Formulation scientists are behind many of the food, personal care, and pharmacological products that enrich our everyday lives. On 18th March 2019, the FSTG group held Formative Formulation, its inaugural event aimed at putting a spotlight on the work of early career formulation scientists in academia and industry. It was a 1-day scientific meeting, welcoming attendees and contributions from all areas of formulation science. 

• 48 early career formulation scientists gathered to present their research work, share their career trajectory to date, and to network with peers.
  
• We had 13 oral presentations and 18 posters, with contributions covering: new oleogels for food formulation; formulation at Unilever and MIF; linking 3D printing performance to formulation and rheology; using rheological measurement to characterise silicon glue formulation; crystal engineering; milling and shearing of formulated particles and powders; formulating photonic pigments via self-assembly.
• Attendees represented both industry (Unilever, Johnson Matthey, Croda, Domino, CPI, Bristol Laboratories, FormFormForm, RB, Quadralene, AkzoNobel, National Physical Laboratory, Lucideon, Qinetiq) and academia (Universities of Cambridge, Leeds, Nottingham, Birmingham, Sheffield, Edinburgh, Liverpool, Strathclyde, UCL, Greenwich)

Summary of talks:
Vincenzo di Bari spoke about the ongoing challenge of reducing trans fat content in food formulations, in particular to meet FDA requirements. He described his research work into rice brax wax, a promising plant wax with compatible structural and rheological properties.

Maria Jiminez-Solomon spoke about the philosophy of Unilever, describing their aims to achieve sustainability in all of their formulations using new technologies such as the automation and computation facilities at the Materials Innovation Factory.

Emily Summerton spoke the overarching formulation strategy at Johnson Matthey, with particular focus on characterisation techniques and the difficulties associated with measuring particle size distributions.

Esther Garcia-Tunon described her research work into 3D printing of yield stress fluids. In particular, she discussed the process of structural breakdown in the nozzle and restructuring after printing. It remains an ongoing challenge to use conventional rheological and surface tension measurements to predict 3D printability.

Vivian Christogianni discussed the role of rheological measurements in characterising formulations of Sugru, a highly filled silicon adhesive composite. Rheology measurements reveal material signatures of aging, both in the packet and during product curing, enabling improved quantification, and therefore design, of the mechanical properties of the product.

Elena Simone spoke about various aspects of crystal engineering, including a platelet-diamond shape transition, crystallised particle stabilisation, solubility and wettability, as well as the challenges of predicting particle morphology.

LiGe Wang discussed the use of numerical modelling to turn the ‘black box’ of particle milling into what he described as a ‘grey box’. Combining discrete element simulations with population balance modelling elucidates some of the breakage mechanisms and dynamics within particle mills, a common feature of formulation.

Richard Parker gave a fascinating talk about structurally coloured pigments built from self-assembly of bottlebrush block copolymers. These pigments offer brilliant colours that may in future be integrated into coatings and paints.

Ranga Radhakrishnan spoke about the rheological properties of concentrated suspensions. In particular he used information about particle-particle contact forces to try to verify a recent theory about the variation of viscosity with flow rate. It was shown that the scaling of the particle contact number close to the jamming point is not consistent with the model assumptions.

Kasia Majerczak gave an interesting talk about the role of small additive molecules in complex mixture, with particular relation to PVA films. She discussed the formation of amorphous and crystalline regions, as well as the role of surfactant on film morphology, diffusion coefficients and kinetics.

Chester Aguirre began his talk with an overview of CPI and its role within the UK’s Catapult network, before going on to discuss formulation from a process engineering point of view. He presented various powder processing projcets that he has been involved in at CPI, such as investigating liquid injection during powder mixing, and the success of techniques for promoting back mixing.

Hikaru Jolliffe presented his experimental and computational research into the prediction of multicomponent tablet properties based on the features of the pure components. His results point to a mixing rule that can give quantitative predictions of the outcomes of tablet formulation.

Remya Norris concluded the days talks by giving an overview of the various coatings formulated by AkzoNobel, including a summary of the generic formulation routes associated with industries such as marine and civil engineering.

Themes:
Formulation science, rheology, processing, characterisation, colloids, encapsulation, powders, analytical chemistry, chemical engineering, gelation, crystallisation, emulsification, detergents, cosmetics, paints, pharmaceuticals, food, chemicals, manufacturing consumer products and more.

Programme:
pdf version

Invited Speakers:
A crystal engineering approach for the design of complex food and pharmaceutical colloidal structures
Dr Elena Simone, University of Leeds

A formulation journey at Unilever
Dr Maria Jimenez-Solomon, Unilever

Understanding the role of processing and formulation on rice bran wax oleogels microstructure
Dr Vincenzo di Bari, University of Nottingham

Molecular migration in poly(vinyl alcohol) mixtures
Katarzyna Majerczak, University of Birmingham

Rheology and characterisation of Sugru mouldable glues (RTV-1 silicone elastomer putty)
Dr Vivian Christogianni, FormFormForm

Powder Processing and the Catapult Network
Chester Aguirre, Centre for Process Innovation

Organising Committee:
Dr Chris Ness, University of Cambridge (contact: This email address is being protected from spambots. You need JavaScript enabled to view it.)
Remya Norris, AkzoNobel Marine Coating
Dr Nathan Flood, HSE

Invited Speaker Abstracts:
A crystal engineering approach for the design of complex food and pharmaceutical colloidal structures
Dr Elena Simone, University of Leeds
Finely mixed multiphase systems made up of two or more immiscible entities, such as foams or emulsions, are commonly used for many pharmaceutical and food applications. For example, topical medications can be formulated in the form of oil and water emulsions with the active pharmaceutical ingredients dissolved in one of the two phases, or as aerated foams for improved drug penetration and reduced sense of greasiness after application. Countless examples of multiphase systems can also be found in the food sector including ice cream, whipped cream and salad dressings. Emulsions and foams are often thermodynamically unstable and the immiscible phases will tend to separate with time, reducing considerably the shelf life of these products with a clear economical loss and increased generation of waste. Surfactants or solid particles (Pickering effect) can be added to multiphase formulations in order to prevent phase separation and increase product stability. Pickering particles have many advantages over surfactants since:
(1) They provide better stability as a result of stronger interfacial adsorption;
(2) Food grade particles that do not have the side effects often associated with surfactants (e.g., irritancy) can be used;
(3) A wider range of dispersity can be achieved via tuning the particle properties;
(4) Nutraceuticals can be used as solid particles and be incorporated in food or pharmaceutical formulations for increased health benefits for consumers.
To date particles for Pickering stabilization have been selected semi-empirically, considering only basic physical and chemical properties of the desired molecule in relation to the immiscible phases (e.g., wettability, solubility), as well as basic particle attributes such as size and shape. However, most studies do not consider that solid particles are often anisotropic, faceted crystal with a complex surface chemistry that is strongly related to the intermolecular interactions within the crystalline structure. Understanding the relationship between these interactions and the properties of solid particles, particularly the ability to stabilize curved interfaces, is a challenging task. Nevertheless, gaining such understanding would enable a more predictive and systematic engineering of solid crystals for improved Pickering stabilized systems. In this work molecular modelling was used to determine both bulk and surface properties of different crystal structures of a flavonoid molecule, quercetin. The strength and nature of the bulk and crystal surface terminated intermolecular interactions were characterised using an empirical force field calculation run on the Mercury package (Cambridge Crystallographic Data Centre, CCDC). This calculation allows the identification of the polar hydrophilic and apolar hydrophobic interactions at the morphologically important crystal surfaces, hence providing a molecular understanding of how a solid particle will interact with different solvents (e.g., water and oils). Such information can allow designing and tailoring of the morphology of solid crystals that can be used for the kinetic stabilization of food foams and emulsions.

Understanding the role of processing and formulation on rice bran wax oleogels microstructure
Dr Vincenzo di Bari, University of Nottingham
Fats have been used for decades in foods to achieve a range of functional and sensorial properties. However, fats contain high amounts of saturated and trans-unsaturated triglycerides and their consumption is considered a risk factor for the development of cardiovascular diseases. In recent years “oleogels” have emerged as promising alternative to fats. Oleogels are edible lipid colloidal systems where a non-triglyceride gelling component (the ‘oleogelator’) forms a 3-dimensional thermo-reversible network physically trapping the liquid oil phase. Among low molecular weight oleogelators, rice bran wax (RBW) is a promising agent known to form crystalline networks with great ability to entrap oil. The aim of this work was to elucidate the effect of processing and formulation on microstructural, textural and rheological properties of RBW oleogels in sunflower oil.  The minimum RBW gelling concentration was 2% (wt%) for a cooling rate of 0.5°C/min which decreased to 0.5% when cooling at 2°C/min. Firmness, yield stress and oil binding capacity of the oleogels increased with increasing RBW concentration and increasing cooling rate. Microstructure visualisation using temperature controlled polarised light microscopy revealed that the network was always formed by RBW crystals appearing as long needle-like particles, with cooling rate only affecting crystal size: when cooling at 0.5, 5 and 50°C/min the average crystal length was 130, 100 and 50 μm, respectively. These findings suggest that a system made up of many small crystals with a high degree of inter-connectivity is developed when applying fast cooling which results in a higher shear elastic modulus (G’) and ability to bind oil. G’ remained constant up to temperatures close to the onset of melting, suggesting material properties are retained over a large temperature range. The addition of PGPR and Span 60 to RBW oleogels significantly increased and reduced the onset of crystallisation, respectively, and all systems containing surfactants displayed a lower G’ than bulk RBW oleogels. At the microstructural level only Span 60 modified the crystalline particle shape, which became spherulitic-like. This work is the first to study in detail the effect of processing on RBW oleogels and to demonstrate that lipophilic surfactants can be used to tailor their microstructural properties. The combination of these parameters to tailor oleogels microstructure can offer a new exciting route for the design of functional systems for fat replacement.

Molecular migration in poly(vinyl alcohol) mixtures
Katarzyna Majerczak, University of Birmingham
Plasticisers, together with a variety of additives, are extensively used to enhance the properties of industrial formulations. However, with the increasing number of substances in the product, the risk of migration of constituent molecules that results in undesired effects also increases. As multi-component systems exhibit many equilibrium and non-equilibrium characteristics, behaviour of those is often hard to predict. Failure to do so may result in reduced shelf life, consumers’ dissatisfaction and adhesive loss in hygiene products. The present work aims to understand the migrate characteristics of small molecules in formulated products, using poly(vinyl alcohol) (PVA) based thin films as a representative system. Fluorescence recovery after photobleaching (FRAP), fluorescence correlation spectroscopy (FCS), atomic force microscopy (AFM), and dynamic light scattering (DLS), have been used to establish the kinetics of molecules’ movement in formulated product. The objectives of this work are:
• Examination of diffusion kinetics of small molecules in PVA thin films;
• Investigation into surface migration of particular surfactants as a function of humidity;
• Integration of the results obtained from AFM and fluorescence methods to acquire localised migration at real time.
To capture the migration kinetics, a well-studied fluorophore – Rhodamine B – was used to probe local environment. It has been found that the diffusion characteristics of Rhodamine B is dependent on the presence of glycerol (plasticiser) and surfactants (cationic/ anionic/ nonionic). Different migration kinetics were observed in thin films of various PVA/glycerol ratio – it is worth noting that diffusion coefficient of Rhodamine B increases and then decreases with increasing glycerol concentration (Fig. 1). The size of PVA molecule increases with decreasing PVA/glycerol ratio, which results in an enhanced steric effect that is likely responsible for inhibiting the probe molecule from migrating freely. For films with the addition of cationic and anionic surfactant, it is likely that surfactant – fluorophore interactions play a main role, slowing down the overall diffusivity of the Rhodamine B (Fig. 2).

Rheology and characterisation of Sugru mouldable glues (RTV-1 silicone elastomer putty)
Dr Vivian Christogianni, FormFormForm
The invention of Sugru was a happy accident. Sugru is a mouldable glue that bonds to anything, to fix things and mend things. It was invented in 2004 to get a new generation fixing again. Sugru formulas combine the advantages of neutral, room-temperature cure and self-adhesion properties. As the putty cures via reaction with atmospheric water it turns into waterproof and flexible silicone elastomer that is stable within a temperature range of -50 to 180°C. Moulding by hand or with simple tools makes this silicone elastomer highly versatile. It has a wide range of applications in engineering, medical, sport, DIY, electronics and telecommunications. For specific industrial applications, it can be customised - hardness, density, resistivity and adhesive properties can be adjusted according to requirements. Developing new routes to characterisation of these types of highly filled formulations are key to their design as well as their mechanical and physical properties.  For an outsider it is not obvious how rheology is related to all these; from polymer characterisation to working time to adhesion to modulus of the cured material.  Therefore, a brief overview of a typical silicone adhesive putty characterisation with emphasis on rheology will be given. This will be followed by a few rheological case studies related to cure kinetics measurements and “rheological fingerprints”.

Powder Processing and the Catapult Network
Chester Aguirre, Centre for Process Innovation
This presentation will introduce work in the powders area at CPI’s National Formulation Centre, ranging from laundry detergents to pharmaceuticals. This includes the processing technologies available in the facility and the integration of Process Analytical Technology for in-line characterization and process control of formulated powders. It will also discuss CPI’s role in the Catapult Network, together with other centres in the UK.  In addition, Chester will also talk about his chemical engineering background and his role at CPI.