Chapter 2 Micromanipulation in Mechanical Characterisation of Single Particles

Many functional industrial products are in the form of microscopic particles. Mechanical characterisation of these particles is essential if physical damage to them in manufacturing processes is to be minimised, and their performance is to be optimised. Several experimental techniques can be used to characterise the mechanical properties of single microparticles, including micropipette aspiration, particle poking, atomic force microscopy, optical trapping and diametrical compression. The details of these techniques and their applications are presented in this review. Among them, diametrical compression has many advantages. It is capable of determining the mechanical properties of both biological and non-biological particles as small as 400 nm in diameter, and can be used for measurements at high deformations, including up to rupture. The technique can be enhanced by mathematical modelling to allow intrinsic mechanical properties to be estimated, for example, the particle (or particle wall) elastic modulus, and viscoelastic and plastic parameters. For biological materials, present and potential applications include studying mechanical damage to animal cells in suspension cultures, yeast and bacterial disruption in downstream processing equipment, changes of the morphology of filamentous microorganisms in submerged fermentations, plant cell behaviour in food processing, flocculation processes, cell mechanics, biomaterials and tissue engineering. For non-biological materials, applications include understanding and controlling particle breakage in processing equipment, handling and transport, and end-use applications.