Inspired by the humble deep-sea sponge, RMITS University engineers have developed a new material with remarkable compressive strength and stiffness that could improve architectural and product designs.
The double lattice design was inspired by the intricate skeleton of a deep-sea sponge known as Venus' flower basket, which lives in the Pacific Ocean.
Lead author of the latest RMIT study into the structure, Dr Jiaming Ma, said extensive testing and optimisation revealed the pattern's impressive combination of stiffness and strength, mixed with an ability to contract when compressed.
It’s this last aspect – known as auxetic behaviour – that opens a whole range of possibilities to apply the design across structural engineering and other applications.
“While most materials get thinner when stretched or fatter when squashed, like rubber, auxetics do the opposite,” Ma said.
“Auxetics can absorb and distribute impact energy effectively, making them extremely useful.”
But while auxetic materials have useful properties, their low stiffness and limited energy absorption capacity limits their applications. The team’s nature-inspired double lattice design is significant because it overcomes these main drawbacks.
“Each lattice on its own has traditional deformation behaviour, but if you combine them as nature does in the deep-sea sponge, then it regulates itself and holds its form and outperforms similar materials by quite a significant margin,” Ma said.
Results show with the same amount of material usage, the lattice is 13 times stiffer than existing auxetic materials, which are based on re-entrant honeycomb designs.
It can also absorb 10 per cent more energy while maintaining its auxetic behaviour with a 60 per cent greater strain range compared to existing designs.
Researcher Ngoc San Ha said the unique combination of these properties opened several exciting applications for their new material.
“This bioinspired auxetic lattice provides the most solid foundation yet for us to develop next generation sustainable building,” he said.
The bioinspired lattice structure could work as a steel building frame, for example, allowing less steel and concrete to be used to achieve similar results as a traditional frame.
The team at RMIT’s Centre for Innovative Structures and Materials tested the design using computer simulations and lab testing on a 3D printed sample made from thermoplastic polyurethane.
They now plan to produce steel versions of the design to use along with concrete and rammed earth structures – a construction technique using compacted natural raw materials.
“While this design could have promising applications in sports equipment, PPE and medical applications, our main focus is on the building and construction aspect,” Ma said.
“We’re developing a more sustainable building material by using our design’s unique combination of outstanding auxeticity, stiffness, and energy absorption to reduce steel and cement usage in construction.
“Its auxetic and energy-absorbing features could also help dampen vibrations during earthquakes.”
The team is also planning to integrate this design with machine learning algorithms for further optimisation and to create programmable materials.