Actuators technologies
Movement, and its subsets of exercising pressure, shifting weight and balance, have been accomplished through mechanical systems usually controlled by electronics. There are linear and rotary actuators, some using purely mechanical means others a mixture of mechanical and fluid power.
Micro movements have become possible using micro-electromechanical systems.
Progress in coordination of movements has been significant, think about two legged robots that can run, jump and avoid obstacles, maintain the equilibrium also in difficult situations even when pushed.
More recently the design of smart materials has made possible the construction of actuators working through the change of shape of a part by sending electrical signals to the material which result in a change in its structure. This is finding applications in many areas, notably in robot movements and prosthetics movements.
Some smart materials have memory of their state so that once the electrical signal is removed they flip back to their original shape.
These characteristics are also being used to create self-assembling systems.
Smart materials can dispose of the need of motors to create movement, within certain power boundaries, and this allows for more complex movement in a limited space. As an example the implementation of a prosthetic human hand movements requires roughly 30 degrees of freedom (30 different movements) and in turns these would require 30 motors resulting in a bulky setting that won’t fit in a human hand size. By using smart materials to simulate actuation through synthetic muscles it is becoming possible to re-create the normal hand movement.
In case of micro power, studies are ongoing to use micro motors, as tiny as complex molecules. These may find application for drug delivery at cell level or for micro surgery inside blood vessels. In perspective these may become rudimentary autonomous systems although within a very well defined ambient.
In bio-interfaces optogenetics has become the leading technology. It is based on the introduction of specific gene/gene modification to make a cell responsive to a specific light wavelength and by using optical fibre reaching the vicinity of the cell it is possible to stimulate specific behaviour at cell (usually neurone) level.
The application of CRISPR/CAS9 technology may further improve optogenetics making it possible to tweak with genes directly without having to use a virus as a vector. At the same time this brings several ethical issues to the fore.