(86b) Interactions and Mechanical Characterization of Spiny Particles
For the interaction between SFPs, the results indicated that the presence of spiny protrusions on a particle surface could either enhance or reduce the interaction force by a factor of 6 times, compared to SFP interaction with a flat substrate. The spiny particle interactions were classified into five distinctive types of force-distance (f-d) curves. These results suggest that the interaction force is highly dependent on the orientation of spines on the surface, which can control whether frictional forces contribute to the observed effective adhesion. A model was developed to compare the effects of pure spine-spine adhesion with spine-spine friction at different orientations.
For the mechanical characterization, the elastic moduli of pollen shells were mapped quantitatively on 5Ã?5 Î¼m2 areas. The values of modulus were determined to be between 7~9Â GPa for ragweed, 3~7 GPa for pecan, and 8~18 GPa for Kentucky blue grass pollen particles. Saturation at a relative humidity of 90% reduces the Kentucky blue grass pollen modulus to 3~6 GPa after absorbing water. These values are used to place in context recent reports of pollen behavior as a filler. To the best of our knowledge, this is the first time that the interactions between complex spiny microstructured particles have been directly measured by AFM. Moreover, pollen grains have excellent mechanical strength as an environmentally-friendly filler for high-performance composites.