Ultrafast Self-Assembly of Colloidal Photonic Crystals during Low-Pressure-Assisted Evaporation of Droplets

Abstract

After evaporation of a sessile colloidal droplet, the coffee stain always emerges with disordered structures. This may be unfavorable for many applications, such as dropletbased printing. Therefore, to realize uniform and ordered patterns is becoming an urgent task. In this work, we realize ultrafast fabrication of uniform colloidal crystals by suppressing the coffee ring effect in flash evaporation of a droplet. The low-pressure environment can tremendously improve the evaporation rate, which will accelerate the colloidal particles to be captured by the gas−liquid interface and self-assemble into ordered structures instantaneously. With the control of the pressure and concentration, the uniform and ordered patterns can be realized in several seconds. The colloidal photonic crystals with diverse structural colors can be easily and rapidly obtained by adjusting the particle sizes. We think this work may have instructive significance in the rapid fabrication of high-quality and high-performance printed electronics.

Photonic crystal gas sensors based on metal–organic frameworks and polymers

“…Zhang et al achieved ultrafast preparation of homogeneous colloidal crystals by suppressing the coffee ring effect in droplet flash evaporation. 49 The low-pressure environment can greatly increase the evaporation rate, which accelerates the capture of colloidal particles by the gas–liquid interface and their instantaneous self-assembly into ordered structures (Fig. 4(II)).…”

“…(h and i) Uniform particle layer on the liquid surface is gradually pulled and divided at last, resulting in fragmentation. (j) Particle layer on the liquid surface eventually spreads out onto the substrate in a fragmented state and even forms a hole 49.…”

Three-Dimensional Deposits from Drying Particle-Laden Drops

“…This advective flow is caused by the liquid from the interior of the drop rushing toward the TPCL, with the TPCL remaining pinned, to replenish the liquid that is lost from the TPCL due to evaporation. − The ubiquitousness of the coffee ring formation has meant that the presence of such ring-like deposits at the TPCL, occurring during the evaporation of drop containing any type of particle, is generically denoted as the “coffee ring”. The inherent self-assembly process associated with the coffee ring formation has been extensively utilized to self-assemble different types of micro/nanoparticles and chemical species for applications, such as pre-concentrating chemical samples before their analyses, , sensitive detection of organic and biomolecules and their properties, − triggering size-dependent particle separation, and fabricating a variety of materials/structures/functional devices, such as immunoassays, photonic − and plasmonic crystals, conducting wires, − porous films, and scaffolds of different materials, and microcantilevers . At the same time, the “coffee ring” formation has also several disadvantages, such as the formation of nonuniform coating/patterning, formation of trench-like and raised ridge structures during three-dimensional (3D) printing with metal nanoparticle ink, , etc.…”

Three-Dimensional Photonic Crystals Based on Porous Anodic Aluminum Oxide

“…An outlook on modern studies in the field of 3D PCs allows us to summarize the advantages and disadvantages of the proposed approach. Up to date, there are two most common ways to the creation of the 3D PCs: “top-down”, e.g., the laser-beam lithography, − and “bottom-up”, e.g., self-assembly from colloidal particles. − Contrary to the laser beam lithography, for which the creation of sub-500 nm structures is a challenge, the proposed approach allows the fabrication of 3D AAO PCs with periods down to 100 nm by a proper choice of the electrolyte composition and anodization voltage (Figure S6). Besides, the developed technique allows us to create thick (several tens of micrometers) PCs.…”