Many biological and non-biological materials in the form of microscopic particles (or microparticles) are used to produce functional products for a wide range of industrial sectors including pharmaceutical and medical, chemical, agrochemical, food and feed, personal and household care. Understanding their mechanical properties is essential for predicting their behaviour in manufacturing and processing, and for maximising their performance in end-use applications. However, it had not been possible to determine the mechanical properties of single microparticles until the author, as the main contributor, developed a novel micromanipulation technique at the University of Birmingham. The technique 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 obtaining force-displacement data of single microparticles at large deformations, including those corresponding to rupture. The technique was enhanced by mathematical modelling and finite element analysis in order to allow intrinsic material properties to be determined, for example, the particle (or particle wall) elastic modulus, viscoelastic and plastic properties, and stress/strain at rupture. For biological materials, applications of this technique include understanding mechanical damage to animal cells in suspension cultures, yeast and bacterial disruption in downstream processing equipment, biomechanics of chondrocytes and chondrons for tissue engineering, and adhesion and cohesion of biofilms and food fouling deposits. For non-biological materials, applications include understanding and controlling particle breakage in processing equipment, and the formulation of microcapsules with optimum mechanical strength to achieve controlled release and targeted delivery of functional active ingredients.
The research on micromanipulation has been sponsored by BBSRC, EPSRC, DEFRA, DTI, EU, the Royal Society K C Wong Fellowships and 19 national and international companies, and has resulted in more than one hundred academic publications. The knowledge generated has also assisted these companies to commercialise particulate functional products
