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New developed hermetically sealed protection for piezo-ceramic actuators

Compact, robust and waterproof – PZT Actuators with Resistance against exposure to Humidity

From medical engineering to mechanical engineering to automotive industry applications – for years piezo-ceramic actuators have been an integral part of a broad range of applications and have proven their effectiveness millions of times over. The only problem: the actuator’s vulnerability to high humidity and the associated reduction in its durability. CeramTec has now succeeded in developing piezo-ceramic actuators with hermetically sealed protection that also offer outstanding long-term stability. This opens up a world of exciting new possibilities in industry and technology.

CeramTec piezo-ceramic actuators are made from hundreds of layers of lead zirconate titanate (PZT) films and exhibit a charge separation when subjected to the deformation process by an external force. With a speed of up to 0.1 milli­seconds, they can react very quickly while simultaneously exerting a force of one to two kilonewtons. Conventional piezo-ceramic actuators are protected by a polymer or ceramic coating. However, micro fissures may form during operation, allowing water molecules to come into contact with the piezoceramic. The stray current that arises as a result of this process reduces the performance capability of the actuator and can even destroy it.

One hundred percent Resistance against exposure to Humidity

This is why CeramTec has developed a special manufacturing process that chemically converts the adsorbed water once the piezo-ceramic actuator has been sealed. The result is a completely water-free environment in the stainless steel housing, which simultaneously serves as a diffusion barrier against external exposure to humidity. Moreover, the bellows ensure the housing maintains a low stiffness, which is essential in order for the actuator to expand freely as voltage is applied.

The electrical connection feedthroughs in the stainless steel housing also play a key role in protecting the actuator from humidity and moisture: They are firmly integrated into the component with a specially developed glass solder and ensure that no humidity enters the interior of the stainless steel housing along the wiring. Even after a 1,000 hours of operation in endurance testing, stray currents in the actuators with hermetically sealed housings still exhibited values of far less than 100 nanoamperes.

New Applications in Industry and Technology

The actuators’ hermetic seals enable applications that were either impossible or extremely difficult to realize until now. Today piezo-ceramic actuators can be used to position drilling and honing tools operated with cooling and lubricating agents. It is also possible to use piezo-ceramic actuators for extended periods without issue, even in extremely humid regions like the tropics. With sufficient encapsulation of the connecting wires, the housed actuator from CeramTec can also be deployed under water.

Power Module as the Solution for higher blocking Forces

The hermetically sealed piezo-ceramic actuators are designed for blocking forces of approximately one to two kilonewtons and travels of up to 45 micrometers. CeramTec developed the Power Module for applications that require significantly higher blocking forces. Just like the individual housing, it is also hermetically sealed and comprises four rows, each with ten piezo-ceramic actuators. Designs with different arrangements including fewer or more actuators are also possible