目的 针对液环轴承中亲水表面引发的液膜非均匀承载,以及超疏水表面因接触线钉扎导致的液膜动态泄漏问题,提出构建超滑表面以实现高支撑力与液膜稳定性的协同调控。方法 以铝为基底,通过激光加工构建微纳结构并进行低表面能改性后,分别制备了亲水表面、超疏水表面及注入油液形成的超滑表面作为轴承的上表面。并在另一超疏水铝基底上利用激光加工出环形亲水图案作为滚环轴承的下表面。探索了不同浸润性上表面对液环轴承支撑力的影响。结果 20 μL的水滴在亲水、超疏水与超滑表面的黏附力分别为0.918、0.091 1和0.246 9 mN,其中超疏水表面因低黏附性抑制液滴吸附,而亲水表面因强黏附力导致液滴呈现非对称分布并引发局部应力集中。对于液环轴承,当其液环厚度为0.2 mm时,亲水、超疏水与超滑表面的最大支撑力分别为0.022、0.058和0.048 N。结论 超疏水表面虽支撑力最高,但其在临界间隙（0.3 mm）下引发液环边缘钉扎,致使拉普拉斯压力失衡并导致泄漏,而超滑表面的支撑力接近超疏水表面,并且能够通过液-液接触模式动态调控液膜,兼顾低黏附与稳定性。下试样旋转时,超滑表面在保持支撑力稳定上更加突出,且液环内的速度分布为线性减小。
Abstract
Liquid-ring bearings represent a critical class of liquid film bearings, leveraging the formation and stability of a liquid ring to support rotating components with advantages such as minimal friction, high load capacity, and effective damping. However, their performance is intrinsically governed by the interfacial interactions between the bearing surfaces and the liquid film. This study directly addresses two significant challenges hindering their optimal operation: (1) the non-uniform load-bearing capacity and localized stress concentrations induced by strong liquid adhesion on homogeneous hydrophilic surfaces, and (2) the dynamic leakage instability stemming from contact line pinning and subsequent Laplace pressure imbalance on superhydrophobic surfaces. To overcome these limitations and achieve a synergistic enhancement of both high supporting force and robust liquid film stability, the work aims to propose and investigate the implementation of Slippery Liquid-Infused Porous Surfaces (SLIPS) within the liquid-ring bearing configuration.
The experimental methodology employed aluminum as the base substrate. To fabricate surfaces with controlled wettability, aluminum substrates underwent laser surface texturing to create defined micro/nanostructures, followed by a low surface energy modification process to achieve superhydrophobicity. Subsequently, SLIPS were generated by infusing lubricating oil into the textured, low-energy surface. For comparative analysis, homogeneous hydrophilic aluminum surfaces were also prepared, likely by omitting the low-energy modification step or utilizing specific laser parameters.
Fundamental characterization of liquid adhesion revealed stark differences: 20 μL water droplets exhibited adhesion forces of 0.918 mN, 0.091 1 mN, and 0.246 9 mN on the hydrophilic, superhydrophobic, and SLIPS surfaces, respectively. The exceptionally low adhesion on the superhydrophobic surface effectively suppressed droplet adsorption and spreading. Conversely, the high adhesion force on the hydrophilic surface promoted asymmetric droplet distribution, leading to detrimental localized stress concentrations under load. In stark contrast, the SLIPS surface demonstrated a moderate yet significantly reduced adhesion force compared to the hydrophilic surface, indicating its potential for improved interfacial dynamics.
Evaluation within the liquid-ring bearing context, specifically with a defined liquid film thickness (ring thickness) of 0.2 mm, yielded critical performance metrics. The maximum supporting forces measured were 0.022 N for the hydrophilic upper surface, 0.058 N for the superhydrophobic upper surface, and 0.048 N for the SLIPS upper surface. This confirmed that the superhydrophobic surface provided the highest load-bearing capacity under these conditions, significantly outperforming the hydrophilic surface. However, this superior force came with a critical stability trade-off. At a critical gap size of 0.3 mm, the superhydrophobic surface induced pinning of the contact line at the edge of the liquid ring. This pinning disrupted the equilibrium of Laplace pressure across the liquid-air interface, ultimately triggering instability and leakage of the liquid film, compromising bearing function. The hydrophilic surface, while more stable against this specific leakage mode than the pinned superhydrophobic surface, suffered from its inherently low supporting force and stress concentration issues.
The SLIPS surface emerges as the solution reconciling these competing demands. While its maximum supporting force (0.048 N) is slightly lower than the superhydrophobic peak, it approaches its performance level and significantly exceeds the hydrophilic surface. Crucially, SLIPS eliminates the contact line pinning problem inherent to superhydrophobic surfaces. This is achieved through its unique liquid-liquid contact interface (oil-water), which enables continuous, near-frictionless reconfiguration of the liquid film under dynamic conditions. This inherent slipperiness allows the SLIPS-based bearing to dynamically regulate the liquid film morphology, maintaining Laplace pressure stability and preventing leakage, even at challenging gap sizes. Consequently, the SLIPS technology successfully delivers a balanced performance, harmonizing a high supporting force (approaching superhydrophobic levels) with exceptional operational stability and minimal adhesion-related stress concentrations.
Theoretical models are developed to quantify the interplay between Laplace pressure, capillary forces, and the resultant supporting forces during liquid-ring deformation. These models demonstrate good agreement with the experimental findings, providing a mechanistic understanding of the observed performance differences. This work provides fundamental insights and a practical surface engineering strategy—specifically, the use of patterned lower surfaces combined with SLIPS upper surfaces—for significantly enhancing the reliability and load capacity of liquid-ring bearings by simultaneously optimizing supporting force and liquid film stability. When the lower sample rotates, the super smooth surface becomes more prominent in maintaining stable support force, and the velocity distribution inside the liquid ring decreases linearly.
关键词
液环轴承 /
拉普拉斯压力 /
超滑表面 /
支撑力 /
黏附力 /
毛细力 /
稳定性
Key words
liquid-ring bearings /
Laplace pressure /
SLIPS surfaces /
supporting force /
adhesion force /
capillary force /
stability
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