Dr Paul Grassia joined TU/e in 2024 following academic posts at University of Strathclyde (2015--2024) and University of Manchester (1998--2015). Prior to this, he undertook postdoctoral research at Stanford University (1996--1998) and University of Chile (1994--1996), a PhD at University of Cambridge (1990--1994), and BSc (Hons) at University of Western Australia (1985--1989).

Working at the interface between engineering, applied mathematics, and physics, Dr Grassia's research studies foams, and does so, for two main reasons: first and foremost, because foams are interesting scientifically in their own right(!), and secondly because they are important in a multitude of engineering, energy and environmental operations (e.g. froth flotation in minerals processing, foam fractionation for energy efficient protein purification, foam-based large scale gas storage, foam-based soil remediation).

Just stop and think what truly amazing materials foams really are: if anyone told you they could make a substance that was 99% by volume air, and 0.999% by volume water, and yet that had flow properties total different from either air or water, would you believe them?

Dr Grassia's research has focussed on different behaviours of foams treated at very different length scales: foam drainage and foam rheology. Work on drainage has primarily been at the continuum scale, whereas that on rheology has been at the bubble scale. One major research success in drainage has been modelling froth flotation systems, and demonstrating the role that thin capillary boundary layers play in flotation tank operation. Meanwhile a major success in rheology has been modelling bubble flows in confined systems (e.g. a microfluidic channel and/or a pore in an underground reservoir), demonstrating how viscous drag effects can lead foam structures to break up.

Dr Grassia's work also studies solid-liquid suspensions and liquid-liquid emulsions (in addition to gas-liquid foams). To a certain extent though solid-liquid suspensions are merely `upside-down foams': solids in suspensions tend to fall, whereas bubbles in foam rise. Dewatering of suspensions or sludges is in fact a particularly important engineering operation, that reduces the volume (and thereby facilitates the disposal of) solid-fluid wastes. Simultaneously this provides a source of clean water, in a far more energy efficient fashion than conventional distillation. Liquid-liquid emulsions meanwhile increase the contact area between two immiscible liquid phases, facilitating the transfer of material from one liquid phase to another. As also happens analogously with foam fractionation, extraction and subsequent purification of materials can then be done in an energy efficient manner.