Using nature’s blueprints to make better material

The image shows mechanical testing of a material manufactured using multimaterial 3D printing.
© A material sample is tested mechanically for strength and toughness. Image courtesy G. Bratzel (MIT).

By: Zhao Qin & Markus J. Buehler; Laboratory for Atomistic and Molecular Mechanics, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology

Nature provides a rich diversity of biological materials such as bone, diatom algae and spider silk. These materials have fascinating mechanical and biological functions achieved at very low energy cost, and with simple basic material building blocks, defined by the chemical structures of the molecules. What has been hindering us in applying those concepts broadly in engineering is that the underlying mechanisms remain largely obscure. In particular, it was not understood how molecules are organized to form the material. The other major obstacle is that engineers are unable to reconstruct the intricate shapes and forms seen in natural materials and actually manufacture them.

Recent advances in nanotechnology and computational tools, combined with new ways of synthesizing materials and structures, now provide approaches to bring that hidden knowledge to light. Our vision of achieving tailored material function from “less” is becoming a reality, and could find applications in industries ranging from construction to healthcare.

We live in an exciting time. One can argue it’s the perfect storm of critical advances in a number of scientific fields that will revolutionize how we design, analyze and make materials. By exploiting advances in basic concepts of physics and chemistry, we can now understand and describe the underlying molecular structure and their mechanisms. This allows natural materials to be translated into synthetic materials.

Being able to describe these materials makes it possible to build a database and systematically classify their properties. Advanced mathematics and new computational methods can be used to extract useful information from this very large database. A key approach is to categorize a material as a set of interacting elements that are represented as a graph to show how a material works.

A fascinating feature of many biological materials is their ability to turn the weakness of their constituents into a strength for the entire system. For example, mineral-based materials like bone and mother-of-pearl exhibit mechanical properties on par with advanced engineering materials, even though their fundamental building blocks are brittle and weak.

The strength of these materials can now be understood by looking at the arrangement of their underlying structure at different scales of magnification, known as length-scales. Multiscale modeling reaches beyond copying information from nature to computational models. It also enables us to improve the detailed arrangements at each level and optimize material functions from the bottom up.

To create such materials in the lab we need synthesis methods that can make structures at very distinct scales, which is now in reach. At the smallest scales, we rely on mechanisms that behave like DNA or protein folding. At larger scales, additive manufacturing is emerging as a powerful tool to “print” complex three-dimensional forms.

The produced materials can have similar material properties as the natural ones, but may use different raw materials like polymers. For example, by using our knowledge of the interplay between a single silk fiber and the architecture in the web we are able to fabricate synthetic spider webs with 3D printing.

Another example of recent work in our laboratory is the design and fabrication of a material that mimics mother-of-pearl (see image above). The material designs are extracted from the rich database of mineral-based biomaterials and made using multi-material printing. This type of additive manufacturing is a possible route for innovation. Such advances are critical for manufacturing, architecture, bioengineering, space exploration and many related areas.

Markus J. Buehler will be speaking about his work later this week at the Biomimcry 3.8 Education Summit & Global Conference. Learn more here.

Tags: Biomimicry

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