Li Ping, Wang Jinxin, Huang Jiale, Xiang Jianhua
School of Mechanical and Electric Engineering, Guangzhou University, Guangzhou 510006, China.
Nanomaterials (Basel). 2022 Aug 22;12(16):2888. doi: 10.3390/nano12162888.
Stabilizing the hydrophobic wetting state on a surface is essential in heat transfer and microfluidics. However, most hydrophobic surfaces of Si are primarily achieved through microtexturing with subsequent coating or modification of low surface energy materials. The coatings make the hydrophobic surface unstable and impractical in many industrial applications. In this work, the Si chips’ wettability transitions are yielded from the original hydrophilic state to a stable transitional hydrophobic state by texturing bamboo-leaf-like hierarchical structures (BLHSs) through a diamond grinding wheel with one-step forming. Experiments showed that the contact angles (CAs) on the BLHS surfaces increased to 97° and only reduced by 2% after droplet impacts. This is unmatched by the current texturing surface without modification. Moreover, the droplets can be split up and transferred by the BLHS surfaces with their 100% mass. When the BLHS surfaces are modified by the low surface energy materials’ coating, the hydrophobic BLHS surfaces are upgraded to be superhydrophobic (CA > 135°). More interestingly, the droplet can be completely self-sucked into a hollow micro-tube within 0.1 s without applying external forces. A new wetting model for BLHS surfaces based on the fractal theory is determined by comparing simulated values with the measured static contact angle of the droplets. The successful preparation of the bamboo-leaf-like Si confirmed that transitional wettability surfaces could be achieved by the micromachining of grinding on the hard and brittle materials. Additionally, this may expand the application potential of the key semiconductor material of Si.
在表面上稳定疏水润湿状态在传热和微流体领域至关重要。然而，大多数硅基疏水表面主要是通过微纹理化并随后涂覆或改性低表面能材料来实现的。这些涂层使得疏水表面在许多工业应用中不稳定且不实用。在这项工作中，通过使用金刚石砂轮一步成型纹理化竹叶状分级结构（BLHSs），使硅芯片的润湿性从原始亲水状态转变为稳定的过渡疏水状态。实验表明，BLHSs表面上的接触角（CAs）增加到97°，并且在液滴撞击后仅降低2%。这是目前未经改性的纹理化表面所无法比拟的。此外，BLHSs表面能够以100%的质量将液滴分裂并转移。当用低表面能材料涂层对BLHSs表面进行改性时，疏水的BLHSs表面升级为超疏水（CA > 135°）。更有趣的是，在不施加外力的情况下，液滴能够在0.1秒内完全自吸入空心微管。通过将模拟值与液滴的实测静态接触角进行比较，确定了基于分形理论的BLHSs表面新的润湿模型。竹叶状硅的成功制备证实了通过对硬脆材料进行磨削微加工可以实现过渡润湿性表面。此外，这可能会扩大关键半导体材料硅的应用潜力。
