Preventing the Cassie-Wenzel Transition Using Surfaces with Noncommunicating Roughness Elements
Preventing the Cassie-Wenzel Transition Using Surfaces with Noncommunicating Roughness Elements
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DOI：
10.1021/la803691m
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发表时间：
2009-04-21
期刊：
影响因子：
3.9
通讯作者：
Garimella, Suresh V.
中科院分区：
文献类型：
--
作者：
Bahadur, Vaibhav;Garimella, Suresh V.
人工结构化表面上的液滴状态的控制和切换在微流体领域中具有重要的应用。目前的工作介绍了使用结构化的表面组成的noncommunicating粗糙度元素，以防止从Cassie到Wenzel状态的液滴的过渡的概念。使用非连通粗糙度元素导致在Cassie状态下液滴下的介质受限。在这样的表面上过渡到Wenzel状态需要排出这种受限介质，这提供了显著增加的抵抗Wenzel过渡，不像由连通粗糙元件组成的表面。这增强了Cassie状态的鲁棒性，并显着降低了Cassie-Wenzel转变的可能性。在目前的工作中，测量表面的电阻的Wenzel过渡的电润湿（EW）电压触发这种转变。可以看出，具有非连通粗糙度元件的表面（凹坑表面）需要比具有连通粗糙度元件的相应表面显著更高的电压来触发Wenzel转变。从目前的工作的研究结果还表明，EW诱导液滴形态控制特性显示出强烈的依赖性的粗糙度元素的性质（通信与非通信）。液滴形态和EW诱导的状态转换控制与非通信的韧性元素的表面上的不同方面进行了分析，可以看出，这样的表面提供了强大的超疏水表面的发展显着的可能性。
Control and switching of liquid droplet states on artificially structured surfaces have significant applications in the field of microfluidics. The present work introduces the concept of using structured surfaces consisting of noncommunicating roughness elements to prevent the transition of a droplet from the Cassie to the Wenzel state. The use of noncommunicating roughness elements leads to a confinement of the medium under the droplet in its Cassie state. Transition to the Wenzel state on such surfaces requires expulsion of this confined medium, which offers significantly increased resistance to the Wenzel transition unlike surfaces consisting of communicating roughness elements. This enhances the robustness of the Cassie state and significantly minimizes the possibility of the Cassie-Wenzel transition. In the present work, the resistance of a surface to the Wenzel transition is measured in terms of the electrowetting (EW) voltage required to trigger this transition. It is seen that surfaces with noncommunicating roughness elements (cratered surfaces) require significantly higher voltages to trigger the Wenzel transition than corresponding surfaces with communicating roughness elements. The findings from the present work also indicate that EW-induced droplet morphology control characteristics show a strong dependence on the nature of the roughness elements (communicating versus noncommunicating). Different aspects of droplet morphology and EW-induced state transition control on surfaces with noncommunicating toughness elements are analyzed; it is seen that such surfaces offer significant possibilities for the development of robust superhydrophobic surfaces.