Multi-layer PZT microactuator having oppositely poled PZT constraining layer
AssigneeMagnecomp Corporation
InventorsKuen Chee Ee, Long Zhang, Peter Hahn, David Glaess
Life of this patent
Estimating the term…
Abstract
A multi-layer piezoelectric microactuator assembly has at least one poled and active piezoelectric layer and one poled but inactive piezoelectric layer. The poled but inactive layer acts as a constraining layer in resisting expansion or contract of the first piezoelectric layer thereby reducing or eliminating bending of the assembly as installed in an environment, thereby increasing the effective stroke length of the assembly. Poling only a single layer would induce stresses into the device; hence, polling both piezoelectric layers even though only one layer will be active in use reduces stresses in the device and therefore increases reliability.
Claims18
A microactuator assembly comprising:
- a first piezoelectric layer and a second piezoelectric layer, each of the first and second piezoelectric layers comprising poled piezoelectric material, the first piezoelectric layer being closer to a surface to which the microactuator assembly is bonded than is the second piezoelectric layer;
- a first electrode on a bottom side of the first piezoelectric layer;
- and
- a second electrode on a top side of the first piezoelectric layer and between the first piezoelectric layer and the second piezoelectric layer, such that a first voltage differential applied across the first and second electrodes induces an electric field across the first piezoelectric layer;
- wherein:
- the first electrode is operatively connected to a first voltage and the second electrode is operatively connected to a second voltage different from the first voltage thereby defining a first voltage differential applied across the first piezoelectric layer, the first voltage differential inducing a first electric field across the first piezoelectric layer causing the first piezoelectric layer to expand or contract;
- and
- substantially no voltage differential is applied across the second piezoelectric layer;
- whereby:
- the second piezoelectric layer acts as a constraining layer to resist expansion or contraction of the first piezoelectric layer;
- and
- the second piezoelectric layer expands or contracts in a direction that is opposite the expansion or contraction of the first piezoelectric layer.
A microactuator assembly comprising:
- a first electrode;
- a first poled piezoelectric layer over the first electrode;
- a second electrode over the first poled piezoelectric layer;
- a second poled piezoelectric layer over the second electrode, the second poled piezoelectric layer expands or contracts in a direction that is opposite an expansion or contraction of the first poled piezoelectric layer;
- a third electrode over the second poled piezoelectric layer;
- wherein:
- the first and second electrodes are electrically accessible from a bottom of the assembly;
- the third electrode is not electrically accessible from the bottom of the assembly, and the third electrode is electrically connected to the second electrode whereby no electric field exists between the second and third electrodes.
Dependencies are inferred from the claim text.