Light‐Directed Assembly of Colloidal Matter

Abstract

The assembly of colloidal particles into 2D or 3D superstructures is significant as the colloidal assembly exhibits collective behavior beyond the sum of single particles. Technically, colloidal particles can either self‐assemble when thermodynamic equilibrium is reached, or directed into specific assembly under external stimulus, such as electric, magnetic, acoustic, or light field. Specifically, light can be focused locally and manipulated in a precise manner, providing the possibility to tailor the assembly kinetics in different degrees of freedom. The understanding of light–matter interaction during the assembly process is challenging but critical for the design and fabrication of diverse colloidal superstructures. In this review, these particles are treated as artificial atoms at colloidal scale to mimic the organization of matter. From this aspect, the light‐directed assembly process is discussed on the basis of the roles of light, including light‐directed nucleation, diffusion, interparticle bonding, and phase control. Beyond what has been observed at atomic scale, colloidal atoms exhibit diversity in size, shape, and composition, and their bonding force is irrelevant to the electronic state, which enriches the geometric complexity of colloidal matter. Finally, the authors summarize the emerging applications of these colloidal superstructures in nanophotonics, nanocatalysis, and nanomedicine, and outline the major challenge and future development.

Core–Shell Particles: From Fabrication Methods to Diverse Manipulation Techniques

“…Figure 4 F illustrates particle trapping on a substrate surface [ 143 ]. A low-intensity laser coupled with a patterned surface traps colloidal particles and sorts them according to the matching patterns [ 144 ]. In the case of metallic particles, 2D surface plasmon excitations at metal–dielectric interfaces direct the assembly with both optical and local thermal-convection forces [ 145 ].…”

Core -Shell Particles: from Fabrication Methods to Diverse Manipulation Techniques

“…[148] A low-intensity laser coupled with patterned surfaces trap colloidal particles and sort them based on the matching patterns. [149] In the case of metallic particles, 2D surface plasmon excitations at metal-dielectric interfaces direct the assembly under the influence of optical and local thermal-convection forces. [150] On the other hand, Yamaguchi et al assembled silica microspheres into hexagonally close-packed arrays or linear particle chains by changing laser power.…”

Assembly and manipulation of responsive and flexible colloidal structures by magnetic and capillary interactions

“…However, they are limited in their ability to form complex directionally oriented structures. 9 Directional colloidal assembly techniques using external fields such as magnetic fields, [10][11][12][13] electric fields [14][15][16][17] and light 18,19 offer efficient ways of overriding the common colloidal interactions and guiding the particles to form out-of-equilibrium structures by accelerating the assembly kinetics. Further, external fields offer more precise control of the dynamics of the assembly process by changing the field parameters and can be used to assemble structures ranging from oriented 2D crystals, 20 nanowires, 21 electro and magnetorheological fluids to other stimuli responsive materials.…”