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Self-sensing materials inspired by nature developed by Scottish University

THE cellular forms of natural materials are at the origin of a new lightweight, 3D printed, intelligent and architectural material, developed by an international team of engineers.

The team, led by engineers from the University of Glasgow, mixed a common form of industrial plastic with carbon nanotubes to create a material that is tougher, tougher and smarter than comparable materials.

Nanotubes also allow otherwise non-conductive plastic to carry electrical charge throughout its structure.

When the structure is subjected to mechanical loads, its electrical resistance changes.

The phenomenon, known as piezoresitivity, gives the material the ability to “feel” its structural health.

The material mimics structures found in nature. Photo by Meggyn Pomerleau on Unsplash.

Using advanced 3D printing techniques that provide a high level of control over the design of the printed structures, the team was able to create a series of complex designs with medium-scale porous architecture.

This reduces the overall weight of each design and optimizes mechanical performance.

The cellular design is similar to porous materials found in the natural world, such as beehives, sponges and bones which are light and sturdy.

The researchers believe their cellular materials could find new applications in medicine, prosthetics, and automotive and aerospace design.

The research is available online as a first article in the journal Advanced Engineering Materials.

In the paper, the researchers describe how they investigated the energy absorption and self-sensing characteristics of three different nano-engineered models that they printed using their custom material, which is made from random copolymer of polypropylene and multi-walled carbon nanotubes.

Of the three designs tested, they found that one had the most effective combination of mechanical performance and auto-sensing capability, a cube-shaped “plate array” incorporating tightly packed flat sheets.

The lattice structure, when subjected to monotonic compression, shows an energy absorption capacity similar to nickel foams of the same relative density.

It also outperformed a number of other conventional materials of the same density.

The research was led by Dr Shanmugam Kumar from the University of Glasgow’s James Watt School of Engineering, alongside colleagues Professor Vikram Deshpande from the University of Cambridge and Professor Brian Wardle from the Massachusetts Institute of Technology .

Dr Kumar said: “Nature has a lot to teach engineers about how to balance properties and structure to create lightweight, high-performance materials.

“We took inspiration from these shapes to develop our new cellular materials, which offer unique advantages over their conventionally produced counterparts and can be fine-tuned to manipulate their physical properties.

“The polypropylene random copolymer we have chosen offers better processability, better temperature resistance, better product consistency and better impact resistance.

“The carbon nanotubes help make it mechanically robust while giving it electrical conductivity.

“We can choose the extent of porosity in the design and engineer the porous geometry to improve mass-specific mechanical properties.

“Lightweight, stronger, self-sensing materials like these have great potential for practical applications.

“They could help make lighter, more efficient car bodies, for example, or back braces for people with conditions like scoliosis that can sense when their bodies aren’t getting optimal support.

“They could even be used to create new architectural electrode shapes for batteries.”

The research was supported by funding from the University of Glasgow and the Engineering and Physical Sciences Research Council.

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