Complex ORAL health products (CORAL): Characterisation, modelling and manufacturing challenges

Toothpastes - and especially specialised pharmaceutical toothpastes, whose major gel component is not water-based - have a surprisingly complex and ill-understood manufacturing process. There is the background fluid, which is already a mixture of a viscous liquid and a polymer; then solid particles are added. These are abrasive and do much of the tooth cleaning; but they also swell during processing, and the system becomes much thicker when they are added. Finally surfactant is added to help the toothpaste to foam in the mouth; and just to complicate matters further, air bubbles also creep in during processing.

In this project, we will systematically address all the stages of toothpaste processing. We will carry out precise small-scale rheological measurements to discover how the particles swell and how they interact once they have swollen: for example, do they absorb parts of the long polymer molecules to form a network, or do partly-absorbed polymers act as "brushes" to push swollen particles apart? We will also measure the overall behaviour of each stage of the system (the background fluid on its own, or with particles, or with bubbles) and create a phase map of system behaviour in terms of its composition. We will use advanced mathematical modelling techniques to derive new equations that can describe the behaviour of a mixture - for example, background fluid and swollen particles - as if it were a single material. Finally, we will use our new constitutive equations in computer simulations to predict the behaviour of the paste in a real processing environment, address the manufacturing challenges such novel formulations entail and propose new strategies to overcome these.

The research needs a team with many different specialist abilities, across experimentation, modelling and simulation, and also needs close ties with industry to ensure we are asking the right questions. GSK is a major collaborator on this project. The project is also supported by Xaar the leader in inkjet printing technology. With the understanding we generate, they hope to make their manufacturing processes both more efficient and more reliable and also develop new formulations to address future customer needs.

The proposed research aims to provide new fundamental insights into complex oral health formulations and to overcome the related high impact manufacturing challenges through a multidisciplinary approach encompassing cutting-edge experimental techniques, mathematical modeling and simulations, spanning from the micro to the macro scale domain. It attempts to connect microscopic and macroscopic behaviour of such formulations, address the process scale-up challenges, the issues of manufacturability in current batch processes, and propose innovative solutions to enable new continuous-flow intensified technology.

The project is fully aligned with the EPSRC future formulations and complex fluids agenda and national developments in the field (e.g. National Formulation Centre); it is very much driven by the increased complexity of novel paste formulations in response to customer needs, the lack of understanding this entails in terms of both fundamental science and processing requirements and the need for a generic framework to design, process and manufacture such complex, soft solid formulations for a variety of applications. The strong engagement of a major healthcare industry (GSK) and a leading inkjet company (Xaar) demonstrate the potential for translation and impact that the research can create with industry through optimization of current formulations and production processes, and development of new formulations and manufacturing technologies, encompassing a move to continuous processing with a more reliable and adaptable process protocol. Continuous processing allows better control, uniform conditions, reduced process time and leads to enhanced energy efficiency, reduced wastage and improved product quality. This will advance the manufacturing capabilities of the partner and other related industries with subsequent benefits to the UK economy. The oral health industry is worth £1 billion in the UK with current growth at 4%; the 3D printing and additive manufacturing technology industry are predicted to have a worldwide size of US$16.8 billion by 2018.

Any improvement in toothpaste manufacture comes with major societal impact, as oral health is critical to overall health, particularly in childhood: dental caries is the number one reason why children aged five to nine are admitted to hospital in England. Toothpastes are the most important and widely used oral care products and many modern ones have pharmaceutical properties such as enamel rebuilding. Our research will help to address manufacturing issues of modern non-aqueous toothpastes and will lead to better control of the product properties which will impact on function and user acceptance.

The project is multidisciplinary with many novel aspects that will advance the science and technologies underpinning the formulation of complex pastes. This knowledge will be passed down to university students through teaching and project work, inspiring the next generation of scientists and engineers. Most notably, the project will result in highly trained and skilled researchers. The substantial sharing of knowledge and techniques between the experimental and modeling streams of the project, and the close interaction with industry will result in the research staff employed in the project acquiring unique skills and knowledge in cutting edge research techniques and scientific concepts in complex fluids and process engineering. This skillset is of extreme importance in manufacturing the future, and will not only enhance future career prospects of the researchers, in either academia or industry, but also benefit the UK's economic growth and competitiveness.