It may sound surprising, but there are examples of living “three-dimensional displays” in the nature around us. Consider, for example, cephalopods, which include squids and octopuses. These creatures are capable of changing their shape, structure, texture and surface color, practically merging and becoming “invisible” in the environment. And recently, researchers from the universities of Iowa and Illinois have created a “smart skin” that can be used in specialized 3D displays and interfaces for visually impaired people. In addition, the same principle can be used to reduce the resistance arising from the movement of sea and river boats, aircraft and ground vehicles.
The basis of the new “wash skin” are twisted springs made of a special polymer. Under the influence of an external electrical action, these springs either compress or straighten, and if they are placed under a layer of elastic coating, the movement of the springs can be used to change the shape of the coating.
Three-dimensional pixels (voxels) of cephalopod skin are actuated in a similar way, only special subcutaneous muscles (papillae muscles) perpendicular to the surface are used for this purpose. The analogues of these muscles are twisted spiral artificial muscles (TSAM). These artificial muscles are controlled by the applied voltage, with a potential of 0.2 volts per centimeter of length they can shorten by 2000% of their original length, and the springs they make change their height by up to one centimeter, providing a sufficiently high force.
“Such spirals made of a special lightweight polymer replace heavy and cumbersome devices based on conventional electric and pneumatic actuators” – the researchers write, “We actuate this artificial skin using fairly weak electrical pulses, eliminating the need for heavy batteries and noisy air compressors. In addition, this control principle provides greater accuracy of movement and simplicity of design in general.”
Multiple springs of individually controlled artificial muscles are mounted on a substrate of soft material and covered with a layer of the same stretchable material. All of this forms a “smart” skin or 3D display surface capable of displaying a potentially unlimited number of combinations.
“All of this opens up the possibility of using such technology in hydrodynamic control systems to reduce water resistance in moving ships and underwater robots, in 3D displays and haptic feedback devices for augmented and virtual reality systems, in automated surgery, etc.”