Controlling droplet spreading with topography
Controlling droplet spreading with topography
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DOI：
10.1103/physrevfluids.2.094002
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发表时间：
2017-01
期刊：
影响因子：
--
通讯作者：
P. Kant;A. Hazel;Mark C. Dowling;A. Thompson;A. Juel
中科院分区：
文献类型：
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作者：
P. Kant;A. Hazel;Mark C. Dowling;A. Thompson;A. Juel
我们提出了一种新的实验系统，可以用来研究皮升液滴在具有地形变化的衬底上扩散的动力学。我们专注于在凹进的体育场形像素内液滴的扩散，并将其应用于POLED显示器的制造，并发现像素的倾斜侧壁可以局部增强或阻碍扩散，这取决于接触线前方的地形梯度是正还是负。局部增强的扩散是通过沿着像素的侧壁形成细尖的溪流，其机制类似于尖角处的毛细上升。我们证明了薄膜模型与实验测量的扩散规律相结合，它将接触线的速度与接触角联系起来，提供了对液体形态演变的良好预测。我们还表明，对于大多数进化，扩展可以用Cox-Voinov定律充分描述。该模型不包括粘性效应，因此，没有捕获细尖溪流传播的时间尺度。尽管如此，这个简单的模型可以非常有效地用于预测液体覆盖的区域，并且可以作为需要精确控制基板上液体的系统的有用设计工具。
We present a novel experimental system that can be used to study the dynamics of picoliter droplet spreading over substrates with topographic variations. We concentrate on spreading of a droplet within a recessed stadium-shaped pixel, with applications to the manufacture of POLED displays, and find that the sloping side wall of the pixel can either locally enhance or hinder spreading depending on whether the topography gradient ahead of the contact line is positive or negative. Locally enhanced spreading occurs via the formation of thin pointed rivulets along the side walls of the pixel through a mechanism similar to capillary rise in sharp corners. We demonstrate that a thin-film model combined with an experimentally measured spreading law, which relates the speed of the contact line to the contact angle, provides excellent predictions of the evolving liquid morphologies. We also show that the spreading can be adequately described by a Cox-Voinov law for the majority of the evolution. The model does not include viscous effects and hence, the timescales for the propagation of the thin pointed rivulets are not captured. Nonetheless, this simple model can be used very effectively to predict the areas covered by the liquid and may serve as a useful design tool for systems that require precise control of liquid on substrates.