Bioinspired problem-solving is the future

Materials World magazine
,
27 Jan 2016

Rhiannon Garth Jones speaks to Tom McKeag about using bioinspired design to create greener solutions at the University of California, Berkeley. 

Tell me a bit about your background.

I come from a design and urban planning background, with 25 years of project management experience in both the private and public sectors. In 2006, I started teaching a subject that was to become a bit of an obsession for me – bioinspired design. Since those first days of learning about and teaching the subject, I have gone on to writing a regular column, founding a non-profit and co-founding a magazine, Zygote Quarterly, teaching at various universities, and speaking publicly on the topic. 

Tell me about the Greener Solutions course.

Interdisciplinary teams of graduate students in public health, chemistry, design and environmental science work to propose sustainable answers for client companies. Team building and project management skills are the first things we impart to these students before they conduct serious research into contemporary problems.

During the semester, students are instructed in a combination of green chemistry, public health, toxicology, and design innovation. Bioinspiration is introduced within the design innovation section and is a key part of the search for new solutions to a range of problems. Green chemistry is the movement to use less harmful chemicals in current products. Bioinspired design is using the principles of nature found in forms, processes and systems to solve human problems. Since much of the work of the Greener Solutions teams involves finding more sustainable materials through better chemistry, the teams are often looking at natural processes that happen at the micro, nano and molecular scale. 

How do they apply that learning?

After a general introduction to these disciplines, the students engage in problem definition, client relations, and some targeted research. Their final product is typically an opportunities map that recommends pathways to improve a company’s products. For example, this year’s clients were software company Autodesk and Method, a maker of green cleaning products. The two student teams made recommendations for greener resins in 3D printing and a low-temperature detergent that could clean oily stains. 

How did they approach the work for Method?

Method was looking for a low temperature laundry cleaner for oil-stained clothes as part of its commitment to offering products that contribute to overall sustainability. Removing oily stains from clothes takes energy of some kind, whether chemical, thermal or mechanical, and finding an alternative to heavy detergents, hot water and a lot of spinning is a path to reducing this energy use – one of the biggest life cycle impacts of laundry operations. The team crafted a design brief for themselves that comprised the use of existing mechanical appliances, operating in water of 5–20°C, exhibiting low toxicity to humans and the environment, and biodegradability.

The researchers examined the main components of laundry detergents and cleaners – surfactants, solvents, enzymes and dispersants – and assessed the hazards of the typical types used. Surfactants reduce the surface tension between materials and therefore help lift dirt from clothes. Solvents break down chemical bonds within formulas, and dispersants keep dirt suspended in the wash liquid. Enzymes also break down chemical bonds, particularly in complex, hydrophobic compounds.

In looking to nature for answers, the team did not just investigate individual organisms, but also pursued general patterns. For example, nature often solves problems through a hierarchy of linear scales. Bone, for instance, exhibits remarkable toughness and strength because of the way part of this composite, proteins, are twisted into braids, bundled and sheathed up through the scales from the molecular to the macro scales. 

What was the end result?

For this problem, the team’s approach comprised recommendations for three levels of solution – the chemical scale, in which they proposed adding certain new chemicals, the formulation scale in which they proposed changing the combination of chemicals in the mix, and the process scale, in which they investigated the entire cleaning system for ways to reduce energy use and lower hazards.

They proposed several innovative solutions to the problem, including strategies inspired by natural deep eutetic solvents, other bio-based solvents, biosurfactants, enzymes, and oil-adhesive surfaces. For each, they described the inspiration, technical feasibility, design concept, potential risks to human and environmental health, and research gaps and priorities. A summary contained a comparison with current practices and recommendations for implementation.

Where else have they applied these theories?

Another project that effectively linked bioinspiration with green chemistry was done in 2013, for Levi Strauss and Company. Two teams looked at two problems in fabric finishing – non-wrinkle treatments and water repellency in denim. 

Non-wrinkle finishes or permanent press treatments used in clothing were typically based on formaldehyde and di-isocyanates. Both of these substances are toxic but extremely effective in preventing wrinkles in clothes. They do it by cross-linking fibres in the cloth so that they cannot be realigned when a cloth gets wet. Wetting breaks the hydrogen bonds typically holding these dry fibres together – when wetted, the fibres get jumbled up and exhibit wrinkles.

Formaldehyde is a serious concern and a cause of nervous system damage, endocrine disruption, nasal cancer, nasopharyngeal cancer, leukemia, and is a skin and respiratory sensitiser. Di-isocyanates are suspected carcinogens, and are a skin, eye and respiratory irritant and an asthmagen. Finding benign substitutes for these substances would be a major improvement in personal health.

Cross-linking occurs in nature, and with help from the Biomimicry Institute, the teams looked at the cross-linking of proteins and sugars. Among the organisms that they looked at were tree frogs and mussels (proteins) and woody plants and flax (polysaccharides). They set their nature-inspired candidates within a decision framework that included technical performance, health considerations, and sustainability. 

Woody plants provided one model. Lignin and hemicellulose are cross-linked within fibrous tissues of many plants, conferring mechanical strength, water repellency and resistance to pathogens. Enzymes mediate the cellulose activation and polymerisation in the plants, and the team recommended that the company investigate some of the enzymes already used in the textile industry. Enzyme processes to clean fabric, for instance, are typically less harsh than more traditional methods.

Another model for the students was the mussel, a marine invertebrate that is able to cling to surf pounded rocks. It does this by extruding a mix of proteins comprising keratin, polyphenols and others in the form of fine filaments or threads. These proteins are functionally graded for either flexibility or rigidity and together create a wide range of durability and strength. When these more acidic proteins contact the alkaline seawater they undergo a phase change, turning from liquid to solid by forming metal-catechol complexes. The threads are part of a three-part anchoring system comprising a stem, thread and plaque. The team recommended that the adhesive property of these byssal threads be investigated for use to either bind cloth fibres or as a durable water repellant coating.

How do your students take this approach beyond their studies?

Nature inspired approaches to problem solving have become an integral part of the Greener Solutions course, and have led to some innovative solutions to problems such as building insulation, cosmetic preservatives, laundry detergent and additive manufacturing resins. The course has led several students to carry on their investigation of these sustainable approaches beyond the bounds of academia – working as researchers at the US Department of Agriculture, Method, and Autodesk, for example.

As material and manufacturing challenges become more complex and interrelated, this interdisciplinary, bioinspired approach to problem solving will become more and more vital to our health and prosperity.

Tom McKeag is the Executive Director of the Berkeley Center for Green Chemistry. Clients have included Levi’s, Hewlett Packard, and Seventh Generation. The Greener Solutions programme has been supported by the California Department of Toxic Substance Control, a Pollution Prevention Grant from Region 9 of the Federal Environmental Protection Agency, and contributions from partner organisations.