纳米粗糙度对胶体液滴蒸发图案的影响机制  

Influence of nano-scaled roughness on evaporation patterns of colloidal droplets

作　　者：张永建[1] 叶芳霞[1] 戴君[1] 何斌锋[1] 臧渡洋[2] 

机构地区：[1]西安文理学院机械与材料工程学院,陕西省表面工程与再制造重点实验室,西安710065 [2]西北工业大学理学院,空间应用物理与化学教育部重点实验室,西安710129

出　　处：《物理学报》2017年第6期173-179,共7页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:51301139);陕西省自然科学基础研究计划(批准号:2016JM1003);陕西省教育厅基金(批准号:16JK2201)资助的课题~~

摘　　要：对比研究了Si O_2胶体液滴在光滑基底与纳米粗糙度基底上的蒸发及其图案形成.实验发现,在光滑基底上,液滴的蒸发伴有显著的"咖啡环效应",沉积图案呈现碗状.而在粗糙基底上蒸发后得到厚度分布较为均匀的蒸发图案,且裂纹密度明显增大.分析显示,纳米粗糙度可抑制液滴内沿基底的回流,极大地削弱了毛细流的补偿作用,导致颗粒在气-液界面富集并形成颗粒膜,从而克服了"咖啡环效应",最终形成厚度分部均匀的蒸发图案.Evaporation of colloidal droplets often leads to various deposited patterns which are not only interesting but also provide a very simple and useful method to fabricate functional materials.The patterns induced by the evaporation can be tuned via several factors,among which the roughness of the substrate is an important one.However,the effect of nano-scaled roughness is scarcely studied and far from being fully understood.In this work,the evaporation and pattern formation of SiO2 colloid droplets are studied on smooth substrate and nano-rough substrate,respectively.The aim of this work is to clarify how the evaporation dynamics and patterns are influenced by nano-scaled roughness.The roughness of the substrate is analyzed by using a scanning electron microscope and an atomic force microscope,the evaporation process and pattern formation are monitored via an in-situ microscope observation.The obtained deposited patterns are analyzed by using stylus profiling.It is found that the evaporation of droplets is accompanied by an obvious ＂coffee ring effect＂ on smooth substrate and the deposition patterns are bowl-shaped.However,uniform thickness evaporation patterns are obtained through evaporation on rough substrate,moreover,the crack density increases obviously.The analysis shows that nano-roughness is able to inhibit the circumfluence of droplets along the substrate,which greatly weakens the compensation for capillary flow,leading to particles gathering at air-droplet interface and formulating a particle layer.This prevents the ＂coffee ring effect＂,and eventually results in the formation of evaporation patterns with uniform thickness.

关 键 词：粗糙度 胶体液滴 蒸发图案 咖啡环效应 

分 类 号：O648[理学—物理化学]