actuator (rus. актуатор otherwise актюатор) — actuating device or an active element thereof that transforms one type of energy (electrical, magnetic, thermal, chemical) into another (most often mechanical), which leads to a specific action defined by a control signal.

Description

The term "actuator" means a device (or an element of a device) that can "act". Usually the term "actuator" refers to a mechanical action, for example, linear movement or rotation. In micro-and nanosystems, piezoelectric or electrostatic effects are often used instead of the electromagnetic energy conversion widely used in macroelectronics.

The simplest electrical actuators include electrostatic devices on the basis of plane-parallel capacitors. Thermal actuators are usually created using the effects of thermal expansion or deformation on the interface of two materials (often a metal-dielectric pair) having different values of the linear thermal expansion coefficient. The elements are heated by passing an electric current through them or by heating the environment. These actuators can develop a great force, but their energy efficiency is very small (usually up to 0,1%).

Chemical control of the actuators can be exercised by changing both the composition of the environment, its acidity and other factors, particularly light. The so-called biological molecular motors can be considered a specific variety of chemical nanoactuators. An example of such a motor is the restriction endonuclease EcoR124I. This tiny device can push and pull a rod-like DNA molecule 2 nanometres in diameter at a rate close to 190 nanometres per second, and the total displacement can reach up to three micrometres. Instead of a "nanobattery" such molecular motors use an ATP (adenosine 5'-triphosphate) molecule, a source of energy used by living cells. An injection of ATP molecules is required to switch on such a "motor".

Another molecular motor - ATP synthase - is intended for the synthesis or hydrolysis of ATP molecules and the transfer of protons (H+) across the cell membrane. In terms of efficiency and force the ATP-synthase considerably outperforms all known natural molecular motors. The force produced by such molecular turbine is typically about 1 pN, and the power is about 1 aW (1·10-18). There are many other nanoactuators that are based on biological molecules, polymers, silicon and other materials.

Illustrations

Nanoactuator - motor. On the left is a pattern, and on the right — a real image from a scanning e

Nanoactuator - motor. On the left is a pattern, and on the right — a real image from a scanning electron microscope. The rotating element known as the rotor is a tiny gold plate sized approximately 250 nm that is attached to the axis represented by a carbon nanotube. The rotor is surrounded by three electrodes, two on the sides and one below. When alternating current with the voltage of some 5 V is supplied to the electrodes, the nanomotor moves.


Authors

  • Goodilin Evgeny A.
  • Shlyakhtin Oleg A.

Sources

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  6. Poole C. P., Owens F. J. Introduction to Nanotechnology. — New Jersey: Wiley–Interscience, 2003. — 388 p.

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