Shape Memory Achieved for Nano-Sized Objects: Overcoming Limitations with Ferroic Oxides

Shape memory for nano-sized objects

Shape memory is a term used to describe alloys that are able to return back to their original shape after deformation. The forces generated by this phenomenon are used to drive many mechanical actuators, such as hydraulic pumps or generators. This shape-memory hasn’t been possible at the nanoscale. Shape-memory alloy objects can only be reshaped if they’re larger than 50 nanometers.

The researchers led by Salvador Pane Professor of Materials of Robotics, ETH Zurich and Xiang Zhong Chen Senior Scientist in his group were able circumvent this limit using ceramic materials. In a paper published in Nature Communications, the researchers demonstrate the shape memory effect on a layer of ferroic oxides that is approximately 20 nanometers thick. Now, the shape-memory technology can be applied to nanoscale machines.

Ferroic oxides are not flexible and brittle when in bulk. They must be fixed to a substrate to create thin layers. To still be able induce the shape memory effect, the researchers applied two different oxides – barium titanate, and cobalt ferrite – in thin layers to a magnesium oxide surface. The two oxides have very different lattice parameters. The tension between the two oxides created a spiraled twisted structure after the researchers removed the two-layered strips from the substrate.


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