Department of Chemical Engineering, Lehigh University, Bethlehem, Pennsylvania 18015, United States.
Langmuir. 2012 Oct 2;28(39):13912-8. doi: 10.1021/la302847g. Epub 2012 Sep 19.
The motion of a droplet can be induced by periodically compressing and extending it between two similar gradient surfaces possessing significant wetting hysteresis. The shape fluctuation of the drop during repeated compression-extension cycles leads to its ratchetlike motion toward the region of higher wettability. A simple model requiring the volume preservation of the drop during the compression-extension cycles is sufficient to account for the effect and predict drop velocity across the surface when drop size and cycle frequency are specified. In connection with this study, we also report a variation of the standard vapor phase adsorption method of preparing a chemically graded surface that allows for good control over the steepness and the length of the active zone. The method can be used to produce a linear or a radial gradient, both of which are employed here to drive droplet motion along these patterns. This type of discrete droplet motion can be used to move drops on surfaces to transport materials within miniaturized digital fluidic devices.
通过在具有显著润湿滞后的两个相似梯度表面之间周期性地压缩和扩展，可以诱导液滴的运动。在重复的压缩-扩展循环期间，液滴的形状波动导致其朝着润湿性更高的区域发生棘轮式运动。在压缩-扩展循环过程中要求液滴的体积保持不变的简单模型足以解释该效应，并在指定液滴尺寸和循环频率时预测液滴在表面上的速度。在与本研究相关的内容中，我们还报告了一种改进的标准气相吸附方法，用于制备化学梯度表面，从而可以很好地控制活性区的陡度和长度。该方法可用于生成线性或径向梯度，在这里两者都用于沿这些图案驱动液滴运动。这种离散的液滴运动可用于在表面上移动液滴，从而在小型化数字流体设备内输送材料。
