Consumer product separation over time
Consumer product separation over time

Who would imagine that to make improvements to personal care and household products, scientists would look to the fields of medicine and geography? Yet that’s exactly what chemists at the University have done – with great success.

Dr Melanie Britton, a Senior Lecturer in Chemistry, and postgraduate student Emma Thompson have combined basic chemistry with magnetic resonance imaging (MRI), which is usually used to scan the body, and an index for measuring spatial correlation called Moran’s I, commonly used by geographers to map terrain, in order to develop greater stability and increase the shelf-life of products from shampoo to fabric conditioner.

They have been able not only to detect the separation of mixtures that make up the products before they’re discernible to the naked eye; they’ve also been able to establish the degree to which they have separated.

Melanie and Emma’s research is detailed in a paper entitled ‘Characterisation of heterogeneity and special autocorrelation in phase separating mixtures using Moran’s I’, written with industrial partners from Procter & Gamble, which funded the three-year project. Published in the Journal of Colloid and Interface Science, it recently won the College of Engineering and Physical Science Paper of the Month award.

‘There is a drive by manufacturers to make better consumer products such as detergents and shampoos by enhancing the properties of those products,’ explains Melanie. ‘For example, detergents are made up of different components, which over time might separate into two or more layers, leading a consumer to think it no longer worked. So, the key is product stability – having the same appearance and properties as when it was manufactured – to give it a viable shelf-life.’

To improve the look and behaviour of complex material, you need to understand the fundamental science: how molecules that make up that material influence the properties. To do so, you need good analytical techniques to probe the system, and you also need good tools by which to study it.

‘We use a technique much more commonly used in hospitals – MRI, a non-invasive technique that can probe optically opaque objects to provide a wealth of chemical and physical information, producing 1D profiles or 2D and 3D images. So, what makes MRI good for looking at the brain makes it really good for looking at consumer products. In fact, this is my passion in science: using MRI, something that’s more commonly used in the medical world, to understand chemical processes and reactions.’

The technique allows scientists to penetrate the material and detect product instability long before it can be seen visually.

‘But what we’ve done is even better than that,’ says Melanie. ‘Let’s imagine you have a material that doesn’t look quite the way it should do. How can you then relate that to its components and how can you design something better? Quantifying this change is really challenging: is the product completely “off”, or just a little bit? So, we’ve done something in addition to using MRI – something that’s never been done before – and that’s to take a technique for analysing images usually used by geographers, called Moran’s I, to quantify the structure of the phase separation of a product. Whether you’ve got two layers of material, one above the other, or you’ve got streaks, Moran’s I allows us to look at those images and show they are different.’

The researchers hadn’t intended to use Moran’s I, she explains. ‘We always planned to bring in MRI, but we were frustrated that we were getting these beautiful images but couldn’t distinguish one from the other in a simple way. Using description wasn’t doing it; we realised we needed a methodology to correlate the two – and that’s when Emma discovered Moran’s I.’

Melanie hopes their work has the potential to bring about improvements in personal care and household products.

‘There are certain areas of science that tend to hit the headlines, such as those associated with the origins of the universe, but what makes a much bigger impact on us is personal care and home products – developing products that are long-lasting and affordable and can be used by people all over the world.’