[论文解读] Revealing Strain Effects on the Graphene-Water Contact Angle Using a Machine Learning Potential

Darren Wayne Lim, Xavier R. Advincula+3 more|arXiv (Cornell University)|Jan 27, 2026

Nanopore and Nanochannel Transport Studies被引用 0

一句话总结

该论文使用机器学习势模拟自由-standing 石墨烯上的水滴，获得了有限尺寸修正的接触角72.1±1.5度，并揭示应变与起伏如何影响润湿性。

ABSTRACT

Understanding how water wets graphene is critical for predicting and controlling its behavior in nanofluidic, sensing, and energy applications. A key measure of wetting is the contact angle made by a liquid droplet against the surface, yet experimental measurements for graphene span a wide range, and no consensus has emerged for free-standing graphene. Here, we use a machine learning potential with approaching ab initio accuracy to perform nanosecond-scale molecular dynamics and provide an atomistic first-principles benchmark for this unsolved problem. We find the contact angle of water on free-standing graphene, after finite-size correction, to be $72.1 \pm 1.5 °$. We also show that the three-phase contact line of a nanoscale water droplet couples strongly to the intrinsic thermal ripples of free-standing graphene, and that graphene's wetting properties are highly sensitive to mechanical strain. Tensile strain makes graphene significantly more hydrophobic, while compressive strain induces coherent ripples that the droplet "surfs", resulting in pronounced anisotropic wetting and contact angle hysteresis. Our results demonstrate that graphene's wetting properties are governed not only by its chemistry but also by its dynamic morphology, offering an additional explanation for the variability of experimental measurements. Furthermore, mechanical strain may be a practical route to controlling wetting in graphene-based technologies, with promising consequences for nanofluidic and nano-filtration applications.

研究动机与目标

• 使用以第一性原理级别机器学习势的纳秒尺度分子动力学来定义自由站立石墨烯的固有石墨烯-水接触角。
• 定量化有限尺寸效应并进行修正，以估计宏观接触角。
• 研究机械应变如何调制石墨烯波纹及由此产生的润湿行为。
• 阐明三相接触线与石墨烯表面波纹的耦合及其对润湿性的影响。

提出的方法

• 开发并验证一个训练于 revPBE-D3 DFT 数据的机器学习势（MLP），以再现水-石墨烯相互作用。
• 进行大规模MD，5400–22680 个原子，模拟自由-standing石墨烯上的水滴（300–4680 分子）。
• 基于时间平均界面和石墨烯高度图的新颖、考虑表面波纹的方法提取接触角。
• 通过线性关系 cos(theta) = cos(theta_infty) - kappa/(gamma_lv a) 应用有限尺寸修正。
• 计算液-蒸汽界面张力 gamma_lv，并从单独的薄 slab 模拟推导 Delta gamma = gamma_sv - gamma_sl。

Figure 1: Finite-size corrected contact angle for water on free-standing graphene. (a) Cross-section of a snapshot of a spherical droplet of 4,680 water molecules on a free-standing, fully-dynamical graphene sheet, with the droplet’s time-averaged interface overlaid in blue. The contact angle is det

实验结果

研究问题

• RQ1 在考虑有限尺寸和动态波纹效应后，自由-standing 石墨烯上水的固有接触角是多少？
• RQ2 机械应变及由此引起的石墨烯波纹变化如何影响石墨烯-水接触角和润湿行为？
• RQ3 三相接触线与石墨烯表面形态的耦合在确定润湿性质中的作用是什么？

主要发现

• 有限尺寸修正后的宏观接触角为 theta_infty = 72.1 ± 1.5 度。
• 液-蒸汽界面张力 gamma_lv = 74.5 ± 1.4 mN/m；Delta gamma = 22.9 ± 1.9 mN/m，表明石墨烯的润湿性较弱为亲水性。
• 最佳拟合线张力值为 kappa = (7.8 ± 3.3) × 10^-12，位于先前工作报道的范围内。
• 拉伸应变使接触角增大，在 +2.0% 应变下达到 84.8 ± 1.2 度，原因是对波纹耦合的削弱。
• 压缩应变诱导长程相干波纹，导致各向异性润湿和接触角滞后；液滴可在波谷处“冲浪”波纹。
• 液滴的存在在石墨烯上引起局部曲率变化，并在接触线附近局部扰动波纹动力学。

Figure 2: Effects of a water nanodroplet on graphene’s rippling dynamics under tensile strain. (a) A representative snapshot of a droplet of 1,000 molecules, which was simulated under varying tensile strain conditions applied biaxially to the graphene sheet. The translucent green plane indicates the