Electrostatic actuation is the basic principle behind the electrostatic voltmeter. A force proportional to the applied voltage is generated between two electrodes. By movement against a return spring, this force can be used to drive a needle behind which a scale calibrated in volts is situated. This principle has enjoyed considerable popularity in recent year with the advent of micromachine technology. A related principle, electroadhesion, is the force of electrostatic attraction used to secure paper on plotter surfaces, lift polymer sheet or metal foil components in robotics. Again, micro-robotics technology can exploit such methods for the handling of very delicate micro-optical parts.

 
 
 

Piezoelectricity, first discovered by the Curie brothers, is a technique belonging to the ferroelectric family of materials used in both actuators and sensors. An applied force produces a voltage, or conversely, an applied voltage results in a small movement. When two wafers of piezoelectric material are sandwitched together they form a bimorph whose operation is analogous to thermally driven bimetal strips. Though the force delivered is less than that available from a single piezoelectric element, the stroke can be much much larger.    A related, second order effect is electrostriction which enjoys a lower hysteresis than simple piezoelectric elements but has a very strong temperature dependance.

 
 
 
 

The ferroelectric family also includes thermally stimulated elements known as infra-red pyrometers. Such sensors are used in human proximity detectors and, owing to their very broad band characteristics can also be used in non contact temperature measurement. The wavelength of the infra-red emission peak being related to the temperature.

 

In addition to conventional pneumatics and hydraulics there also exists what are known as smart fluids. Examples include electrorheological and magnetorheological fluids. An electrorheological fluid is an emulsion whose state changes from that of a normal Newtonian to a thixotropic fluid when subjected to high electric field. By analogy, a magnetorheological fluid undergoes a similar liquid to solid phase change under the influence of a magnetic field.  The electrorheological fluid shown here becomes so solid when energised that the receptacle holding the fluid can be lifted free from the table by the inserted conical electrode.

These are just a few of the interesting technologies with which we are constantly involved. At International Phoretics we have expertise in all such fields of smart materials and systems . For further information contact us at:

Tel: (49) 941 943 1108

Fax: (49) 941 943 1424

gareth.monkman@e-technik.fh-regensburg.de