论文标题
机械变形对表面力测量的影响
The influence of mechanical deformations on surface force measurements
论文作者
论文摘要
表面力的实验研究通常涉及两个在培养基上相互作用的简单且定义明确的几何形状的固体。可以解释对其表面相互作用的直接测量，以揭示限制中的基本物理，即独立于特定的几何形状。但是，实际固体是可变形的 - 由于它们的相互作用，它们可以改变形状 - 这可能会影响力测量。这些方面经常不考虑，并且仍然很了解。我们已经在干燥的气氛和具有表面力平衡（SFB）的离子液体中进行了实验，结合了表面相互作用的测量和同时对几何形状的原位表征。首先，我们发现，尽管约翰逊 - 肯德尔 - 罗伯茨（JKR）模型可以解释接触半径与跨氮的力的变化，但对于（离子）液体，它仅由Derjaguin-Muller-Muller-Toporov（DMT）模型很好地描述。其次，我们发现云母不仅弯曲，而且会经历压缩。通过进行比平时较厚的实验，我们能够以高精度进行研究，并使用7 um云母进行1 nm的压缩。这些发现表明，在某些情况下，在跨纳米夹层液体中测量的结构力必须解释为跨液体跨液体的表面力的卷积和限制固体的机械响应。我们讨论了云母厚度的影响，并提出了一个缩放标准，以区分固体变形可忽略不计的情况以及何时占主导地位。
Experimental investigations of surface forces generally involve two solid bodies of simple and well-defined geometry interacting across a medium. Direct measurement of their surface interaction can be interpreted to reveal fundamental physics in confinement, i.e. independent of the particular geometry. However real solids are deformable - they can change shape due to their mutual interaction - and this can influence force measurements. These aspects are frequently not considered, and remain poorly understood. We have performed experiments in a dry atmosphere and across an ionic liquid with a Surface Force Balance (SFB), combining measurement of the surface interactions and simultaneous in-situ characterization of the geometry. First we find that, whilst the variation of the contact radius with the force across dry nitrogen can be interpreted by the Johnson-Kendall-Roberts (JKR) model, for the (ionic) liquid it is well described only by the Derjaguin-Muller-Toporov (DMT) model. Secondly, we find that mica does not only bend but also experiences a compression. By performing experiments with substantially thicker mica than usual we were able to investigate this with high precision, and find compression of order 1 nm with 7 um mica. These findings imply that, in some cases structural forces measured across nanoconfined liquids must be interpreted as a convolution of the surface forces across the liquid and the mechanical response of the confining solids. We discuss the influence of mica thickness, and propose a scaling criterion to distinguish situations where the solid deformation is negligible and when it is dominant.
