Nanoindentation for direct evaluation of adhesion at the cell wail-adhesive interface AFM-based polarity characterization of wood surfaces

摘要

Two new methods operating at the sub-microscopic level addressing fundamental aspects of wood interfacial adhesion are introduced. As first method, nanoindentation was further developed enabling to characterize the adhesion directly at the wood cell wall-adhesive interface. First results show significant differences of the adhesion energy depending on the local anatomical position of the interface. Depending on the polar nature of the adhesive system used, adhesion energy is higher to S2 and lower to S3 cell wall elements or the opposite way around. In order to better understand observations from nanoindentation based adhesion measurements, an atomic force microscopy (AFM) technique called Quantitative Nanomechanical property Mapping (QNM) was introduced into wood science to characterize the local polar nature of the adherent wood. QNM records amongst others the local adhesion force of an AFM tip with given polarity when the tip is pulled off the surface. The technique operates in dynamic scanning mode and allows the mapping of the local distribution of surface polarity. First results show clear differences in polarity of native inner cell lumen surfaces (S3) compared to mechanically (e.g. by microtoming) exposed S2 surfaces.