Piezoelectric technology opens exciting possibilities for fluid power valves. Since piezoelectric actuators are capacitive devices, they require near-zero power to hold them in a specified position, regardless of whether that position is fully open, fully closed, or anywhere in between. Conventional electrically actuated fluid control valves typically use electromagnetic actuators. They consume power while being held at any position other than their default zero position. Therefore, valves which utilize piezoelectric actuators can save substantial amounts of electric actuation energy compared to conventional valves. Piezoelectric valves are structurally very simple, as they typically have only one active part: a “piezostack,” which translates due to simple tensile or compressive strain, or a “piezobender,” which takes the form of a beam whose tip displaces due to bending induced in the beam.
Despite their many benefits, replacing magnetic actuators with piezoactuators is not straightforward. Fabricating piezoelectric actuators requires specialized processes. Piezostacks produce extremely small displacements, while piezobenders produce extremely small forces. Matching their force and displacement to the requirements of a valve operator is challenging. A piezoactuated valve also performs differently than a conventional valve. As a result, piezoelectric valves have been slow to reach the commercial market.
MEMS-based piezoelectric proportional valves have been under development by this research group since June 2010 with promising results. Nevertheless, the previous project has brought to light that some of the MEMS fabrication procedures involved in manufacturing “thoroughbred” MEMS valves are still experimental in nature. As a result, prototypes that can be taken to commercialization are not likely for another five years or more.
In the course of developing the thoroughbred MEMS valves, a new and unique type of piezoelectric flow control valve has been invented. The new family combines some of the features of the MEMS valves that have been demonstrated successfully with some conventional, non-MEMS based, elements. They are defined as “hybrid MEMS” valves. Revolutionary yet commercializable hybrid MEMS valves prototypes are expected in only about two years.