Area of Expertise
Foam Science and Engineering
Multiphase Flows and Multiphase Mass Transfer
Ink Jet Printing and Direct Write Processes
Prize And Awards
PhD (University of Cambridge) 1990--1994
BSc (Hons, 1st class) (University of Western Australia) 1985--1989
Dr Grassia's research focuses on foams and allied multiphase systems including solid-liquid suspensions and liquid-liquid emulsions.
Chemical engineering applications abound. Foams are used in froth flotation for extracting valuable metals, in foam fractionation for purifying proteins, and in manufacturing polymeric materials to name a few. Foams flowing in porous media can be used for soil remediation and aquifer remediation, for immobilising captured waste gases like CO2, and for storing useful gases like hydrogen. Foams can also be a major nuisance in bioreactors, whilst even laundry wash detergents tend to contain additives to reduce the volume of foam. Solid-liquid suspensions meanwhile are processed in minerals tailings operations, and also when treating sewage sludges so as to extract clean water from waste and reduce waste volumes. Liquid-liquid emulsions meanwhile form the basis of many foodstuffs, and household and personal care products.
What all of the above systems have in common is that they consist of a discrete phase (whether gas bubbles, solid aggregates or liquid droplets) suspended in a continuous liquid phase. Moreover the energetics of the interface between the discrete and continuous phase dominate the system behaviour, whilst the individual discrete phase elements interact with their neighbouring discrete phases. These interfacial properties and interactions, make foam (second perhaps only to graphene!) simultaneously both very light but very tough.
To understand these systems one needs to understand both their physics and their physical chemistry. Moreover one needs to understand the physics and chemistry at a multitude of scales ranging from the nanometre scale of individual surfactant molecules within a foam film to the kilometre scale over which foam might propagate in improved oil recovery operations. Multiple time scales also determine the behaviour: individual surfactant molecules can enter and leave molecular aggregates called micelles on the order of microseconds, whereas the supermarket shelf life of a chocolate mousse can be up to some weeks.
In summary, foams have attracted the attention of humanity ever since the goddess Aphrodite (literally `risen from foam') was said to have been born from the sea foam on the shore of the Mediterranean. In the 21st century, foams continue to exert both their scientific fascination and their engineering utility.