Micro-mechanical properties of single high aspect ratio crystals

Abstract

This work describes a new method to measure breakage strength and elastic modulus of single crystal cantilevers using atomic force microscopy. Crystal breakage is an important but poorly understood factor in mechanical processing of organic crystals. In this study, 300 μm long beta glutamic acid, needle-shaped crystal cantilevers are bent and broken in an atomic force microscope. We report the first directly measured distribution of breakage strength and Young's modules of an organic crystal material. The distribution follows a Weibull distribution; 50% of the crystals break at less than 22.4 MPa and have a Young's modulus below 1.90 GPa and we observed that stronger crystals are stiffer, and thicker crystals break easier. The data generated from the single crystal cantilever method provides fundamental material properties essential for understanding undesirable crystal fracture due to forces exerted on crystals in manufacturing processes such as crystallisation, filtration and drying.