Abstract Achieving control over the directionality of active colloids is essential for their use in practical applications such as cargo carriers microfluidic devices. So far, guidance spherical Janus was mainly realized using specially engineered magnetic multilayer coatings combined with external fields. Here we demonstrate that step-like submicrometre topographical features can be used reliable docking and guiding platforms chemically colloids. For various topographic (stripes, squares or...

Catalytically active Janus micro-spheres are capable of autonomous motion and can potentially act as carriers for transportation cargo at the micron-scale. Focusing on cases in which a single or pair micro-motors is used carrier, we investigate complex dynamics exhibited by various carrier–cargo composites.

Micron-sized particles moving through solution in response to self-generated chemical gradients serve as model systems for studying active matter. Their far-reaching potential applications will require the sense and respond their local environment a robust manner. The hydrodynamic fields, which induce particle motion, probe are modified by that very environment, including confining boundaries. Focusing on catalytically Janus paradigmatic example, we predict near hard planar wall such...

Abstract The pursuit of chemically-powered colloidal machines requires individual components that perform different motions within a common environment. Such can be tailored by controlling the shape and/or composition catalytic microparticles; however, ability to design particle remains limited incomplete understanding relevant propulsion mechanism(s). Here, we demonstrate platinum microparticles move spontaneously in solutions hydrogen peroxide and their rationally designed shape....

Superhydrophobic coatings repel liquids by trapping air inside microscopic surface textures. However, the resulting composite interface is prone to collapse under external pressure. Nanometer-size textures should facilitate more resilient owing geometry and confinement effects at nanoscale. Here, we use in situ x-ray diffraction study of superhydrophobic state arrays $\ensuremath{\approx}20\text{ }\text{ }\mathrm{nm}$-wide silicon with cylindrical, conical, linear features defined...

For active particles the interplay between self-generated hydrodynamic flow and an external shear flow, especially near bounding surfaces, can result in a rich behavior of not easily foreseen from consideration driving mechanisms isolation. instance, under certain conditions, exhibit "rheotaxis", i.e., they align their direction motion with plane spanned by normal surface move or against flow. To date, studies rheotaxis have focused on elongated (e.g., spermatozoa), for which be understood...

The propulsion of micro- and nanoparticles using ultrasound is an attractive strategy for the remote manipulation colloidal matter biocompatible energy inputs. However, physical mechanisms underlying acoustic are poorly understood, our ability to transduce into different types particle motions remains limited. Here, we show that three-dimensional shape a can be rationally engineered direct desired powered by ultrasound. We investigate dynamics gold microplates with twisted star ( C nh...

Catalytically active particles suspended in a liquid can move due to self-phoresis by generating solute gradients via chemical reactions of the solvent occurring at parts their surface. Such be used as carriers micro-scale. As simple model for carrier-cargo system we consider catalytically particle connected thin rigid rod inert cargo particle. We show that velocity composite strongly depends on relative orientation link. Accordingly, there is an optimal configuration linkage. The subtlety...

Topological defects that form on surfaces of ordered media, dubbed boojums, are ubiquitous in superfluids, liquid crystals (LCs), Langmuir monolayers, and Bose–Einstein condensates. They determine supercurrents impinge electrooptical switching polymer-dispersed LCs, mediate chemical response at nematic-isotropic fluid interfaces, but the role surface topology appearance, stability, core structure these remains poorly understood. Here, we demonstrate robust generation boojums by controlling...

Colloidal particles dispersed in a liquid crystal lead to distortions of the director field. The are responsible for long-range effective colloidal interactions whose asymptotic behaviour is well understood. short distance interaction, however, sensitive structure and dynamics topological defects nucleated near strong anchoring regime. full non-linear theory required order determine interaction at separations. Spherical with sufficiently planar degenerate nucleate pair antipodal surface...

Catalytically active Janus particles suspended in solution create gradients the chemical composition of along their surfaces, as well any nearby container walls. The former leads to self-phoresis, while latter gives rise chemi-osmosis, providing an additional contribution self-motility. Chemi-osmosis strongly depends on molecular interactions between diffusing species and wall. We show analytically, using approximate "point-particle" approach, that by chemically patterning a planar substrate...

Abstract Liquid crystal skyrmions are topologically protected spatially-localized distortions of the director field which exhibit particle-like properties including translational motion in oscillating electric fields. Here, we develop a collective variable model skyrmion dynamics, extending approach Long and Selinger proposed earlier for one dimensional systems. The relates to complex dynamics width twist wall around core. evolves non-reciprocal way, quantifying squirming deformations high...

Colloidal crystals belong to a new class of materials with unusual properties in which the big challenge is grow large-scale structures given symmetry well-controlled and inexpensive way. Recently, template-assisted crystallization was successfully exploited experimentally case colloidal particles dispersed isotropic fluids. In liquid crystal (LC) colloids, are subjected long-range anisotropic elastic forces originating from deformation underlying order parameter. These effective...

Various aspects of self-motility chemically active colloids in Newtonian fluids can be captured by simple models for their chemical activity plus a phoretic-slip hydrodynamic boundary condition on surface. For particles shapes (e.g., spheres) --as employed many experimental studies-- which move at very low Reynolds numbers an unbounded fluid, such effectively map onto the well studied so-called squirmers (S. Michelin and E. Lauga, J. Fluid Mech. 747, 572 (2014)). Accordingly, intuitively...

Three-dimensional (3D) simulations of the structure liquid crystal (LC) torons, topologically protected distortions LC director field, under material flows are rare but essential in microfluidic applications. Here, we show that torons adopt a steady-state configuration at low flow velocity before disintegrating higher velocities, line with experimental results. Furthermore, partial slip conditions boundaries, induces reversible elongation also consistent observations. These results contrast...

Hybridization of a genus-1 handlebody and solitonic structure in chiral nematic liquid crystals, induced by an electric field.

Liquid crystals are known for their optical birefringence, a property that gives rise to intricate patterns and colors when viewed in microscope between crossed polarisers. Resulting images rich geometric serve as valuable fingerprints of the liquid crystal's intrinsic properties. By using machine learning techniques, it is possible extract from information about, e.g., crystal elastic constants, scalar order parameter, local orientation director, etc. Machine can also be employed identify...

Complete wetting of geometrically structured substrates by one-component fluids with long-ranged interactions is studied theoretically. We consider periodic arrays rectangular or parabolic grooves and lattices cylindrical pits. show that the midpoint interfacial heights within pits are related in same way as for complete wedge cone filling. For sufficiently deep cavities vertical walls small undersaturation, an effective planar scaling regime emerges. The exponent $\ensuremath{-}1/3$ all...

The wetting by perfluoromethylcyclohexane of a well-defined silicon grating with channel width 16 nm has been studied using transmission small angle x-ray scattering. Prefilling, capillary filling, and postfilling regimes have identified. A detailed comparison the data theory reveals importance long-ranged substrate-fluid fluid-fluid interactions for determining behavior on these length scales, especially at onset condensation in prefilling regime.

Topologically nontrivial field excitations, including solitonic, linked, and knotted structures, play important roles in physical systems ranging from classical fluids liquid crystals, to electromagnetism, classic, quantum theories. These excitations can appear spontaneously during symmetry-breaking phase transitions. For example, cosmological theories, cosmic strings may have formed configurations influencing the Early Universe development, whereas crystals transient tangled defect lines...

Polymer dispersed liquid crystals are a useful model system for studying the relationship between surface topology and defect structures. They comprised of polymer matrix with suspended spherical nematic drops topologically constrained to host defects an elementary hedgehog charge per droplet, such as bulk or point closed disclination loops. We control genus surfaces confining micrometer-sized tangential boundary conditions molecular alignment imposed by matrix, allowing us avoid or, on...

Significance Colloidal dispersions are abundant in nature, fundamental science, and technology, with examples ranging from fog milk to colloidal models of atomic crystals glasses quantum dots used fabricating the third-generation solar cells. Despite recent progress exquisite control geometric shape topology constituent particles, thus far only single-component building blocks have been fabricated or found occurring nature. We develop multicomponent linked particles lacking connectivity...

Significance Understanding the properties of elastic membranes with superparamagnetic particles advances design autonomous, soft robots. Magnetic fields readily penetrate most materials and can be used remotely to induce rapid precise changes in membrane shape. Here, we compare analytical numerical models molecular dynamics simulations explain how rapidly precessing biaxial magnetic control forces on magnetoelastic membranes. These are closely linked its actuating behavior potential...