A remarkable feature of active matter is the propensity to self-organize. One striking instance this ability generate spatial structures cluster phase, where clusters broadly distributed in size constantly move and evolve through particle exchange, breaking or merging. Here we propose an exhaustive description dynamics apolar matter. Exploiting large statistics gathered on thousands Janus colloids, measure aggregation fragmentation rates rationalize resulting distribution fluctuations. We...

Active colloids constitute a novel class of materials composed colloidal-scale particles locally converting chemical energy into motility, mimicking micro-organisms. Evolving far from equilibrium, these systems display structural organizations and dynamical properties distinct thermalized colloidal assemblies. Harvesting the potential this new requires development conceptual framework to describe intrinsically nonequilibrium systems. We use sedimentation experiments probe equation state...

We study experimentally the response of a dense sediment Brownian particles to self-propulsion. observe that ergodic supercooled liquid relaxation is monotonically enhanced by activity. By contrast nonergodic glass shows an order magnitude slowdown at low activities with respect passive case, followed fluidization higher activities. Our results theoretical predictions approach transition, summing up shift line. propose nonmonotonicity due competing effects activity: (i) extra energy helps...

We investigate the hopping dynamics of a colloidal particle across potential barrier and within viscoelastic, i.e., non-Markovian, bath report two clearly separated timescales in corresponding waiting time distributions. While longer timescale exponentially depends on height, shorter one is similar to relaxation fluid. This short signature storage release elastic energy inside that strongly increases rate. Our results are excellent agreement with numerical simulations simple Maxwell model.

Optimizing the energy efficiency of driving processes provides valuable insights into underlying physics and is crucial importance for numerous applications, from biological to design machines robots. Knowledge optimal protocols particularly at microscale, where supply often limited. Here, we experimentally theoretically investigate paradigmatic optimization problem moving a potential carrying load through fluid, in finite time over given distance, such way that required work minimized. An...

Abstract Spinning objects moving through air or a liquid experience lift force—a phenomenon known as the Magnus effect. This effect is commonly exploited in ball sports but also of considerable importance for applications aviation industry. Whereas forces are strong large objects, they weak at small scales and eventually vanish overdamped micrometre-sized particles simple liquids. Here we demonstrate roughly one-million-fold enhanced force spinning colloids viscoelastic fluids. Such fluids...

We study experimentally a sediment of self-propelled Brownian particles with densities ranging from dilute to ergodic supercooled, nonergodic glass, polycrystal. In compagnon letter, we observe nonmonotonic response activity relaxation the glass state: dramatic slowdown when become weakly self-propelled, followed by speedup at higher activities. Here map supercooled states standard passive glassy physics, provided monotonic shift packing fraction and replacement ambient temperature effective...

We study experimentally-using Janus colloids-and theoretically-using Active Brownian Particles- the sedimentation of dilute active colloids. first confirm existence an exponential density profile. show experimentally emergence a polarized steady state outside effective equilibrium regime, i.e. when v_s is not much smaller than propulsion speed. The experimental distribution polarization very well described by theoretical prediction with no fitting parameter. then discuss and compare three...

The presence of liquid water in frozen media impacts the strength soils, growth frost heave, plant life and microbial activities, or durability infrastructures cold regions. If effect confinement on freezing is well known, never pure solutes depressing point are naturally found. Moreover, combination solute poorly understood. We imaged dynamics a model porous medium with various salt (KCl) concentrations. showed that front, initially heterogeneous due to confinement, drives enrichment...

We perform micro-rheological experiments with a colloidal bead driven through viscoelastic worm-like micellar fluid and observe two distinctive shear thinning regimes, each of them displaying Newtonian-like plateau. The behavior at larger velocities is in qualitative agreement macroscopic rheological experiments. second process, observed Weissenberg numbers as small few percent, appears to have no analog macro findings. A simple model introduced earlier captures the behavior, implies that...

The motion of a colloidal probe in viscoelastic fluid is described by friction or mobility, depending on whether the moving with velocity feeling force. While Einstein relation describes an inverse relationship valid for Newtonian solvents, both concepts are generalized to time-dependent memory kernels fluids. We theoretically and experimentally investigate their considering two observables: recoil after releasing that was moved through equilibrium mean squared displacement (MSD). Applying...

Abstract We experimentally investigate the transient recoil dynamics of a colloidal probe particle in viscoelastic fluid after driving force acting on is suddenly removed. The corresponding displays two distinct timescales which are excellent agreement with microscopic model considers to be coupled bath particles via harmonic springs. Notably, this exhibits sets eigenmodes correspond reciprocal and non-reciprocal conditions can confirmed our experiments. expect findings relevant under where...

<title>Abstract</title> When objects move within a classical fluid, this leads to viscous friction, which is irreversibly converted into heat. In particular, at microscopic length scales, such energy loss detrimental applications making use of externally and self-propelled colloidal particles as heat engines microrobots. Here, using particle in viscoelastic we experimentally demonstrate recuperation (ER), where up 30\% the coupled surrounding can be recovered useful work. This effect due...

Cryopreservation is the only fully established procedure to extend lifespan of living cells and tissues, a key activities spanning from fundamental biology clinical practice. Despite its prevalence impact, central aspects cryopreservation, such as cell's physicochemical environment during freezing, remain elusive. Here we address that question by coupling in situ microscopic directional freezing visualize their surroundings with freezing-medium phase diagram. We extract spatial distribution...

We study the temperature-dependence of critical Casimir interactions in a micellar solution nonionic surfactant C₁₂E₅ dissolved water.

The motion of Brownian particles in nonlinear baths, such as, e.g., viscoelastic fluids, is great interest. We theoretically study a simple model for bath, where two are coupled via sinusoidal potential. This model, which an extension the famous Prandtl–Tomlinson has been found to reproduce some aspects recent experiments, as shear-thinning and position oscillations [R. Jain et al., “Two step micro-rheological behavior fluid,” J. Chem. Phys. 154, 184904 (2021)]. Analyzing this detail, we...

We experimentally study the motion of a colloidal particle, translated back and forth within viscoelastic, i.e. non-Markovian bath. The particle starts in equilibrium before forward motion, but only partially relaxes at turning point. During backward we measure systematic (negative) heat flow from bath to particle. Our observations are good agreement with simple model that describes time-delayed response fluid. expect our results be important for realization optimization novel types...

When a colloidal probe is forced through viscoelastic fluid which characterized by long stress-relaxation time, the excited out of equilibrium. This leading to number interesting effects including non-trivial recoil when driving force removed. Here, we experimentally and theoretically investigate transient dynamics non-spherical particles, i.e., dumbbells. In addition translational dumbbells, also find pronounced angular reorientation results from relaxation surrounding fluid. Our findings...

Optimizing the energy efficiency of driving processes provides valuable insights into underlying physics and is crucial importance for numerous applications, from biological to design machines robots. Knowledge optimal protocols particularly at microscale, where supply often limited. Here we investigate experimentally theoretically paradigmatic optimization problem moving a potential carrying load through fluid, in finite time over given distance, such way that required work minimal. An...

Spinning objects which move through air or liquids experience a Magnus force. This effect is commonly exploited in ball sports but also of considerable importance for applications and fundamental science. Opposed to large where forces are strong, they only weak at small scales eventually vanish overdamped micron-sized particles simple liquids. Here we demonstrate an about one-million-fold enhanced force spinning colloids viscoelastic fluids. Such fluids characterized by time-delayed response...

When a colloidal probe is forced through viscoelastic fluid which characterized by long stress-relaxation time, the excited out of equilibrium. This leading to number interesting effects including non-trivial recoil when driving force removed. Here, we experimentally and theoretically investigate transient dynamics non-spherical particles, i.e., dumbbells. In addition translational dumbbells, also find pronounced angular reorientation results from relaxation surrounding fluid. Our findings...

Abstract When a colloidal probe is forced through viscoelastic fluid which characterized by long stress-relaxation time, the excited out of equilibrium. This leading to number interesting effects including non-trivial recoil when driving force removed. Here, we experimentally and theoretically investigate transient dynamics non-spherical particles, i.e., dumbbells. In addition translational dumbbells, also find pronounced angular reorientation results from relaxation surrounding fluid. Our...