0000000001235102

AUTHOR

R. Wulfert

showing 3 related works from this author

Discontinuous thinning in active microrheology of soft complex matter

2016

Employing theory and numerical simulations, we demonstrate discontinuous force thinning due to the driven motion of an external probe in a host medium. We consider two cases: an ideal structureless medium (modeling ultrasoft materials such as polymer melts) and a dilute bath of interacting repulsive particles. When the driving of the probe exceeds a critical force, the microviscosity of the medium drops abruptly by about an order of magnitude. This phenomenon occurs for strong attractive interactions between a large probe and a sufficiently dense host medium.

Microrheologychemistry.chemical_classificationPhysicsThinningFOS: Physical sciences02 engineering and technologyPolymerMechanicsCondensed Matter - Soft Condensed Matter021001 nanoscience & nanotechnology01 natural sciencesCondensed Matter::Soft Condensed MatterMicroviscositychemistryChemical physics0103 physical sciencesSoft Condensed Matter (cond-mat.soft)010306 general physics0210 nano-technologyOrder of magnitudePhysical Review E
researchProduct

Driven Brownian particle as a paradigm for a nonequilibrium heat bath: Effective temperature and cyclic work extraction

2017

We apply the concept of a frequency-dependent effective temperature based on the fluctuation-dissipation ratio to a driven Brownian particle in a nonequilibrium steady state. Using this system as a thermostat for a weakly coupled harmonic oscillator, the oscillator thermalizes according to a canonical distribution at the respective effective temperature across the entire frequency spectrum. By turning the oscillator from a passive "thermometer" into a heat engine, we realize the cyclic extraction of work from a single thermal reservoir, which is feasible only due to its nonequilibrium nature.

Canonical ensemblePhysicsWork (thermodynamics)Thermal reservoirStatistical Mechanics (cond-mat.stat-mech)Non-equilibrium thermodynamicsFOS: Physical sciencesMechanics01 natural sciencesThermostat010305 fluids & plasmaslaw.inventionClassical mechanicslaw0103 physical sciences010306 general physicsHarmonic oscillatorBrownian motionCondensed Matter - Statistical MechanicsHeat engine
researchProduct

Nonequilibrium depletion interactions in active microrheology.

2017

Entropic depletion forces arise between mesoscopic bodies that are immersed in a suspension of macromolecules, such as colloid-polymer mixtures. Here we consider the case of a driven colloidal probe in the presence of another, passive colloidal particle, both solvated in an ideal bath of small spherical particles. We calculate the nonequilibrium forces mediated by the depletants on the two colloidal particles within a dynamical superposition approximation (DSA) scheme. In order to assess the quality of this approximation, and to obtain the colloidal microstructure around the driven probe, we corroborate our theoretical results with Brownian dynamics simulations.

Microrheologyendocrine systemMesoscopic physicsChemistrydigestive oral and skin physiologyNon-equilibrium thermodynamicsGeneral ChemistryCondensed Matter Physicscomplex mixtures01 natural sciences010305 fluids & plasmasSuspension (chemistry)body regionsCondensed Matter::Soft Condensed MatterSuperposition principleColloidClassical mechanicsChemical physics0103 physical sciencesBrownian dynamics010306 general physicsMacromoleculeSoft matter
researchProduct