Actuators generally use an energy source to move or control mechanical components. They are often found in motors and various machines. Many kinds of mechanical devices have been miniaturized over the years, but this process typically requires the individual components to be much smaller as well. Miniaturization in the 21st century has progressed to the point that microactuators and other parts are so small that powerful microscopes often have to be used to see them. Industrial processes such as lithography and micro machining are used to make a microactuator, and there are various types that can be made as well.
An electrostatic microactuator is one common variety, but scientists can also build electromagnetic varieties that can produce more power to energize a device like a motor. They are sometimes difficult to make, but are fabricated with methods typically used for making integrated circuits. Motors as small as about 0.04 inches (1 millimeter) across have been made, and have often been used by researchers to insert tiny catheters into biological cells.
There is also a piezoelectric microactuator with composite materials that react similar to crystals, which when pushed on, create an electrical voltage. Thin films can be deposited onto silicon that can produce motion over very short distances. They have sometimes been used in micro miniature rotors. Ultrasonic microactuators are often used in small motors built into piezoelectric devices. These can be integrated into autofocus mechanisms of small cameras, for example.
Moving mechanical components can be built on a small scale, but an electrostatic microactuator is typically made of a material that bends on the basis of electrical charges. Motion is generally microscopic in scale and a small amount of force is produced. Some rotational motors and linear motion comb drives have been developed based on this principle.
Microactuators can be used to build tiny mirrors for displays and projectors. Microscopic current relays and small mechanisms to control hard drives often make use of such miniature devices. They are often called Micro-Electromechanical Systems (MEMS), a category which include many kinds of miniature moving parts.
Production of microactuators can be accomplished by etching parts into silicone. Lithography is often used for making circuits. Light, chemicals, and a layer composed of the parts to be added are typically combined in this process. The finished product is usually produced in layers, while micro machining often involves lasers and scanning electron microscopes, for example, to place individual atoms and cells. Both processes can be used to move microactuator parts and build a micro-miniature device.
