Effects of Substrate Heating and Wettability on Evaporation Dynamics and Deposition Patterns for a Sessile Water Droplet Containing Colloidal Particles
Effects of Substrate Heating and Wettability on Evaporation Dynamics and Deposition Patterns for a Sessile Water Droplet Containing Colloidal Particles
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DOI：
10.1021/acs.langmuir.6b02769
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发表时间：
2016-11-15
期刊：
影响因子：
3.9
通讯作者：
Sharma, Atul
中科院分区：
文献类型：
--
作者：
Patil, Nagesh D.;Bange, Prathamesh G.;Sharma, Atul
实验研究了基片温度、基片润湿性和粒子浓度对含胶体粒子的固着水滴蒸发的影响。时变液滴的形状和温度的液-气界面分别使用高速可视化和红外热成像测量。通过光学显微镜定性观察蒸发液滴内颗粒的运动，并通过光学轮廓仪测量最终颗粒存款的轮廓。在未加热的亲水性基材上，蒸发后形成环状存款，如文献中广泛报道的，而在加热的亲水性基材上，在本工作中报道了具有内部存款的较薄的环。后者是由于马兰戈尼对流，和记录的运动的颗粒以及测量的温度梯度跨越液-气界面证实了这一假设。环的变薄与衬底温度成比例，并被认为是在较大的衬底温度下更强的Marangoni对流。在未加热的疏水基底的情况下，由于接触线的非常早的脱钉，形成内部存款。另一方面，在加热的疏水基底的情况下，基底加热以及较大的颗粒浓度有助于接触线的钉扎，这导致具有内部存款的薄环。我们提出了一个政权图预测三种类型的存款，即环，薄环与内部存款，和内部存款为不同的衬底温度，衬底润湿性，和颗粒浓度。一阶模型证实了液-气界面温度测量和测量的环轮廓随衬底温度的变化。
Effects of substrate temperature, substrate wettability, and particle concentration are experimentally investigated for evaporation of a sessile water droplet containing colloidal particles. Time-varying droplet shapes and temperature of the liquid gas interface are measured using high-speed visualization and infrared thermography, respectively. The motion of the particles inside the evaporating droplet is qualitatively visualized by an optical microscope and the profile of the final particle deposit is measured by an optical profilometer. On a nonheated hydrophilic substrate, a ring-like deposit forms after the evaporation, as reported extensively in the literature, while on a heated hydrophilic substrate, a thinner ring with an inner deposit is reported in the present work. The latter is attributed to Marangoni convection, and recorded motion of the particles as well as measured temperature gradient across the liquid gas interface confirms this hypothesis. The thinning of the ring scales with the substrate temperature and is reasoned to stronger Marangoni convection at larger substrate temperature. In the case of a nonheated hydrophobic substrate, an inner deposit forms due to very early depinning of the contact line. On the other hand, in the case of a heated hydrophobic substrate, the substrate heating as well as larger particle concentration helps in the pinning of the contact line, which results in a thin ring with an inner deposit. We propose a regime map for predicting three types of deposits namely, ring, thin ring with inner deposit, and inner deposit for varying substrate temperature, substrate wettability, and particle concentration. A first-order model corroborates the liquid gas interface temperature measurements and variation in the measured ring profile with the substrate temperature.