recent years, owing to the necessity of reducing the physical size of
electronic devices, micro-fabrication techniques have emerged which also make
it possible the production of very small mechanical components, including
miniature actuators P.R.Ouyang et.al. 2008.
Shape memory alloy actuator:
The working of SMA
actuators is based upon the shape memory effect (SME) of some alloys i.e.
Nitinol (an alloy of nickel and titanium metals). SME is a phenomenon to regain
its original shape when it is exposed to higher temperature or magnetic field.
This property to deflect under external load and return to its initial shape
when subjected to some kind of magnetic field or higher temperature make it
suitable for the use in various industrial applications. These actuators can be
formed into wire, bar and rod and used in the temperature range of -100 0C
to +100 0C. As an actuator, it is capable of achieving up to 5%
strain and 50,000 psi recovery stress, resulting in ? 1 Joule/gm of work
output. P. R. Ouyang et.al.
Ionic polymer metal composites (IPMCs):
IPMCs are the electroactive polymers that can use as both
sensors and actuators. IPMC actuator is composite of Nafion membrane sandwiched
between two thinly coated Pt electrodes on each side of the polymer. The
hydrated cations accumulated on one side of the IPMC resulting in a swelling,
this deformation resulting in the actuation of the IPMC actuators. For an
effective operation of IPMC actuator aqueous environment is the best because it
uses hydrated cations.
The fabricated device with IPMC actuator dimensions of
5 mm?×?2 mm?×?1 mm reached a maximum displacement of 400 ?m
when a square wave of 9 V was applied to the top-bottom electrode
pair. Guo-Hua Feng and Jen-Wei Tsai 2010.
The piezoelectric actuator (PZT) is a
well-known commercially available device for managing extremely small
displacements in the range of 10 pm (1 pm = 10?12
m) to 100 ?m Adriaens H, Koning WL, Banning R (2000).