Formulated products in the cosmetic, food, coatings and pharmaceutical industry are typically structured fluids, that is, fluids that are engineered to exhibit desired properties such as texture, spreadability, and stability. This is achieved by carefully designing the product composition, so as to obtain a certain internal structure on the microscale, which results in the desired flow properties and performance on the macroscale. Because of an increasing demand for environmentally friendly, healthier, and better performing formulated products, the formulations industry is increasingly in need of predictive models for rapid, effective, and sustainable screening of new products.
One reason why it remains difficult to provide such predictive models, is the challenge of reproducing the flow conditions during processing of the product, and those during use by the consumer, in laboratory tests. The realistic conditions of flow of a structured fluid during production or use are “extreme” compared to what is accessible with existing experimental methods. As a consequence, the unknown effects of extreme deformation limit the possibility to develop predictive models for sustainable screening of new products. If this understanding becomes available, the cost of development of new products will be reduced, resulting in cost savings for the industry on the one hand, and in the overall increased sustainability of the products.
To deliver this vision, the ExtreFlow project has introduced a radically innovative approach to explore and characterize the regime of extreme deformation of structured fluids and interfaces. After the successful completion of the project it is now possible to reproduce the flow conditions of an industrial plant on a fluidic chip, by combining cutting-edge techniques including acoustofluidics, microfluidics, and high-speed microscopy. This new methodology enables high-precision measurements of macroscopic stresses and evolution of the microstructure under extreme flow conditions that were so far inaccessible with existing methods.
In the course of the project we revealed emerging phenomena of structured interfaces that have no counterpart at lower strain rates, and had so far eluded observation. For instance we discovered dynamic capillary interactions between colloids bound to the surface of an ultrasound-driven bubble, which lead to unique microstructures.
The novel phenomena emerging upon extreme deformation can be exploited to design new processes and for adding new functionality to formulated products. The results of this research program will guide the development of predictive tools that can tackle the time scales of realistic flow conditions for applications to virtual screening of new formulations.
