Getting back to nature

Materials World magazine
,
3 Apr 2017

New industrial applications highlight the breadth and depth of innovation that can be found when looking to nature, as Iris Anderson, Chris Holland and Angela Morris explain. 

Natural materials have been used in society for thousands of years. While historically a cornerstone of trade and society, substitution with mass-produced synthetic polymeric materials in the past century has seen their popularity decrease, but the tides may be changing. Researchers and industrialists are finding new ways to use old materials, bringing together millions of years of natural ‘R&D’ to harness the material properties of sustainable and renewable resources.

Natural materials come in many forms, and inspiration for new applications stems not just from using the material as-is, but also understanding how they are formed and what structures are responsible for their properties. Bioinspiration is shared throughout the natural materials community and new research into industrial applications highlights the breadth and depth of innovation that can be found when looking to nature. 

Silk is the world’s oldest commercial fibre. For millennia, the cocoon of the Chinese silkmoth Bombyx mori has been unravelled and fashioned into textiles that have been traded from east to the west forming the Silk Road. As a textile, its properties are lustrous, strong and flexible, and many of today’s synthetic fibres were originally developed to replicate and commercially replace it. However, none have quite managed to match silk’s properties, a challenge that has recently been taken on by those developing synthetic spider silks. 

Spinning silk

Using the mechanically superior spider silk as both inspiration and a molecular template, several global efforts are focused on recreating silk for a diverse range of applications. Companies in the USA, Germany, Sweden and Japan have been tirelessly working on the development of genetically engineered spider silk-like proteins made by microorganisms such as bacteria or yeast, which can be extracted and spun into a fibre. As a result, there have been numerous prototypes unveiled that indicate its burgeoning commercial reality, from the North Face Moon Parka jacket debuted by Spiber, Japan, to the biodegradable Adidas Futurecraft biofabric trainer made from AMsilk’s Biosteel. According to Adidas, the trainer launched in 2017 is 15% lighter than its usual trainer fabrics, designed by editing the proteins of silk during the fermentation process. The companies now believe this will inspire future research into custom-grown silks for trainers and bulletproof vests. 

We may wear a lot more bioengineered silk in the future. In March 2017, USA-based company Bolt Threads, gave 50 people the chance to be the first to own a piece of synthetic spider silk textile by purchasing the first commercial 100% bioengineered silk product – a US$314 tie. The company combined genetically modified yeast, water and sugar, and used yeast fermentation to produce a liquid silk protein. Once the protein is harvested and purified into a powder, it is wet spun into fibres, twisted into yarns for fabric and knitted into the tie.

Whether or not it is possible to fully replicate all of the properties of a natural spider silk fibre remains to be seen, but this is a clear step forward in next-generation fibre production using natural materials. If successful, these threads could be used for a variety of different applications, from high-end fashion and luxury goods to technical fabrics. As technology improves, it may be possible to start harnessing silk's other properties such as its biocompatibility for use in drug delivery and regenerative medicine and superior toughness to make high-performance fibres. 

Pharmaceutical packaging

Beyond textile use, another natural fibre has found a seemingly unusual application in helping deliver vaccines across the world. In 2005, the World Health Organisation (WHO) reported that up to 50% of all vaccines transported globally were ruined due to poor distribution procedures. Today, the problem remains unchanged. What credible and sustainable passive packaging solution can help solve this humanitarian issue? 

According to the WHO, vaccine damage is caused mostly by failings in cold chain logistics and current man-made insulated packaging materials. Polymer-based insulated packaging materials, such as polystyrene (EPS) can struggle to maintain temperature control when exposed to ambient extremes. While EPS manufacturers are making modest improvements in product development with existing materials, the properties of the materials allow only incremental advances toward becoming more sustainable and effective. More radical thinking is required to create an innovative, disruptive solution.

In a bid to create a sustainable and natural alternative, UK-based company, Woolcool, has developed an economic argument to use wool in medical packaging as a replacement for EPS. Wool was first considered as a possible solution because of its crimped nature – when wool fibres are packed together, they form millions of tiny air pockets that trap air to keep warmth in during winter and out in the summer. Wool's advantage over synthetic materials is its breathability and ability to absorb and release moisture from the surrounding air, without compromising its thermal efficiency, making it ideal as a packaging material where thermal stability is required. 

Furthermore, employing coarse waste wool – a by-product of the meat industry – will make use of an otherwise widely wasted material to ensure the safe and effective delivery of medicines, vaccines and blood products, while also protecting the environment. However, the real challenge for Woolcool is not proving the performance of wool but rather convincing the pharmaceutical industry, which operates in an increasingly regulatory environment. Significant improvements to Good Distribution Practice standards and the safe, cost-effective delivery of drugs to patient can be achieved with immediate effect by implementing new material solutions. 

Underpinning science 

The UK is fortunate to have many research establishments working to solve functionality problems in a sustainable way using biomass, a source of natural materials that embodies the essence of developing renewable resources for novel applications. Snow Business, UK, was keen to invent a new environmentally friendly fluid that could be pumped out of its snow machines in a foam form to create the effect of snowflakes for use at events and in the film industry. Working with Dr Wuge Briscoe and PhD student Elizabeth Mould at the University of Bristol, UK, Snow Business and the EPSRC funded a project to develop an artificial snow that was fully biodegradable and environmentally friendly. 

This proved a challenge, but the underpinning science focused on the stability of thin liquid films – affecting how the foam forms and how long it holds its shape using polymers to ensure that the snow will not melt – and also on foaming agents for melting snow. The research delivered two possible new fluid formulations – EcoFlake and ProFlake. EcoFlake was designed be suitable for use in the rainforest, and in collaboration with the Eden Project, UK, was given a trial run in its biome. The snowflakes required for the project needed to be delicate, causing no damage to the tropic plants environment. The team therefore used plant-based materials, taking inspiration from its other products that use recycled paper paper or pulp for outside settings and biodegradable polylactide for inside snow to form a plant-based material mixture, currently awaiting patent approval. The snow demonstrated no ill effects to any of the plants, giving EcoFlake the green light for use in similar environments. ProFlake is an aqueous blend of anionic, non-ionic, and zwitterionic surfactants, solvents, and stabilisers used in artificial falling snow machines that aerate the liquid into a stream of air, allowing it to fall like natural snow.

Nature undoubtly holds the answer to questions we have yet to ask. New R&D will be fundamental in cataloguing current natural material biodiversity and providing new resources for material application. One such example is algae. The Culture Collection of Algae and Protozoa is the most diverse of its kind, with around 3,000 strains of marine and freshwater algae, protists and seaweeds based at the Scottish Marine Institute in Oban. Algae can either be microscopic single-celled microalgae or larger, more complex multi-cellular macroalgae (seaweed). They are present worldwide in both freshwater and marine habitats across a wide range of environments. Like plants, most algae use photosynthesis to capture light energy to convert inorganic substances into simple sugars and other molecules. 

Microalgae is a promising biomass that is yielding various products. This is a feedstock outside the food-versus-fuel debate and is full of bioactive molecules, whereby scientists are still discovering the vast array of products that can be derived from them. These include soluble proteins, (poly) unsaturated fatty acids, pigments and carbohydrates and can be used as an important ingredient for food, animal feed, chemical, cosmetics and health industries, alongside energy production. 

It appears the more we look, the more we find. Acknowledging the potential of these natural materials has come as a direct result of countless generations of product development, which may lead to even more innovative, sustainable solutions to diverse applications. 

Chris Holland is Chair of the IOM3 Natural Materials Association and Head of the Natural Materials Group in the Materials Science Department at the University of Sheffield, UK, where his team specialises in silk and other biopolymers. 

Iris Anderson is ambassador for the Biobased and Biodegradeable Industries Association and an EU evaluator.

Angela Morris is CEO of the Wool Packaging Company, which produces Woolcool. She has a background as a designer of packaging in various natural materials, including cardboard, cork and wood for various high street retailers and the National Trust.