Ali Kerem Erdem, Fabian Denner and Luca Biancofiore*,
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引用次数: 0
摘要
含有分散颗粒的蒸发无梗液滴被用于不同的技术应用中,如 3D 打印、生物医学和微制造,在这些应用中,准确预测颗粒的分散和沉积非常重要。此外,液滴与基底之间的相互作用也必须考虑在内:尤其是接触线的运动必须仔细建模。为此,研究通常局限于针状接触线或运动接触线,以简化基础数学模型和数值方法,而忽略了在蒸发过程中两种情况都会出现的事实。在这里,我们提出了一种考虑到两种接触线状态的数值算法,通过预定义的阈值接触角来区分两种状态。经过详细验证后,这种新算法被应用于研究这两种情况对蒸发无柄液滴中颗粒的分散和沉积的影响。具体来说,本文分析的重点是以下几个方面的影响:(i) 通过改变极限接触角和扩散速度来改变接触线运动特性;(ii) 马兰戈尼数(表征热汽蚀的重要性);(iii) 蒸发数(量化蒸发的重要性);(iv) 达姆克勒数(颗粒沉积速率的度量);(v) 佩克莱特数(比较颗粒浓度的对流和扩散)。当热毛细管变得占主导地位或极限接触角变大时,接触线附近的颗粒积聚会减少,这反过来又意味着更多颗粒沉积在液滴中心附近。相反,增加蒸发数会支持接触线附近的颗粒积聚,而较大的达姆克勒数和/或较小的佩克莱特数会产生更均匀的最终沉积模式。最后,较大的特征扩散速度会导致较少的颗粒沉积在液滴中心。
Numerical Analysis of the Dispersion and Deposition of Particles in Evaporating Sessile Droplets
Evaporating sessile droplets containing dispersed particles are used in different technological applications, such as 3D printing, biomedicine, and micromanufacturing, where an accurate prediction of both the dispersion and deposition of the particles is important. Furthermore, the interaction between the droplet and the substrate must be taken into account: the motion of the contact line, in particular, must be modeled carefully. To this end, studies have typically been limited to either pinned or moving contact lines to simplify the underlying mathematical models and numerical methods, neglecting the fact that both scenarios are observed during the evaporation process. Here, a numerical algorithm considering both contact line regimes is proposed whereby the regimes are distinguished by predefined threshold contact angles. After a detailed validation, this new algorithm is applied to study the influence of both regimes on the dispersion and deposition of particles in an evaporating sessile droplet. In particular, the presented analysis focuses on the influence of (i) the contact line motion characteristics by varying the limiting contact angle and spreading speed, (ii) the Marangoni number, characterizing the importance of thermocapillarity, (iii) the evaporation number, which quantifies the importance of evaporation, (iv) the Damköhler number, a measure of the particle deposition rate, and (v) the Peclet number, which compares the convection and diffusion of the particle concentration. When thermocapillarity becomes dominant or the limiting contact angle is larger, the particle accumulation near the contact line decreases, which, in turn, means that more particles are deposited near the center of the droplet. In contrast, increasing the evaporation number supports particle accumulation near the contact line, while a larger Damköhler number and/or smaller Peclet number yield more uniform final deposition patterns. Finally, a larger characteristic speed of spreading results in fewer particles being deposited at the center of the droplet.
期刊介绍:
Langmuir is an interdisciplinary journal publishing articles in the following subject categories:
Colloids: surfactants and self-assembly, dispersions, emulsions, foams
Interfaces: adsorption, reactions, films, forces
Biological Interfaces: biocolloids, biomolecular and biomimetic materials
Materials: nano- and mesostructured materials, polymers, gels, liquid crystals
Electrochemistry: interfacial charge transfer, charge transport, electrocatalysis, electrokinetic phenomena, bioelectrochemistry
Devices and Applications: sensors, fluidics, patterning, catalysis, photonic crystals
However, when high-impact, original work is submitted that does not fit within the above categories, decisions to accept or decline such papers will be based on one criteria: What Would Irving Do?
Langmuir ranks #2 in citations out of 136 journals in the category of Physical Chemistry with 113,157 total citations. The journal received an Impact Factor of 4.384*.
This journal is also indexed in the categories of Materials Science (ranked #1) and Multidisciplinary Chemistry (ranked #5).