The Science of Flow: How Rheology Is Changing Medicine, Manufacturing and More

At Swansea University, Aniqah Majid meets researchers who are unlocking the power of non-Newtonian fluids – from blood clotting diagnostics to cleaner oil recovery – using a little-studied science with big real-world impact

FRANCESCO Del Giudice has a syringe in hand and is squeezing a solution of 99.2% water and 0.8% polymer into a test tube. 

“As you can see, the solution is expanding as it flows out of the syringe,” he says, demonstrating the phenomenon of rheology of a non-Newtonian fluid (pictured above). “If you were to do this with [100%] water, a Newtonian fluid, then the solution would just shrink as it flows. This can also be seen when you turn a water tap on slightly.”

I am at Swansea University to meet Del Giudice, an associate professor and head of the Rheological Microfluidic Laboratory, and his colleague Dan Curtis, also an associate professor and head of the Advanced Rheometry Laboratory, to learn more about rheology – the science of how fluids flow and deform. Both professors’ labs come under the Complex Fluids Research Group, which is concerned with the behaviour of non-Newtonian, or viscoelastic, fluids – solutions that cannot be defined as fixed states of solid, liquid or gas, but something in between.

Non-Newtonian fluids behave as different states depending on the amount of stress, or shear, they endure. Shear-thickening fluids, such as cornflour and custard, become more solid-like when subjected to rapid stress. In contrast, shear-thinning fluids like xanthan gum or tomato ketchup become less viscous and more fluid under faster stress.

Toothpaste is another example of a non-Newtonian fluid called Bingham liquid, as Del Giudice explains. “In the tube it is in a solid state, as when you tip it, it does not fall out. But apply pressure to the tube and the paste comes out like a liquid, only to behave like a solid again when it sits on the toothbrush without sinking [through the bristles]. and then a liquid again when it is applied to the teeth.”

Real-world examples are essential for understanding what Del Giudice and Curtis describe as being a complex science, a reason they say why many universities in the UK do not study it in depth.

“Complex fluids are called complex for a reason. When you try to study microscopic flow – the flow around an obstacle – you cannot use the Navier-Stokes equations like you would for all Newtonian fluids, you need a specific and modified equation for every different type of non-Newtonian fluid,” explains Del Giudice.

Yet rheology and complex fluids are fundamental across chemical engineering disciplines, underpinning industries such as pharmaceuticals, drug development, and oil and gas. These sectors have long supported south Wales’ industrial landscape – with oil refining still prominent in Pembroke through the Valero refinery, and drugmaking represented by the Penn Pharmaceuticals plant in Tredegar.

University routes

The labs of both Del Giudice and Curtis are found at the university’s Bay Campus, home to most of the university’s mathematics and engineering disciplines. A “global exemplar”, the campus feels completely removed from the university and Swansea as a city, taking a more futuristic landscape – Del Giudice tells me they shot a big Hollywood superhero film here recently. The campus reflects the new-age research being done within its walls, with Del Giudice and Curtis studying the rheology of complex fluids to develop novel technologies in modern biotechnology and heavy industry.

Rheology and complex fluids are fundamental across chemical engineering disciplines, underpinning industries such as pharmaceuticals, drug development, and oil and gas

Swansea University is the only university in the UK which has a dedicated complex fluids research group within its chemical engineering discipline. The topic is introduced in the second year of its undergraduate course with the classification of non-Newtonian fluids, and further in the four-year course where students learn rheometry and the how to use rheometers – a piece of equipment that measures how materials deform and flow when under stress. Rheology is also explored more widely in a two-year master’s degree.

The study of rheology and complex fluids has been a staple for the university for more than 20 years and was established by Rhodri Williams, a former professor at Swansea and an IChemE Fellow, whose research focused on blood clotting and drug therapy. “Rhodri was actually the one who started the work on non-Newtonian fluids and its cavitation in blood work,” says Del Giudice.

Curtis’ work builds on Williams’, focusing on blood flow and the development of observational techniques and drug therapies for treating clotting-related diseases. Del Giudice’s, meanwhile, aligns with Curtis and fellow professor Karl Hawkins’ work and focuses on healthcare application. Del Giudice specifically looks at the microfluidic flow of complex fluids, which involves studying processes on a microscale not typically achievable via conventional techniques, including using a rheometer.

His current research includes improving single cell analysis (SCA) to improve diagnostics and aid the development of new drugs. One field he is working on is liquid biopsy, a blood test used for identifying cancerous cells. Del Giudice has been using microfluidic devices – miniature systems that can manipulate fluids at a microscale – and rheology to improve the efficiency of SCA analysis. 

Del Giudice explains: “To identify cancerous cells, we look at a biomarker called circulating tumour cells, which, if you are able to spot them in time, you can remove at an early stage before the development of a tumour in the body, thus avoiding the need for advanced cancer treatments.”

He adds: “The issue with this process comes in the cells’ infrequency – they are one in 10,000 to 100,000 cells, which means that to effectively hit those cells you need a system for the blood that can read all cells.”

This is a difficult feat to achieve as even flow cytometers, the conventional equipment used to identify and measure cells, can miss out or lose them. In SCA, barcode beads are used to “tag” cells and help researchers separate and identify them. For efficient tracking, cells and beads need to be paired as consistently as possible and captured within a droplet of fluid. However, cells can arrive whenever they want, and Del Giudice says it is difficult to develop a consistent stream of drops with both a cell and bead in it. The odds of having a droplet with both a cell and functionalised bead is roughly 5%, which is unfeasible for SCA.

In a 2022 study, Del Giudice demonstrated that non-Newtonian fluids can enhance encapsulation for single cell analysis by using mineral oil and polymer solutions to create a viscoelastic medium

In a 2022 study, Del Giudice demonstrated that non-Newtonian fluids can enhance encapsulation for SCA by using mineral oil and polymer solutions to create a viscoelastic medium. The viscoelastic fluid improved the synchronisation of particle formation with droplet generation, significantly increasing encapsulation efficiency.

Del Giudice says: “What we did was to engineer the fluid and an ordering phenomenon to synchronise the arrival of the bead and the cell to the formation of the droplet. Here we were able to push the likelihood of synchronisation from 5% to 40%.”

The professor is collaborating with postdoctoral research associate Anoshanth Jeyasountharan on the technology for the newly founded spinout, Siora. Together, they aim to improve the chances of successfully encapsulating single cells in droplets. Research is being run out of Del Giudice’s lab at Swansea, but he says the team intend to move out of the university with grant support.

How rheometers work

In a different building on the Bay Campus, Curtis’ lab is littered with rheometers of all shapes and sizes. High-precision instruments – many of which have been customised to tackle the unique challenges posed by the substances under study – they apply controlled deformations or stresses to materials.

“They are not as complex as they look. It would take me around a week to build something like that,” he says pointing to a rheometer of about 1.5 m.

He adds: “What we try and do with these rheometers is find different ways of using them for particular phenomena.”

Curtis describes the research in his lab as exploratory, using rheometry to better categorise materials and define their rheological properties. This approach helps experts in medicine, manufacturing and other fields gain deeper insight into material capabilities. The team works with a wide variety of substances, from biological samples such as model blood systems and collagens to industrial fluids like inks, adhesives and muds. By precisely measuring how these materials respond to deformation, the researchers can uncover clues about their microstructure and predict how they will perform in real-world conditions.

He explains: “As a rheologist, we know the difference between a solid and a liquid is very broad, so we use rheometers to study the properties of materials to figure out where they fall in the spectrum – and that’s critical for understanding how it will behave in a process, in the body, or in the environment.”

Curtis shows me one of his rheometers, which is connected to a computer that tracks the movement and displacement of a material. The software visualises these differences, revealing whether the material flows more like a solid or a liquid.

He continues: “Just using conventional means of testing a material, say squeezing it in between your hands, is insufficient. What we do is take a sample of it and put it between two plates, where one of the plates is slowly and subtly moving and tickling the material, so that even the smallest changes in the structure or behaviour is detected.

“We use these to precisely measure the properties of a material, both to understand and predict their microstructure and how they will react in a given process.”

Blood work

Curtis is collaborating with fellow professor Karl Hawkins, whose research involves using rheological techniques to develop biomarkers for blood coagulation. Hawkins is based on the other side of Swansea at the university’s main Singleton Campus. He splits his time between his lab there and Morriston Hospital, where he is conducting research with Suresh Kumar Gopala Pillai, a doctor and consultant in emergency and intensive care medicine.

Hawkins explains that research into the rheology of blood coagulation is particularly significant for south Wales – and the UK more broadly – where heart disease is a growing concern.

“Our new ‘clot busting’ project, funded by the EPSRC, is all about developing a rheometrical technology so we can better assess therapeutic intervention for treating blood clots,” he says.

“We intend to use this technology at Morriston Hospital with stroke patients. Here we take a patient’s blood before and after the administration of a ‘clot-busting’ drug, and monitor, using rheometry, to assess the effects this drug has on clot formation and clot breakdown.”

Hawkins adds that research into rheological techniques remains relatively novel, with Swansea collaborating with a small number of university partners – among them, the University of Pennsylvania in the US. This research is vital for advancing more effective anticoagulants, including alternatives to warfarin, which can sometimes fail to prevent blood clotting.

Pillai runs the research lab at Morriston Hospital, strategically located next to the A&E unit. This proximity, he says, allows him to retrieve blood samples from patients and begin testing as quickly as possible.

“Because it’s so close, we can do a rheological reading in around 15 to 30 minutes,” he says.

Pillai explains how his research measures the “gel point” of blood, the moment the blood turns from a liquid into a solid, and how that might determine what medication a patient needs.

He says: “We measure the gel point to establish a biomarker which we analyse according to a health range. Most people fall within the standard deviation ‘healthy index’ of blood, but falling to either side, your blood could either be hypercoagulable [clots too easily], or it is not clotting properly.”

For those who fall outside the normal range, Pillai says disease is likely the underlying cause – enabling a targeted drug treatment programme to be developed.

“This is what we call translation medicine, where research goes from the lab to patient care and we are given the freedom to try and see if rheological techniques work.”

As part of his research, Pillai is currently collaborating with the hospital to collect blood samples from patients with various heart conditions – including those who have experienced strokes.

Oil slurry

While rheological research in biotechnology is well-established, its application in the oil and gas industry remains in its infancy – despite the sector’s abundance of complex fluids.

To the west of Swansea is Pembroke, a quiet town best known for its medieval castle. It is also home to Valero’s sole UK oil refinery – strategically located near Pembroke Port.

I am here to meet Ben Diment, the senior health and safety manager at the refinery, and two chemical engineering students, Charlotte Todd and Ben Phillips-Harries, who are both nearing the end of their placements at the site.

Todd, who is a completing her BEng at Swansea, is working in process safety, sifting through research papers and site reports to understand how to make processes safer and more efficient.

At the refinery, Phillips-Harries is focused on the sludge storage units, working to improve oil recovery by upgrading recycled sludge to a “good enough” grade so it can re-enter the crude processing stream.

Diment says: “This plan has been in the works for a long time, but Ben (Phillips-Harries) is looking for a solution using the equipment and resources we already have on site.”

This includes a centrifuge located near one of the main storage tanks. Widely used across the industry, centrifuges can recover up to 70% of oil from tanks. Valero, however, says it prioritises high-quality recovery, aiming to minimise chemical additives that could compromise the reclaimed oil and require removal before re-entering the processing stream.

Curtis, who’s joined me on the visit, explains that rheological techniques could offer a solution to Valero’s challenge. By analysing the rheology of the sludge, Phillips-Harries could determine the most suitable equipment for recycling – tailoring configurations based on the properties of the sludge.

Beyond Swansea University’s investment in rheology, research into complex fluids is rapidly expanding across the UK, driven by growing support within the Engineering and Physical Sciences Research Council portfolio. According to the UKRI, complex fluids generate £180bn (US$242bn) of sales per year for the UK in a market with estimated global sales totalling £1tn. The UKRI also point out that the main research applications for this area in the UK include healthcare, manufacturing and oil and gas.

Beyond the labs and centrifuges, what is clear is that rheology is more than just a niche academic field – it’s a powerful, practical lens through which chemical engineers can solve some of today’s most complex problems. Whether it’s detecting cancer earlier, designing better blood-thinning treatments, or optimising oil recovery with minimal waste, rheology is quietly shaping innovation at every scale.

As Swansea University continues to lead the UK’s research into complex fluids, and with industry and clinical partners applying this knowledge in real-world settings, the message is clear: understanding how fluids behave – even those that defy definition – could be key to unlocking solutions in healthcare, sustainability and energy for decades to come.