Investigation of Humidity-Dependent Capillary Force
Investigation of Humidity-Dependent Capillary Force
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DOI：
10.1021/la000770o
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发表时间：
2000-09
期刊：
影响因子：
3.9
通讯作者：
Xudong Xiao;L. Qian
中科院分区：
文献类型：
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作者：
Xudong Xiao;L. Qian
由于强烈的毛细凝聚作用，观察到氮化硅原子力显微镜（AFM）针尖与氧化硅之间的粘附力随着湿度的增加先增大后减小。相比之下，由于毛细凝聚作用较弱，发现原子力显微镜针尖与N - 十八烷基三甲氧基硅烷（OTE，CH₃(CH₂)₁₇Si(OCH₂CH₃)₃）自组装单分子层（SAM）之间的粘附力几乎与湿度无关。发现通常用于宏观物体的公式无法解释我们的数据。利用一个精确的公式和一个假定的针尖形状，我们可以将观察到的在高湿度下二氧化硅粘附力的降低解释为是由于当弯月面的尺寸变得与针尖尺寸相当时毛细压力减小所致。然而，在经典连续介质理论的框架内无法理解观察到的二氧化硅粘附力的延迟起始现象。我们将这种延迟起始归因于分子厚度的超薄水膜的特性……
Due to the strong capillary condensation, the adhesion force between a Si3N4 atomic force microscope (AFM) tip and silicon oxide was observed to first increase and then decrease with an increase of humidity. In contrast, due to weak capillary condensation, the adhesion force between the AFM tip and the N-octadecyltrimethoxysilane (OTE, CH3(CH2)17Si(OCH2CH3)3) self-assembled monolayer (SAM) was found to be almost independent of humidity. It was found that the formulation commonly used for macroscopic objects fails to explain our data. Using an accurate formulation and an assumed tip shape, we can explain the observed decrease of adhesion for SiO2 at high humidity as being due to the decreased capillary pressure force when the dimension of the meniscus becomes comparable with the tip size. However, the observed late onset of adhesion of SiO2 cannot be understood within the framework of the classical continuum theory. We attribute this late onset to the properties of an ultrathin water film at molecular thic...