Actuator device structure

Abstract

An actuation device (1) includes a first actuator element (7a) and a second actuator element (7b), each comprising a piezoelectric layer on a first side (2a) of the actuation device. The width of each actuator element is at least five times its corresponding thickness. A movable element (4) is connected at least to the first actuator element such that actuation of the first actuator element causes movement of the movable element. A reinforcing ring (8a) is located on a second side (2b) of the actuation device opposite to the first side and is positioned relative to the first side between the first and second actuator elements.

Description

Technical Field

[0001] The present invention relates to piezoelectric actuators for use in a range of applications, particularly, but not exclusively, piezoelectric actuators for movable mirror devices. Background Technology

[0002] It is known that applying voltage can actuate mechanical structures to achieve the rotation and displacement of small devices such as micromirrors.

[0003] Existing scanning micromirrors (SEMs) are operated by actuating actuators surrounding a central mirror. Typically, the actuators receive current and oscillate on one or two axes. In micromirror applications, actuators can be driven by electromagnetic, electrostatic, thermoelectric, or piezoelectric effects. Magneto-actuated micromirrors using Lorentz forces are the most common in industry because they are suitable for both static and dynamic operation.

[0004] The applicant has proposed an actuation device for achieving tilting motion and translational “piston” motion in its previous publication WO 2022 / 172012. These piezoelectric actuation devices operate by applying a voltage to a piezoelectric layer deposited on a wide and thin actuator arm (i.e., the width of the actuator arm is more than ten times its thickness).

[0005] One challenge recognized in the development of these actuators is that, due to their unique structure, they are prone to buckling, which limits their deflection range. This problem becomes even more pronounced for larger deflection angles, as the actuator arm experiences greater bending and torsion.

[0006] The present invention aims to solve this problem. Summary of the Invention

[0007] In a first aspect, the present invention provides an actuation device comprising: a first actuator element and a second actuator element, each of the first actuator element and the second actuator element comprising a piezoelectric layer on a first side of the actuation device, wherein the width of each actuator element is at least five times its corresponding thickness; a movable element connected at least to the first actuator element such that actuation of the first actuator element causes movement of the movable element; and a reinforcing ring on a second side of the actuation device opposite to the first side and positioned opposite the first side between the first actuator element and the second actuator element.

[0008] In a second aspect, the present invention provides a method for manufacturing an actuation device, the method comprising: providing a device layer and a body layer; depositing a piezoelectric material on the device layer to form a first actuator element and a second actuator element on a first side of the actuation device; wherein the body layer is on a second side of the actuation device opposite to the first side; etching away a portion of the body layer to form a reinforcing ring on the second side of the actuation device, the reinforcing ring being opposite to a position on the first side between the first actuator element and the second actuator element.

[0009] Therefore, it can be seen that, according to the invention, a reinforcing ring is provided, which can alleviate mechanical stress on the actuator, thereby reducing the risk of buckling. Compared with similar devices without a reinforcing ring, this advantageously contributes to achieving an increased range of motion for the actuator, and in particular, it advantageously contributes to achieving an increased range of vertical deflection for the actuator. As those skilled in the art will understand, buckling is a sudden change in the shape of a component under load and can become problematic when actuation applications require precise positioning of the component. The applicant has found that the actuator implementing the invention helps to provide an increased maximum range of motion for the actuator before buckling occurs.

[0010] By utilizing the strain-reducing structure described above, embodiments of the present invention can provide even greater deflection in devices of the type described in the applicant's earlier publication - WO 2011 / 033028 A1.

[0011] Vertical deflection of up to ±35 μm (70 μm total stroke) has been achieved using embodiments of the present invention at an applied voltage of 20 V. For comparison, some practical embodiments of the present invention disclosed in WO 2011 / 033028 A1 have a stroke of 9 μm. The long-stroke piston motion achieved by the present invention can be used in optical devices, such as allowing three-dimensional image scanning or for use in MEMS Fourier transform infrared (MEMS FTIR) spectrometers. Applications outside the optical field can also benefit from the non-buckling long-stroke motion achievable according to the present invention, such as micropumps, microfluidic devices, and microspeakers.

[0012] Actuation of the first actuator element and optionally the second actuator element can cause dimensional and / or deformation changes in the actuator element to produce movement of the movable element. A voltage can be applied to the piezoelectric layer of the actuator element to move the movable element in a desired direction. Forming the first actuator element in the form of a thin film, i.e., having a width at least five times its thickness, allows for large movements of the movable element, such as large deflections. In one set of embodiments, the width of the first actuator element is at least ten times its thickness. Similarly, in one set of embodiments, the width of the second actuator element is at least ten times its thickness.

[0013] In one set of embodiments, actuation of one or both actuator elements causes the movable element to translate vertically (i.e., along a direction perpendicular to the plane of the piezoelectric layer). This vertical translation can be considered a “piston” motion in contrast to a more typical tilting motion. For example, the movable element can function like a diaphragm to generate sound waves. In such embodiments, the movable element is typically not optically reflective (although this possibility is not excluded, of course).

[0014] In one set of embodiments, each actuator element comprises an annular shape. The first and second actuator elements may be concentric. Preferably, the annular shape is circular, i.e., the actuator element is annular; however, the actuator element may have other shapes, such as elliptical. The first and second actuator elements may have equal widths (e.g., the width of the annulus is the difference between the radius of its outer circle and the radius of its inner circle). In one set of embodiments, the maximum dimension of the first actuator element (e.g., outer width or outer diameter) is smaller than the corresponding maximum dimension of the second actuator element. Therefore, the second actuator element may surround the periphery of the first actuator element. For example, the outer edge of the first actuator element may be connected to the inner edge of the second actuator element.

[0015] Any number of additional actuator elements (e.g., a third actuator element, a fourth actuator element, a fifth actuator element, etc.) can be present. Similarly, as the number of additional actuator elements varies proportionally, additional corresponding reinforcing rings can be present. In one set of embodiments, the actuation device has multiple reinforcing rings, each reinforcing ring positioned opposite the first side between adjacent actuator elements. In such a set of embodiments, there will be a corresponding multiple actuator elements; for example, the actuation device according to an embodiment of the invention may have four actuator elements and three reinforcing rings. The applicant has determined that by increasing the number of actuator elements and reinforcing rings, the maximum possible deflection of the actuation device (e.g., vertical deflection) can be increased before buckling occurs, and in particular, the maximum possible piston movement of the actuation device can be increased before buckling occurs. In fact, the applicant has found that the maximum deflection varies proportionally with the total number of reinforcing rings and actuator elements. Therefore, in a preferred set of embodiments, the actuation device includes multiple reinforcing rings. For example, the actuation device may include at least three reinforcing rings.

[0016] In one set of embodiments, multiple piezoelectric actuator elements can be independently addressed using corresponding voltages. The actuation device can be actuated by selectively applying voltages to one or more independently addressable piezoelectric elements.

[0017] In one set of embodiments, each actuator element includes an inner actuator portion and an outer actuator portion, or a set of actuator portions. Therefore, each actuator element may include multiple actuator portions. Both the inner and outer actuator portions may include corresponding different piezoelectric regions. Both the inner and outer actuator portions may include a continuous ring with a width approximately half the width of each actuator element. Alternatively, in one set of embodiments, each actuator element is circumferentially divided into multiple portions, which may be independently addressable, allowing voltage to be selectively applied to each portion; for example, each actuator element may include M independently addressable piezoelectric portions.

[0018] In one set of embodiments, actuator portions can be grouped such that a group of actuator portions can be addressed independently of those not in the group. In these embodiments, voltage can be selectively applied to each actuator portion within the group, causing only that group of actuator portions to be actuated. In these embodiments, those actuator portions included in the group may not be addressable independently of each other.

[0019] Each actuator portion, both internal and external, may include at least one distinct piezoelectric region, such as a piezoelectric region made of lead zirconate titanate (PZT). In one set of embodiments, the internal and external actuator portions can be addressed independently using corresponding voltages. Therefore, one or more internal and external actuator portions can be actuated individually. Individual actuation of the internal and external actuator portions facilitates upward and downward deflection—for example, depending on the number of piezoelectric portions, it could be up-and-down piston movement or tilting movement.

[0020] In one set of embodiments, the actuation device includes N reinforcing rings and N+1 actuator elements. In embodiments where each actuator element includes a single inner actuator portion and a single outer actuator portion, the actuation device may include N reinforcing rings and 2(N+1) actuator portions.

[0021] In one set of embodiments, the actuation device includes a substrate, such as a frame. The outermost actuator element may be attached to the substrate.

[0022] Typically, an actuation device includes control electronics configured to control actuation of the actuator elements, for example, by selectively applying voltage to one or more actuator elements or portions thereof. In a first operating mode, voltage can be applied to the external portions(s) of each actuator element(s). This can cause vertical deflection of the actuator element and piston movement of the movable element along a first direction. In a second operating mode, voltage can be applied to the internal portions(s) of each actuator element(s). This can cause vertical deflection of the actuator element and piston movement of the movable element along a second direction opposite to the first direction.

[0023] In one set of embodiments, a movable element is connected to the innermost actuator element (e.g., a first actuator element). The movable element and the first actuator element may include a common edge. This common edge may be the outer periphery of the movable element and the inner edge of the first actuator element. In another set of embodiments, a substrate is connected to the outermost actuator element. The substrate and the outermost actuator element may include a common edge. This common edge may be the outer periphery of the outermost actuator element and the inner edge of the substrate. The substrate and the movable element may each provide anchoring regions for movement of the actuation device relative to these regions.

[0024] In one set of embodiments, the actuation device provides three degrees of freedom for the movable element, for example, tilting along two directions about two orthogonal axes and translation along a third mutually orthogonal direction. This can be achieved by each actuator element having multiple piezoelectric portions adjacent in azimuth. Such piezoelectric portions can have an annular sector shape. The angle opposite to each piezoelectric portion can be between 45° and 180°. The opposite angle is preferably common to all piezoelectric portions. For example, the angle opposite to each piezoelectric portion can be 45°, 90°, or 120°. When the actuator element each includes multiple piezoelectric portions adjacent in azimuth, pitch-tilt motion can be achieved by selective actuation of the piezoelectric portions. In one set of embodiments, each actuator element includes an inner portion and an outer portion, each inner portion and outer portion including a corresponding multiple piezoelectric portions adjacent in azimuth. The piezoelectric portions are preferably independently addressable.

[0025] The reinforcing ring, the first actuator element, and the second actuator element preferably comprise a common material, such as silicon. The actuation device can be manufactured, for example, by photolithographic etching of the device layer and the body layer to form the reinforcing ring and the actuator element. The actuator element and any portion thereof can be formed by photolithographic etching of the device layer, and the reinforcing ring can be formed by etching of the body layer.

[0026] The piezoelectric material is preferably not deposited directly on the device layer. In one set of embodiments, the piezoelectric material is deposited between a first electrode and a second electrode on the device layer. In another set of embodiments, each piezoelectric layer is a piezoelectric stack, wherein the piezoelectric stack may include a platinum layer, a PZT layer, and a gold layer, with the PZT sandwiched between the gold layer and the platinum layer. The device layer may include silicon. The thickness of the device layer may be between 2 μm and 10 μm.

[0027] In one set of embodiments, the actuation device includes, for example, a silicon-on-insulator (SOI) wafer as a starting material, the SOI wafer comprising a device layer, a buried oxide layer, and a body layer. The device layer and body layer may be made of silicon. The thickness of the device layer can range from 2 μm to 10 μm. The thickness of the buried oxide layer can be approximately 500 nm. The thickness of the buried oxide layer can range from 300 nm to 700 nm.

[0028] Each of the first and second actuator elements may include multiple layers. In one set of embodiments, the first and second actuator elements include three layers: a piezoelectric layer, a device layer, and a body layer, arranged, for example, in the order of piezoelectric layer, device layer, and body layer. The reinforcing ring may be made of the body layer. While the device layer may have a uniform thickness throughout the actuator, the body layer is preferably non-uniform in thickness throughout the actuator—for example, the body layer may be thicker at the reinforcing ring and thinner at the actuator element, or the body layer may be completely removed below the actuator element.

[0029] In one set of embodiments, the reinforcing ring protrudes from the second side of the actuator and protrudes to a degree equal to 100 µm to 1 mm (e.g., 300 µm to 500 µm). The width of the reinforcing ring (e.g., the distance between the radially inner surface and the radially outer surface of the reinforcing ring) can be between 30 µm and 100 µm (e.g., 30 µm to 90 µm). For example, in a preferred embodiment, the width of the reinforcing ring is about 40 µm. The applicant has found that these specific dimensions are optimal for reducing the risk of buckling while allowing sufficient range of motion. Furthermore, a width of about 40 µm to 50 µm is a good trade-off between thinness, which maintains a large range of motion and reduces the area and mass occupied by the ring, and is easy to manufacture. This means that reinforcing rings of these widths can be manufactured in a controlled and repeatable manner. As those skilled in the art will understand, a narrower reinforcing ring occupies less space on the actuator, thus allowing more area for the actuator elements.

[0030] In one set of embodiments, the mass per unit area of ​​the movable element is greater than that of the first actuator element and the second actuator element. For example, the movable element may be only slightly thicker than the actuator element, or a supplementary mass block may be attached to the movable element, typically on the side opposite the outward-facing surface of the movable element in use. The larger mass per unit area of ​​the movable element can, for example, prevent deformation of the movable element when the first actuator is actuated by increasing its stiffness. The thickness of the aforementioned reinforcing ring can be comparable to the thickness of the movable element.

[0031] When a supplementary mass block is provided, the supplementary mass block can be any suitable size or shape; however, in one set of embodiments, the supplementary mass block includes a cylindrical shape whose maximum width (e.g., diameter) is equal to or greater than its thickness, for example, at least twice its thickness, or at least five times its thickness. The width of the mass block can be the same as the width of the movable element.

[0032] In one set of embodiments, the movable element comprises multiple individually addressable piezoelectric segments. Therefore, the movable element can be a deformable movable element that can change shape when actuated (e.g., the surface of the deformable movable element can change its curvature). When actuated, there can be a minimum (e.g., zero) lift around the periphery of the deformable movable element and a maximum (e.g., several hundred micrometers) lift at the center of the deformable movable element, resulting in a curved profile. The extent of this maximum lift can depend on the diameter of the movable element; for example, if a larger lift is desired, a movable element with a larger diameter can be selected. The deformable movable element can be thicker or thinner than the actuator element. For example, a deformable movable element thicker than the actuator arm will provide a smaller maximum lift; however, reduced flexibility can provide better optical reflective properties. During rapid movement of the movable element, a more flexible deformable movable element may be more prone to dynamic deformation. Therefore, slightly reducing its flexibility by controlling the thickness of the deformable movable element can help prevent such unpredictable or undesirable deformation.

[0033] In one set of embodiments, the thickness of the deformable movable element is equal to or within 25% of the thickness of the actuator element, for example, within 10% of the thickness of the actuator element.

[0034] In one set of embodiments, the movable element has an optically reflective surface (e.g., a gold coating or a mirror coating). This allows the movable element to function as a movable mirror.

[0035] When the actuation device is in a balanced state, that is, when the actuator element is not actuated, at least one surface of the movable element may be coplanar with the actuator element.

[0036] The overall width of the actuator can be less than 1 cm. The width of the movable element can be between 0.3 mm and 25 mm, and the thickness can be between approximately 100 μm and 400 μm. The width of each actuator element can be between approximately 600 μm and 700 μm. The width of each section of the actuator element can be between approximately 300 μm and 350 μm.

[0037] Features of any aspect or embodiment described herein may be applied to any other aspect or embodiment described herein in any appropriate context.

[0038] When referring to different embodiments or groups of embodiments, it should be understood that these different embodiments or groups of embodiments are not necessarily different, but can overlap. Attached Figure Description

[0039] Some preferred embodiments of the invention will now be described by way of example only with reference to the accompanying drawings, in which: Figure 1 This is a schematic diagram of the actuation device for implementing the present invention; Figure 2 yes Figure 1 A second view of the actuator; Figure 3 yes Figure 1 The cross-section of the actuator; Figure 4 yes Figure 3 Perspective view of the cross-section shown; Figure 5 Some dimensions of the cross-section of the actuator are shown; Figure 6 A close-up view of a CAD drawing of the reinforcing ring of the actuation device implementing the present invention is shown; Figure 7A The first actuation mode of the actuation device is shown; Figure 7B The second actuation mode of the actuation device is shown; Figure 8A and Figure 8B This demonstrates how the first and second actuation modes achieve piston movement in two directions; Figure 9A and Figure 9B This demonstrates how the von Mises stress varies throughout the device under both the first and second actuation modes; Figure 10 This is a photograph showing a second embodiment of the actuation device; Figure 11This is a schematic diagram illustrating how the actuation device according to the second embodiment can be actuated; Figure 12 This is a photograph showing the third embodiment; Figure 13 This is a schematic diagram illustrating how the actuator element of the actuation device according to the third embodiment can be actuated; Figure 14A and Figure 14B This is a schematic diagram illustrating how a deformable, movable element can be actuated; Figure 15 This is a CAD drawing of the third embodiment of the actuation device; Figure 16 This is a photograph illustrating the fourth embodiment; Figure 17 This is a schematic diagram illustrating how the actuation device according to the fourth embodiment can be actuated; and Figure 18 The manufacturing steps A to F for manufacturing an actuation device according to an embodiment of the present invention are illustrated by a schematic flowchart. Detailed Implementation

[0040] Figure 1 An actuation device 1 according to a first embodiment of the present invention is shown. Figure 2 It shows Figure 1 Another perspective view of the actuating device 1 shown. The actuating device 1 has a first side 2a and a second side 2b opposite to the first side 2a. Although Figure 1 A perspective view is shown from the second side 2b (i.e., the bottom side), but Figure 2 A perspective view of the actuator 1 as seen from the first side 2a of the actuator 1 is shown.

[0041] The actuating device 1 has four concentric ring-shaped actuator elements 7a-7d. At the center of the actuating device 1 is a movable element 4 connected to the innermost actuator element 7a. The actuator elements 7a-d and the movable element 4 are arranged such that actuation of the actuator elements 7a-d causes movement of the movable element 4. The mass per unit area of ​​the movable element 4 is greater than that of the actuator elements 7a-d, thereby keeping the movable element 4 rigid and flat when the actuating device 1 is actuated.

[0042] On the lower side 2b of the actuator 1 are three concentric reinforcing rings 8a-c. The reinforcing rings 8a-c are located on the lower side 2b and between adjacent actuator elements 7a-d. The reinforcing rings 8a-c extend from the lower side of the actuator 1 in a direction perpendicular to the xy plane (i.e., the piezoelectric layer plane) in the form of concentric walls. (See below for reference.) Figures 3 to 5 Describe the dimensions of these reinforcing rings 8a-c.

[0043] Each actuator element 7a-d is annular, and its width (the difference between the inner and outer radii) is at least five times its thickness (the dimension perpendicular to its width). Figure 1 and Figure 2 In the illustrated embodiment, each actuator element 7a-d has two portions: an inner portion 5a-d and an outer portion 6a-d. The inner portion 5a-d and the outer portion 6a-d are annular, similar to the actuator element 7a-d itself. Each of these portions 5a-d and 6a-d includes a piezoelectric layer, for example, made of lead zirconate titanate (PZT). Each piezoelectric portion 5a-d and 6a-d can be independently addressed to apply a voltage to it via a voltage supply module (not shown) to cause the piezoelectric material to contract or expand.

[0044] Go to Figure 3 A cross-sectional view of the actuator 1 can be seen. In this view, the structures of the two sides 2a and 2b of the actuator 1 can be seen. Figure 4 Provided Figure 3 Another perspective view of the cross-section shown. Figure 3 and Figure 4 The diagram shows that each reinforcing ring 8a-c is located between adjacent actuator elements 7a-d.

[0045] Oriented toward the center of the actuator 1, the innermost reinforcing ring 8a is located on the lower side 2b and opposite to the region between the innermost actuator element 7a and its adjacent actuator element 7b. The inner portion 5a of the innermost actuator element 7a is adjacent to the movable element 4, and the outer portion 6a of the innermost actuator element 7a is adjacent to the innermost reinforcing ring 8a.

[0046] At the periphery of the actuation device 1, the outermost actuator element 7d is anchored to the substrate (not shown) at its edge. The inner portion 5d of the outermost actuator element 7d is adjacent to the outermost reinforcing ring 8c, and the outer portion 6d of the outermost actuator element 7d is adjacent to the substrate. The actuator elements 7b and 7c between the innermost actuator element 7a and the outermost actuator element 7d are defined by corresponding reinforcing rings 8a-c.

[0047] As in Figure 3 and Figure 4 As can be seen, actuator 1 has a total width of less than 1 cm. Movable element 4 has a width between 2 mm and 4 mm and a thickness of approximately 400 μm. Each reinforcing ring 8a-c has a width of approximately 40 μm and a thickness of approximately 400 μm. Each actuator element 7a-d has a width of approximately 600 μm, and each portion of actuator elements 5a-d and 6a-d has a width of approximately 300 μm. These dimensions are... Figure 5 It is shown more clearly in the middle.

[0048] The aforementioned structure helps to allow the long-stroke piston movement of the actuator 1 without buckling. In particular, the arrangement of the inner portions 5a-d and the outer portions 6a-d relative to the reinforcing rings 8a-c helps to allow the long-stroke piston movement of the actuator 1 without buckling. Using this structure, the applicant has measured a total stroke length of up to 70 μm.

[0049] The following describes how this particular arrangement helps to achieve this long-stroke piston movement of the movable element 4.

[0050] To achieve the desired movement of the movable element 4, a specific piezoelectric portion must receive a voltage to actuate it. The following will explain... Figures 6 to 9B The accompanying drawings describe these specific sections and the deflections they produce. In the drawings, sections with applied voltages are indicated by adding a "+" sign to these sections. Figures 1 to 9B The purpose of the embodiments presented is that the polarity of the applied voltage causes the piezoelectric layer to contract radially. However, as those skilled in the art will understand, voltages of opposite polarity can have the opposite effect, i.e., the layer will expand.

[0051] Figure 6 The image shows a close-up view of one of the reinforcing rings, reinforcing ring 8a. (See image for details.) Figure 6 As can be seen, the reinforcing ring 8a is located on the second side 2b of the actuator, opposite to the first side 2a, and is positioned on the first side 2a between the first actuator element 7a and the second actuator element 7b. The first actuator element 7a is shown having two distinct piezoelectric regions, thus providing an inner actuator portion 5a and an outer actuator portion 6a with a small gap between them. Similarly, the second actuator element 7b has two distinct piezoelectric regions, thus providing an inner actuator portion 5b and an outer actuator portion 6b with a small gap between them.

[0052] Figure 7a shows the actuator 1' in a first operating mode, indicated by a single apostrophe ('), wherein voltage is applied to the external portions 6a'-6d' of each actuator element 7a'-7d'. (Go to...) Figure 8A We can see the vertical deflection generated by actuator elements 7a'-7d' and the piston movement of movable element 4'.

[0053] As those skilled in the art will understand, the voltage applied to the outer portions 6a'-6d' causes the piezoelectric material of the outer portions 6a'-6d' to contract radially. The width-to-thickness ratio of the actuator elements 7a-d implies that they possess a degree of flexibility, which allows stress on the piezoelectric layer to be transmitted along the width of each actuator element. Therefore, the contraction of the piezoelectric layer of the outer portions 6a'-6d' causes the actuator elements to bend, such that the inner edge of each inner portion 5a'-5d' of each actuator element in the actuator elements 7a'-7d' is vertically raised, i.e., each reinforcing ring 8a-c is translated along the positive z-direction. The substrate (not shown) and the reinforcing rings 8a-c at the periphery of the actuator 1 provide a rigid anchor for the outermost portions 6a'-6d', relative to which the outermost portions 6a'-6d' deform.

[0054] Figure 8A The upward arrow shows the displacement of the movable element 4' along the positive z-direction perpendicular to the xy-plane (i.e., the xy-plane is the plane in which the movable element 4' is at rest).

[0055] Figure 7B The actuator 1” is shown in a second operating mode, indicated by double apostrophes (“), wherein voltage is applied to the internal portions 5a”-5d” of each actuator element 7a”-7d”. Similarly, alternating piezoelectric portions have voltage applied to them. Figure 8B The vertical deflection produced by actuator elements 7a”-7d” and the “piston” movement of movable element 4” are shown using down arrows in the second mode.

[0056] The voltage applied to the inner portions 5a”-5d” causes the piezoelectric material of these portions to contract radially. The flexibility of the actuator elements 7a”-7d” allows stress to be transmitted across the width, causing the contraction of the piezoelectric layer in the outer portions 6a’-6d’ to cause the actuator elements to bend. The contraction causes the inner edge of each inner portion 5a’-5d’ in each actuator element of the actuator elements 7a’-7d’ to be vertically lowered, i.e., translated along the negative z-direction by each reinforcing ring 8a-c. The movable element 4” and the reinforcing rings 8a-c provide a rigid anchor for the innermost portions 5a” to 5d”, relative to which the innermost portions 5a” to 5d” deform. Therefore, the movable element 4” is displaced along the negative z-direction perpendicular to the xy plane (i.e., the xy plane is the plane of the movable element 4” when at rest). Thus, the second mode causes the movable element 4” to move in the opposite direction to the movement associated with the first mode.

[0057] Figure 9A and Figure 9BThe von Mises stress (N / m) is shown in the first and second modes. 2 How it varies throughout the entire actuator.

[0058] Figure 9A The von Mises stress on the actuator 1' operating in the first mode is shown, wherein the movable element 4' deflects along the positive z-direction. Figure 9B The von Mises stress on the actuator 1” operating in the second mode is shown, wherein the movable element 4’ is deflected along the negative z-direction. For both modes, the von Mises stress at the inactive portion where no voltage is applied is between 0 and 0.5 × 10⁻⁶. 8 N / m 2 Between, and at the active part where the voltage is applied, the von Mises stress is approximately 1.5 × 10⁻⁶. 8 N / m 2 Therefore, the von Mises stress is greatest at the location where the piezoelectric layer receives the voltage. The presence of reinforcing rings between the actuator elements limits the stress from becoming excessive and thus reduces the risk of buckling.

[0059] Figure 10 An actuation device 10 according to a second embodiment of the present invention is shown. The structure of the device 10 is similar to the arrangement described above, as it contains four actuator elements 20a-d and three reinforcing rings (not shown), as well as a movable element 40 at the center of the actuation device 10. The actuation device 10 also has a base plate 21 to which the outer actuator elements 20d are attached.

[0060] In this embodiment, each actuator element 20a-d has an inner ring and an outer ring of the actuator portion, each of which is segmented into four separate parts. Therefore, there are eight separate actuator portions, meaning each portion has a separate piezoelectric region. For example, the innermost actuator element 20a has four inner actuator portions 12a, 13a, 14a, 15a and four outer actuator portions 16a, 17a, 18a, 19a. Figure 10 As can be seen, the actuator sections are arranged in quadrants. Each piezoelectric section in sections 12a-19a is in the shape of a ring sector with an angle of 90°. These sections 12a-19a are independently addressable, meaning that voltage can be selectively applied to any one of the piezoelectric layers in these sections 12a-19a. By actuating a subset of the actuator sections, a "pitch-tilt" motion can be achieved. The aforementioned "piston" motion can be achieved by applying voltage to all internal sections (e.g., 12a-15a) of each actuator element 20a-d or to all four external sections (e.g., 16a-19a) of each actuator element 20a-d.

[0061] Tilt motion can be achieved by applying voltage to one or more internal portions (e.g., 12a) in one quadrant or half of the actuator and to a corresponding external portion (e.g., 19a) in the quadrant or half of the actuator that is diametrically opposite to the other quadrant or the other side.

[0062] Figure 11 This demonstrates that the control electronics can address independently to... Figure 10 A schematic diagram of the different piezoelectric components that are actuated by the actuation device. Figure 10 and Figure 11 In the depicted actuation device, each actuator element has eight actuator sections (e.g., 12a-19a), and there are a total of four actuator elements. Therefore, for... Figure 10 and Figure 11 The actuation device 10 comprises four actuator elements: a northwest inner (NW-I) actuator section, a northwest outer (NW-O) actuator section, a northeast inner (NE-I) actuator section, a northeast outer (NE-O) actuator section, a southeast inner (SE-I) actuator section, a southwest inner (SW-I) actuator section, and a southwest outer (SW-O) actuator section. For the four actuator elements, this equates to a total of 32 independently actuable piezoelectric actuator sections, allowing for both piston and tilting movements. Different sections are indicated by different shading.

[0063] When a voltage is applied to actuate the device, the control electronics can supply voltage to all piezoelectric parts with the same label (e.g., one or more of NW-I, NW-O, NE-I, NE-O, SE-I, SW-I, and SW-O), thereby actuating a specific subset of the piezoelectric parts. This can help achieve large deflection angles and large deflection heights.

[0064] although Figure 10 and Figure 11 The diagram shows eight piezoelectric parts for each actuator element, but this is only one of many possibilities.

[0065] Figure 12 A photograph of an actuator 100 according to a third embodiment of the present invention is shown, and Figure 15A corresponding CAD drawing of an actuation device 100 according to a third embodiment of the present invention is shown. The actuation device 100 according to the third embodiment has six piezoelectric portions for each actuator element 107a-d, each piezoelectric portion having an angle of approximately 120° around the deformable movable element 400. For example, the innermost actuator element 107a has three inner piezoelectric portions 101a, 102a, 103a and three outer piezoelectric portions 104a, 105a, 106a. The actuation device 100 also has a substrate 121 to which the outer actuator elements 107d are attached. The deformable movable element 400 has an annular, independently addressable piezoelectric portion 141, which is annular in shape.

[0066] Similar to Figure 11 , Figure 13 The diagram illustrates different piezoelectric components, each of which can be independently addressed by control electronics for... Figure 12 The actuating device (i.e., the actuating device according to the third embodiment) is actuated. Figure 12 and Figure 13 In the actuation device depicted, each actuator element has six piezoelectric portions (e.g., 101a-106a), and there are a total of four actuator elements. Therefore, for Figure 12 and Figure 13 The actuation device 100 has each actuator element comprising 30 inner (30 I) actuator sections, 30 outer (30 O) actuator sections, 150 inner (150 I) actuator sections, 150 outer (150 O) actuator sections, 2700 inner (2700 I) actuator sections, and 270 outer (270 O) actuator sections. For four actuator elements, this corresponds to a total of 24 piezoelectric actuator sections, which can be independently actuated, allowing for piston movement and tilting movement. Different sections are indicated by different shading.

[0067] Although the deformable mirror has been described in conjunction with only the third embodiment, it should be understood that the deformable mirror can be combined with any other embodiment of the invention. Figure 14A and Figure 14B This illustrates how the deformable mirror 400 can be implemented using one or two piezoelectric actuator sections. Figure 14A A deformable element 400 is shown, which has only one annular piezoelectric element 141 around the edge of the movable element 400, thus providing only defocusing functionality. Figure 14B A deformable element 400 is shown, having a circular inner piezoelectric portion 140 and an annular outer piezoelectric portion 141. Having two independently addressable portions 140, 141 allows the deformable element 400 to deform in two directions, thereby providing both focusing and defocusing functions.

[0068] Figure 16 An actuation device 110 according to a fourth embodiment of the present invention is shown. The structure of this device 110 is similar to that of the first embodiment because it contains four actuator elements 20a-d, three reinforcing rings (not visible), and a movable element 440 at the center of the actuation device 110, wherein each actuator element has an inner piezoelectric actuator portion and an outer piezoelectric actuator portion. The actuation device 110 also has a substrate 221 to which the outer actuator element 207d is attached. Figure 16 The diagram also shows control electronics, namely control line 250, for applying voltage from a power source (not shown) to each piezoelectric element in the piezoelectric section. These piezoelectric elements I1, O1, I2, O2, I3, O3, I4, and O4 are... Figure 17 As shown in the image.

[0069] The actuation devices 1, 10, 100, and 110 described herein can be fabricated using photolithography or other etching methods. For example, the actuation devices 1, 10, 100, and 110 may have a device layer 3 bonded to the body layer. A piezoelectric (e.g., PZT) material can be deposited on the device layer 3 to provide a different piezoelectric layer for each piezoelectric portion. Metal electrodes (e.g., Ag and Pt electrodes) can be disposed above and below the piezoelectric layer for applying a voltage to the piezoelectric layer.

[0070] During manufacturing, a portion of the body layer can be etched away to form reinforcing rings 8a-c relative to the positions of the second side 2b of the actuators 1, 10, 100, 110 and the adjacent actuator elements of the first side 2a.

[0071] Figure 18 Steps A to F of the process for manufacturing actuators 1, 10, 100, and 110 are shown. Figure 18 The figure shown depicts a cross-section of one of the actuators 10, 100, and 110.

[0072] The process begins with step A, in which a 400 μm silicon-on-insulator (SOI) wafer is set as the starting material, the wafer having a 500 nm BOX (buried oxide) layer 201 sandwiched between an 8 μm device layer 202 and a 400 μm bulk (e.g., silicon) layer 200.

[0073] Step B is an oxidation step in which 1.6 μm SiO2 layers 203 and 204 are formed below the body layer 200 and above the device layer 202.

[0074] Next is the stacking deposition step, namely step C. The PZT stack is deposited on the SiO2 layer 203 adjacent to the device layer 202. The PZT stack is made of a 2 μm PZT layer 206 sandwiched between the top electrode 207 and the bottom electrode 205. In this case, the top electrode 207 is a 250 nm gold layer and the bottom electrode 205 is a 100 nm platinum layer.

[0075] Next is step D, in which the structuring and etching of PZT 206 and electrodes 205, 207 will form individual piezoelectric portions. Here, cavities 208a-h are formed in the PZT stack, thereby forming different piezoelectric regions.

[0076] Then, in step E, a movable surface, such as a mirror, is defined by etching away the top SiO2 layer and device layer 202 to form the central cavity where the movable surface is located.

[0077] Finally, step F involves etching away the body layer 200 and the bottom SiO2 layer 204 to form a plurality of reinforcing rings 8a, 8b, 8c between the cavities 210a-d formed by the etching.

[0078] Those skilled in the art will understand that the invention has been described by way of one or more specific embodiments, but the invention is not limited to these embodiments; and many variations and modifications are possible within the scope of the appended claims.

Claims

1. An actuating device, comprising: A first actuator element and a second actuator element, each of the first actuator element and the second actuator element including a piezoelectric layer on a first side of the actuation device, wherein the width of each actuator element is at least five times its thickness. A movable element, the movable element being at least connected to the first actuator element such that actuation of the first actuator element causes movement of the movable element; and A reinforcing ring is located on the second side of the actuation device opposite to the first side, and is positioned relative to the first side between the first actuator element and the second actuator element.

2. The actuation device according to claim 1, wherein, The actuator elements are arranged such that actuation of one or both actuator elements causes the movable element to translate vertically.

3. The actuation device according to claim 1 or 2, wherein, Each of the actuator elements comprises a ring shape.

4. The actuation device according to any of the preceding claims, wherein, Each actuator element comprises multiple actuator sections.

5. The actuation device according to claim 4, wherein, At least some of the actuator sections can be independently addressed using the corresponding voltage.

6. The actuation device according to claim 5, wherein, Each actuator section can be addressed independently using the corresponding voltage.

7. The actuation device according to any of the preceding claims, wherein, The actuation device includes N reinforcing rings and N+1 actuator elements.

8. The actuation device according to any of the preceding claims, wherein, The actuation device is arranged to allow the movable element to move in three degrees of freedom.

9. The actuation device according to any of the preceding claims, wherein, The reinforcing ring protrudes from the second side of the actuation device and has a thickness between 100 μm and 1 mm along the protruding direction.

10. The actuation device according to any of the preceding claims, wherein, The mass per unit area of ​​the movable element is greater than the mass per unit area of ​​the first actuator element and the second actuator element.

11. The actuation device according to any of the preceding claims, wherein, The movable element includes multiple individually addressable piezoelectric portions.

12. The actuation device according to any of the preceding claims, wherein, The movable element has an optically reflective surface.

13. The actuation device according to any of the preceding claims, wherein, The actuation device includes a silicon-on-insulator (SOI) wafer.

14. A method of manufacturing an actuating device, comprising: Provides device layer and body layer; as well as A piezoelectric material is deposited on the device layer to form a first actuator element and a second actuator element on the first side of the actuator device; The body layer is located on the second side of the actuation device opposite to the first side; Its features are: A portion of the body layer is etched away to form a reinforcing ring on the second side of the actuator, the reinforcing ring being positioned opposite the first side between the first actuator element and the second actuator element.

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