Nano‐scale shear mode testing of the adhesion of nanoparticles to a surface‐support

Abstract

Using atomic force microscopy (AFM/SFM), the strength of the adhesion between nanoparticles (NPs) and a flat gold surface was studied. By scanning in contact mode, a lateral force was applied to the NPs, depending on the cantilever stiffness and the setpoint value of the topography feedback. In this way, a threshold force for NP detachment was determined. The sample under investigation consisted of arrays of tungsten NPs deposited on top of a flat gold surface. The NPs were generated using electron beam deposition (EBD) and the precursor gas W(CO)6. Owing to the array‐wise arrangement of the NPs, any change in their position was comparatively easy to detect by deviation from the array points. The beam dwell time was employed as a parameter to control the NP size. The force threshold value for particle detachment was found to increase with the beam dwell time. Loose NPs moved by the scanning tip displayed increased lateral forces. These appeared in the lateral force images as continuous tracks. After expansion of the scan area such tracks were seen to mostly originate from the edges of the previous scans where the NPs had piled up. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Nucleation and Epitaxy-Mediated Phase Transformation of a Precursor Cadmium Carbonate Phase at the Calcite/Water Interface

“…The highest lateral signal attained for each particle before it was removed was then used as a measure of its relative adhesion. This method is similar to nanoshaving, and has previously been demonstrated as a method suitable for the study of local adhesion in general , and particle adhesion during mineral growth in particular . Due to the difficult and unreliable nature of lateral force calibration, relative values were used rather than absolute lateral force values. − For each experiment the average lateral signal value obtained for the epitaxial islands at 10 nN was used as an internal standard due to their constant height and known phase.…”

Size Dependence of Shape and Stiffness of Single Sessile Oil Nanodroplets As Measured by Atomic Force Microscopy

“…Similar to other soft matter, accurate AFM imaging of oil droplets requires careful selection of the imaging parameters to minimize the forces applied to the sample surface. In general, dynamic modes are favorable over contact mode imaging as the latter implies considerable lateral forces which may dislodge loosely bound entities 34 or cause shear deformation. 35 When operating in AM mode, a major parameter is the set point (SP) ratio A sp /A 0 < 1, where A sp and A 0 denote the cantilever oscillation amplitude in feedback and in the interaction-free case, respectively.…”

Force calibration in lateral force microscopy: a review of the experimental methods

“…Due to the scaling of k x and k z with t 3 (equations (2. 19) and (2.20)), any method involving thickness measurements is inherently error-sensitive [65]. For applications beyond the quick estimation of the CL spring constant, mitigation strategies should be applied, such as the replacement of the CL thickness with a parameter related to its effective thickness [66].…”

“…Considering that in many cases microbial cells are exposed to hydrodynamic shear fields, the application of lateral forces can be used to measure the critical shear strength of such cell-surface interfaces. Similarly, the shear strength of nanoparticles adhering to a support surface has been studied [19]. As compared with macroscopic techniques averaging over a large number of nano-scale entities, LFM allows for force measurements on single particles, a prerequisite for studies of the relationship between particle shape and the critical force required for dislodgement of a particle.…”