Welcome to the Micromanipulation Research Group
Micromanipulation - Size Matters
There are many functional products containing biological and non-biological microscopic particles (or microparticles) over a wide range of industrial sectors including chemical, agrochemical, food and feed, pharmaceutical and medical, human care and household care. For biological microparticles, understanding their mechanical properties under different physiological states is crucial to bioprocessing and tissue engineering, e.g. animal cell culture to produce monoclonal antibody, mechanical disruption of yeast and bacteria to extract intracellular proteins, and mechanical stimulation of chondrocytes for cartilage tissue engineering. For non-biological microparticles, they should have desirable chemical composition, structures and mechanical properties. Understanding the mechanical properties of such microparticles is essential to predicting their behaviours in manufacturing, handling and performance in end-use applications.
Over the last 20 years, novel micromanipulation techniques have been developed by the of Micromanipulation and Microencapsulation Group at the University of Birmingham, led by Professor Zhibing Zhang, to measure the mechanical properties of single microparticles, including animal cells, yeast, bacteria, pollen grains, microspheres and microcapsules, particle-particle adhesion, particle adhesion on surface, adhesion and cohesion of biofilms or food fouling deposits on surfaces, and applied to characterise the mechanical properties of these biological and non-biological materials, which are related to their structures and functions.
The basic principle of micromanipulation is the compression of a single particle (for example, a cell in a drop of medium) between two parallel surfaces. These are usually the flat end of a glass probe and a microscope slide surface. Figure 1 shows a single tomato cell being compressed. As the probe is driven by a micromanipulator towards the slide, a transducer measures the force being imposed on the particle. A force-displacement curve can be generated from the data. Unlike other methods, large deformations are possible, including to bursting for cells. Mathematical modeling of the force-displacement data based on analytical or finite element analysis can be applied to determine the intrinsic mechanical property parameters of the particle materials, e.g. Young’s modulus, Poisson ratio, yield stress and stress at failure.
Figure 1: Single plant cell positioned between a force probe and glass slide.
Recent work includes using micromanipulation to study the biomechanics of single chondrocytes and chondrons and their biological responses with Dr N. Kuiper and Professor A. El Haj, Keele University. There have also collaborations with Dr J. Pritchard, School of Biosciences, University of Birmingham, on single plant cell mechanics, and with Dr P. Hartley, School of Mechanical Engineering, University of Birmingham, on mathematical modelling of yeast cell walls.
In addition, the Micromanipulation and Microencapsulation Group has established a research area in formulation of particulate functional products for pharmaceutical, nutraceutical, oral care and fabric care applications based on micro/bioencapsulation. For example, dextran-hydroxy-ethyl-methacrylate microspheres with a protein drug embedded, which may be used to achieve sustained release in blood stream, are shown in Figure 2. Different functional microparticles, particularly microcapsules with a core/shell structure, have been formulated using a range of techniques, including polymerization, coacervation, solvent evaporation, extrusion/gelation, fluidised bed coating, and direct compaction. The active ingredients which have been encapsulated included oil soluble droplets, water soluble powders, nutraceutical enzyme and probiotic cells.
Figure 2: Dextran-hydroxy-ethyl-methacrylate microspheres
prepared by emulsion polymerisation for sustained drug delivery.
Recent work includes development of a novel nanomanipulation technique to measure the mechanical properties of single nano-particles and to understand the rupture mode of microcapsules (Figure 3) in collaboration with Professor A. M. Donald, FRS, at Cavendish Laboratory, University of Cambridge, and the formulation of smart microcapsules for controlled release of small molecules in collaboration with Professor J. Preece, School of Chemistry, University of Birmingham.
Figure 3: The image of a M-F microcapsule after it was compressed to rupture
under high vacuum of ESEM (5kV, spot size 4). The diameter of the microcapsule was 16.50 µm.
Our vision is to be the world-leading research group in micromanipulation and microencapsulation, in which young talents can become future stars in their own scientific research areas via doing highly innovative research projects in interdisciplinary areas.
Our group is proud of our international reputation in developing novel micromanipulation techniques to mechanically characterize micro-particles for various academic and industrial applications, and of our novel research in microencapsulation of different active ingredients for pharmaceutical, nutraceutical, agrochemical, fabric care and human care applications.
We will keep on developing innovative scientific research in micromanipulation and microencapsulation with major impacts on academia and industry, and improving our international standing.
For details, please contact:
Prof. Zhibing Zhang
Tel: 0121 414 5334