So Fujinami

Nano-palpation AFM and its quantitative mechanical property mapping

We review nano-palpation atomic force microscopy, which offers quantitative mechanical property mapping especially for soft materials. The method measures force-deformation curves on the surfaces of soft materials. The emphasis is placed on how both Hertzian and Derjaguin-Muller-Toporov contact mechanics fail to reproduce the experimental curves and, alternatively, how the Johnson-Kendall-Roberts model does. We also describe the force-volume technique for obtaining a two-dimensional map of mechanical properties, such as the elastic modulus and adhesive energy, based on the above-mentioned analysis. Finally, we conclude with several counterpart measurements, which describe the viscoelastic nature of soft materials, and give examples, including vulcanized isoprene rubber and the current status of ISO standardization.

Young's Modulus Mapping on Hair Cross-Section by Atomic Force Microscopy

It is important for the understanding of the complexity of a human hair structure to observe the ultra-structures and to measure their mechanical properties at the same point of the specimen. We examined the extremely smooth surface of the hair cross-section by force modulation (FM) method and Youngs modulus mapping method by analyzing force curves (FCs) in two-dimensional lattice being installed in an atomic force microscope (AFM). Consequently, the FM method was used to evaluate the changes in structural and mechanical properties in the internal structures of hair in air and in water performing any pre-treatment (chemical modification) on hair specimen. It was also possible to determine the semi-quantitative changes caused by the chemical damages of hair and the repairing effect of conditioning agents at nano-size level with Youngs modulus mapping method.

RECENT PROGRESS OF NANO-MECHANICAL MAPPING

Nano-mechanical mapping by atomic force microscopy has been developed as an useful application to measure mechanical properties of soft materials at nanometer scale. To date, the Hertzian theory was used for analyzing force- distance curves as the simplest model among several contact mechanics between elastic bodies. However, the preexisting methods based on this theory do not consider the adhesive interaction in principle, which cannot be neglected in the ambient condition. A new analytical method was introduced to estimate the elasticity and the adhesive energy simultaneously by means of the JKR theory, describing adhesive contact between elastic materials. Poly(dimethylsiloxane) (PDMS) and isobutylene-co-isoprene rubber (IIR) were analyzed to verify the applicable limit of the JKR analysis. For elastic samples such as PDMS, the force-deformation plots obtained experimentally were consistent with JKR theoretical curves. Meanwhile, for viscoelastic samples, especially for IIR, the experimental plots revealed large deviations from JKR curves depending on scanning velocity and maximum loading force. Some nano-rheological arguments were employed based on the difference between these specimens.

Polymer nanotechnology applied to polymeric nano-soft-materials

We have been developing new techniques to evaluate polymer nano-alloys and nano-composites. This nanotechnology can be classified into nano-three dimensional (3D) measurement, nano-physical properties evaluation systems, and nano-spectroscopy. As for the nano-3D measurement, we developed polymer oriented energy-filtered 3D transmission electron microscopy. With this method, we can access important 3D structural and elemental information that cannot be obtainable from ordinary TEM. Nano-physical properties evaluation systems were also established by developing atomic force microscopy force-distance curve measurement. The distribution of mechanical properties such as Youngs modulus and adhesive energy was quantitatively obtained on high lateral resolution. These methods give new pieces of information unobtainable by the conventional techniques on polymer nanotechnology. Several results are shown here.