Force volume mode

In the current work a Digital Instmments Dimension 3000 SPM was operated in force-volume mode using a probe with stiffness selected to match the stiffness of the sample. Standard silicon nitride probes with a nominal spring constant of 0.12 or 0.58 N/m were used for recombinant and native resilin samples. These samples were characterized in a PBS bath at a strain rate of 1 Hz. For synthetic rubbers, silicon probes with a nominal spring constant of 50 N/m were used and the material was characterized in air. Typically, at least three force-volume plots (16 X 16 arrays of force-displacement curves taken over a 10 X 10 p.m area) were recorded for each of the samples. 

Contact and Force Volume Mode AFM Visualization of the Morphology... 

Walczyk W, Main N, Schbnherr H. Hydrodynamic effects of the tip movement on surface nanobubbles a combined tapping mode, lift mode and force volume mode AFM study. Soft Matter 2014 10 5945. 

In cases where AFM tips have been functionalized with special chemical end groups, they can be used to map out chemical interactions between tip and surfaces using either the force volume mode or the friction force microscopy. For both types of experiments, the term chemical force microscopy has been introduced (reviewed in Ref ]274]). 

A fundamental problem in force volume mode is the relatively long acquisition time that can easily amount to tens of minutes and can give rise to excessive drift. This and the memory usage for storing all data points limit the resolution of the force maps to typically 64 x 64 data points compared to the typical 512 x 512 pixels for standard AFM images. A critical point that has hindered the widespread use of force volume is automated data evaluation, which is currently not part of standard AFM software of the commercial suppliers. Since some thousand force curves have to be evaluated for each data set, sophisticated software routines have to be developed by the users for automated analysis to efficiently use force volume mode. 

Practical adhesion mapping can be performed in the so-called force-volume (FV) mode. In this mode, f-d curves are acquired for each pixel. Thus, information is obtained on attractive forces before the tip contacts the surface, indentation in the contact region (see Sect. 4.3), adhesive interactions, and the dissipated energy (as area under the f-d curve, compare Fig. 4.3). 

These include contact force imaging (CFI) mode, in which the tip is scanned across the sample surface at constant force, tapping mode in which the tip oscillates close to the surface enabling either the forces or phase relationships between load and displacement to be used to form the image, and local force spectroscopy or force/volume imaging in which the variation of force with tip/sample separation at a point can be used to study local interachons. 

The main purpose of middle layers is to provide additional (thermal) insulation. Nowadays, these layers are often made of fleece materials with good air entrapment properties. Their thermal conductivity (typically 0.03-0.04 W/mK) is near from air (0.026 W/mK). The thermal resistance of such layers is directly correlated with their thickness, provided that no air movement occurs within the fabric. Thermal conductivity and air permeability also are generally dependent on the fabric density (Yip and Ng, 2008). Conduction has been shown to be the main heat transfer mechanism through textile layers as long as the fibre volume fraction is higher than 9% (Woo et al., 1994). However, materials with very low density (like spacer materials) allow radiant and convective heat transfer. This was demonstrated by Das et al. (2012) who compared a spacer fabric middle layer with two non-woven middle layers and showed that the contribution of this spacer fabric to the overall insulation was higher than the two other samples in a non-convective mode, while it was the lowest in a forced convective mode. The positive effect of metallised interlayers with low emissivity on the reduction of... 

Fig. 11 Friction force micrograph of PE lamella on mica left, friction forces increase from dark to bright contrast) and laterally resolved adhesion forces right, dark - 80 nN, bright -50nN pull-off force) collected in the so-called force-volume (FV) mode (see Sect. 5.2.2). Since the measurement was carried out in air, the forces are dominated by capillary forces. The contrast in the friction force micrograph is related to the orientation of the folds on the polymer lamella siuface, which are oriented along the crystal edge in each sector. (Reprinted with permission from [158]. Copyright 1999 American Chemical Society)...

The simplest mode of IGC is the infinite dilution mode , effected when the adsorbing species is present at very low concentration in a non-adsorbing carrier gas. Under such conditions, the adsorption may be assumed to be sub-monolayer, and if one assumes in addition that the surface is energetically homogeneous with respect to the adsorption (often an acceptable assumption for dispersion-force-only adsorbates), the isotherm will be linear (Henry s Law), i.e. the amount adsorbed will be linearly dependent on the partial saturation of the gas. The proportionality factor is the adsorption equilibrium constant, which is the ratio of the volume of gas adsorbed per unit area of solid to its relative saturation in the carrier. The quantity measured experimentally is the relative retention volume, Vn, for a gas sample injected into the column. It is the volume of carrier gas required to completely elute the sample, relative to the amount required to elute a non-adsorbing probe, i.e. 

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