dip-pen lithography, [5] block copolymerbased patterning, [6] ink-jet printing, [7] and other techniques [8] have been used for different purposes and material types. Much attention has also been paid to 2D colloidal crystalline patterns, [9][10][11] which are useful in structure development and optical applications. Colloidal crystalline patterns are usually close-packed structures fabricated through Langmuir-Blodgett processes, [12,13] dip coating, [14,15] spin-coating, [16,17] electrodeposition, [18] floating and lift-up, [19,20] and other techniques. [21] Nonclose-packed structures can be achieved by etching the close-packed crystal patterns with plasma, [14,15,17,[22][23][24][25][26] ion beams, [13,[27][28][29] and electron beams. [30] Particle spacing can be controlled by the etching time. For inorganic corepolymer shell colloids, a thermal combustion method has been used to fabricate nonclose-packed inorganic colloidal patterns. [16,18] In some cases, nonclose-packed colloidal arrays may be achieved by deposition of core-shell and hydrogel colloids onto flat substrates in solutions and subsequent air-drying, [31,32] but spaces among the colloids are micrometer scale and the degree of crystalline order is low. Meanwhile, close-packed colloidal crystals can transform into nonclose-packed crystal patterns by stretching or swelling poly(dimethyl siloxane) (PDMS) substrates. [33][34][35] To fix the prepatterned colloidal arrays, the substrates should remain either stretched or swelled under certain conditions, and the pattern should be further transferred onto other substrates. Such a prepattern and transfer method could be advantageous to avoid damage to organic and polymer substrates caused by etching or thermal treatment. Nevertheless, there is a continual demand to develop a simpler method for nonclose-packed crystalline patterns without etching/combustion or transferring prepatterned colloids on substrates regardless of material types and surface structures of substrates. Additionally, it remains a challenge to effectively manipulate the structures of colloidal crystal monolayers, e.g., the size and morphologies of the colloidal particles. At the same time, a versatile method is also required to cover the fabrication of an ordered array of hybrid colloids comprising inorganic and organic particles. 2D nonclose-packed colloidal crystal patterns have received considerable attention in various fields, but it remains a challenge to fabricate patterns and manipulate their geometries regardless of substrate types and structures. Herein, a simple approach is developed for producing nonclose-packed hydrogel colloidal crystalline patterns on flat and periodically micropatterned substrates by exposing close-packed colloidal crystal monolayers to salt aqueous solutions. The patterns are achievable on flat surfaces like silicon, glass, graphene, poly(ethylene terephthalate), and poly(dimethyl siloxane) surfaces. Hydrogel colloidal spheres can deform into disk-like or hemispherical particles on different material subst...
Tunable non‐close‐packed colloidal crystal patterns with disk‐like or hemispherical colloidal shapes, formed by exposing close‐packed colloidal crystal to aqueous salt solution, are achievable on various flat and periodically micro‐patterned substrates. Also, inorganic‐polymer hybrid colloidal crystal patterns can be readily prepared. These colloidal patterns are useful as anti‐reflective layers and printable‐erasable substrates. This is reported by Ji Eun Song, Eun Chul Cho, and co‐workers in article number https://doi.org/10.1002/admi.201800138.
Manipulation of both pore diameters and heights of two-dimensional periodic porous polymer films is important to extensively control their characteristics. However, except for using different sized colloid templates in replication methods, an effective method that tunes these factors has rarely been reported. We found that both parameters are controllable by adjusting the flow behaviors of polystyrene colloids and curing resin precursors during the preparation of phenolic resin and poly(dimethylsiloxane) periodic porous films by embedding their precursors into colloidal crystal monolayers. We adjust the flow behaviors by either varying film preparation temperatures (≥glass transition temperature of polystyrene) or using the precursors mixed with different amounts of solvents that renders the colloids viscous. Consequently, the pore diameters and film heights change by 36–56 and 56–84%, respectively. Such modulation results in the change in height to diameter ratios and the areal fractions of resins at air–film interfaces, thereby significantly changing the water contact angles on these surfaces and their photonic characteristics. This straightforward method does not require additional steps, differently sized colloids, or different amounts of precursors for these parameter controls.
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