Suitable for fibres or robots in the body

Alloys that can return to their original structure after deformation have a so-called shape memory. This phenomenon and the resulting forces are used in many mechanical drive systems, for example in generators or hydraulic pumps. However, this shape memory effect has not yet been utilised in the small nano range: In many alloys with shape memory, objects only return to their original shape if they are larger than around 50 nm.

Replace muscle fibres or parts of the spine

Researchers led by Salvador Pané, Professor of Robotic Materials at ETH Zürich, and Xiang-Zhong Chen, a scientist in this group, are circumventing this limitation with the help of ceramic materials. In a study, they demonstrate the shape memory effect on a layer of materials about twenty nanometres thick, so-called ferroic oxides. This is the smallest sample size on which such an effect has ever been observed. This achievement means that the shape memory effect can now also be applied to tiny machines on the nanoscale.

In the nanoscale structures developed from ferroic oxides, electrical energy triggers a shape memory effect. They are also highly elastic, resilient and allow flexible movements. The reaction to electrical energy is better suited to numerous applications than the punctual temperature manipulations that otherwise cause the shape memory effect. An example of such an application: Thanks to their high elasticity, the oxides could replace muscle fibres or parts of the spine. Another application is novel nanoscale robotic systems. In this application, the mechanical movement that occurs when switching between the two structural forms can be used to drive tiny motors.

In another study, the researchers were able to further develop free-standing oxide structures in such a way that their magnetoelectric properties can be precisely controlled and adjusted. Such moulded oxides could be used for the production of nanorobots, among other things. These are implanted in the body to stimulate cells or repair tissue. External magnetic fields could transform such nanorobots into a different structure. They perform certain functions in the human body, for example.

says Salvador Pané. And finally, magnetoelectric moulded oxides could be used in nanoscale devices such as tiny antennas or sensors.

Article from "medizin & technik" from 17 March 2023