Both systems contain surfactants, such as cooking oils or lipids from your lungs. They self-assemble in air and change the properties of the droplets.
“Both of these systems are difficult to study under the conditions you would find them in the real world, as keeping tiny droplets intact during an experiment is challenging," explains Adam Squires from the University of Bath.
“We have previously used acoustic levitation to study the self-assembly of cooking oil components, but the droplets produced using this technique are still larger than those produced in real life," adds his collaborator Adam Milsom from the University of Birmingham. Also from the University of Birmingham and part of this research team, Christian Pfrang has carried out multiple neutron reflectometry experiments at ISIS to investigate the effect of cooking emissions on indoor air quality, winning the 2025 ISIS societal impact award for this work.
Working with Allen Haddrell from the University of Bristol, the team has developed a sample environment that uses an electric field to levitate tiny, charged droplets so that the structure of surfactants inside them can be studied.
They initially tried using this setup at Diamond Light Source, but the X-rays neutralised the droplets causing them to sink. Thanks to the neutron not having a charge, this does not happen during their experiments at ISIS. Neutron experiments also give them the ability to selectively deuterate their system to focus their studies on the surfactant components of interest.
In this experiment, they are working with Leide Cavalcanti to use small angle neutron scattering on Zoom to look, for the first time, at how biologically relevant lipids organise themselves in tiny droplets. They will then expand their study to lipids with the same structures as those found in cooking emissions.
This work will build on their results from experiments using acoustic levitation and laser tweezers to produce small droplets, and their reflectometry work. This will give them an insight into how well these other techniques are replicating what is happening in the real world.
The image above shows the droplets levitating in the sample environment setup on Zoom.
