We show that DNA-linked anisotropic doublets composed of paramagnetic colloidal particles can be endowed with controlled propulsion when floating above a flat plate and subjected to magnetic field precessing around an axis parallel the plate. The mechanism for this artificial swimmer does not involve deformations, it makes use minimal two degrees freedom needed propel at low Reynolds numbers. combine experimental observations theoretical analysis fully characterizes velocity in terms...

This perspective article will give an overview of recent experimental results related to the realization and use anisotropic magnetic colloids, i.e. microscopic particles having shape, composition or structured surface which set a preferred magnetization direction. The possibility remotely controlling these soft matter building blocks via external fields makes them ideal for wide range applications, from their as active microrheological probes infer viscoelastic properties complex fluids...

We demonstrate a general method to assemble and propel highly maneuverable colloidal carpets which can be steered via remote control in any direction of the plane. These micropropellers are composed by an ensemble spinning rotors readily used entrap, transport, release biological cargos on command hydrodynamic conveyor-belt effect. An efficient cargo transportation combined with remarkable "healing" ability surpass obstacles great potential towards development multifunctional smart devices...

We study propulsion arising from microscopic colloidal rotors dynamically assembled and driven in a viscous fluid upon application of an elliptically polarized rotating magnetic field. Close to confining plate, the motion this self-assembled worm results cooperative flow generated by spinning particles which act as hydrodynamic "conveyor belt." Chains propel faster than individual ones, until reaching saturation speed at distances where induced-flow additivity vanishes. By combining...

Abstract The process of crystallization is difficult to observe for transported, out-of-equilibrium systems, as the continuous energy injection increases activity and competes with ordering. In emerging fields such microfluidics active matter, formation long-range order often frustrated by presence hydrodynamics. Here we show that a population colloidal rollers assembled magnetic into large-scale propelling carpets can form perfect crystalline materials upon suitable balance between...

To achieve permanent propulsion of micro-objects in confined fluids is an elusive but challenging goal that will foster future development microfluidics and biotechnology. Recent attempts based on a wide variety strategies are still far from being able to design simple, versatile, fully controllable swimming engines the microscale. Here we show DNA-linked anisotropic colloidal rotors, composed paramagnetic particles with different or similar size, controlled when subjected magnetic field...

This article reports several recent discoveries related to the controlled transport of paramagnetic colloidal particles above magnetic garnet films. The films are thin uniaxial ferromagnetic in which domains can be organized into symmetric patterns consisting stripes or bubbles and generate strong local field gradients. Application an external homogeneous on a larger scale compared spatial periodicity pattern film modulates potential generated at its surface induces motion placed film....

Abstract Artificial spin ice systems, namely lattices of interacting single domain ferromagnetic islands, have been used to date as microscopic models frustration induced by lattice topology, allowing for the direct visualization arrangements and textures. However, engineering frustrated states in which individual spins can be manipulated situ real-time observation their collective dynamics remain both challenging tasks. Inspired recent theoretical advances, here we realize a colloidal...

We study the collective dynamics of interacting paramagnetic colloids transported via a magnetic ratchet effect above modulated periodic potential. Upon increasing modulation frequency, particles undergo series dynamic transitions, from continuous smectic flow to disorder flow, and later enter into two phase regime, ending in complete pinned state. In disordered phase, system organizes density waves due traffic jams, as granular systems, while regime shows strong similarities with plastic...

Different phoretic driving mechanisms have been proposed for the transport of solid or liquid microscopic inclusions in integrated chemical processes. It is now shown that a substrate was chemically modified with photosensitive self-assembled monolayers enables direct control assembly and large ensembles micrometer-sized particles drops were dispersed thin layer anisotropic fluid. This strategy separates particle driving, which realized by AC electrophoresis, steering, achieved elastic...

Hydrodynamic interactions (HIs), namely, solvent-mediated long-range between dispersed particles, play a crucial role in the assembly and dynamics of many active systems, from swimming bacteria to swarms propelling microrobots. We experimentally demonstrate emergence long-living hydrodynamic bound states model microswimmers at low Reynolds numbers. A rotating magnetic field forces colloidal hematite microparticles translate constant frequency-tunable speed close bounding plane viscous fluid....

Complex behavior in soft materials comes from the interactions between its components and geometrical constraints associated with lattice structures. Frustration is one classical example of such complex leading to a plethora phases new phenomena. In this Colloquium case ice rule discussed how it reflects other materials.

Paramagnetic particles in a liquid above solid dynamically self-assemble into two-dimensional (2D) viscoelastic clusters processing magnetic field if the precession angle exceeds magic angle. Hexagonal rotate with frequency proportional to of field. The rotation is explained by shear waves excited that can be visualized slightly cluster and visualization modes are independent techniques probe rheological properties cluster. We find agreement between both when determining 2D viscosity eta(c)...

We demonstrate a new concept for the propulsions of abiological structures at low Reynolds numbers. The approach is based on design flexible, planar polymer with permanent magnetic moment. In presence an external, uniform, rotating field these deform into three-dimensional shapes that have helical symmetry and translate linearly through fluids Re between 10(-1) 10. mechanism motility involves reversible deformation breaks their generates propulsion. These elastic propellers resemble...

We study the motion of paramagnetic colloidal particles placed above magnetic bubble domains a uniaxial garnet film and driven through lattice by external field modulation. An tunable precessing propels either in localized orbits around bubbles or superdiffusive ballistic array. This results from interplay between driving rotating signal, viscous drag force periodic energy landscape. explain transition terms incommensurability transit frequency particle unit cell modulation frequency....

We report on the dynamical behavior of paramagnetic ellipsoidal particles dispersed in water and floating above a flat plane when subjected to an external precessing magnetic field. When field long axis are same plane, two clear regimes distinguished which follow modulation synchronously or asynchronously. Both also observed precesses at angle theta<90 degrees with respect normal confining while transition frequency increases decreasing precession angle. combine experimental observations...

Abstract Field-driven direct assembly of nanoscale matter has impact in disparate fields science. In microscale systems, such concept been recently exploited to optimize propulsion viscous fluids. Despite the great potential offered by miniaturization, using self-assembly achieve transport at remains an elusive task. Here we show that a hybrid propeller, composed ferromagnetic nanorod and paramagnetic microsphere, can be steered fluid variety modes, from pusher puller, when pair is...

We investigate phase separation in a chiral fluid, made of spinning ferromagnetic colloids that interact both via hydrodynamic and dipolar forces collectively organize into separated circulating clusters. show that, at high frequency, hydrodynamics dominate over attractive magnetic interactions impede coarsening, forcing the particles to assemble collection finite rotating clusters controllable size. introduce minimal particle-based model unveils fundamental role boundary plane...

We study the transversal motion of paramagnetic particles on a uniaxial garnet film, exhibiting longitudinal ratchet effect in presence an oscillating magnetic field. Without field, thermal diffusion coefficient obtained by video microscopy is D(0) ≈ 3 × 10(-4) μm2/s. With exhibits giant enhancement almost four decades and pronounced maximum as function driving frequency. explain experimental findings with theoretical interpretation terms random disorder effects within film.

We describe the realization and controlled transport of water-based microreactors dispersed in a nematic liquid crystal transported by application an alternating electric field through mechanism induced charge electrophoresis. characterize propulsion speed these terms droplet size, strength frequency applied show how to use them microscale colloidal cargoes coalesce water miscible chemicals. Controlled motion microdoplets anisotropic fluids is rich research which unveils new perspectives...

Dipolar particles are building blocks in several fields of science and technology, but making rings from interacting ferromagnetic colloids is challenging, due to strong thermal fluctuations at the microscale. This study shows that, under right conditions, magnetic microparticles can...

The realization of micromotors able to dock and transport microscopic objects in a fluid medium has direct applications toward the delivery drugs chemicals small channels pores, functional wireless microrobots lab‐on‐a‐chip technology. A simple general method tow particles water by using remotely controllable light‐activated hematite microdockers is demonstrated. These anisotropic ferromagnetic can be synthesized bulk present remarkable ability activated light while independently manipulated...

Metastable phases may be spontaneously formed from other metastable through nucleation. Here we demonstrate the spontaneous formation of a phase an unstable equilibrium by spinodal decomposition, which leads to transient coexistence stable and phases. This phenomenon is generic within recently introduced scenario landscape-inversion transitions, experimentally realize as structural transition in colloidal crystal. exhibits rich repertoire new phase-ordering phenomena, including two connected...

Abstract Understanding microscale transport across heterogeneous landscapes is relevant for many phenomena in condensed matter physics, from pinning of vortices dirty superconductors, to electrons on liquid helium, skyrmions, and active matter. Here, we experimentally investigate the clogging jamming field tunable interacting colloids driven through a quenched disordered landscape fixed obstacles. We focus emergent phenomenon clogging, that has been much investigation at level single...