Instability and Soft Patterning Laboratory, Department of Chemical Engineering , Indian Institute of Technology Kharagpur , Kharagpur 721 302 , West Bengal , India.
J Phys Chem B. 2020 Feb 20;124(7):1266-1274. doi: 10.1021/acs.jpcb.9b08809. Epub 2020 Feb 11.
We report the evaporative drying-mediated pattern formation of dilute aqueous NaCl solution droplets on a hydrophobic surface made of cross-linked PDMS at elevated temperatures. Experiments were performed with various salt concentrations (0.08 to 2 M). Depending on the substrate temperature () and initial salt concentration (), a variety of unique deposition morphologies are obtained. Double salt rings are obtained at low (0.08 and 0.1 M) at ≈ 75 °C. With the increase in , the deposition morphology transforms into a single peripheral ring with a central deposition zone that is devoid of any salt deposition. On the other hand, at lower and lower , a single outer ring deposit surrounding a central region covered with dendritic salt deposits is observed. The variation in the morphology as well as the number of rings formed is attributed to the relative strengths of the radially outward capillary-driven flow, inward Marangoni flow, and inward diffusive transport of the salt ions. A morphology phase diagram shows the collective dependence of the final deposition pattern as a function of both and .
我们报告了在交联 PDMS 疏水表面上，升高温度下稀 NaCl 水溶液液滴的蒸发干燥介导的图案形成。实验在不同盐浓度（0.08 到 2 M）下进行。根据基底温度（）和初始盐浓度（），可以得到各种独特的沉积形貌。在低（0.08 和 0.1 M）和 ≈ 75°C 时，得到双盐环。随着的增加，沉积形貌转变为具有无盐沉积的中央沉积区的单个外围环。另一方面，在较低的和较低的下，观察到单个外环沉积物围绕着中央区域，该区域覆盖着树枝状盐沉积物。形态的变化以及形成的环的数量归因于径向向外的毛细驱动流、向内的 Marangoni 流以及盐离子向内扩散输运的相对强度。形态相图显示了最终沉积图案作为和的函数的集体依赖性。
