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Understanding of the role of dilution on evaporative deposition patterns of blood droplets over hydrophilic and hydrophobic substrates.
Journal of Colloid and Interface Science ( IF 9.9 ) Pub Date : 2020-06-12 , DOI: 10.1016/j.jcis.2020.04.109
R Iqbal 1 , Amy Q Shen 2 , A K Sen 1
Affiliation  

Blood is a complex colloidal suspension which carries myriads of information about human health. Understanding the evaporation dynamics and its consequent deposition patterns have direct relevance in disease detection. We report evaporation dynamics of whole and diluted blood droplets over hydrophilic (glass) and hydrophobic (PDMS, polydimethylsiloxane) substrates. Our experiments show that blood drops evaporating on a hydrophilic substrate exhibit radial and orthoradial cracks in the coronal region and random cracks in the central region. Using Griffith’s energy criterion, we show that crack formation takes place when the capillary pressure and the resulting compressive stress inside the evaporating droplet exceeds critical stress which depends on the elastic modulus, interfacial energy, and the particle concentration of the system. The width of the coronal region (w), the film thickness (h) at the contact line, and the crack pitch (p) decrease with increasing blood dilution. In the dilution range of 2.0–0.8% HCT (hematocrit), the transition from the cracking to the non-cracking regime is observed, which can be attributed to inadequate compressive stress available even after the evaporation of the blood droplet is completed. For the hydrophobic substrate, buckling instead of cracking is observed for the whole blood droplets, which can be attributed to the distinct wetting and evaporation kinetics. The buckling of the blood drop on a hydrophobic surface is attributed to the competition between capillary pressure originated due to the formation of an elastic network of RBCs (red blood cells) and the menisci formed between adjacent RBCs, and the critical buckling pressure. With increasing blood dilution, a transition from buckling (between 21 and 42% HCT) to cracking (between 21 and 2.0% HCT) of the droplets, and eventually to the non-cracking regime (between 2.0 and 0.8% HCT) is observed. Our study unravels the interesting attributes about one of the important physico-chemical factors (i.e. % HCT) that affect the evaporation of blood droplets and the resulting deposition patterns on substrates with different hydrophobicity.



中文翻译:

了解稀释对亲水性和疏水性基质上的液滴蒸发沉积模式的作用。

血液是一种复杂的胶体悬浮液,可携带无数有关人类健康的信息。了解蒸发动力学及其导致的沉积模式与疾病检测有着直接的关系。我们报告了在亲水性(玻璃)和疏水性(PDMS,聚二甲基硅氧烷)基质上整个和稀释的血滴的蒸发动力学。我们的实验表明,在亲水性基质上蒸发的血滴在冠状区域显示出径向和正径向裂纹,在中央区域显示出随机裂纹。使用格里菲斯(Griffith)的能量准则,我们表明,当毛细管压力和蒸发液滴内部产生的压应力超过临界应力时会发生裂纹形成,临界应力取决于弹性模量,界面能和系统的颗粒浓度。w),漆膜厚度(H)在接触线上,裂纹间距(p)随着血液稀释度的增加而降低。在2.0–0.8%HCT(血细胞比容)的稀释范围内,观察到了从龟裂到非龟裂的过渡,这可以归因于即使在液滴蒸发完成后也没有足够的压缩应力。对于疏水性底物,在整个液滴中观察到屈曲而不是破裂,这可以归因于独特的润湿和蒸发动力学。水滴在疏水表面上的屈曲归因于由于RBC(红细胞)的弹性网络和相邻RBC之间形成的弯液面的形成而产生的毛细管压力与临界屈曲压力之间的竞争。随着血液稀释的增加,观察到液滴从屈曲(HCT在21%至42%之间)到破裂(21%至2.0%HCT之间)到最终的非破裂状态(2.0%至0.8%HCT之间)过渡。我们的研究揭示了一种重要的物理化学因素(即%HCT)的有趣属性,这些因素会影响液滴的蒸发以及在疏水性不同的基材上产生的沉积模式。

更新日期:2020-07-03
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