New dimensions at the microscale – imaging and simulating dissolution dynamics of tablets and agglomerates
Tomographic measurements at the micro-scale enable micro-scale phenomena to be understood and modelled. This has been a new frontier for our research in tomography. This theme is of critical importance in a number of areas, especially in controlled release of drugs and efficacy of consumer products (tablets, detergents, powders, food, cement etc). Our new work used micro-x-ray tomography to verify advanced structural simulations of the way in which materials dissolves and releases chemical components. It also enables improved understanding of the concomitant physical decomposition and disintegration.
There have been two main achievements of our recent work. First, advancing our understanding of utilising voxelated x-ray tomographic data alongside new digital three dimensional simulation models . As reviewed  comparison of space-defined or property defined variations require careful consideration. It is not a matter of fusing images – since such methods can result in very high propagation of error. Modelling process behaviour is best undertaken by tracking process parameters directly. New guidance for this has been provided .
Secondly, micro-tomograph structural data, tagged with voxel properties, has been used to build predictive simulations models for chemical behaviours. This has been applied to dissolution of compacts (e.g. tablets), Fig 1 , and in the dissolution response of agglomerates, Fig 2 . This has applications in pharmaceutical, agrochemical and food science.
Figure 1: a) An X-ray shadow image, a reconstructed cross-sectional slice and a 3D view of the scanned Aspirin tablet. The 3D view has a quarter of the tablet digitally cut out to reveal the internal structure. (b) Cross-sectional views of the tablet in its initial and disintegrated states. 
Figure 2: Direct prediction of agglomerate dissolution using tomographic data for structure linked with digital 3d computation. The graph shows different rates of chemical release are dependent on the geometry of the agglomerates. 
Author Information: Richard A Williams, Xiaodong Jia, Institute of Particle Science and Engineering, School of Process, Environmental and Materials Engineering, Email: email@example.com, firstname.lastname@example.org
- “An integrated methodology to evaluate permeability based on measured microstructures”, C. Selomulya, T.M. Tran, R.A. Williams, and R. Amal, AIChE Journal, 52, 10 (2006), pp.3394-3400, ISSN 0001-1541.
- “Errors Implicit in digital particle characterisation”, M. Zeidan , X. Jia and R.A. Williams, Chemical Engineering Science, 62, 7, (2007), pp. 1905-1914, ISSN: 0009-2509.
- “Combining X-ray microtomography with computer simulation for analysis of granular and porous materials”, R. Moreno-Atanasio, R.A. Williams and X. Jia, Particuology, 8, 2, pp.81-99, (2010), ISSN No: 1674-2001, doi:10.1016/j.partic.2010.01.001.
- “From microstructures of tablets and granules to their dissolution behaviour”, X. Jia & R.A. Williams, Dissolution Technologies, 13, 2, (2006) pp.11-19, ISSN: 1521-298X.
- “A hybrid mesoscale modelling approach to dissolution of granules and tablets”, X. Jia and R.A. Williams, Chemical Engineering Research & Design, 85, A7, (2007), ISSN: 0263-8762 (electronic ISSN: 1744-3563).