Multi-layer PZT microactuator having a poled but inactive PZT constraining layer
First Claim
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1. A multi-layer piezoelectric 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 disposed underneath 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 is a substantially inactive piezoelectric layer and acts as a constraining layer to resist expansion or contraction of the first piezoelectric layer; and
an overall expansion of contraction of the microactuator assembly is made to be greater in response to the first voltage differential being applied across the first piezoelectric layer than if the second piezoelectric layer were not present.
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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.
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Citations
18 Claims
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1. A multi-layer piezoelectric microactuator assembly comprising:
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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 disposed underneath 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 is a substantially inactive piezoelectric layer and acts as a constraining layer to resist expansion or contraction of the first piezoelectric layer; and an overall expansion of contraction of the microactuator assembly is made to be greater in response to the first voltage differential being applied across the first piezoelectric layer than if the second piezoelectric layer were not present. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A multi-layer piezoelectric microactuator assembly comprising:
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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; a third electrode over the second poled piezoelectric layer; wherein; the first and second electrodes are electrically accessible from a bottom of the assembly; and the third electrode is not electrically accessible from the bottom of the assembly, wherein;
each of the first and second electrodes is connected to one of a driving voltage and ground, and the third electrode is not connected to either a driving voltage or a ground. - View Dependent Claims (14, 15, 16, 17, 18)
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Specification