State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China; School of Engineering Science, University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China.
State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China; School of Engineering Science, University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China.
J Colloid Interface Sci. 2023 May;637:522-532. doi: 10.1016/j.jcis.2023.01.102. Epub 2023 Jan 24.
The rich variety of patterns induced by evaporating drops containing particles has significant guidance for coating processes, inkjet printing, and nanosemiconductors. However, most existing works construct a uniform pattern by suppressing the coffee ring effect, and establishing the connection between them is still an academic challenge.
We report uniform, polygonal, and coffee ring patterns obtained by adjusting the solute concentration that sets in when an ethanol drop with dissolved ibuprofen is deposited on a silicon wafer.
Pattern formation involves rich hydrodynamic events: spreading, evaporative instability, dewetting, film formation, and particle deposition. Based on the distinct multiscale properties, this series of patterns is directly connected from the perspective of fractal geometry, which allows us to name them "fractal deposition patterns". A theoretical model considering film stability is established to explain the mechanism behind pattern formation, which is well verified by experiments. This work has presented a unique strategy that can directly connect uniform, polygonal, and coffee ring patterns under the same physics, hoping to provide instructive guidance for practical applications.
含有粒子的蒸发液滴所产生的丰富图案模式对涂层工艺、喷墨打印和纳米半导体具有重要的指导意义。然而，大多数现有工作通过抑制咖啡环效应来构建均匀的图案，并且它们之间的联系仍然是学术上的挑战。
我们报告了通过调整溶质浓度来获得均匀的、多边形的和咖啡环图案，当含有布洛芬的乙醇液滴沉积在硅片上时，溶质浓度会达到饱和。
图案形成涉及丰富的流体动力事件：铺展、蒸发不稳定性、去湿、成膜和颗粒沉积。基于明显的多尺度特性，从分形几何的角度来看，这一系列图案是直接相关的，这使我们能够将它们命名为“分形沉积图案”。建立了一个考虑薄膜稳定性的理论模型来解释图案形成的机制，该模型通过实验得到了很好的验证。这项工作提出了一种独特的策略，可以在相同的物理条件下直接连接均匀、多边形和咖啡环图案，希望为实际应用提供有指导意义的启示。
