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Surfaces tend to be made smoother in order to gain flatness or in order to fulfill the need for more precise and reproducible positioning of parts. Adhesion or even sticking of the surfaces is a major showstopper for these applications. There are several measures that can be taken in order to reduce spontaneous adhesion. Quantification of the effectiveness of the chosen solution is most often done using an atomic force microscope (AFM) with probes varying from 1 nm to 8 μm of contact diameter. A serious disadvantage in measuring adhesion by sharp tips is the wear of the tips. Sharp tips wear easily, resulting in undefined contact areas. When the real area of contact is not well defined, the quantification of the adhesion force is not significant. In the current study results of AFM measurements from literature with different tip diameters of colloidal probes are compared with AFM cantilevers with a plateau tip and using probes from large spheres using an alternative setup in combination with a Universal Nano-mechanical Analyzer (UNAT). Test results are shown. Another part of the study deals with a deliberately roughening of smooth surfaces to minimize (spontaneous) adhesion. Good agreement has been found with existing results. © 2012 Elsevier B.V. All rights reserved.

Adhesion measurements were performed by AFM (Atomic Force Microscopy). It was shown that many parameters need to be controlled in order to provide reproducible and quantitative results. Adhesion forces were shown to depend on combination of materials characteristics and testing geometry as well as experimental protocol (contact time, contact force and contact area). This contact area was modified by means of FIB (Focused Ion Beam) milling and deliberate abrasion. As a result, a drastic change in adhesion could be observed. Still, those are problems connected to adjustment of interacting surfaces. © 2010 Elsevier B.V. All rights reserved.

A theoretical investigation of van der Waals forces acting between two solid silicon surfaces at separations from zero to approximately 20 nm is presented. We focused our efforts on the analysis of different factors that can cause deviations from the classical pressure-distance dependence p ∼ 1/D3. It is demonstrated that a layer (oxide or water) at any of the surfaces influences the pressure up to distances, which are an order of magnitude larger than its own thickness. A jump on the p(D) curve is expected at contact of the adsorbed liquid layers. The retardation of van der Waals forces at 5 < D < 20 nm has the similar effect on the pressure as 1 nm oxide layers. At the far end of this range the pressure decreases by 30% due to the retardation. Nanoscale roughness plays a great role when the surfaces are close-to-contact, the crucial factor is the height distribution of asperities. However, their curvature and surface density are also important, as well as the amount of adsorbed water. © 2009 Elsevier B.V. All rights reserved.

Confidential

Confidential

Confidential