If you have to build a nanoscale full-featured robot, you need to incorporate complex electronic circuits, antennas, optical and other types of sensors into its design. But the most important thing is that you have to be able to move the robot in some way, otherwise the whole thing makes very little sense. And not so long ago, researchers at Cornwall University developed micron actuators based on materials that have “shape memory”. Such actuators can be integrated into the design of micro robots made of conventionally two-dimensional materials, and they can make the micro robot bend and make other movements that contribute to its movement. And as a demonstration of the capabilities of the new micron actuators, researchers have created the world’s smallest origami, which can roll itself into a given shape or return to its original shape.
The new micron actuators can bend with a radius of curvature of less than one micron, hence their name – micron actuator. Note that this figure is the smallest in the world today of any other such thing. Moreover, it is this bending radius of the actuator that determines what minimum size microscopic robots can have in the design of which they, these actuators, have been used.
The principle of a micron actuator is the “correct” use of one of the common electrochemical reactions. The actuators consist of a nanometer layer of platinum, layers of titanium, titanium dioxide and solid layers of silica glass, which consist of about 30 atomic layers. When a positive electrical potential is applied to such a structure, oxygen atoms from the air penetrate deep into the platinum and react by electrochemical oxidation. This produces mechanical stresses within the platinum layer, and it bends evenly along the lines that are bounded by the faces of the surface areas covered by the hard and inert glass layer.
Note that the mechanical stresses and the bending caused by them persist after the applied electric potential is removed. And the return to the initial form is carried out by applying an electric potential of reversed polarity to the structure, which leads to a reverse reaction, the reaction of electrochemical reduction.
