(448v) Mechanical Characterization of Pollen Grains By Atomic Force Microscopy

Plant pollen grains are gaining interest as a unique adhesive micro-structured particle and a promising filler for polymer composites, due to their light-weight, high strength and sustainable nature. Sporopollenin, the major component of pollen shell, is one of the toughest naturally-occurring polymers with extreme chemical and thermal stability. Mechanical properties of pollen shells have a significant influence on the performance of composites, as well as the adhesion of pollen grains. However, there exist few literature reports of mechanical characterization of individual pollen grains. Here, the mechanical properties of three pollen species were also characterized by atomic force microscopy (AFM), including ragweed, pecan and Kentucky blue grass.

In the mechanical characterization, the elastic moduli of pollen shells were mapped quantitatively on 5Ã?5 μm² areas. The values of modulus were determined to be between 7~9 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.