Author: Elena Corujo Simon

Insect wings – tackling antimicrobial resistance

Last April, Arabella Heath, a Biochemistry undergraduate student, and Mia Hughes, a Chemistry undergraduate, joined IMSE for a day to experience the work environment in an Operations team. Together, they explored the topic of antimicrobial resistance and how we can keep antibiotics working by combining molecular science and engineering research. Coincidentally, a couple of weeks ago, the U.K. government updated its strategy to tackle antimicrobial resistance for the next 5 years. In this blog, Arabella and Mia explore how the surface of insect wings is inspiring innovation on antimicrobial ‘smart’ surfaces to reduce bacterial infections in hospitals.

The prevalence of antimicrobial resistance

Summer is approaching, and we are all dreading the familiar sound of insects buzzing that accompanies the season. But who knew that studying some insects like cicadas and dragonflies might hold the key to tackling antimicrobial resistance (AMR)? AMR occurs when antimicrobial treatment is no longer effective at treating bacteria, viruses, fungi and other parasites. It leads to increased infections rates and severe illnesses. AMR is a major threat for the development of global public health. AMR caused an estimated 1.27 million deaths in 2019 worldwide and this is set to rise to 10 million by 2050. This issue requires new and innovative solutions because evolving bacteria are outsmarting our current available antibiotics.

Steps on how antibiotic resistance happens. 1. Lots of germs, some are drug resistant. 2. Antibiotics kill the bacteria causing the illness, as well as good bacteria protecting the body from infection. 3. The drug-resistant bacteria are now allowed to grow and take over. 4. Some bacteria give their drug-resistance to other bacteria, causing more problems.
How Antibiotic Resistance happens. Image credit: Lumen learning.

Insects wings v Bacterial infections

Remember as a child, trying to stretch bubbles into different shapes before they pop? Now, imagine pulling apart millions of little bubbles before they can float away. This is exactly how cicada’s wings work. They are lined with rows of spiky nano-protrusions which pull on bacterial ‘bubbles’ landing on the surface, stretching their membranes until they burst. Cicada wings use force to render the bacteria useless, which means that they don’t develop resistance or become harder to treat. This simple mechanism could be used to kill common bacteria that plague hospitals, like E. coli.

Cicada wing
Cicada wing. Image credit: Mathew Wills

Mimicking cicada wings to create smart surfaces

Scientists have been working to synthesize biodegradable polymers that mimic the ripple effect of cicada wings. Materials such as clingfilm-like sustainable polymers can be stretched and relaxed in specific directions to create tiny spikes in the structure, on the nano and micro scale. This new technique is also inexpensive in comparison to other methods that generate complex patterns on polymers. And because it can be easily scaled up, it also has a potential use as self-cleaning surfaces in hospitals.

On the left: image of a cicada. On the right: zoomed-in image of cicada wing surface showing nano structures.
Nano structures on cicada wing.Image credit: Zhang et al. Cicada Wings A Stamp from Nature for Nanoimprint Lithography. Small 2006 2 12 1440 1443.

Materials science inspired by nature

Apart from tackling hospital infections, this antimicrobial technology has potential impact in various other industries and applications, from door handles to food packaging. In fact, you could soon have this cicada-inspired molecular engineering inside you, as part of an implant!

Cicada wings themselves hold more secrets, with thrilling implications for material science. Their waxy coating has ‘super-hydrophobicity’ properties, repelling water into droplets and making cicadas self-cleaning. In addition, cicada wings are anti-reflective allowing them to camouflage -explaining why you can hear them but never see them at night -, a property which could be harnessed into solar cell technology.

Water droplets on cicada wing highlighting the hydrophobic properties.
Water droplets on cicada wing highlighting the hydrophobic properties. Image credit: Kaitlyn Melton _ Flickr

More research in this area will show how effective cicada wing-inspired materials are for a wide variety of applications. For now, we are looking forward to this amazing technology becoming incorporated into everyday life.

Giving textile waste and dyes a second chance

Following on our blogs exploring circular economy and zero waste, we welcome our new guest blogger, Dr. Antonio Ovejero-Perez. A postdoc from the Department of Chemical Engineering, Antonio’s research is focused on extracting dyes from textiles waste. 

Who hasn’t heard a family member say: “Back in the day, I only got new clothing for Christmas or birthday”? Now, in our fast-paced world things have changed. How many times a year do we buy clothes? Trends come and go quickly, and “fast fashion” has become more and more popular. 

But what is it? Fast fashion refers to the rapid production and consumption of inexpensive clothing items, often imitating current trends from the catwalk or celebrity culture. It prioritizes speed and affordability, resulting in frequent turnover of collections and low-cost garments. The New York Times first used the term to describe Zara’s mission to have garments in stores for just 15 days. This model involves design, production, and rapid distribution. Fast fashion creates large quantities of garments in very short periods of time at a low price.

Growth of clothing sales and decline in clothing utilisation since 2000.
Growth of clothing sales and decline in clothing utilisation since 2000. Source: Euromonitor International Apparel & Footwear 2016 Edition; World Bank, World development indicators – GD (2017)

This system encourages excessive consumption and clothes are used fewer times due to the social pressure of fashion trends. In addition, the consumer normally prefers to spend less money and change styles more often rather than buying more expensive garments that last long but will fall quickly out of popularity.

Fast fashion environmental consequences

The problem lies in the rapid production of garments. It is estimated that 92 million tonnes of textile waste are produced every year, expected to reach 34 million tonnes by 2030. The presence of dyes in the fabrics and the need for homogeneous input for fibre recycling complicates its recycling. Currently, textile waste is either incinerated or landfilled. Nowadays, recycled plastic bottles are the only source of recycled polyester for garment production, rather than recycled clothing. Thus, new raw materials are used for textile production: cotton (2.5% of farmland) and synthetic materials like polyester (342 million barrels of oil annually), driving environmental impact.

 

Image of mountains of clothes from waste generated by the textile and clothing industry
Textile waste generated by the clothing industry as a consequence of fast fashion. Source: University of Queensland.

But textile waste accumulation is not the only problem of the fast fashion industry. The excessive demand of clothing requires huge amounts of energy that, normally, come from non-renewable sources. The textile and fashion industry accounts for a 10% of global carbon emissions, more than the aviation and shipping sectors combined. Water consumption is also substantial, accounting for 20% of global wastewater production per year. In addition, the textile dyeing part of the process uses 43 million tonnes of chemicals a year.

Tackling the fast fashion problem

But is it all the consumer’s fault? Consumers do have responsibility and the chance to change habits to put pressure on retailers. But the textile industry also needs to change, producing clothes more sustainably and reusing both dyes and textiles. As previously mentioned, textile recycling is limited by the presence of dyes; thus, technologies that are able to recover dyes from textiles are needed. However, making that in a sustainable way is not easy.

Recovering dyes from textile waste to be reused

In this sense, in our group, and in one of the startups founded in our group, DyeRecycle Ltd., we use a low-cost green solvent to selectively extract dyes from fabric wastes, enabling circular economy. Using this method, we can recover a decoloured polyester fabric with intact properties for mechanical and chemical recyclers. In addition, the dye-rich green solvent can be used as a dye bath to dye new garments, or be recovered and sold, as it comes unaltered out of the process. This way, our technology tackles textile accumulation and chemicals and water usage problems in one solution.

Textiles samples coloured by using recycled dyes.
Textiles samples coloured by using recycled dyes. Source: DyeRecycle LtD.

Upcycling palm oil waste to mitigate climate change

Let’s check our shopping list, does it include items such as shampoo, detergent, margarine or cookies? According to the WWF, it is highly likely that some or all these items contain palm oil. You have probably heard about the negative connection between palm oil and deforestation and displacement of wildlife. However, you might be unaware of the large amount of waste generated during its production. Here, IMSE’s latest guest blogger, PhD researcher from Future Materials Group,  Dharu Smaradhana, discusses his research into waste generated by palm oil production and its potential as sustainable material.

Palm oil is criticised due to deforestation concerns, but replacing it with other vegetable oils is not a straightforward solution. Palm oil is the most land-efficient vegetable oil crop. It supplies 40% of the world’s demand while using less than 6% of the land allocated for all vegetable oil production. Alternatives like soybean, coconut or sunflower oil require considerably more land which could lead to additional environmental damage.

Comparison of palm oil yields to other vegetable oils.
Comparison of palm oil yields to other vegetable oils. Image credit: Valori news

Palm oil environmental impact beyond deforestation

Currently, nearly half of all packaged products contain palm oil, from foods and personal care items to animal feed and biofuels. Palm oil use is inevitable, but it carries environmental challenges. The Roundtable on Sustainable Palm Oil (RSPO) was founded in 2004 to promote sustainable palm oil production that protects forests and community rights. Nevertheless, mitigating the waste generated from palm oil production is another critical issue that needs addressing.

Production of palm oil generates many solid wastes, notably from empty fruit bunches (EFB). Every ton of palm oil generates around 1.1 tons of EFB. This bulky and moist waste presents considerable disposal challenges. Incinerating EFB contributes to environmental pollution, while simply discarding it results in the release of methane, thereby increasing greenhouse gas emissions.

Empty fruit bunches in palm oil plantation.
Palm oil plantation in Palawan, Philippines. Image credit: USAID Biodiversity and Forestry Flickr

Upcycling palm oil waste into construction materials

As material engineers, we also recognise the transformative potential of EFB in revolutionising the production of board products used in the construction and furniture industries such as particleboard and fibreboard. Conventionally, these boards are manufactured by combining wood fibres with synthetic binders like urea-formaldehyde, and then compressing the mixture under heat. However, these fossil-derived polymers present health hazards and pose environmental concerns due to their inability to degrade naturally.

Considering the challenges, EFB fibres emerge as an eco-friendly substitute for traditional wood fibres, enhancing sustainability in agriculture and industry. Our initiative involves producing EFB boards using cellulose from pulp as the binder, avoiding the use of synthetic products. Following simple manufacturing steps mimicking the paper-making process, EFB boards match the mechanical performance of commercial fibreboards.

Round EFB board utilising cellulose as the binder.
EFB board utilising cellulose as the binder. Credit: Dharu Smaradhana.

Circular economy and climate change mitigation

Lifecycle assessment (LCA) studies also show that the EFB board substantially reduces the environmental impact. Particularly, in terms of global warming potential, when compared to traditional fibreboards that utilise fossil-derived binders.

By upcycling waste from palm oil production in such an innovative way, we are contributing to climate change mitigation and advancing towards a more sustainable, circular economy.

Multidisciplinary approach to Zero Waste

Have you ever given an object a second life? Reusing yogurt pots to grow plants or a mug with a broken handle turned into a pencil holder. I recently made cushions out of coffee beans sacks from the nearby roasters. You probably also recycle glass bottles and carry a tote bag when going shopping, reducing the number of plastic bags.

Empty yogurt pots used to grow plants.
Re-using yogurt pots to grow plants. Image credit: Flickr, Ilja Klutman.

From linear to circular economy

These are all examples of a circular economy. Established as a concept in the 70s, circular economy is the system of production and consumption that reduces waste to a minimum. Extending a product’s life is achievable by re-using, repairing, recycling and sharing, all of which create further value. Circular economy is the opposite of the linear economy model, where goods are simply thrown away after use.

Circular economy diagram.
Circular economy model to reduce waste. Image credit: Centro de Documentacion Europea de Almeria

Inventing new ways to reuse and recycle objects is fun and sustainable. However, it only tackles waste generation from the consumption side, ignoring the production and transport part of a product life cycle. Waste is not just created when an object is discarded but also beforehand, when it is made. Sourcing materials, fabrication processes leading to left-overs, transport and packaging also contribute to waste production.

What counts as waste?

The first step towards achieving zero waste is to determine the stages at which it is produced. This can be done through an approach called life-cycle assessment (LCA). LCA is the evaluation of the environmental impact of goods or services throughout their entire life, from “cradle to grave”.

Multidisciplinary approach to achieve zero waste

Researchers at the Institute for Molecular Science and Engineering (IMSE) use the LCA approach to tackle waste at the beginning of the lifecycle, during the design phase. Using a molecular science approach, scientists examine materials’ structure and properties, considering how well they can be recycled. Meanwhile, from the engineering side, they assess manufacture processes and energy requirements, transport options and ultimately material performance.

Above all, the circular economy and LCA approaches aim to consider the entire life of a product. Improving one part of the cycle – e.g. manufacturing – should not simply shift the impact to another part of the cycle – e.g. recycling/degradation. Let’s think about plastics. Choosing an easier to recycle polymer to make a new plastic object could have consequences during transport and even function. Would faster degradation affect how we use an object or the way we transport it? The opposite also applies, making an object very durable will affect how it degrades and pollutes the environment after use.

Life cycle assessment of plastic production.
Assessing the environmental impacts across the life cycle of plastics requires multidisciplinary approaches. Image credit: European Environment Agency

Reaching zero waste will require a wide vision of the lifecycle, using multidisciplinary approaches and collaborating across expertise. That is not to say that you should stop reinventing objects you already have! The perfect occasion would be following the international day of zero waste on the 30th of March  –  what would you be re-using or repairing to celebrate?