MONOLITHIC PZT ACTUATOR, STAGE, AND METHOD FOR MAKING

Abstract

A monolithic, bulk piezoelectric actuator includes a bulk piezoelectric substrate having a starting top surface and an opposing starting bottom surface and a at least two electrodes operatively disposed on the bulk piezoelectric substrate consisting of at least two discrete electrodes disposed on either/both of the starting top surface and the starting bottom surface and at least one electrode disposed on the respective other starting bottom surface or starting top surface. A stage includes a base, at least two of the monolithic, bulk piezoelectric actuators disposed on the base, a movable platform disposed on the base, and a respective number of deformable connectors each having a first connection to a respective one of the piezoelectric actuators and a second connection to a respective portion of the movable platform. A method for monolithically making a monolithic, bulk piezoelectric actuator involves a direct write micropatterning technique.

Claims

1. A monolithic piezo actuator, comprising: a bulk piezoelectric substrate having a starting top surface and an opposing starting bottom surface; and a plurality of electrodes operatively disposed on the bulk piezoelectric substrate, consisting of: a plurality of discrete electrodes disposed on at least one of the starting top surface and the starting bottom surface and at least one electrode disposed on the at least one of the respective starting bottom surface and the starting top surface.

2. The piezoelectric actuator of claim 1, wherein the bulk piezoelectric substrate has at least one intermediate surface.

3. The piezoelectric actuator of claim 1, characterized by an operative condition comprising an out-of-plane twisting motion.

4. A method for monolithically making a piezoelectric actuator, comprising: providing a bulk piezoelectric (PZT) material that includes an electrode disposed on a starting top surface thereof and on an opposing starting bottom surface thereof; and using a direct write micropatterning technique to remove at least a portion of the electrode on at least one of the starting top surface and the starting bottom surface, such that the monolithic, bulk PZT material comprises a plurality of electrodes consisting of a plurality of discrete electrodes on the at least one of the starting top surface and the starting bottom surface and at least one electrode on the at least one of the respective starting bottom surface and the starting top surface.

5. The method of claim 4, wherein the direct write (maskless) micropatterning technique includes at least one of laser micromachining, water-jet drilling, ultrasonic drilling, electrical discharge machining, laser-assisted etching, and micro-CNC machining.

6. The method of claim 4, further comprising removing at least a portion of at least one of the non-electrode containing starting top surface and the non-electrode containing starting bottom surface to form at least one non-electrode containing intermediate surface.

7. The method of claim 6, comprising forming asymmetric intermediate surfaces in the respective non-electrode containing regions of the starting top surface and the starting bottom surface.

8. The method of claim 4, comprising forming the monolithic piezoelectric actuator into a beam shape in a length, L, direction characterized by a width, W and a height, H, where W is less than or about equal to H and W, H<<L.

9. The method of claim 4, comprising forming the monolithic piezoelectric actuator into a plurality of monolithic, contiguous segments, each next adjoining segment of which has an in-plane orientation along the length, L, that is different than that of its respective prior segment by between greater than zero degrees to +90 degrees.

10. The method of claim 4, comprising forming the monolithic piezoelectric actuator into a curvilinear shape along the length, L, direction.

11. A method for making a stage, comprising: providing a plurality of the actuators according to claim 4; providing a moveable PZT platform; providing a respective plurality of deformable connectors each having a first connection to a respective one of the plurality of piezoelectric actuators and a second connection to a respective portion of the movable platform.

12. The method of claim 11, further comprising forming a monolithic, bulk PZT device in the moveable PZT platform.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0050] FIG. 1(a) schematically shows the process flow used for fabricating a Bulk PZT bimorph.

[0051] FIG. 1(b) shows an image of a fabricated 10 mm long, 0.45 mm wide, 0.5 mm thick bulk PZT bimorph for in-plane actuation.

[0052] FIG. 1(c) schematically shows a top view of the bulk PZT bimorph unactuated (left) and actuated for lateral, in-plane deflection (right), according to illustrative embodiments of the invention.

[0053] FIG. 2(a) shows a schematic cross sectional view of a monolithic piezoelectric actuator in which the non-electrode containing starting top surface has been direct write micropatterned to form a non-electrode containing intermediate surface.

[0054] FIG. 2(b) shows a schematic cross sectional view of a monolithic piezoelectric actuator in which the non-electrode containing starting bottom surface has been direct write micropatterned to form a non-electrode containing intermediate surface.

[0055] FIG. 2(c) shows a schematic cross sectional view of a monolithic piezoelectric actuator in which the non-electrode containing starting top surface and the non-electrode containing starting top surface have been direct write micropatterned to form non-symmetrical, non-electrode containing intermediate surfaces, according to illustrative aspects of the invention.

[0056] FIG. 3 schematically illustrates in a top view a two section monolithic, contiguous PZT bimorph in an unactuated (top) and an actuated (bottom) state for providing in-plane deflection, according to an illustrative aspect of the invention.

[0057] FIG. 4 shows a photograph of a stage comprising a base, a rotatable platform, four quadratically positioned monolithic, contiguous PZT bimorph actuators, and four respective springs each connected to an actuator and the rotatable platform, according to an exemplary embodiment of the invention. A device is shown mounted on the rotatable platform.

[0058] FIG. 5 schematically illustrates a four actuator stage (center), a cross sectional view of one of the monolithic PZT actuators comprising the stage (lower left), a table showing a positive or a negative voltage that can be applied to the numbered electrodes V1-V8 of the four PZT actuators to achieve a desired motion, and a graph showing angular and linear speeds of the actuators depending on the provided excitation, according to illustrative aspects of the invention.

[0059] FIG. 6(a) is a cross sectional view of capacitors formed by selective depolarization of PZT.

[0060] FIG. 6(b) shows the capacitor in use as part of the associated electronic circuitry, according to illustrative aspects of the invention.

[0061] FIG. 7 schematically illustrates a monolithic, piezoelectric gyroscope design according to an illustrative aspect of the invention.

[0062] FIG. 8 shows a monolithically fabricated piezoelectric gyroscope (FIG. 7) placed in a DIP package (left), and mounting the piezoelectric gyroscope on the rotatable (dither) platform of the stage, according to illustrative aspects of the invention.

DETAILED DESCRIPTION OF NON-LIMITING, EXEMPLARY EMBODIMENTS

[0063] An embodiment of the invention is a monolithic, bulk piezoelectric actuator 100-1 capable of in-plane (lateral) motion with substantially no out-of-plane (transverse) motion, as illustrated, respectively, in FIGS. 1a and 1c. Referring to FIG. 1a, the bulk piezoelectric actuator 100-1 is derived from a commercially available bulk PZT and consists of a bulk PZT material 101 and electrodes 102.sub.T and 102.sub.B on top and bottom surfaces, respectively, of the bulk PZT material 101. FIG. 1a also schematically shows the process flow used for fabricating the monolithic, bulk PZT actuator 100-1 from the monolithic, bulk PZT plate 100.

[0064] As further illustrated in the lower left Initial Cross Section AA diagram of FIG. 1a, the top and bottom electrodes 102.sub.T and 102.sub.B are provided on what are referred to as the starting top surface 108 and the starting bottom surface 109 of the bulk PZT plate 100. As further illustrated in the diagrams along the top of FIG. 1a, a direct write micropatterning technique is used on the bulk PZT plate 100 to remove a portion of the starting top surface electrode 102.sub.T and a portion of the starting bottom surface electrode 102.sub.b, such that the monolithic, bulk PZT material 100 now comprises two discrete electrodes 102a, 102b on the starting top surface and two discrete electrodes 102c, 102d on the starting bottom surface resulting in monolithic, bulk PZT actuator 100-1.

[0065] It is to be appreciated that although two discrete electrodes on each of the starting top surface and the starting bottom surface are shown, the invention contemplates an operable monolithic, bulk PZT actuator having at least two discrete electrodes disposed on at least one of the starting top surface and the starting bottom surface and at least one electrode disposed on the other respective starting bottom surface and starting top surface. When there are no intermediate PZT surfaces (described further below) the embodied actuator exhibits substantially only lateral (i.e., in the plane of the length, L, direction) motion (see FIG. 1c) upon application of a voltage.

[0066] Further as illustrated in FIG. 1c, the monolithic, bulk PZT actuator is in the geometry of a beam; i.e., having a cross sectional width, W and Height, H, where W is less than or about equal to H, and a length, L, where L is much greater than W or H.

[0067] Referring again to FIG. 1a, it schematically illustrates a method for monolithically making a piezoelectric actuator. As shown from left to right, a bulk piezoelectric (PZT) material that includes an electrode disposed on a starting top surface thereof and on an opposing starting bottom surface thereof is provided. A direct write micropatterning technique is used to remove at least a portion of the electrode on at least one of the starting top surface and the starting bottom surface, such that the monolithic, bulk PZT material comprises a plurality of electrodes consisting of a plurality of discrete electrodes on the at least one of the starting top surface and the starting bottom surface and at least one electrode on the at least one of the respective starting bottom surface and the starting top surface. The direct write (maskless) micropatterning technique includes at least one of laser micromachining, water-jet drilling, ultrasonic drilling, electrical discharge machining, laser-assisted etching, and micro-CNC machining. The direct write technique allows precision removal of PZT and/or electrode material, optionally with double-side (top-bottom) alignment capability.

[0068] Electrical excitation of electrodes patterned on the PZT plate generates motion, whose direction and amplitude are controlled by the polarity and magnitudes of electrical potentials on the electrodes formed on the device. An advantageous feature of the embodied invention is that it allows monolithic fabrication of actuators from commercially available piezoelectric plates without any mask making, lithography, or electrode deposition step, all of which increase the time and cost of manufacture. Furthermore, the ability to double side align the electrodes can yield almost doubling of the actuator displacements in certain actuation arrangements, and allows more complex displacement vectors at the tip due to an additional electrode formed on the back side.

[0069] FIG. 1b shows an image of a fabricated 10 mm long, 0.45 mm wide, 0.5 mm thick bulk PZT bimorph (two electrodes top and bottom) for in-plane actuation.

[0070] The direct write micropatterning technique can also be advantageously employed to created intermediate PZT material surfaces (211, 212, 213, 214, others) as illustrated in FIG. 2(a, b, c). Depending upon the number of discrete electrodes on the starting top and bottom surfaces of the bulk PZT, the monolithic, bulk PZT actuators having symmetric or asymmetric, electrodeless intermediate surfaces can provide both controllable in-plane and/or out-of-plane (planar and/or twisting) motion(s) depending upon starting surface electrode number, sizes, and applied voltages. It will be appreciated that according to the embodied invention, electrodes are only disposed on the starting top and bottom surfaces and never on any of the intermediate PZT surfaces.

[0071] Still further advantageously as illustrated in FIG. 3, the monolithic, bulk PZT actuator 301 can be fabricated into a plurality of contiguous segments 301.sub.n (two segments 301.sub.n1, 304.sub.n2 shown), such that when voltage is applied, the actuator experiences in-plane (plane of the paper) motion. As illustrated, subsequent segment 301.sub.2 is oriented (in-plane) at an angle of 90 degrees from preceding segment 301.sub.1; however, it is to be appreciated that the angle between adjoining contiguous segments can be any angle between greater than zero degrees to 90 degrees. The plurality of segments may also proceed in a curve manner such as an in-plane potato peel shape.

[0072] FIG. 4 shows a stage 400 that includes a base 406, a plurality (four shown) of multi-segment (301.sub.1, 301.sub.2, 301.sub.3, etc.), monolithic, bulk PZT actuators 401 piezoelectric actuators disposed quadratically on and about the base, a movable platform 407 disposed on the base, and a plurality (four shown) of deformable connectors 412 each having a first connection 412a to a respective one of the plurality of piezoelectric actuators 401 and a second connection 412b to a respective portion of the movable platform 407. Electrode connections are also illustrated. The multi-segment, monolithic, bulk PZT actuators 401 can be of the no-intermediate surface type (FIG. 1) or of the electrodeless-intermediate surface type (FIG. 2).

[0073] FIG. 5 illustrates a stage 501 that schematically shows an actuator or actuator segment in cross section. The illustrated actuator or actuator segment has two electrodes each on the starting top and bottom surfaces of the bulk PZT and no intermediate surfaces. The table in FIG. 5 illustrates controllable motion control of the actuators and thus of the moveable platform by virtue of the voltage polarity applied to each of the electrodes.

[0074] As mentioned hereinabove, it would be advantageous to integrate passive electrical components such as capacitors, resistors, and inductors into a device (e.g., sensor) mounted on or in the rotatable platform of the piezoelectric motion stage as embodied herein, for buffering and filtering electronic signals. FIG. 6a shows a cross sectional view of capacitors formed by selective depolarization of PZT. FIG. 6b similarly shows a capacitor in use as part of the associated electronic circuitry. The same direct write micropatterning technique and process flow as used for monolithically fabrication the embodied bulk, monolithic piezoelectric actuators can be used to form the electrical components.

[0075] In addition to a sensor, one may wish to have a piezoelectric device, including but not limited to piezoelectric gyroscopes, accelerometers, and energy harvesters, mounted on or integrally formed in the rotatable platform of the motion stage. From cost and integration standpoints, it would be especially advantageous and beneficial to form these components directly, monolithically in a PZT material, co-fabricated with the motion stage, using direct write micropatterning, with the lateral actuator as the elemental component. FIG. 7 schematically illustrates an illustrative direct write micropatterned monolithic, piezoelectric gyroscope. FIG. 8 shows the monolithically fabricated gyroscope incorporated into a piezoelectric rotatable (dither) platform of the motion stage, as illustrated in FIGS. 4 and 5. Monolithic integration of a piezoelectric device on a stage suspended far from the stage's base also allows thermal isolation of the device. This is useful for thermal actuation and sensing applications of bulk-PZT, which relies on generation or sustaining of large temperature gradients between the stage's base and the device.

[0076] While several inventive embodiments have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the function and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications is deemed to be within the scope of the inventive embodiments described herein. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the inventive teachings is/are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific inventive embodiments described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, inventive embodiments may be practiced otherwise than as specifically described and claimed. Inventive embodiments of the present disclosure are directed to each individual feature, system, article, material, kit, and/or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and/or methods, if such features, systems, articles, materials, kits, and/or methods are not mutually inconsistent, is included within the inventive scope of the present disclosure.

[0077] All definitions, as defined and used herein, should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and/or ordinary meanings of the defined terms.

[0078] The indefinite articles a and an, as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean at least one.

[0079] The phrase and/or, as used herein in the specification and in the claims, should be understood to mean either or both of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Multiple elements listed with and/or should be construed in the same fashion, i.e., one or more of the elements so conjoined. Other elements may optionally be present other than the elements specifically identified by the and/or clause, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, a reference to A and/or B, when used in conjunction with open-ended language such as comprising can refer, in one embodiment, to A only (optionally including elements other than B); in another embodiment, to B only (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc.

[0080] As used herein in the specification and in the claims, or should be understood to have the same meaning as and/or as defined above. For example, when separating items in a list, or or and/or shall be interpreted as being inclusive, i.e., the inclusion of at least one, but also including more than one, of a number or list of elements, and, optionally, additional unlisted items. Only terms clearly indicated to the contrary, such as only one of or exactly one of, or, when used in the claims, consisting of, will refer to the inclusion of exactly one element of a number or list of elements. In general, the term or as used herein shall only be interpreted as indicating exclusive alternatives (i.e. one or the other but not both) when preceded by terms of exclusivity, such as either, one of, only one of, or exactly one of. Consisting essentially of, when used in the claims, shall have its ordinary meaning as used in the field of patent law.

[0081] As used herein in the specification and in the claims, the phrase at least one, in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements. This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase at least one refers, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, at least one of A and B (or, equivalently, at least one of A or B, or, equivalently at least one of A and/or B) can refer, in one embodiment, to at least one, optionally including more than one, A, with no B present (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including elements other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other elements); etc.

[0082] It should also be understood that, unless clearly indicated to the contrary, in any methods claimed herein that include more than one step or act, the order of the steps or acts of the method is not necessarily limited to the order in which the steps or acts of the method are recited.

[0083] In the claims, as well as in the specification above, all transitional phrases such as comprising, including, carrying, having, containing, involving, holding, composed of, and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases consisting of and consisting essentially of shall be closed or semi-closed transitional phrases, respectively, as set forth in the United States Patent Office Manual of Patent Examining Procedures, Section 2111.03.