University of California, Santa Barbara mechanical engineer Jonathan Berger has used geometry to design Isomax, a solid foam that is stronger, more efficient, and higher quality than other materials currently on the market.
According to Berger, in comparison to other engineering materials, Isomax has the highest stiffness to lightness ratio, meaning that for its low density, it has the highest stiffness and can resist crushing and shearing forces that would flatten denser materials.
The goal of Isomax is to answer the question of how to add space to stuff. Void space is an aspect that plays an important role in the qualities of every object, such as foods, shoes, and buildings. How the space is utilized contributes to the object’s characteristics such as stiffness, straight, weight, and flexibility.
“We can make the walls of the cells thicker and denser at one end and then thinner at the other end,” Berger said. “Because it has certain symmetries and alignments and achieves the theoretical bounds for stiffness, there is no other material like it.”
The key behind the technology is geometry. The foam has two basic shapes: the triangle and the cross. Taking both into three-dimensional space, the cells look like pyramids, some with three diagonal faces and a base and others with four diagonal faces reinforced with diagonal intersecting walls inside that resemble the insides of wine cases.
According to Berger, each shape was chosen because of its unique properties. The intersecting walls are ideal for resisting perpendicular crushing forces, while the pyramidal shapes resist shearing forces. These cells are made to withstand forces from all directions while maintaining low density, making an ideal structural material.
“Jonathan’s achievement opens up opportunities to make structures that engineers will be able to exploit to improve things like implants, sandwich panels for structural stiffness and strength, and multifunctional devices like heat sinks that can also be stiff and strong,” said Robert McMeeking, UCSB professor of materials and mechanical engineering, and one of Berger’s mentors. “His invention is also timely as new fabrication techniques such as 3-dimensional printing now make it possible to manufacture novel geometries such as the one that he has invented.”
The solid foam’s versatility can be used as a functionally graded material that is useful in situations where the object has different physical properties than another part. For example, the walls could be removed to leave a lattice structure that could serve as a replacement for knees or other bones that provide structure while allowing for blood flow.
According to Berger, Isomax’s low density for stiffness means that things made from it require less material for the desired amount of strength. The material for certain objects, such as vehicles, could make them more energy efficient, and the foam’s repeating structure makes it easy to manufacture and scale to demand.
Isomax is still in the early stages of development, but Berger continues to refine it and prepare it for the market through Nama Development, a company he formed with the help of UCSB’s Technology Management Program.