Film Drying
Researchers: Prof. Alex Routh
The Background
Understanding how patterns form in drying dispersions could provide valuable insights into health conditions, but these processes are not yet fully understood.
Work Needed
Further investigation is required to link the drying patterns of blood to specific medical conditions, with potential to create simple diagnostic tools that are accessible and effective.
Our Work
We are studying how drying blood droplets form unique patterns to develop diagnostic methods for conditions like anaemia, aiming to create test strips that improve blood donation processes.
Background
If you take your coffee, put it in a petri dish and dry it down, you will get a pattern. This is the origin of the very technical term ‘coffee rings’ and these patterns can be observed in drying dispersions across many different scales and contexts…
We can take a sample of water containing small particles, spread it as a film and dry it. The final morphology will display cracks. Natural examples are dried river beds, mud cracks in your garden, crack patterns in old oil paintings (called craquelure), and even the surface of Mars! The same sort of patterns form, but the size of them varies considerably. Understanding how these patterns form has been studied across disciplines from art conservation through to geology.
Our Work
Blood is just a dispersion of particles (red blood cells) in water. We are drying human blood samples and looking at the final droplet morphology. When you dry blood samples in a petri dish in a controlled environment, the resulting morphology can only depend on the initial state of the blood, so this is a physical measure or diagnostic.
Our aim is to elucidate something about the patient physiology from the final pattern. At present we have concentrated on looking at anaemia by investigating the volume fraction of blood. We are working with medical experts and the blood transfusion service on this, with an aim to manufacture blood test strips to address the blood donor retention problem.

Time sequence of a drying droplet of blood

Drying dispersions of polystyrene particles with varying initial volume fractions and contact angles. Red points indicate accumulation of material at the edge of the drop – visible as a dark ring. Black points indicate absence of a so called coffee-ring …
Implications
Our findings could be beneficial within medical settings, particularly with improving the experience of giving blood for potential blood donors.
Future Directions
We are hoping to study malaria and diabetes through observing these ‘coffee rings’ in blood, thinking about how differing blood cell rigidity can indicate certain medical conditions.
Publications
Alexander F. Routh, Drying of Thin Colloidal Films, Reports on Progress in Physics 76 046603 2013.
Michael J Hertaeg, Clare R. Rees-Zimmerman, Alexander F Routh, Rico F Tabor and Gil Garnier, Pattern formation in evaporating particle suspensions, Journal of Colloid and Interface Science 591: 52-57 2021.
Michael J Hertaeg, Alexander F Routh, Rico F Tabor and Gil Garnier Pattern formation in blood drops, Phil. Trans of the Royal Soc. A, 379: 20200391 2021.
Sheila J. Bhatt and Alexander F. Routh, Optical transmission profilometry for tracking time-resolved particle redistribution in sessile colloidal suspensions, Scientific Reports 14:637 2024.
Sheila Bhatt, Peter Smethurst, Gil Garnier, Alexander F. Routh, Front-tracking and gelation in sessile colloidal suspensions: what can they tell us about human blood?, accepted by Biomacromolecules.