Researchers at the University of Surrey, England, and Université Claude Bernard, France, have been investigating how liquid formulations dry on a nano level, and they say their findings could have implications for a wide range of liquid-based products, including many in the beauty industry.
The research, which has been published in the journal Physical Review Letters, describes the discovery of a new mechanism that separates particles according to their size during the drying of wet coatings.
Formulation of multi action products
The researchers used computer simulation and material experiments to illustrate how coatings of liquid-based formulation with different particles size dry to form two different layers.
The scientists point out that this discovery could be used to formulate products with dual actions, and in skin care products, this could point to formulations with barrier protection, alongside other skin care properties.
"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,” said Dr Andrea Fortini, of the University of Surrey and lead author.
“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 bottom. This happens naturally."
Dr. Fortini also makes specific notes about sunscreens in his research, believing that the findings could help optimize formulations because of the “self-layering” that has been observed.
“In a sunscreen, most of the sunlight-blocking particles could be designed to push their way to the top, leaving particles that can adhere to the skin near the bottom of the coating,” said Dr. Fortini.
“Typically the particles used in coatings have sizes that are 1000 times smaller than the width of a human hair so engineering these coatings takes place at a microscopic level. "
The research project is currently ongoing, with the team stating that they are now focusing on how to control the width of the layers by changing the type and amount of small particles in the coating and exploring their use in other products.