Use of atomic force microscopy

Includes a description of membrane rafts and microdomains within membranes, and a new box on the use of atomic force microscopy to visualize them. 

The so-called dip-pen nanolithography is one of these promising novel techniques. It has been developed by Ch. Mirkin etal. and is based on the use of Atomic Force Microscopy (AFM) tips to deposit functionalized molecules on appropriate surfaces. The molecules are first deposited in solid state on the tip. The transport to the surface happens by means of the water meniscus between the tip and the surface that is present in air of usual humidity. Gold surfaces are preferably used to deposit thiol molecules forming strong Au-S bonds. The places were thiol molecules are deposited simply depend on the software moving the AFM tip on the surface. Figure 13 explains in a simplified manner the process. 

The use of atomic force microscopy (AFM) and flow injection QCM in tandem provided important information about the surface coverage and orientation on gold of a thiolated DNA probe, as reported by Zhou and co-workers [58]. The effect of using a different alkanethiol to reorient the... 

First, it is the experimental and theoretical (including computer modeling) investigation of adsorption layers formed on solid surfaces by natural and synthetic polymers, especially by poly electrolytes. Such studies, and in particular those involving the use of Atomic Force Microscopy (AFM, see Chapter VII), provide important information regarding the optimal conditions for the use of polymers for flocculation or stabilization of disperse systems (Chapter VII), and establish the theoretical basis for understanding the mechanism behind the action of structural-mechanical barrier. 

Elemental and molecular surface chemistry plays an important role in the acceptance of an implant material [2-12]. In the study of the elemental and chemical composition of polymeric surfaces, XPS, secondary ion mass spectrometry (SIMS), and surface energy evaluations have emerged as the dominant methods for surface analysis. This is due to the ability of XPS to provide qualitative and quantitative elemental and chemical information (10-100 A), which is complemented by the molecular information obtained from SIMS over the outermost 5-25 A. Surface wettability measurements provide a rapid and quantitative measurement of the inherent surface wettability of a solid sample. When these measurements are accompanied by a Zisman plot, the polarity and critical surface tension (7. ) of the solid surface may be determined. The critical surface tension is a measure of the surface free energy (yj of solid materials. The surface morphology of the lenses studied here was investigated through the use of atomic force microscopy (AFM). The sensitivity of the technique allows submicrometer (to Angstroms) sized features to be examined. 

The use of Atomic Force Microscopy for the characterization of oxide materials is still limited but the high resolution capabilities of the method show promise for the study of a wide variety of surfaces. Both the principles of the technique and the instrumentation must be advanced so that a wider range of morphologies can be studied with resolution approaching that achieved at present on relatively smooth surfaces. 

Advances in the use of atomic force microscopy to study flaw sites and the relaxation of indentation on the surface of glass to study cracks, (see figure 4)... 

W. R. Bowen, T. A. Doneva, and J. A. G. Stoton, Colloids Surf. A, 201,73 (2002). The Use of Atomic Force Microscopy to Quantify Membrane Surface Electrical Properties. 

Differences in the surface conductivity with surface termination of diamond can be applied to the nanolithographic modification of diamond surfaces by use of atomic force microscopy (AFM) techniques [50-52]. Modification can be carried out by applying an electrical bias to the sample surface via a conductive cantilever tip, e.g., Au coated Si (Fig. 8.8). Surface modification using such an AFM technique is relatively general, and has been achieved for semiconductor materials such as Si [53], GaAs [54] and metals such as Ti [55]. Recently, Tachiki et al. and Kondo et al. have applied this technique to single-crystal homoepitaxial diamond thin films, undoped and boron-doped, respectively. In this section, we discuss the properties of diamond surfaces modified via AFM techniques and possible applications. 

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