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Department of Chemical Engineering and Biotechnology




Our interests lie in the study of soft solids and surfaces, with particular applications in the food, pharma and chemicals industries.

Micro-Structured Materials

We study the formation and processing behaviour of structured semi-solid materials. The main area of interest is in solid-liquid pastes or doughs, composed of particulate solids surrounded by continuous liquid phase(s). These are common in the food, detergent, agro-chemicals, pharmaceutical and catalysis industries, and are frequently formed into particular shapes by extrusion. The underlying physics is complex and we use aspects of plasticity theory, fluid mechanics, rheology and soil mechanics to describe these systems. We also work on bubbly liquids and complex food fluids.

This work is part of the Paste, Particle and Polymer Processing Group activity, in association with Sarah Rough and Bart Hallmark, and continues the activity started by John Bridgwater and Malcolm Mackley. Our activities are focused around

  • Fundamental studies : investigations of phenomena, such as wall slip, liquid phase migration, agglomeration and spheronisation;
  • Process modelling : developing models of paste forming processes, such as rolling/calendering or screen extrusion;
  • Product design : relating function, processing and formulation to deliver particular product properties.
  • Rheology: using modern devices and theory to describe how soft solids deform and flow, and respond to formulation and processing

Ongoing projects include the extrusion of tungsten carbide pastes (with Sarah Rough) to understand monitor micro-structural development and defect formation, the rheology of bubbly liquids (aka cake batters and foamed cement, with Bart Hallmark), and extrusion-spheronisation of pharmaceutical materials (with Sarah Rough).

Fouling and Cleaning Mechanisms

A whole class of unwanted micro-structured materials can be found as fouling deposits on heat transfer surfaces, in distribution systems and other equipment. Fouling is a common (and expensive) operating problem in many processes, particularly the food industry, where the deposits formed can act as harbours for other problem species (e.g. bacteria ). This work relates to long-standing efforts in heat transfer and approaches the problem at three related scales:

  • Fundamental studies of deposit formation and removal, with particular focus on deposit structure and modelling;
  • Design, control and operation of individual heat exchanger units, both in production and during cleaning (e.g. for aspectic processing);
  • Design and operation of large heat transfer networks, such as are used in energy intensive processes.

Recent work has lookied at water scaling on copper surfaces (with Stuart Clarke) and novel, non-disruptive, in-situ methods for studying the growth or removal of soft layers in conjunction with John Chew  (University of Bath). The soft layers include biofilms and protein matrices undergoing swelling for controlled release.

Our interest in cleaning in the food and phrarma sectors has grown considerably over the last decade. A particular focus is the flow behaviour of liquid jets impinging on vertical walls and their cleaning behaviour. This work features collaborations with the University of Manchester, TU Braunschweig, TU Dresden and DAMTP here in Cambridge.

The paper by Ishiyama et al. in Heat Transfer Engineering (2014) brought the strands of soft-solids and fouling together in a unified framework for managing fouling and cleaning cycles, where deposit ageing (converting deposit from a soft solid to a hard material) is a key factor. The Matlab code for this work is available from Dr Edward Ishiyama.

Ian was awarded an ScD by the University of Cambridge for his work in this field in 2013.


BA, MEng, Chemical Engineering, University of Cambridge, 1989

PhD, Chemical Engineering, University of British Columbia, 1994

Visiting Academic, Technical University of Braunschweig, 2008-

ScD, University of Cambridge, 2013

Cambridge/Canterbury Fellow, 2015

CEng, CSci, FIChemE


Key publications: 

Landel, J. and Wilson, D.I. (2021) The fluid mechanics of cleaning and decontamination of surfaces, Ann. Rev. Fluid Mech., 53, 147-171.

Wang, R., Snead, M.P., Alexander, P. and Wilson, D.I. (2020) Assessing bulk emulsification at the silicone oil and saline solution interface in a 3D model of eye, Acta Opthalomologica aos.14539.

Yang, J., Bhagat, R.K., Fernandes, R.R., Nordkvist, M., Gernaey, K.V., Kruehne, U., Wilson, D.I. (2019) Cleaning of toothpaste from vessel walls by impinging liquid jets and their falling films: quantitative modelling of soaking effects, Chem. Eng. Sci., 208, 115148.

Tsai, J-H., Cuckston, G.L., Hallmark, B. and Wilson, D.I. (2019) Fluid-dynamic gauging for studying the initial swelling of soft solid layers, AIChE Journal.2019;65:e16664.

Bhagat, R.K., Jha, N.K., Linden, P.F. and Wilson, D.I. (2018) On the origin of the hydraulic jump in a thin liquid film, J. Fluid Mech. 851, R5

Patel, M.J., Blackburn, S. and Wilson, D.I. (2018) Modelling of pastes as viscous soils - lubricated squeeze flow, Powder Tech323, 250-268

Bryan, M.P., Rough, S.L. and Wilson, D.I. (2018) Measurement of the wall slip behaviour of a solid granular soap in ram extrusion, Powder Tech, 323, 76-85.

Bhagat, R.K., Perera, A.M. and Wilson, D.I. (2017) Cleaning vessel walls by moving water jets: simple models and supporting experiments, Food Bioproducts Proc., 102, 31-54.

Hallmark, B., Bryan, M.P., Bosson, G.E., Butler, S.A., Hoier, T.P., Magens, O.M., Pistre, N., Pratt, L., Ward, B-A.P., Wibberley, S.R. and Wilson, D.I. (2016) A portable and affordable extensional rheometer for field testing, Meas. Sci. Tech., 27, 125302.

Parkin, J., Widjaja,  K. S., Bryan,M. P., Rough, S. L., Wilson, D. I. (2016) Experimental validation of a dimensional analysis of spheronisation of cylindrical extrudates, Power Tech298 73-83.


Google Scholar Profile

Other information

Ian is called by his second name : he is D.I. Wilson on publications (listed on the P4G website).



Teaching and Supervisions

Research supervision: 

Details of folk who are working with or have worked with Ian are given on the P4G website.

Please note that Ian is not hosting research interns for the forseeable future owing to the COVID-19 pandemic.

Professor of Soft Solids and Surfaces
 Ian  Wilson

Contact Details

Office phone: 
Takes PhD students


Person keywords: 
product engineering
particle technology
heat exchanger