possible to…
Micron-sized self-propelled (active) particles can be considered as model systems for characterizing more complex biological organisms like swimming bacteria or motile cells. We produce asymmetric microswimmers by soft lithography and study…
An artificial microswimmer drifts in response to spatio-temporal modulations of an activating suspension medium. We consider two competing mechanisms capable of influencing its tactic response: angular fluctuations, which help it explore…