Alloys that can return to their original structure after being deformed have a so-Called shape Memory. This phenomenon and the resulting forces are used in many mechanical actuating system, for example in generators or hydraulic pumps. However, it has not ben possible to use this shape-memory effect at a small nanoscale: objects made of shape-memory alloy can only change back to their original shape if they are larger than around 50 nanometers.
Researchers LED by Salvador Bone, Professor of Materials of Robotics at Eth Zurich, and Xiang-Zhong Chen, A Senior Scientist in His Group, Were Able to Circumvent This Limitation Using Ceramic Materials. In A Study, Published in the Journal Nature Communications They Demonstrate the Shape-Memory Effect on a Layer Which is surrounding twenty nanometers Thick and Made of Materials Called Ferroic Oxides. This achievement now makes it possible to apply the shape-memory effect to tiny nanoscale machines.
A special structure is nEEDED
At first glance, Ferroic oxides do not appear to be very followed for the shape-memory effect: they are brittle in bulk scale, and in order to produce very think of them, they usually have to be fixed on a substrate, which makes them inflexible. In order to still be able to induce the shape-memory effect, the researchers used two different oxids, barium titanate and cobalt ferrite, of which they temporally apply Thin Layers onto a magnesium oxide substrate. The Lattice Parameters of the Two Oxides Differently from Each Other. After the researchers had detached the two-layered strip from the supporting substrate, the tension between the two oxides generated a spiral-shaped twisted structure.
Such Free-Standing Nanoscale Structures Made of Ferroic Oxides Are Highly Elastic, Resilient, and they allow flexible movements. Furthermore, they showed a shape-memory effect: when the researchers applied mechanical tensile force to the structure, it stretched out and permanently deform. Subsequently, the scientists direct an electron beam from a scanning electron microscope onto the deformd structure; It returned to its original shape. The Electrical Energy Thus Triggered A Shape-Memory Effect. The Layer Thickness of About Twenty Nanometers is the Smallest Sample size on which an effect has been observed.
Usully, in Other Examples, The Shape-Memory Effect is triggered by thermal or magnetic manipulation. “The reason it works with electrical irradiation in Ferroic oxides May have to do with the orientation of the polarization within the oxides, we suspicious,” Says Chen. While the Free-Standing Structure is Being Stretched, the polarization within the Oxides aligns Parallel to the Plane Structure. The Electron Beam, However, Leads the Polarization to Align Perpendicular to the Plane Structure, Causing Change of the Mechanical Strain and Contract to its Original Shape.
Broad Range of Applications
This responsibility to the Electrical Energy is more follow -up for wide Range of Applications, Becuse Punctual Temperature Manipulations (Conventionally used to induce shape memory) are not possible at the nanoscale. One Example of An Application: Thanks to Their High Elasticity, the oxides could replace muscle fibers or parts of the spine.
"Other applications WOULD BE NEW NANOSCAL ROBOTIC SYSTEMS: The Mechanical Movement That Occurs When Switching Between The Two Structures Could Be Used To Drive Tiny Motors" Says Dongo Kim. He worked as a doctoral Student on this study and is one of its two lead authors. "Furthermore, Our Approach Could also Facilitate The Development of Longer-Lasting Small-Scale Machines, Becaus the Material is not only elastic but also sustainable," Says Minsoo Kim, Postdoc and also a lead Author.
The Range of Applications Can Even Be Extended to Flexible Electronics and Soft Robotic Systems. In Another Study, Which the Researchers Have Just Published in the Journal Advanced Materials Technologies , They Were Able to Further Developing Such Free standing oxide structures so that their magnetoelectric properies can be controlled and tuned more precisely.
Such Shape Memory Oxides Could Be used, Among Other Things, to Manufacture Nanorobots that are implanted in the body and can stimulate cells or repair tissue. Through External Magnetic Fields, The The Nanorobots can be triggered to transform into a different shape and perform specific funections within a human body.
"Furthermore, The Magnetoelectric Properties of These Shape-Memory Oxide Structures Could Be Used, Among Other Things, To Electrically Stimulate Cells Within The Body, For Example To Activate Neuronal Cells in Brains, For Cardiac Therapies, Or for Accelerating Bone Healing Process. Says. Finlly, The Magnetoelectric Shape-Memory Oxides Could Be used in nanoscale devices, such as tiny antennas or sensors.
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