Instrument-Dependent Cadherin Monolayer Interactions

We introduce two theoretical models for predicting forces between cadherin-coated sphere and plane. The first model is based on a continuum theory previously developed for the interaction of large objects embedded in liquids. The second model takes into account size effects, which are relevant in the cadherin measurements, as the size of the tip is frequently comparable to the size of geometrical features of the cadherin. We use the models to compare force–separation curves in atomic force microscopy and surface force apparatus

Article Negentropy Generation and Fractality in the Dry Friction of Polished Surfaces

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The emergence of multifrequency force microscopy

Atomic force microscopy uses the deflection of a cantilever with a sharp tip to examine surfaces, and conventional dynamic force microscopy involves the excitation and detection of a single frequency component of the tip’s motion. Information about the properties of a sample is, however, encoded in the motion of the probe and the dynamics of the cantilever are highly nonlinear. Therefore, information included in the other frequency components is irreversibly lost. Multifrequency force microscopy involves the excitation and/or detection of several frequencies of the probe’s oscillation, and has the potential to overcome limitations in spatial resolution and acquisition times of conventional force microscopes. It could also provide new applications in fields such as energy storage and nanomedicine. Here we review the development of multifrequency force microscopy methods, highlighting the five most prominent approaches. We also examine the range of applications offered by the technique, which include mapping the flexibility of proteins, imaging the mechanical vibrations of carbonbased resonators, mapping ion diffusion, and imaging the subsurface of cells.We are grateful for financial support from the Ministerio de Ciencia e Innovación (CSD2010-00024, MAT2009-08650).Peer reviewe

Controlled assembly of micrometer-sized spheres: theory and application

Site-selective assembly of 5 m amine-functionalized glass spheres from aqueous suspensions onto gold surfaces patterned with carboxylic acid and methyl-terminated thiols has been achieved through the introduction of a variable tilt flow cell. In situ microscope imaging has been employed to study the four phases of assembly independently, and the relative roles of electrostatic attraction and capillary emersion have been explored. In contradiction to the commonly recognized electrostatic assembly model, detailed theoretical analysis and experimental evidence are presented to support a mechanism where patterning occurs at the point of meniscus contact. Control of pattern quality is demonstrated through the comparison of results obtained from a variety of experiments, and the best conditions for the assembly of monolayer features are identified. Finally, evidence for the extension of this assembly method to the production of singlet sphere arrays is discussed