Gel-controlled droplet spreading
Gel-controlled droplet spreading
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DOI：
10.1017/jfm.2017.844
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发表时间：
2018-02-25
影响因子：
3.7
通讯作者：
Balmforth, N. J.
中科院分区：
文献类型：
--
作者：
Jalal, M.;Seyfert, C.;Balmforth, N. J.
研究了热响应流体在受热表面上的铺展和静止液滴。该流体在高温下经历可逆的凝胶形成。使用基于谱域光学相干断层扫描和随时间变化的散斑图案的实验方法检查液滴内凝胶形成的时空图案。凝胶的形成可以分为两个阶段：第一，从接触线开始出现薄壳。第二，凝胶层出现在加热板上方，然后向上膨胀。我们将凝胶形成的第一阶段归因于溶剂蒸发和通过空气加热，第二阶段归因于通过来自基底的流体的热传导。接触线处的凝胶形成可能是阻止扩散液滴的原因，但在接触线阻止时，我们的实验方案无法检测到，这表明这是在微观长度尺度上发生的。总体而言，基板加热提供了控制热响应流体的液滴的最终形状的有效方式。
Spreading and stationary droplets of a thermally responsive fluid on a heated surface are studied. The fluid undergoes a reversible gel formation at elevated temperature. The spatio-temporal pattern of gel formation within the droplet is examined using an experimental method based on spectral domain optical coherence tomography and time varying speckle patterns. Two stages of gel formation can be distinguished: first, a thin crust appears starting at the contact line. Second, a gel layer appears above the heated plate and then expands upward. We attribute the first stage of gel formation to solvent evaporation and heating through the air and the second to thermal conduction through the fluid from the base. Gel formation at the contact line is likely responsible for the arrest of spreading droplets, but was not detectable with our experimental protocol at the time of contact line arrest, suggesting that this arose over a microscopic length scale. Overall, substrate heating provides an effective way to control the final shape of droplets of thermo-responsive fluids.