Controlling Liquid Wetting of Textured Surfaces using Ultrasound

使用超声波控制纹理表面的液体润湿

• 批准号: 1361919
• 负责人: Nathan Crane
• 金额: $ 36.84万
• 依托单位: University of South Florida
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-01-01 至 2019-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1361919&HistoricalAwards=false
• 关键词: Controlling; Liquid; Wetting; Textured; Surfaces

Successful implementation of many common manufacturing processes rely on controlling when, where, and how fluids and liquids wet a solid. This includes processes like painting, bonding, cleaning, soldering,and brazing. This ability to control if and when a liquid wets a surface is also of importance in self-cleaning and stain resistant surfaces. Such surfaces can provide important technological and economic advantages in a variety of applications by, for example, reducing maintenance and cleaning costs of equipment and buildings such as naval ships, improving efficiency of solar cells by preventing haze and dirt buildup on their surfaces outdoors, and lowering the friction of objects moving through a liquid. This project examines how high frequency vibrations, i.e., ultrasound, can be used to change the wetting state of a liquid on a surface based on the relationship between the size scale of the surface texture and the vibration frequency. The combination of texture and applied vibration will enable new control over where and when a liquid wets a surface or de-wets from it. Potential applications include controlling bonding locations, facilitating separation of bonded components for recycling, and improving the wetting of powders by liquids. The research efforts will be integrated with the education of both graduate and undergraduate students. The project will also be used to enhance outreach programs with local K-12 schools through new educational activities on vibration and acoustics. Textured surfaces (ones with surface roughness) can be stable in multiple wetting states. The two extreme conditions occur when a fluid or liquid penetrates into the recesses of the texture (Wenzel state) and when the fluid rests on top of the peaks of the texture (Cassie state). The Wenzel state has much stronger adhesion due to the larger contact area. For each fluid/substrate combination, one state will typically have lower energy, but there is an energy barrier that must be overcome in order to transition to the lower energy wetting states. Prior work has demonstrated that transitions can be achieved by vibrating a droplet at its characteristic frequency. However, this is impractical in many applications because every droplet has different vibration frequencies. This project will use frequencies that are characteristic of the surface structure so that they can work on droplets of arbitrary sizes. Specifically, the project will identify the energy required at different frequencies, compare the effectiveness of different vibrational modes, and evaluate the impact of asymmetric vibrations on the fluid wetting. These objectives will be accomplished by both experimental measurements of the pressure to move the wetting front of a liquid on a patterned surface and numerical modeling of the contact lines subjected to vibration.

成功实施许多常见的制造过程取决于控制何时，何地以及液体和液体如何润湿固体。 这包括绘画，粘合，清洁，焊接和铜管等过程。 这种控制液体是否和何时湿润表面的能力在自我清洁和耐染色表面也很重要。 这样的表面可以在各种应用中提供重要的技术和经济优势，例如，通过降低设备和建筑物的维护和清洁成本，例如海军船只，通过防止在室外的表面上堆积雾化和污垢，并降低物体的摩擦，从而提高太阳能电池的效率。该项目研究了如何根据表面纹理的尺寸和振动频率之间的关系来研究高频振动，即超声波的高频振动。 纹理和施加振动的结合将使液体从何处和何时从其表面或驱动器湿润的地方进行新的控制。 潜在的应用包括控制粘合位置，促进粘合组件的分离以进行回收，并改善液体粉末的润湿。 研究工作将与研究生和本科生的教育融合在一起。 该项目还将通过有关振动和声学的新教育活动来加强与本地K-12学校的外展计划。在多个润湿状态下，纹理表面（具有表面粗糙度的表面）可以稳定。 当流体或液体渗透到质地凹处（Wenzel状态）时，并且当流体静置在质地峰（Cassie状态）的顶部时，就会发生这两个极端条件。 由于接触面积较大，温泽尔状态具有更强的粘附力。 对于每个流体/底物组合，一个状态通常具有较低的能量，但是必须克服一个能量屏障才能过渡到较低的能量润湿状态。 先前的工作表明，可以通过以其特征频率振动液滴来实现过渡。 但是，这在许多应用中是不切实际的，因为每个液滴都有不同的振动频率。 该项目将使用表面结构特征的频率，以便它们可以在任意大小的液滴上工作。 具体而言，该项目将在不同频率下确定所需的能量，比较不同振动模式的有效性，并评估不对称振动对流体润湿的影响。 这些目标将通过两种实验测量的压力来实现，以将液体的润湿前部移动在图案化表面上的润湿前部以及经受振动的接触线的数值建模。