Active particles as mechanical probes of glassy environments

Nature Materials (2019)

Understanding the complex entanglement between structural and dynamical properties of glasses is a great scientific challenge. A powerful technique to study such relations on a microscopic scale is microrheology, where one analyzes the translational dynamics of an externally driven probe particle. Here we experimentally investigate the mechanical properties of a colloidal glassy system by measuring simultaneously the translational and the rotational dynamics of an...

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Diffusing Wave Paradox of Active Particles in Traveling Light Pulses

Nature Communications (2019)

Despite lacking a brain, living amoebae are amazingly effective organisms when navigating through complex environments, solving maze problems or even mimicking the layout of man-made transportation networks. The underlying mechanism for such targeted motion is the emission of traveling chemical waves from a few leader cells which then triggers a collective behavior within entire colonies. Since amoebae exhibit positive chemotactic behavior, one would expect them...

Orientational and directional locking of colloidal clusters driven across periodic surfaces

Nature Physics (2019)

When particles are driven across crystalline surfaces, their trajectories do not necessarily follow the applied force but become locked to the substrate lattice directions. Such directional locking, being relevant for bottom-up nanodevice assembly and particle sorting has been intensively studied for isolated or single particles. Here we experimentally study the motion of extended colloidal clusters sliding over a periodically corrugated surface. We observe that both...

Group formation and cohesion of active particles with visual perception-dependent motility

Science, 364, 70 (2019)

Microscopic swimmers with visual perception of group members form stable swarms

Birds, fish and bacteria often gather into groups or swarms. This so-called collective behaviour requires all group members to continuously and reciprocally adapt their movements. It can be a challenging task, however, for researchers to ascertain the specific environmental stimuli that individuals respond to within the context of their group; in addition to optical and acoustic...

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