Colloids exposed to random potential energy landscapes: From particle number density to particle-potential and particle-particle interactions.

Colloidal particles were exposed to a random potential energy landscape that has been created optically via a speckle pattern. The mean particle density as well as the potential roughness, i.e.

Effect of fluid-colloid interactions on the mobility of a thermophoretic microswimmer in non-ideal fluids.

Janus colloids propelled by light, e.g., thermophoretic particles, offer promising prospects as artificial microswimmers.

Chemotactic predator-prey dynamics.

A discrete chemotactic predator-prey model is proposed in which the prey secrets a diffusing chemical which is sensed by the predator and vice versa. Two dynamical states corresponding to catching and escaping are identified and it is shown that steady hunting is unstable. For the escape process, the predator-prey distance is diffusive for short times but exhibits a transient subdiffusive behavior which scales as a power law t¹/³ with time t and ultimately crosses over to diffusion again.

Dynamics of a microorganism moving by chemotaxis in its own secretion.

The Brownian dynamics of a single microorganism coupled by chemotaxis to a diffusing concentration field that is secreted by the microorganism itself is studied by computer simulations in spatial dimensions d=1,2,3 . Both cases of a chemoattractant and a chemorepellent are discussed. For a chemoattractant, we find a transient dynamical arrest until the microorganism diffuses for long times.