Colloidal Drop Deposition on Porous Substrates: Competition among Particle Motion, Evaporation, and Infiltration

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• 作者：Min Pack ; Han Hu ; Dong-Ook Kim ; Xin Yang ; Ying Sun
• 刊名：Langmuir
• 出版年：2015
• 出版时间：July 28, 2015
• 年：2015
• 卷：31
• 期：29
• 页码：7953-7961
• 全文大小：640K
• ISSN：1520-5827

文摘

Recent interest in printable electronics and in particular paper- and textile-based electronics has fueled research in inkjet printing of colloidal drops on porous substrates. On nonporous substrates, the interplay of particle motion and solvent evaporation determines the final deposition morphology of the evaporating colloidal drop. For porous substrates, solvent infiltration into the pores adds a layer of complexity to the deposition patterns that have not been fully elucidated in the literature. In this study, the deposition of picoliter-sized aqueous colloidal droplets containing nanometer- and micrometer-sized particles onto nanoporous anodic aluminum oxide substrates is examined for different drop and particle sizes and relative humidities as well as pore diameters, porosities, and wettabilities of the porous substrates. For the cases considered, solvent infiltration is found to be much faster than both evaporation and particle motion near the contact line, and thus when the substrate fully imbibes the solvent, the well-known 鈥渃offee-ring鈥?deposition is suppressed. However, when the solvent is only partially imbibed, a residual droplet volume exists upon completion of the infiltration. For such cases, two time scales are of importance: the time for particle motion to the contact line as a result of both diffusion and advection, t_P, and the evaporation time of the residual drop volume, t_EI. Their ratio, t_P/t_EI, determines whether the coffee-ring deposition will be formed (t_P/t_EI < 1) or suppressed (t_P/t_EI > 1).