Laboratory for Alternative Energy Conversion (LAEC), School of Mechatronic Systems Engineering, Simon Fraser University, Surrey, BC, V3T 0A3, Canada.
Sci Rep. 2022 Sep 1;12(1):14867. doi: 10.1038/s41598-022-19111-w.
The capillary action is a unique feature of micro-grooves with numerous applications. This spontaneous flow eliminates the need for an extra pumping device to deliver a liquid. Capillary action depends on physical properties and features of the solid surface, as well as on thermophysical properties of the liquid. In this study, our previously proposed unifying capillary rise model is extended to include the effect of surface roughness. A new characteristic length scale is proposed that includes salient geometrical parameters, such as micro-grooves height, width, and surface roughness. Furthermore, it is shown that by using the proposed characteristic length scale, it can be determined whether the capillary action would occur in a given micro-groove and liquid. Various metallic and polymeric surfaces with a wide range of surface roughness are fabricated from aluminum, stainless-steel, natural graphite sheet, and 3D-printed stainless-steel and a polymer. A profilometer and sessile drop method are used to measure surface roughness and the contact angles, respectively. The present unifying model is compared against our measured data, and it is shown that it can predict the capillary rise in rough micro-grooves with less than a 10% relative difference. It is observed that the capillary height can be increased for a wetting surface by introducing surface roughness and by using optimal micro-groove cross-sections that are triangular as opposed to rectangular. The proposed compact, unifying model can be used to predict the capillary rise for any given micro-groove cross-section, and as a design tool for numerous industrial and biomedical applications, such as heat pipes, power electronic cooling solutions, sorption systems, medicine delivery devices, and microfluidics that utilize capillary micro-grooves.
毛细作用是具有众多应用的微槽的独特特征。这种自发流动不需要额外的泵送装置来输送液体。毛细作用取决于固体表面的物理特性和特征，以及液体的热物理特性。在这项研究中，我们之前提出的统一毛细上升模型被扩展到包括表面粗糙度的影响。提出了一个新的特征长度尺度，该尺度包括突出的几何参数，如微槽的高度、宽度和表面粗糙度。此外，结果表明，通过使用所提出的特征长度尺度，可以确定在给定的微槽和液体中是否会发生毛细作用。使用轮廓仪和悬滴法分别测量表面粗糙度和接触角，从铝、不锈钢、天然石墨片以及 3D 打印不锈钢和聚合物制造了具有广泛表面粗糙度的各种金属和聚合物表面。将现有的统一模型与我们的测量数据进行比较，结果表明，它可以预测具有小于 10%相对差异的粗糙微槽中的毛细上升。观察到通过引入表面粗糙度并使用三角形而不是矩形的最佳微槽横截面，可以增加润湿表面的毛细高度。所提出的紧凑统一模型可用于预测任何给定微槽横截面的毛细上升，并且可作为许多工业和生物医学应用的设计工具，例如热管、电力电子冷却解决方案、吸附系统、药物输送装置和利用毛细微槽的微流控。
