Lessons from Spiders and Mussels on Manufacturing
Lessons from Spiders and Mussels on Manufacturing
We live in a world of manufactured things. In the developed world we are surrounded by more mass-produced material goods than any other society at any other time in human history.
For many of us in this increasingly urban world, our daily environment is almost completely manufactured. At no time during a typical day do we step onto the earth, touch a plant or look at a view that is not dominated by the products of technology.
While this technology has brought wondrous things, it has also brought destruction and waste, and thoughtful designers are considering anew the manufactured consequences of their ideas. To be sure, this will not be sufficient to halt the degradation of our planet. I believe a change in the growth-at-any-cost paradigm is required for that. Rethinking the methods of manufacturing, however, executed with wiser decisions about how to distribute those goods, will be essential to allow future generations to share our world.
Ironically, nature has quite a bit of advice to offer the technological society that has so abused her. Her rules are different, and her agenda inscrutable, but learning a few simple lessons could reap great rewards for technology while sparing the earth its usual ration of abuse. Understanding how nature is built is a promising pathway to innovation that should not be ignored. Understanding how nature builds, however, may be more important.
Professor Julian Vincent, retired director of the biomimetics and natural technologies program at the University of Bath's Department of Mechanical Engineering, believes that the biggest benefit from bio-inspired design lies in improving manufacturing methods. “Developing new material processing techniques based on bio-inspired processes - that’s where the progress will be…always has been,” he said.
Vincent has spent a long career looking at natural materials for their best advantages, investigating everything from how pine cone bracts might inspire smart clothing, to leaf folding as a model for deployable structures, to the mechanical efficiencies of jumping robots.
He has also spent a great deal of time comparing natural and technological methods for solving design challenges, and has been an advocate of TRIZ, a Russian typology of problems and solutions, as a framework for transferring lessons from nature to technology.
He co-authored the Journal of The Royal Society paper “Biomimetics: its practice and theory” in 2006. Using the TRIZ system, he and his colleagues compared six parameters used to solve problems across scales, first in technology and then in nature. Their conclusion was that there was only a 12 percent overlap between the two approaches and that the technological approach predominantly used energy to solve problems (particularly at the smaller scales) while nature more typically used information and structure.
Vincent continues to be most intrigued by the search for a theoretical framework for biomimetics and is busy writing an ontological treatise on biological functions and design processes. To date he has looked at approximately 280 of these functions and 80 criteria within the energy parameter alone. The goal is to create an ontology that can identify industrial applications and match them with biological solutions.
If his Royal Society paper suggests a veritable gold mine of new and unique energy-saving solutions available to the designer, why haven’t we seen more bio-inspired solutions within our sustainable designs? I imagine that the explanation lies in the word “translation.” Vincent notes that while the two approaches may share general functional categories, like adhesion, they are wildly different in their material components, how these materials are made and how they are structured and arrayed.
Natural organisms build principally with two polymers (proteins and polysaccharides), a couple of minerals (calcium and silica) and occasionally throw in some metals like manganese, zinc or iron for hardening.
Proteins make up a lot of the tough, durable materials organisms need to bend, flex and resist stress. Spider silk, collagen (tendons, skin), elastin and keratin (hair, horns, nails) are examples. Polysaccharides include materials like chitin (lobster shell) and cellulose (wood fiber), relatively hard materials that provide stiffness, as well as gels and fillers. All of these materials, importantly, are produced and maintained in a water environment, something that technical processes often avoid as degrading.
Several characteristics distinguish these natural materials, making them both frustrating to replicate and full of tantalizing promise. Since they are made from only 20 amino acids, for instance, proteins share a common base and chemical conversance. Their shape, moreover, determines their wide diversity and the specific information embedded within. This allows creatures like the spider or the mussel to create a full range of proteins in silk or byssus to suit the demands of the environment or the needs of its life cycle.
The fine tuning that means adaptability (and therefore survival) in nature could mean operational efficiency for us, but it is based on a chemical component system that we now only admire from a distance.
These materials are arranged in a hierarchical structure and it is this hierarchy that distinguishes many natural solutions from artificial. Hierarchies provide for two important characteristics in systems: They allow subsystems to be semi-independent and optimized, thus allowing the system to be multifunctional and less prone to collapse, and they allow material properties (solutions to problems) across scales. It is the latter property that particularly interests Vincent.
Too often, he says, our processes have stripped both the information and the hierarchical structure out of materials and material systems, while it is these very solutions that nature uses so successfully. For example, solving both the needs for stiffness and fracture resistance seems contradictory, but this is done by many organisms, including the abalone. Fracture resistance generally involves avoiding concentrations of stress and the generation of energy to create new surfaces (wider cracks). Stiffness requires the lack of suppleness that would mitigate such concentrations and strain.
How to have both? You solve them at different scales, and one can do that efficiently only within a hierarchical system. According to Vincent, stiffness is typically solved at the nanometer scale and toughness at the micrometer to centimeter scale. The two properties can be controlled independently and a bioceramic, like the calcium carbonate in nacre, for instance, can be nearly as stiff as any technical ceramic, but will also be a thousand times more durable because of the hierarchical structure that includes proteins (at a bigger scale).
The recent book “Bulletproof Feathers: How Science Uses Nature’s Secrets to Design Cutting-Edge Technology” contains a chapter by Vincent in which these ideas are expounded in several thematic sections. He believes that understanding embedded information, hierarchy and scale can lead to innovation, and that there is great promise in recombining material properties in new hierarchical ways, rather than merely changing the chemical compositions of materials.
How then, can we arrive at a brighter future by using some of these material lessons from nature? Vincent has several prescriptions for closing the gap between the merely admired and the constructively emulated. The ultimate goal would be to create polymers that are packed with information caused by their structure and chemistry. These polymers, due to their embedded information, would drive the very processes used to assemble them into increasing levels of hierarchy.
To do this, scientists and engineers will have to know more about how to embed information in molecules and create an aqueous manufacturing regime in which to guide self-assembly in a hierarchical progression. He notes that current self-assembly methods have not gone beyond three scale levels of manufacture, although electrospinning, at the 3-micrometer diameter scale, shows promise. Electrospinning is the elongation of fibers from a polymer droplet using electrical fields and has been done down to a less-than-1-micrometer diameter size. Much research is now engaged in a race to the small with labs attempting diameters in the 100-nanometer range.
They will have to develop a simplified chemical template set of a few foundational formulas and understand complex side-chain reactions and control the side groups necessary to create variation.
They will also have to understand more fully the complex morphologies of the various types of materials (fibers, composites, cellular) and their structural hierarchies. This will require an accelerated commitment to many different methods of measurement of manufactured materials, and the increased ability to make scale prototypes in the lab.
Finally, says Vincent, all this research will have to be driven by open minds.
Tom McKeag teaches bio-inspired design at the California College of the Arts and University of California, Berkeley. He is the founder and president of BioDreamMachine, a nonprofit educational institute that brings bio-inspired design and science education to K12 schools.
Spider web - CC license by Flickr user Tobyotter