Controlling Adhesion Force by Means of Nanoscale Surface Roughness

Abstract

Control of adhesion is a crucial aspect in the design of microelectromechanical and nanoelectromechanical devices. To understand the dependence of adhesion on nanometer-scale surface roughness, a roughness gradient has been employed. Monomodal roughness gradients were fabricated by means of silica nanoparticles (diameter ∼12 nm) to produce substrates with varying nanoparticle density. Pull-off force measurements on the gradients were performed using (polyethylene) colloidal-probe microscopy under perfluorodecalin, in order to restrict interactions to van der Waals forces. The influence of normal load on pull-off forces was studied and the measured forces compared with existing Hamaker-approximation-based models. We observe that adhesion force reaches a minimum value at an optimum particle density on the gradient sample, where the mean particle spacing becomes comparable with the diameter of the contact area with the polyethylene sphere. We also observe that the effect on adhesion of increasing the normal load depends on the roughness of the surface.

Measuring adhesion on rough surfaces using atomic force microscopy with a liquid probe

“…It is usually assumed that the process takes place in a regime of small strains, that the materials are homogeneous, isotropic, linearly elastic, and that the tips are perfectly smooth. On this last point, previous studies [6–8] have demonstrated the high sensitivity of adhesion to interfacial roughness showing a drop in F adh of more than an order of magnitude with increasing roughness, down to the atomic limit [9]. …”

High Accuracy and Sensitivity Method of the Observation of the Surface’s Morphology Changes by Means of Atomic Force Microscopy with Cyclic, Precise Sample Positioning

“…Also the changes of the mechanical properties at nanoscale were reported as the result of the environmental conditions [3,7] or local, nanoscale wear [16]. It should be emphasized, that the issue of the mechanical non-homogeneity must be also carefully analyzed, in particular while the sample is used as the stiffness/ Young modulus reference material [17] or the adhesion phenomena is investigated [18]. The observation of the changes of the material's properties requires certain approach, which should provide the reliability of the data.…”

A facile method towards rough morphology polymer brush for increased mobility of embedded nanoparticles

“…Control of adhesion forces is important particularly in devices that employ M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT microelectromechanical and nanoelectromechanical systems [15], and in non-fouling coatings where a decrease in adhesion forces could significantly reduce the probability of any form of non-specific adsorption. In these cases, the increase in surface roughness was found to be beneficial in reducing adhesion.…”

“…In these cases, the increase in surface roughness was found to be beneficial in reducing adhesion. Various strategies have therefore been developed to increase the nanoscale roughness including the deposition of nanoparticles [15,16] and inorganic films [17] as well as the control of surface morphology by means of polymer coatings [18].…”