Researchers from the University of Surrey in collaboration with the Université Claude Bernard, Lyon published their research today in the journal Physical Review Letters, describing a physical mechanism that separates particles according to their size during the drying of wet coatings.
The previously unknown mechanism in how particles dry could help in improving the performance of a wide variety of goods we use everyday, from paints to medicine and even sunscreens. Using computer simulations, researchers were able to show through experiments that when coatings of different sized particles such as paint dry, the coatings spontaneously form two layers.
To put it simply, the researchers found that as a coating of paint dries, the smaller particles team up and push the larger particles to the bottom. This is important in a number of applications, like sunscreen for example. A lotion could be developed that has a surface level of small sun-blocking particles while the bottom layer could be large sticky particles that adhere to the skin.
The team discovered this mechanism can be used to control the properties of both layers independently. This in itself could enhance the performance of coatings across a variety of industries, reports the Irish Examiner.
“When coatings such as paint, ink or even outer layers on tablets are made, they work by spreading a liquid containing solid particles onto a surface, and allowing the liquid to evaporate. This is nothing new, but what is exciting is that we’ve shown that during evaporation, the small particles push away the larger ones, remaining at the top surface whilst the larger are pushed to the bottom. This happens naturally,” says lead author Dr. Andrea Fortini, of the University of Surrey.
According to Phys.Org, the team is continuing with additional research to understand how to control the width of the layers by varying the type and size of the particles in the coating. They are also going to look into industrial applications for this mechanism.
This fascinating study, “Focus: Particles Stratify by Size in Thin Films,” was published in the online journal Physical Review Letters on March 18, 2016.
