Abstract

The contact time dependence of adhesion force is not well understood. Adhesion forces between a tipless silica cantilever and some samples with different hydrophilicity were measured to study the dependence at low relative humidity (16 ± 1%). Dependent adhesion forces were observed on hydrophilic samples. The adhesion force has three distinct trends: sharply increasing at first, then followed by moderately increasing and at last remaining almost unchanged (reaching saturation). The saturation time is varied for different samples: from several seconds to tens of seconds. The more hydrophilic the sample surface is, the longer the saturation time is. The increasing tendency is well explained by a model of water thin-film flow. It takes some time for the liquid absorbed on a surface to flow into a growing water bridge due to a large viscosity. The viscosity of the film on a more hydrophilic sample may be larger because of stronger interaction between the film and the sample surface, eventually resulting in a longer saturation time. The reported results may help deepen the understanding of the mechanism of adhesion and explain other experimental results concerning AFM parameters.

摘要

粘附力的接触时间依赖性还不是很清楚。测量了无尖二氧化硅悬臂和一些具有不同亲水性的样品之间的粘附力，以研究低相对湿度 (16 ± 1%) 下的依赖性。在亲水样品上观察到依赖性粘附力。粘附力具有三个明显的趋势：首先急剧增加，然后适度增加，最后几乎保持不变（达到饱和）。不同样品的饱和时间不同：从几秒到几十秒。样品表面越亲水，饱和时间越长。水薄膜流动模型很好地解释了这种增加趋势。由于粘度大，吸收在表面上的液体需要一些时间才能流入不断增长的水桥。由于膜与样品表面之间的相互作用更强，因此在更亲水的样品上膜的粘度可能更大，最终导致更长的饱和时间。报告的结果可能有助于加深对粘附机制的理解，并解释有关 AFM 参数的其他实验结果。