A 3D liquid self-shaping strategy is reported for rapidly patterning materials over a series of compositions and accurately achieving micro- and nanoscale structures. The predesigned template selectively pins the droplet, and the surface energy minimization drives the self-shaping processing. The as-prepared 3D circuits assembled by silver nanoparticles carry a current of 208–448 μA at 0.01 V impressed voltage, while the 3D architectures achieved by two different quantum dots show noninterfering optical properties with feature resolution below 3 μm. This strategy can facilely fabricate micro-nanogeometric patterns without a modeling program, which will be of great significance for the development of 3D functional devices.
The mechanism of droplet drying is a widely concerned fundamental issue since controlling the deposition morphology of droplet has significant influence on printing, biology pattern, self-assembling and other solution-based devices fabrication. Here we reveal a striking different kinetics-controlled deposition regime beyond the ubiquitous coffee-ring effect that suspended particles tend to kinetically accumulate at the air-liquid interface and deposit uniformly. As the interface shrinkage rate exceeds the particle average diffusion rate, particles in vertical evaporation flow will be captured by the descending surface, producing surface particle jam and forming viscous quasi-solid layer, which dramatically prevents the trapped particles from being transported to drop edge and results in uniform deposition. This simple, robust drying regime will provide a versatile strategy to control the droplet deposition morphology, and a novel direction of interface assembling for fabricating superlattices and high quality photonic crystal patterns.
(Yanan Li, Qiang Yang, Mingzhu Li, Yanlin Song. Rate-dependent interface capture beyond the coffee-ring effect [J]. Scientific reports, 2016, 6:24628.)