Colloidal particles, detachment from surfaces

In conclusion, field-flow fractionation is a relatively simple technique for the study of adhesion and detachment of submicrometer or supramicrometer colloidal particles on and from solid surfaces. 

Despite the criticisms above, the vOCG approach has been frequently and successfully used over recent years to interpret polymer solubility in water [14] (this is not possible using the y approach ), protein adsorption on clays [57] and conducting polymers (see Section IV.A.2 below), cell adhesion to copolymer surfaces [65], yeast-yeast and yeast-bacteria adhesion [72], fiber-matrix adhesion [69], and the hydrodynamic detachment of colloidal particles from glass plates [70]. 

Freitas A, Sharma M (2001) Detachment of particles from surfaces an AFM study. J Colloid Interface Sci 233 73-82... 

To measure the adhesion forces between colloids (fouling) and the surface layer, or between the surface layer and the substrate, AFM is seen as reliable and simple, as discussed earlier. Bowen et ah [36] introduced a new technique for the direct measurement of the force of adhesion of a single particle by AFM. AFM, in conjunction with the colloid probe technique, allows a direct quantification of membrane fouling through the measurement of pull-off (detachment) forces, when the probe is retracted from the surface after contact has been made. 

PS colloids at all acrylic acid concentrations tested. However, at low acrylic acid concentrations the particles detached easily from the surface. Only at concentrations above % wt/wt the silica particles were sufficiently strongly bonded to the surface that they remained attached even after several centrifugation steps. The size of the silica particles did not depend on the size of the PS colloids but is determined by the amount of tetraethoxysilane. 

Surface prop>erties can be modified by thin layers of grafted polymers on a surface (not only flat substrates, but also colloidal particles, fibers, etc). These layers can be fabricated by grafring-from (as radical polymerization at the interface) and grafring-to (as tethering of the polymer chains from solution) methods. Grafted surfaces using smart temperature-responsive polymers can modulate cell adhesion and detachment properties in dependence on the temprerature. Cells adhere and proliferate on hydrophobic surfaces rather than hydrophilic ones. They tend to adhere to the surface with appropriate hydrophobidty. Polymer brush systems can be used to control adsorption mechanism, for example, protein adsorption or adsorption of nanopartides. 

The release or detachment of the fine particles from the collector surface is assumed to be induced by the hydrodynamic forces in the case of non-Brownian particles or by the colloidal forces in the case of Brownian particles [131]. For non-Brownian fine particles, the rate of hydrodynamic particle entrainment is considered to be proportional to the difference between the wall shear stress and the critical shear stress [123] ... 

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