Nanoparticles in a Capillary Trap: Dynamic Self-Assembly at Fluid Interfaces

It was recently shown by us that spherical particles floating on a fluid-fluid interface can be self-assembled, and the lattice between them can be controlled, using an electric field. In this paper we show that the technique can also be used to self assemble rod-like particles on fluid-fluid interfaces. The method consists of sprinkling particles at a liquid interface and applying an electric field normal to the interface, thus resulting in a combination of hydrodynamic (capillary) and electrostatic forces acting on the particles. A rod floating on the fluid interface experiences both a lateral force and a torque normal to the interface due to capillarity, and in the presence of an electric field, it is also subjected to an electric force and torque. The electric force affects the rods’ approach velocity and the torque aligns the rods parallel to each other. In the absence of an electric field, two rods that are initially more than one rod length away from each other come in contact so that they are either perpendicular or parallel to the line joining their centers, depending on their initial orientations. In the latter case, their ends are touching. Our experiments show that in an electric field of sufficiently large strength, only the latter arrangement is stable. Experiments also show that in this case the electric field causes the rods of the monolayer to align parallel to one another and that the lattice spacing of a self-assembled monolayer of rods increases.

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Fluid Interfaces

Coatings ◽

10.3390/coatings10101000 ◽

2020 ◽

Vol 10 (10) ◽

pp. 1000

Author(s):

Eduardo Guzmán

Keyword(s):

Oil Recovery ◽

Self Assembly ◽

Deep Understanding ◽

Functional Materials ◽

Fluid Interfaces ◽

Dynamic Features ◽

Physico Chemical ◽

Structures And Properties ◽

Different Types

Fluid interfaces are promising candidates for the design of new functional materials by confining different types of materials, e.g., polymers, surfactants, colloids, or even small molecules, by direct spreading or self-assembly from solutions. The development of such materials requires a deep understanding of the physico-chemical bases underlying the formation of layers at fluid interfaces, as well as the characterization of the structures and properties of such layers. This is of particular importance, because the constraints associated with the assembly of materials at the interface lead to the emergence of equilibrium and dynamic features in the interfacial systems that are far from those found in traditional 3D materials. These new properties are of importance in many scientific and technological fields, such as food science, cosmetics, biology, oil recovery, electronics, drug delivery, detergency, and tissue engineering. Therefore, the understanding of the theoretical and practical aspects involved in the preparation of these interfacial systems is of paramount importance for improving their usage for designing innovative technological solutions.

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Self assembly of nanorods on microspheres at fluid–fluid interfaces

Physical Chemistry Chemical Physics ◽

10.1039/d0cp02396e ◽

2020 ◽

Vol 22 (25) ◽

pp. 14201-14209

Author(s):

Neethu Thomas ◽

Sanjana Shivkumar ◽

Ethayaraja Mani

Keyword(s):

Self Assembly ◽

Fluid Interfaces

Interfacial self-assembly of nanoparticles on curved substrates.

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Assembling responsive microgels at responsive lipid membranes

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1807790116 ◽

2019 ◽

Vol 116 (12) ◽

pp. 5442-5450 ◽

Cited By ~ 11

Author(s):

Meina Wang ◽

Adriana M. Mihut ◽

Ellen Rieloff ◽

Aleksandra P. Dabkowska ◽

Linda K. Månsson ◽

...

Keyword(s):

Self Assembly ◽

Lipid Membranes ◽

Lipid Membrane ◽

Soft Materials ◽

Fluid Interfaces ◽

Biomedical Sciences ◽

Interfacial Assembly ◽

Colloidal Assembly ◽

Long Range Ordering ◽

Adsorption Desorption

Directed colloidal self-assembly at fluid interfaces can have a large impact in the fields of nanotechnology, materials, and biomedical sciences. The ability to control interfacial self-assembly relies on the fine interplay between bulk and surface interactions. Here, we investigate the interfacial assembly of thermoresponsive microgels and lipogels at the surface of giant unilamellar vesicles (GUVs) consisting of phospholipids bilayers with different compositions. By altering the properties of the lipid membrane and the microgel particles, it is possible to control the adsorption/desorption processes as well as the organization and dynamics of the colloids at the vesicle surface. No translocation of the microgels and lipogels through the membrane was observed for any of the membrane compositions and temperatures investigated. The lipid membranes with fluid chains provide highly dynamic interfaces that can host and mediate long-range ordering into 2D hexagonal crystals. This is in clear contrast to the conditions when the membranes are composed of lipids with solid chains, where there is no crystalline arrangement, and most of the particles desorb from the membrane. Likewise, we show that in segregated membranes, the soft microgel colloids form closely packed 2D crystals on the fluid bilayer domains, while hardly any particles adhere to the more solid bilayer domains. These findings thus present an approach for selective and controlled colloidal assembly at lipid membranes, opening routes toward the development of tunable soft materials.

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Chains of cubic colloids at fluid–fluid interfaces

Soft Matter ◽

10.1039/d0sm01815e ◽

2021 ◽

Author(s):

Carmine Anzivino ◽

Giuseppe Soligno ◽

René van Roij ◽

Marjolein Dijkstra

Keyword(s):

Self Assembly ◽

Fluid Interfaces ◽

Assembly Process ◽

Fluid Interface ◽

Chain Formation ◽

Capillary Interactions

Inspired by recent experimental observations of spontaneous chain formation of cubic particles adsorbed at a fluid–fluid interface, we theoretically investigate whether capillary interactions can be responsible for this self-assembly process.

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