Centrifugation-Assisted Growth of Single-Crystalline Grains in Microcapsules

Abstract

Colloidal crystals have been tailored in a format of microspheres to use them as a building block to construct macroscopic photonic surfaces. However, the polycrystalline grains grown from the spherical surface usually exhibit low reflectivity. Although single-crystalline microspheres have been produced, it is difficult to control the crystal orientation. Here, we design spherical microcapsules with density anisotropy that contain single-crystalline grains along the heavy side. The microcapsules spontaneously align to have a heavy side down under the action of gravity and display a bright and uniform reflection color from the entire surface of the grains. Key to the success is the use of gentle centrifugal force to initiate nucleation and grow single-crystalline grains from the heavy side through depletion attraction. The microcapsules have density anisotropy due to the heterogeneity of the shell thickness, which causes them to self-align under centrifugation. At the same time, particles are accumulated on the heavy side, which produces many tiny grains on the heavy side immediately after the centrifugation. With controlled depletion attraction among particles, only a few grains survive during postincubation through Ostwald ripening, and one or a few giant single-crystalline grains are finally produced along the heavy side of each microcapsule.

Production of Photonic Supraballs Composed of Single-Crystalline Colloidal Arrays through Osmosis-Induced Consolidation

“…Monodisperse colloids spontaneously produce crystalline lattices, which have been used as photonic materials with bandgap properties. − The colloidal crystals have been tailored in a format of spherical microparticles by employing emulsion droplets as a confining geometry. , The photonic supraballs have served as structural colorants, ,− colorimetric microsensors, − display pixels, − and optically encoded microcarriers, − which are difficult to apply with a bulk film format. In addition, the emulsion droplets provide a tool to study the crystallization behavior of colloids under spherical confinement. − It has been revealed that single-crystalline face-centered cubic (fcc) structures with surface termination to fit into a sphere are energetically more favorable than onion-like or polycrystalline structures. ,− The photonic supraballs composed of single-crystalline colloidal arrays are optically anisotropic as the crystal planes responsible for diffraction vary depending on the orientation of supraballs. , Therefore, the single supraballs show various reflection colors from their entire projection as they rotate.…”

Uniaxial extending neural probes for bleeding-absent implantation

“…2c). This phenomenon can be attributed to a diffusive mass flow resulting from a concentration gradient induced by the UV intensity gradient, which serves as the primary driving force for molecules within our aligned hydrogel scaffold 31 . This gradient, absent in thermo-curing hydrogels, serves as the primary force propelling molecules within our aligned hydrogel scaffold.…”

Dynamic Orientation Control of Gold Nanorods in Polymer Brushes by Their Thickness Changes for Plasmon Switching

“…[28][29][30][31][32] Among these soft matters, polymer brushes offer greater advantages in terms of devices as they allow control of nanostructure arrangements on solid substrates by nanoscale conformation changes without macroscale size changes of the matrix. [33][34][35][36][37][38] These characteristics, as well as the inherent anisotropy of polymer brushes, are expected to be more suitable to control the orientation of anisotropic nanoparticles.…”