Atomic force microscopy AFM tips

Chen et al. (2007) have developed a nanoinjector that injects compounds immobilized on MWNT-atomic force microscopy (AFM) tips into the cells. First, a MWNT-AFM tip was fabricated from a normal AFM tip with an MWNT on one end. Next, a compound of interest was immobilized on the MWNT-AFM tip through a disulfide bond linkage. After MWNT-AFM tip was tapped on the cell, the cantilever was further lowered and the MWNT nanoneedle then penetrated the membrane. Once inside the cell, the disulfide linkage was broken under the cells reducing environment and the compound of interest was released inside the cell. The MWNT-AFM tip was then removed from the cell. In this study, protein was... 

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. 

Figure 6.14 Schematic of a modified atomic force microscopy (AFM) tip used for TERS. Reprinted from Yeo, B.-S., Stadler, )., Schmid, T. et al. (2009) Chemical Physics Letters, 472, 1. Copyright (2009), with permission from Elsevier.

The WITec alpha300 R confocal Raman microscope can be upgraded to perform atomic force microscopy (AFM), tip-enhanced Raman spectrometry and near-field scanning optical microscopy, and is arguably the most versatile instrument for Raman microspectroscopy available today. 

Exact measurements turned out difficult, however, as the manipulation of such tiny objects led to experimental problems. The performance of tensile tests, for example, requires a device to clamp objects just a few nanometers thick. The employment of two atomic force microscopy (AFM) tips movable against each other proved its worth here (Figure 3.45). 

Force spectroscopy, though originally conceived as a tool for calibrating the atomic force microscope, has become an invaluable tool for studying adhesive interactions on the nanometer scale [29 - 31]. In force spectroscopy the deflection of an atomic force microscopy (AFM) tip is measured as a sample is moved into and then out of contact with the tip. The characteristic hysteresis observed as the sample is retracted is due to adhesion between the tip and sample. The point at which the adhesion is broken and the AFM tip pulls off the sample surface is characterized by a sharp discontinuity in the... 

A hollow needle-hke capillary is not essential for electrospinning — a droplet on a sohd electrode behaves similarly. Ultrafine droplets picked up by an atomic force microscopy (AFM) tip, nanofabricated microfluidic channels (Kameoka and Craighead 2003), or by a dip-pen type tip (Sun et al. 2006) have been electrospun successfiiUy. 

Recently developed nanofabrication techniques include dip-pen nanolithography (DPN), which uses functionalized atomic force microscopy (AFM) tips to deposit biomolecules on surfaces with pattern features as small as 10 nm [68]. Used for the creation of protein nanoarrays and virus arrays, this technique can create patterns with multiple components [68,69]. Enzymes have also been selectively deposited for biochemical modification of self-assembled monolayers [70]. While nanofabrication techniques are effective for patterning two-dimensional surfaces, these methods are quite limited in terms of processing time and are not suitable for three-dimensional scaffolds. 

Hou at al. [24] reported the synthesis of poly(methyl methacrylate) (PMMA) nanobrushes on silicon based on localized surface-initiated polymerization. To achieve this, self-assembled monolayers (SAMs) of octadecyltrichlorosi-lane (OTS) were first generated on a silicon surface. Introduction of nanostructures was achieved on these SAM surfaces using a conductive atomic force microscopy (AFM) tip, which led to the oxidation of OTS SAMs. These... 

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