School of Chemical Engineering, The University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom.
Langmuir. 2011 Sep 20;27(18):11489-500. doi: 10.1021/la202060f. Epub 2011 Aug 26.
The adhesive characteristics of thin films (0.2-2 μm) of linear poly(dimethylsiloxane) (PDMS) liquids with a wide range of molecular weights have been measured using an atomic force microscope with a colloid probe (diameters 5 and 12 μm) for different separation velocities. The data were consistent with a residual film in the contact region having a thickness of ∼6 nm following an extended dwell time before separation of the probe. It was possible to estimate the maximum adhesive force as a function of the capillary number, Ca, by applying existing theoretical models based on capillary interactions and viscous flow except at large values of Ca in the case of viscoelastic fluids, for which it was necessary to develop a nonlinear viscoelastic model. The compliance of the atomic force microscope colloid beam was an important factor in governing the retraction velocity of the probe and therefore the value of the adhesive force, but the inertia of the beam and viscoelastic stress overshoot effects were not significant in the range of separation velocities investigated.
已使用带有胶体探针的原子力显微镜（探针直径为 5 和 12μm）测量了具有较宽分子量范围的线性聚二甲基硅氧烷（PDMS）液体的薄膜（0.2-2μm）的粘附特性，用于不同的分离速度。在分离探针之前的扩展停留时间后，接触区域中的残余膜的厚度约为 6nm，数据与这一结果一致。通过应用基于毛细相互作用和粘性流动的现有理论模型，可以估计最大粘附力作为毛细数 Ca 的函数，除了在粘性弹性流体的情况下 Ca 值较大的情况外，对于粘性弹性流体，有必要开发一个非线性粘弹性模型。原子力显微镜胶体束的柔量是控制探针缩回速度和因此粘附力值的一个重要因素，但在研究的分离速度范围内，梁的惯性和粘弹性过冲效应并不显著。
