Silicone memory?
Metamaterial can be reprogrammed with different properties.
If you need a material that can literally be changed to suit you over time, read on. Metamaterials – meaning “beyond matter” – are engineered materials with properties not found in nature. Tian Chen of École Polytechnique Fédérale de Lausanne, Switzerland, has gone one better, reporting in
Nature a metamaterial that can be reprogrammed to have different mechanical properties after it is already made.
“I wondered if there was a way to change the internal geometry of a material’s structure after it’s been created,” says Chen. “For example, when you twist your ankle, you initially have to wear a stiff splint to hold the ankle in place. Then as it heals, you can switch to a more flexible one. Today you have to replace the entire splint, but the hope is that one day, a single material can serve both functions.”
The material is made of small mechanical units, called m-bits, that are analogous to computer bits.
In a hard drive, tiny pieces of digital information can be stored as bits. Magnetic bits can be programmed to switch between the values of 0 and 1, or off/on, by magnetising them in different directions. That binary code can be controlled by an external electromagnetic circuit, which changes the direction of those bits to recode the hard drive with a new memory.
This principle is somewhat like Chen’s material, except that he used mechanical units instead. His m-bits are made of silicone and magnetic powder and have a shape that allows each individual cell to move between a compressed and decompressed state. These two states act as the programmable binary code, like computer bits.
“You can activate and deactivate individual cells by applying a magnetic field. That modifies the internal state of the metamaterial, and consequently its mechanical properties,” says Chen.
In this case Chen aimed to alter the stiffness of the material. When cells are switched on by the magnetic field, the material is stiff; switched off, it’s more flexible.