Nanyang Technological University (Singapore) and California Institute of Technology (US) have recently published a paper in Nature, detailing research into a new chain mail-like “smart fabric” that changes stiffness when compressed.
The chain mail itself is printed with Nylon, and each chain link is in the shape of an octahedron, as you can see below. The hollowness of the unit particles allows low density and yet high tensile stiffness from the overall fabric.
Octagonal units make the whole (Image credit: NTU Singapore)
The individual “unit particles” are topologically interlocked, meaning that they are linked like chain mail, constraining the unit particles to form the shape of a continuous loose fabric. The paper does indeed state that the fabric is more like a 2 dimensional structure overall, despite the obviously 3 dimensional unit particles. The chain mail specimens were printed in single pieces, ready to function.
To control the stiffness, the researchers placed the chain mail into a transparent plastic back, and removed the air from the bag using vacuum. This effectively compressed the unit particles together, causing the unit particles to jam together, restricting the movement of each particle, and therefore increasing the stiffness of the overall fabric structure. In fact the mechanism by which these particles lock together is called “jamming transition”, because they jam together, see?
The pressure increases the packing density of the fabric, causing each particle to have more contact with its neighbours, resulting, for the octahedron-based fabric, in a structure that is 25 times more rigid.
When formed into a flat, table-shaped structure and vacuum-locked in place, the fabric could hold a load of 1.5kgs, more than 50 times the fabrics’ own weight.
The nature of the octahedrons also means that the structure can lock into non-planar shapes as well, such as this bridge shape…