'Watching paint dry' is a metaphor for a boring and pointless activity. In reality, the drying of liquids is a complex process and the imperturbable appearance to the eye can hide a wealth of dynamics occurring inside the liquid. The effect of these internal processes is to change the distribution of materials in the deposit left after drying. We are all familiar with the coffee-ring effect, where split coffee dries to form a ring of solids at the edge of the spill - of little use if you are trying to coat a surface uniformly. This project is all about the drying of droplets, either in air or on a surface; one isolated droplet, two droplets merging or many droplets in a spray. We seek to understand how drops dry and how to control where the particles or molecules in the drop end up after the drop evaporates. When do you get a solid particle or a hollow particle? A round one or a spiky one? A uniform particle or one with shells? Or on a surface: a coffee-ring or a pancake? A uniform deposit, a layered one or a bull's eye? Are particles crystalline or amorphous, are different components mixed or separated? There are a myriad of possibilities for controlling the microstructure and properties of the final particle or film. Drying is complicated for three main reasons. First, many transport processes (evaporation, heat flow, diffusion, convection) occur simultaneously and are strongly coupled. For example, in a small droplet of alcohol and water evaporating on a surface, the liquid inside the drop will flow around in a doughnut pattern tens of times each second. Second, the conditions in a drying droplet are often far from equilibrium. For example, a small water droplet in air or on a smooth clean surface can be cooled to -35 degrees C without freezing. So to understand drying one needs to understand the properties of fluids far from equilibrium. It is generally not possible to predict the final outcome of drying from the properties of simple solutions near equilibrium. Third, drops do not dry in isolation. They may merge or bounce, coalesce or chase each other across a surface. The evaporation of one droplet affects its neighbours. Moving droplets change the flow of air around other droplets, coupling the motion of droplets. Why does anyone care, beyond the intellectual fascination with the bizarre outcomes of droplet drying? Drying of droplets turns out to be a rather important process in practical applications: spray painting, graphics printing, inkjet manufacturing, crop spraying, coating of seeds or tablets, spray cooling, spray drying (widely used in food, pharmaceutical and personal care products), drug inhalers and disinfection, to give a few examples. The physics and chemistry underlying all these applications is the same, but if manifests itself in different ways and the desired outcome varies between applications. The first challenge addressed by this project is one of measurement: how do you work out what is going on in a droplet that is less than a tenth of a millimetre across and may dry in less than a second? We have already developed sophisticated measurement tools but will need to extend these further. Another challenge is one of modelling: to understand the drying process we need a theoretical framework and computer models to explain - and predict - experimental observations. We will begin looking at the fundamental processes occurring in single drops in air and on a surface and then explore what happens when drops interact or coalesce. This fundamental understanding will be fed into improved models of arrays, clouds or sprays of droplets that are encountered in most practical applications (such as spray coating, spray drying, inhalers or inkjet manufacturing). We will use an Industry Club to engage with companies from a range of different sectors. This Club will provide a forum for sharing problems, ideas and solutions and for disseminating the knowledge generated in the project.

Our Hub research is driven by the societal need to produce medicines and materials for modern living through novel manufacturing processes. The enormous value of the industries manufacturing these high value products is estimated to generate £50 billion p.a. in the UK economy. To ensure international competitiveness for this huge UK industry we must urgently create new approaches for the rapid design of these systems, controlling how molecules self-assemble into small crystals, in order to best formulate and deliver these for patient and customer. We must also develop the engineering tools, process operations and control methods to manufacture these products in a resource-efficient way, while delivering the highest quality materials. Changing the way in which these materials are made, from what is called "batch" crystallisation (using large volume tanks) to "continuous" crystallisation (a more dynamic, "flowing" process), gives many advantages, including smaller facilities, more efficient use of expensive ingredients such as solvents, reducing energy requirements, capital investment, working capital, minimising risk and variation and, crucially, improving control over the quality and performance of the particles making them more suitable for formulation into final products. The vision is to quickly and reliably design a process to manufacture a given material into the ideal particle using an efficient continuous process, and ensure its effective delivery to the consumer. This will bring precision medicines and other highly customisable projects to market more quickly. An exemplar is the hubs exciting innovation partnership with Cancer Research UK. Our research will develop robust design procedures for rapid development of new particulate products and innovative processes, integrate crystallisation and formulation to eliminate processing steps and develop reconfiguration strategies for flexible production. This will accelerate innovation towards redistributed manufacturing, more personalisation of products, and manufacturing closer to the patient/customer. We will develop a modular MicroFactory for integrated particle engineering, coupled with a fully integrated, computer-modelling approach to guide the design of processes and materials at molecule, particle and formulation levels. This will help optimise what we call the patient-centric supply chain and provide customisable products. We will make greater use of targeted experimental design, prediction and advanced computer simulation of new formulated materials, to control and optimise the processes to manufacture them. Our talented team of scientists will use the outstanding capabilities in the award winning £34m CMAC National Facility at Strathclyde and across our 6 leading university spokes (Bath, Cambridge, Imperial, Leeds, Loughborough, Sheffield). This builds on existing foundations independently recognised by global industry as 'exemplary collaboration between industry, academia and government which represents the future of pharmaceutical manufacturing and supply chain R&D framework'. Our vision will be translated from research into industry through partnership and co-investment of £31m. This includes 10 of world's largest pharmaceutical companies (eg AstraZeneca, GSK), chemicals and food companies (Syngenta, Croda, Mars) and 19 key technology companies (Siemens, 15 SMEs) Together, with innovation spokes eg Catapult (CPI) we aim to provide the UK with the most advanced, integrated capabilities to deliver continuous manufacture, leading to better materials, better value, more sustainable and flexible processes and better health and well-being for the people of the UK and worldwide. CMAC will create future competitive advantage for the UK in medicines manufacturing and chemicals sector and is strongly supported by industry / government bodies, positioning the UK as the investment location choice for future investments in research and manufacturing.