Design Principles for New Soft Materials

Lead Research Organisation: University of Edinburgh
Department Name: Sch of Physics and Astronomy

Abstract

Soft materials include colloids, polymers, emulsions, foams, surfactant solutions, powders, and liquid crystals. Domestic examples are (respectively) paint, engine oil, mayonnaise, shaving cream, shampoo, talcum powder and the slimy mess that appears when a bar of soap is left in contact with a water. High tech examples of each type are used in drug delivery, health foods, environmental cleanup, electronic displays, and in many other sectors of the economy. Soft materials also include the lubricant that stops our joints scraping together; blood; mucus, and the internal skeleton that controls the mechanics of individual cells.

The intention of this Programme is to use a combination of theoretical and experimental work, alongside large scale computer simulation, to establish scientific design principles that will allow the creation of a new generation of soft materials demanded by 21st Century technologies. This will require significant advances in our scientific understanding of the generic, as well as the specific, connections between how a material is made and what its final properties are. As soft materials become more complex and sophisticated, they will increasingly involve microstructured and composite architectures created from components that may be living, synthetic, or a combination of the two. The design principles we seek will ultimately allow scientists to start from a specification of the interactions between these components, and then create new materials by intentional design, rather than simply trying out various ideas and hoping that one of them works.

There could be great rewards from being able to do this. Even in long-established industries (such as the food industry, home cleaning, personal care products, paints etc.) products made of soft materials are continually being updated or replaced. This is often in order to make them healthier, safer, or more environmentally friendly to produce. Currently, however, the process of developing new soft materials, or improving existing ones, usually involves a large element of trial and error. A set of design principles, based on secure fundamental science, could speed up that process. This would reduce costs, increase competitiveness, and improve the well-being of consumers.

The benefits would be even greater in new and emerging industries such as renewable energy. Soft composite materials have many potential applications for use in high-energy low-weight batteries; low cost solar cells; hydrogen fuel cells; and possibly biofuels. However the design requirements for these applications are demanding, and often involve quite complex microstructures with specific functionality. The same applies in other emerging areas, such as industrial biotechnology and tissue engineering, where soft materials are used to create specific environments in which enzymes, cells or other live components can be used to perform particular tasks. As well as shortening lead-times and costs, by establishing the general principles needed to put new design ideas into practice, we hope to allow innovative soft-matter products to be created that otherwise might never come to market at all.

Planned Impact

The research planned in this Programme addresses areas where improved scientific understanding can guide the design of new soft materials of high functionality. There is broad relevance not only to academic beneficiaries (as detailed separately above) but also to a range of industrial sectors such as food, personal care, functional ceramics, pharmaceuticals, environmental remediation, display technology, catalysis, energy storage, industrial biotechnology, agrochemicals, and renewable energy. Several of these sectors feature prominently in Research Council priority initiatives such as those in Manufacturing the Future, Energy, and Healthcare Technology.

The potential impact of successfully delivering this Programme is substantial. For example, in foods and personal care products it can take five or six years to develop a new product line. Even in these relatively mature technologies, evolving market demands, alongside changing environmental and health regulations can require product reformulation at relatively short notice. All too often, substitution of even a single ingredient with another of apparently similar properties causes the whole formulation to fail, with expensive consequences. These might be avoidable, if the formulation of soft matter products were more firmly grounded in scientifically secure design principles, of the type that we hope to establish with this Programme.

These avenues will be pursued with our Project Partners: four international companies with strong UK operations that directly involve the manufacture and processing of soft materials (Unilever, Mars Chocolate, Syngenta, Johnson Matthey).

Among emerging technologies, the potential gains are even greater. The ability to rationally design new soft materials could not only shorten lead times and costs but allow products to be created that otherwise might never come to market at all. Areas of the economy that could benefit include functional ceramics; (bio-)catalysis; environmental cleanup; and industrial biotechnology. In several of these sectors (as well as in pharmaceuticals and foods) there are exciting possibilities for creating new materials in which some of the components are biologically active (enzymes) or indeed alive (bacteria, tissues). Examples include cell scaffolds for tissue engineering; electrodes for microbial fuel cells; and food gels to deliver specific health benefits. Some such materials already exist, but most have been designed by trial and error.

Another large opportunity for impact is in energy materials (batteries, fuel cells, photovoltaics) where low cost, self-assembled structures for electrodes, light-harvesting photon collectors and other components are now urgently needed. Some of the most promising conceptual avenues towards the complex and specific microstructures required involve soft matter -- either directly, or as precursors or templates for the final product. A step change in our science-based capability to design and develop such materials is now needed, if the challenges of low-cost renewable energy storage and generation are to be met.

Publications

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Allen RJ (2019) Bacterial growth: a statistical physicist's guide. in Reports on progress in physics. Physical Society (Great Britain)

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Arlt J (2018) Painting with light-powered bacteria. in Nature communications

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Arnaouteli S (2016) Just in case it rains: building a hydrophobic biofilm the Bacillus subtilis way in Current Opinion in Microbiology

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Ballesta P (2013) Slip of gels in colloid-polymer mixtures under shear in Soft Matter

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Becker NB (2012) Non-stationary forward flux sampling. in The Journal of chemical physics

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Blanco E (2019) Conching chocolate is a prototypical transition from frictionally jammed solid to flowable suspension with maximal solid content. in Proceedings of the National Academy of Sciences of the United States of America

 
Description This programme employed a combination of theoretical and experimental work, alongside large scale computer simulation, to establish scientific design principles that will allow the creation of a new generation of soft materials. We have advanced our scientific understanding of the generic, as well as the specific, connections between how a material is made and what its final properties are. We have also significantly expanded our understanding of the impacts of the addition of living components to new materials and formulations.

Highly cited and influential works examine the behaviour of "active particles", comparing the behaviour of motile bacteria with that of synthetic motile particles. This allows understanding and control of the macroscopic structures formed by these particles, with consequences for the design of "active materials" - materials that can convert chemical energy into work. Our work also yielded insights into how cells move in three dimensions, with implications for tumour cell migration.

We have further provided fundamental breakthrough insight into the process of shear thickening, where a sample increases in viscosity with an increase in shear rate, transitioning from fluid-like to solid-like. Such suspensions occur widely in applications, from ceramics and bullet-proof armour, through cement and even chocolate. Shear thickening fluids have impact on industrial processes, causing fouling in pipes or blockages of spraying equipment. We have settled a long-running dispute regarding the physical processes that give rise to shear thickening.

We have additionally examined the self-assembly of biomolecules into higher-order structures. This has wide-ranging implications for the study of, for e.g., the inappropriate self-assembly of proteins into filamentous aggregates implicated in Alzheimer's Disease. It also provides insight into the macroscopic 3D architectures assembled by bacteria to form bacterial biofilms. Biofilms are ubiquitous communities of microbes that occupy surfaces or environmental niches, where they encase themselves in a polymeric matrix that protects them from physical and chemical insult including effective treatment with antimicrobials. Biofilms have both beneficial and detrimental impacts on our day-to-day lives, engendering an estimated global industrial impact of ~$5 trillion per annum.
Exploitation Route The formulation market is worth approximately ~£180Bn per annum to the UK, and underpins products in many sectors in the economy, including food and drink, home and personal care, paints and coatings, oil and gas, and pharmaceuticals. Our underpinning research into the soft matter physics of multi-component and multi-phase products, including those comprising living components, has uncovered design principles that enable the development of new formulations, or the reformulation of existing products to meet modern specifications. We have worked closely with a range of small, medium and large enterprises to translate this fundamental research into product development and improvement.
Sectors Agriculture, Food and Drink,Chemicals,Healthcare

 
Description As part of this award, we established the "Edinburgh Complex Fluids Partnership", to advance and innovate complex fluid design and processes through scientific excellence. We translate our understanding of the fundamental physics that governs how components (such as colloids, polymers, liquid crystals etc.) interact with one another in complex fluids, to advance industrial formulations. By applying the design principles of soft matter physics to formulations, ECFP is able to help companies understand their formulations and guide them towards solutions to the challenges they face. Furthermore, a more complete understanding of the generic principles underlying formulation behaviour can lead to innovation, e.g. through new process methods or reduction in the number of ingredients. The themes of Formulation Science, Microorganisms Interacting with Complex Structures, Advanced Soft Materials and Instrument Development have all emerged as areas of strength where we use our expertise to support industry. ECFP endeavours to improve product performance, the consumer experience and help companies switch to more sustainable resources and more efficient processes. ECFP has worked with large multinational and small to medium sized companies in many sectors, including Personal Care, Food, Agrochemicals, Pharmaceuticals, Veterinary, Paints and Coatings, and the Chemical Industry. ECFP researchers undertake contract, consultancy, and collaborative research.
First Year Of Impact 2012
Sector Agriculture, Food and Drink,Chemicals,Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology
Impact Types Economic

 
Title Differential Dynamic Microscopy 
Description A high-throughput technique for characterising the motility of spermatozoa using differential dynamic microscopy. A movie with large field of view records thousands of cells at once and yields averaged measurements of the mean and standard deviation of the swimming speed, head oscillation amplitude and frequency, and the fraction of motile spermatozoa. The ease and rapidity of our method has been desmonstrated by performing on-farm characterisation of bull spermatozoa motility, and the technique validated by comparing laboratory measurements with tracking. 
Type Of Material Physiological assessment or outcome measure 
Year Produced 2019 
Provided To Others? Yes  
Impact Establishment of the company Dyneval, providing an automated, portable and easy-to-use instrument for characterisation of sperm samples on-site. 
 
Title A Phenomenological Description of BslA Assemblies Across Multiple Length Scales 
Description Intrinsically interfacially active proteins have garnered considerable interest recently due to their potential use in a range of materials applications. Notably, the fungal hydrophobins are known to form robust and well organized surface layers with high mechanical strength. Recently it was shown that the bacterial biofilm protein BslA also forms highly elastic surface layers at interfaces. Here we describe several self-assembled structures formed by BslA, both at interfaces and in bulk solution, over a range of length scales spanning from nanometers to millimeters. First, we observe transiently stable and highly elongated air bubbles formed in agitated BslA samples. We study their behavior in a range of solution conditions and hypothesize that their dissipation is a consequence of the slow adsorption kinetics of BslA to an air/water interface. Second, we describe elongated tubules formed by BslA interfacial films when shear stresses are applied in both a Langmuir trough and rheometer. These structures bear a striking resemblance, although much larger in scale, to the elongated air bubbles formed during agitation. Taken together, this knowledge will better inform the conditions and applications of how BslA can be utilized in the stabilization of multiphase materials. 
Type Of Material Database/Collection of data 
Year Produced 2016 
Provided To Others? Yes  
 
Title Conching chocolate is a prototypical transition from frictionally jammed solid to flowable suspension with maximal solid content 
Description The mixing of a powder of 10-50┬Ám primary particles into a liquid to form a dispersion with the highest possible solid content is a common industrial operation. Building on recent advances in the rheology of such 'granular dispersions', we study a paradigmatic example of such powder incorporation: the conching of chocolate, in which a homogeneous, flowing suspension is prepared from an inhomogeneous mixture of particulates, triglyceride oil and dispersants. Studying the rheology of a simplified formulation, we find that the input of mechanical energy and staged addition of surfactants combine to effect a considerable shift in the jamming volume fraction of the system, thus increasing the maximum flowable solid content. We discuss the possible microscopic origins of this shift, and suggest that chocolate conching exemplifies a ubiquitous class of powder-liquid mixing. 
Type Of Material Database/Collection of data 
Year Produced 2019 
Provided To Others? Yes  
 
Title Interfacial rheology of sterically stabilized colloids at liquid interfaces and its effect on the stability of Pickering emulsions 
Description Particle-laden interfaces can be used to stabilize a variety of high-interface systems, from foams over emulsions to polymer blends. The relation between the particle interactions, the structure and rheology of the interface, and the stability of the system remains unclear. In the present work, we experimentally investigate how micron-sized, near-hard-sphere-like particles affect the mechanical properties of liquid interfaces. In particular, by comparing dried and undried samples, we investigate the effect of aggregation state on the properties of the particle-laden liquid interface and its relation to the stability of the corresponding Pickering emulsions. Partially aggregated suspensions give rise to a soft-solid-like response under shear, whereas for stable PMMA particulate layers a liquid-like behaviour is observed. For interfacial creep-recovery measurements, we present an empirical method to correct for the combined effect of the subphase drag and the compliance of the double-wall ring geometry, which makes a significant contribution to the apparent elasticity of weak interfaces. We further demonstrate that both undried and dried PMMA particles can stabilize emulsions for months, dispelling the notion that particle aggregation, in bulk or at the interface, is required to create stable Pickering emulsions. Our results indicate that shear rheology is a sensitive probe of colloidal interactions, but is not necessarily a predictor of the stability of interfaces, e.g.~in quiescent Pickering emulsions, as in the latter the response to dilatational deformations can be of prime importance. 
Type Of Material Database/Collection of data 
Year Produced 2017 
Provided To Others? Yes  
 
Title Painting with bacteria: Smart templated self assembly using motile bacteria (Raw data) 
Description This is the complete dataset. The processed data is available on DataShare. 
Type Of Material Database/Collection of data 
Year Produced 2018 
Provided To Others? Yes  
 
Title Particle-size effects in the formation of bicontinuous Pickering emulsions 
Description We demonstrate that the formation of bicontinuous emulsions stabilized by interfacial particles (bijels) is more robust when nanoparticles rather than microparticles are used. Emulsification via spinodal demixing in the presence of nearly neutrally wetting particles is induced by rapid heating. Using confocal microscopy, we show that nanospheres allow successful bijel formation at heating rates two orders of magnitude slower than is possible with microspheres. In order to explain our results, we introduce the concept of mechanical leeway i.e. nanoparticles benefit from a smaller driving force towards disruptive curvature. Finally, we suggest that leeway mechanisms may benefit any formulation in which challenges arise due to tight restrictions on a pivotal parameter, but where the restrictions can be relaxed by rationally changing the value of a more accessible parameter. 
Type Of Material Database/Collection of data 
Year Produced 2015 
Provided To Others? Yes  
 
Title Quantitative morphological characterization of bicontinuous Pickering emulsions via interfacial curvatures 
Description Bicontinuous Pickering emulsions (bijels) are a physically interesting class of soft materials with many potential applications including catalysis, microfluidics and tissue engineering. They are created by arresting the spinodal decomposition of a partially-miscible liquid with a (jammed) layer of interfacial colloids. Porosity L (average interfacial separation) of the bijel is controlled by varying the radius (r) and volume fraction (f) of the colloids (L ~ r/f). However, to optimize the bijel structure with respect to other parameters, e.g. quench rate, characterizing by L alone is insufficient. Hence, we have used confocal microscopy and X-ray CT to characterize a range of bijels in terms of local and area-averaged interfacial curvatures; we further demonstrate that bijels are bicontinuous using an image-analysis technique known as `region growing'. In addition, the curvatures of bijels have been monitored as a function of time, which has revealed an intriguing evolution up to 60 minutes after bijel formation, contrary to previous understanding. 
Type Of Material Database/Collection of data 
Year Produced 2016 
Provided To Others? Yes  
 
Title Soft Bijel X-ray CT test 
Description X-ray CT image stacks, can be opened with ImageJ. 
Type Of Material Database/Collection of data 
Year Produced 2018 
Provided To Others? Yes  
 
Title SYNTHETIC MULTIPHASE SYSTEMS 
Description A synthetic multiphase product comprising BsIA is presented. Methods of producing a synthetic multiphase product comprising BsIA, and applications of BsIA in synthetic multiphase products are also presented. 
IP Reference WO2016027078 
Protection Patent application published
Year Protection Granted 2016
Licensed Commercial In Confidence
Impact N/A
 
Title SYNTHETIC MULTIPHASE SYSTEMS 
Description A synthetic multiphase product comprising BsIA is presented. Methods of producing a synthetic multiphase product comprising BsIA, and applications of BsIA in synthetic multiphase products are also presented. 
IP Reference EP3182836 
Protection Patent granted
Year Protection Granted 2017
Licensed Commercial In Confidence
Impact In progress
 
Title Synthetic Multiphase Systems 
Description A synthetic multiphase product comprising BsIA is presented. Methods of producing a synthetic multiphase product comprising BsIA, and applications of BsIA in synthetic multiphase products are also presented. 
IP Reference US2017267730 
Protection Patent granted
Year Protection Granted 2017
Licensed Commercial In Confidence
Impact In progress
 
Title Synthetic Multiphase Systems 
Description A synthetic multiphase product including an isolated biofilm surface layer protein A (BsIA), wherein the BsIA has the amino acid sequence set forth in SEQ ID NO: 28 or a variant thereof that is at least 80% identical to SEQ ID NO: 28. 
IP Reference US2020207813 
Protection Patent granted
Year Protection Granted 2020
Licensed Commercial In Confidence
Impact In progress
 
Description Complex Fluids demonstrations at Dunbar Scifest 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact ECFP ran an interactive workshop at the Dunbar SciFest. Around 400 people visited the Soft Matter in Action stand and played with demonstrations highlighting the research from the group, including our ever popular vat of cornstarch in water as a model non-Newtonian fluid. Visitors also made edible gel capsules, investigated viscous coiling, and met our collection of fluffy microbes.
Year(s) Of Engagement Activity 2015
 
Description ECFP at Eat Drink Discover Scotland 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact We joined the Scottish Food and Drink Federation to share the excitement of food science with school pupils who attend Eat Drink Discover Scotland. We used hands on experiments to highlight our research and explain how complex fluids are important in foods . Pupils played with an extremely non newtonian mixture of corn starch and water. They also learnt how to encapsulate liquids into edible spheres.
Year(s) Of Engagement Activity 2014
 
Description Flow and stability of complex formulations workshop 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Industry/Business
Results and Impact We jointly hosted a workshop on the flow and stability of complex formulations. This second workshop of the Scottish Formulation Network will bring together academic and industry participants to discuss how structure and interactions in multicomponent mixtures control stability and flow properties.
Year(s) Of Engagement Activity 2016
 
Description Informulation2: Design principles for future formulations 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact We hosted Informulation2015, an event that brings together academic and industry participants to encourage collaboration for future projects. We explored how function, structure, interactions and dynamics in complex mixtures can lead to informed design for future formulations.
Year(s) Of Engagement Activity 2015
 
Description Interactive Formulation Science Workshop 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Industry/Business
Results and Impact Presented an Interactive Formulation Science workshop at the Natural Product Biotechnology conference in Inverness this November to illustrate key concepts through live experimental demonstrations and promote networking. This was a significant new conference for people with interests in high value natural products, their application in drug discovery, foods and nutraceuticals, personal care products and cosmeceuticals, and other biotech applications.
Year(s) Of Engagement Activity 2014
 
Description International Year of Light 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact Members of the consortium joined eminent scientists and speakers at the Royal Society of Edinburgh to celebrate the launch of the International Year of Light. They showcased modern light microscopy techniques used to image swimmers at the microscale, such as swimming bacteria and self-propelled synthetic colloids. They showed how light can be used to control their swimming abilities and create spatial patterns at the microscopic level.
Year(s) Of Engagement Activity 2015
 
Description Soft Matter in Action at Doors Open Day 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact Researchers introduced over 300 people to the delights of soft matter as part of Doors Open Day. This city-wide event allows members of the public to see behind the scenes of building across Edinburgh. At the JCMB, visitors were able to see the rheo-imaging set up in action, visit the food science preparation laboratory, and see examples of active soft matter in the form of bacteria and Janus particles.
Year(s) Of Engagement Activity 2014