Atomic force microscopy origins

The investigation was then extended to a monolayer formed from dipalmitoyl phosphatidyl choline and the same amphiphilic photochromic polypeptide XXIII.11211 When the monolayer was kept in the dark, the polypeptide molecules arranged themselves perpendicularly to the membrane (the water/air interface) and formed a bundle of helices which could be observed by atomic force microscopy as a transmembranous particle of about 4 nm in diameter. Irradiation with UV light and the consequent trans—>tis isomerization of the azobenzene moiety caused a bending of the molecular main chain, which in turn produced a destabilization and dena-turation of the bundle of helices in the monolayer. After removal of the light, the polypeptide molecules reverted to their original bundle structure. 1211... 

Regarding the spatial aspects of the enzymatic degradation of CA-g-PLLA, a surface characterization [30] was carried out for melt-molded films by atomic force microscopy (AFM) and attenuated total-reflection Fourier-transform infrared spectroscopy (ATR-FTIR) before and after the hydrolysis test with proteinase K. As exemplified in Fig. 3 for a copolymer of MS = 22, the AFM study showed that hydrolysis for a few weeks caused a transformation of the original smooth surface of the test specimen (Fig. 3a) into a more undulated surface with a number of protuberances of 50-300 nm in height and less than a few micrometers in width (Fig. 3b). The ATR-FTIR measurements proved a selective release of lactyl units in the surface region of the hydrolyzed films, and the absorption intensity data monitored as a function of time was explicable in accordance with the AFM result. 

In addition to defining their molecular structures, it is of considerable interest to understand the physical properties of the fibrils and the nature of the forces that lead to their stability. To this end, we have been studying a range of different fibrils by means of experimental approaches originally developed within the rapidly developing field of nanotechnology, such as atomic force microscopy (AFM), in conjunction with computer simulation methods [35]. 

The goal of this chapter is to provide an overview of the measurement of colloidal forces at liquid/Iiquid interfaces, using predominately atomic force microscopy (AFM)-First, some of the types and origins of the relevant colloidal forces are introduced. This is followed by a general description of the operation of AFM at rigid interfaces. The next sections focus on forces at liquid/Iiquid interfaces, beginning with a discussion of other measuring techniques employed at liquid/Iiquid interfaces, followed by a summary of... 

A further refinement of the scale of phase separation was recently demonstrated by Xia and Friend using inkjet printing (IJP) and thereby doubhng the EQE [238]. As demonstrated by fluorescence and atomic force microscopies, this originates from a more rapid drying process of inkjet printed films as compared to spin cast ones (see Fig. 50). The small volume and hence the large surface to voliune ratio of each IJP droplet led to this fast evaporation and drying. 

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... 

---