arXiv subjects

Laura Rossi

Publications and source records attributed to Laura Rossi.

3 recordsLinked to original sources

arXiv2021

Self-assembly of Colloidal Superballs Under Spherical Confinement of a Drying Droplet

Understanding the relationship between colloidal building block shape and self-assembled material structure is important for the development of novel materials by self-assembly. In this regard, colloidal superballs are unique building blocks because their shape can smoothly transition between spherical and cubic. Assembly of colloidal superballs under spherical confinement results in macroscopic clusters with ordered internal structure. By utilizing Small Angle X-Ray Scattering (SAXS), we probe the internal structure of colloidal superball dispersion droplets during confinement. We observe and identify four distinct drying regimes that arise during compression via evaporating droplets, and we track the development of the assembled macrostructure. As the superballs assemble, we found that they arrange into the predicted paracrystalline, rhombohedral C1-lattice that varies by the constituent superballs' shape. This provides insights in the behavior between confinement and particle shape that can be applied in the development of new functional materials.

cond-mat.soft↗

arXiv2021

Magnetic coupling in colloidal clusters for hierarchical self-assembly

Manipulating the way in which colloidal particles self-organise is a central challenge in the design of functional soft materials. Meeting this challenge requires the use of building blocks that interact with one another in a highly specific manner. Their fabrication, however, is limited by the complexity of the available synthesis procedures. Here, we demonstrate that, starting from experimentally available magnetic colloids, we can create a variety of complex building blocks suitable for hierarchical self-organisation using a simple scalable process. Using computer simulations, we compress spherical and cubic magnetic colloids in spherical confinement, and investigate their suitability to form small clusters with reproducible structural and magnetic properties. We find that, while the structure of these clusters is highly reproducible, their magnetic character depends on the particle shape. Only spherical particles have the rotational degrees of freedom to produce consistent magnetic configurations, whereas cubic particles frustrate the minimisation of the cluster energy, resulting in various magnetic configurations. To highlight their potential for self-assembly, we demonstrate that already clusters of three magnetic particles form highly nontrivial Archimedean lattices, namely staggered kagome, bounce and honeycomb, when viewing different aspects of the same monolayer structure. The work presented here offers a conceptually different way to design materials by utilizing pre-assembled magnetic building blocks that can readily self-organise into complex structures.

cond-mat.soft↗

arXiv2019

Shape and Interaction Decoupling for Colloidal Pre-Assembly

Creating materials with structure that is independently controllable at a range of scales requires breaking naturally occurring hierarchies. Breaking these hierarchies can be achieved via the decoupling of building block attributes from structure during assembly. Here, we demonstrate both geometric and interaction decoupling in pre-assembled colloidal structures of cube-like particles with rounded edges. Through computer simulations and experiments, we show that compressing a small number of such cubes in spherical confinement results in clusters with highly reproducible structures that can be used as mesoscale building blocks to form the next level of structural hierarchy. These clusters demonstrate geometric decoupling between particle shape and cluster structure; namely, for clusters of up to nine particles, the colloidal superballs pack consistently like spheres, despite the presence of shape anisotropy and facets in the cubic-like particles. We confirm that cluster structure is also decoupled from inter-particle interaction, showing that the same structures arise from the spherical confinement of both non-magnetic and magnetic colloidal cubes with strong dipolar interactions. To highlight the potential of these superball clusters for hierarchical assembly, we demonstrate, using computer simulations, that clusters of six to nine particles can self-assemble into high-order structures that differ from those of similarly shaped particles without pre-assembly. These results demonstrate decoupling for anisotropic building blocks that can be further exploited for hierarchical materials development.

cond-mat.soft↗