Hemispherical Arrays of Colloidal Crystals Fabricated by Transfer Printing

Abstract

The self-assembly of colloidal spheres is an effective strategy for producing nanopatterns. To use colloidal crystals in lithographic applications, the key challenge is to fabricate a monolayer of colloidal crystals uniformly over a large area. A simple and effective method for fabricating a colloidal crystals monolayer from a 3D colloidal crystal is described. The top layer of a surface-etched 3D colloidal crystal is picked up on a PDMS stamp, and by simply heating the receiving substrate, the polymeric colloidal crystal can be easily transferred to many types of substrates, including curved or flexible materials, without utilizing a glue layer. Moreover, the colloidal spheres are deformed to hemispheres during the transfer process, which is a suitable form of a lithographic mask for both dry and wet etching processes. An array of silicon nanocones and gold dots is demonstrated by pattern transfer from an array of hemispherical polymeric particles. In addition, it is also shown that the transferred hemispherical array has good antireflective properties.

Shaping in the Third Direction; Synthesis of Patterned Colloidal Crystals by Polyester Fabric-Guided Self-Assembly

“…The current methods of colloidal-crystal synthesis [ 30 , 35 , 36 , 37 , 38 ] work only with a single solid/liquid/gas interface ( Figure 6 h) and offer only flat or convex crystals. Triangular prisms are often produced when the “capillary-bridge-mediated-assembly” phenomenon/technique is used [ 57 , 58 , 59 ].…”

“…The simultaneous controlled presence of multiple types of surface planes in these photonic crystals would greatly enrich their photonic bands and, consequently, their potential applications. A curved surface exposes different packed planes, and this can be seen in round colloidal crystals, such as spheres, hemispheres, cylinders and rings [ 35 , 36 , 37 , 38 ]. Compared with the flat surfaces of CCs, which present different colors when observed from different angles, the curved surfaces show the same color, which is independent of the viewing angle [ 39 , 40 ].…”

Fabrication of Polystyrene/ZnO Micronano Hierarchical Structure Applied for Light Extraction of Light-Emitting Devices

“…LED covered with PS hemisphere layers could have a more increased output power than the LED covered with PS microspheres, due to the increased effective refractive index result from the enhanced contact area of the PS hemispheres. 38 On the other hand, for the porous ZnO nanoparticle layer, we have to consider another light-extracting mechanism. Because the effective refractive index of the ZnO nanoparticle layers is much larger than that of air, light which otherwise totally internally reflected in the ITO substrate can significantly escape and enter the ZnO nanoparticle layer.…”

Colloidal Transfer Printing–Mediated Fabrication of Zinc Oxide Nanorods for Self‐Cleaning Applications

“…In this approach, the array is first created on a “known” surface on which the parameters are well optimized and subsequently transferred to the target substrate . However, this approach could not be adopted for the growth of ZnO NRs, till, recently, all existing colloidal transfer printing techniques required modification of the target substrate with an adhesion promoting layer, which, in turn, hindered the ZnO NR growth on the seed layer. In this article, we have adopted our recently developed transfer printing protocol that relies on UV‐Ozone (UVO) mediated degradation of a sacrificial PMMA layer and does not alter the properties of the target substrate, onto which the colloidal array is transferred to.…”