JP2024022559A - actuator unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an actuator unit that reduces unevenness in the distribution of stress and heat and increases the reliability of an electrical element.

SOLUTION: An actuator unit for a MEMS device comprises: a substrate 110 having a first surface; a membrane 140 provided at least partially on the first surface 110A of the substrate; a fluidic path comprising a fluidic chamber formed in the substrate, in which the membrane provides one of the fluidic chamber walls; an electrical element 120 provided on the membrane and at least partially over the fluidic chamber, in which the electrical element comprises a first electrode 121 disposed on the membrane for connection to first electrical wiring, a ceramic member 123 disposed on the first electrode, and a second electrode 122 disposed on the ceramic member for connection to second electrical wiring; and a peripheral structure for reducing unevenness in the distribution of stress and heat in the electrical element, for suppressing generation of a weak part to the minimum, and for increasing the reliability of the electrical element.

SELECTED DRAWING: Figure 4

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to the field of microelectromechanical systems (MEMS), and in particular to actuator units of electrical components for MEMS devices, such as, but not limited to, electromechanical actuators. It may find particularly useful use as actuator elements in droplet ejection heads. The actuator unit is particularly useful for improving reliability through stress and thermal management.

The present disclosure relates to actuator units comprising electrical elements for electrical components for microelectromechanical systems (MEMS) devices, particularly, but not limited to, electromechanical actuators. It may find particularly useful use as actuator elements in droplet ejection heads.

Droplet ejection heads are still widely used today, whether in more traditional applications, such as inkjet printing, or 3D printing, or other material deposition, or rapid prototyping techniques. Therefore, fluids used in droplet ejection heads often require new chemistries to adhere to new substrates and enhance the functionality of the materials being deposited.

A variety of fluids can be deposited by the droplet ejection head. For example, a droplet ejection head can eject droplets of liquid that move toward a receiving medium, such as paper or card, ceramic tile, or a shaped article (e.g., can, bottle, etc.) to form an image.

Liquid droplets can be used to construct structures, for example by depositing an electrically active fluid onto a receiving medium, such as a circuit board to enable prototyping of electrical devices, or by depositing an electrically active fluid onto a receptive medium, such as a circuit board, or biological material. Alternatively, droplets of a solution containing chemicals can be deposited onto a receiving medium, such as a microarray of assay tubes.

The droplet deposition head can be used in applications that do not use a receiving medium. For example, fine vapor and mist can be produced by a droplet ejection head to control humidity in a greenhouse mist system.

Droplet ejection heads continue to evolve and specialize to become suitable for new and/or increasingly difficult ejection and deposition applications. However, although numerous developments have been made, there is still room for improvement in the field of droplet ejection heads. Specifically, specifications for droplet ejection heads are becoming increasingly difficult, often requiring improvements in their structure and manufacturing technology.

The electrical elements of a MEMS device are typically manufactured by depositing a series of layers disposed on a first substrate, for example, by one or more techniques known in the thin film art. To obtain a flexible membrane, one or more intermediate layers are usually formed between the substrate and the electrical element.

A typical electrical device can have a structure in which a ceramic member is interposed between two conductive layers forming first and second electrodes. The ceramic member may, for example, be a thin film of a ceramic material exhibiting ferroelectric behavior, for example a piezoelectric material or a relaxer/ferroelectric crossover material. Commonly used ceramic materials include lead-based ceramics with perovskite structures, especially lead zirconate titanate (PZT), doped PZT and PZT-based solid solutions. They may be deposited by several deposition techniques known in the art, such as sputtering, chemical vapor deposition (CVD), chemical solution deposition (CSD).

In recent years, lead-free alternative materials using similar deposition techniques, such as (K,Na)NbO ₃ -based materials, (Ba,Ca)(Zr,Ti)O ₃ -based materials, and (Bi,Na,K)TiO Significant efforts are being made to develop ₃ -based materials.

Electrical elements formed from such materials are deposited layer by layer on said first substrate, usually a wafer, containing several arrays of electrical elements, the first and second electrodes being It can be described as forming a bottom electrode supporting a thin film of piezoelectric or relaxer/ferroelectric crossover material, and a top electrode covering the ceramic member.

The first or bottom electrode may be a common electrode or may be patterned to form separate electrode arrays, each associated with a separate electrical element. Similarly, the second or top electrode may be a common electrode or may be patterned to form separate electrode arrays, each associated with a separate electrical element. Similarly, thin film materials may or may not be patterned. Thus, an individual electrical element may comprise a patterned thin film of ceramic material or a region of a thin film of unpatterned ceramic material that is common to two or more electrical elements. Individually addressable regions of the electrical elements can be defined by patterning at least one of the electrodes of each electrical element.

The electrical connection of the electrical element to the drive circuit can be ensured using electrical wiring that is connected directly to the electrodes of the electrical element.

To ensure electrical insulation of the electrodes and electrical wiring, one or more insulating or passivation layers are also deposited at various stages of the formation of the electrical element. One or more insulating or passivation layers protect the various functions of the electrical element from chemical attack caused by the external environment or by chemicals used either in the manufacturing process or during operation of the electrical element. .

In order to further protect the electrical element from the external environment, in particular moisture and other chemical species, a second substrate, e.g. a protective layer, e.g. a capping layer, is usually bonded to the first substrate. The second substrate may include a recess for accommodating one or more electrical elements.

Typically, multiple electrical elements are formed simultaneously on the surface of the substrate. The plurality of electrical elements are typically arranged in an array.

After the electrical element is formed, a cavity, eg, a fluid chamber, can be provided in the substrate beneath the electrical element, eg, by etching the substrate from a side opposite to that on which the electrical element is formed. A flexible membrane forms one of the walls of each fluid chamber.

In operation, the ceramic member of the electrical element deforms in response to the application of a predetermined electric field through the first and second electrodes. Typically, the electrical element is formed partly on the substrate and partly on the fluid chamber, so that deformation of the ceramic member can result in different levels of stress at different locations on the electrical element. become. In particular, the region of the electrical element above the fluid chamber will be subjected to lower stress compared to the region located at the interface between the substrate and the fluid chamber. This is because, unlike a membrane that deforms together with the ceramic member, the base material itself does not deform due to the deformation of the ceramic member. This can cause the various components of the electrical element to separate from each other or from the substrate.

One challenge in providing reliable electrical components is properly managing the stresses that the electrical elements are subjected to and the location where each electrical element is placed symmetrically relative to each other, such as, but not limited to, The aim is to ensure that regions located at both ends of the element in a particular direction experience the same level of stress. This reduces the presence of weak points that can easily fail, thereby impairing the performance of the electrical component and affecting the overall performance of the electrical component.

In some configurations, an example of which is shown in FIGS. 1-3, the actuator unit 200 includes a substrate 110 and an electrical element 120 formed on the first surface 110A of the substrate 110 and on the membrane 140. and. The electric element includes a ceramic member 123 interposed between a first (or lower) electrode 121 and a second (or upper) electrode 122 in the thickness direction 505. The second electrode 122 and the ceramic member 123 are patterned. As shown in FIG. 1, the ceramic member 123 (and the electrical element 120) extends in the first direction 510, and the second electrode 122 is substantially connected to the surface of the ceramic member 123 in contact with the second electrode 122. pattern is formed in the same shape. Actuator unit 200 further includes a fluid chamber 195 formed within substrate 110. In some cases, the ceramic member 123 may be chamfered, ie, have sloped edges, as shown in FIGS. 1 and 2.

When the electrical element 120 is actuated and the ceramic member 123 deforms toward the corresponding fluid chamber 195, the portion of the electrical element that overlaps the interface between the fluid chamber and the substrate 110 is fixed to the substrate and therefore has a high While under stress, the area above fluid chamber 195 can deform. This may cause failure of the electrical element due to delamination.

In this case, the second electrode 122 is connected via an electrical wiring 160 that passes through a via 161_a formed above the second electrode 122 at one end of the element 120 and connects to the second electrode 122 at an electrical connection point 161. Connect to a drive circuit (not shown). This is illustrated in FIG. 2, which shows the part of the actuator unit circled in FIG. FIG. 2 further shows that electrical element 120 can also include one or more passivation layers 150 and one or more insulating layers 170 to protect various parts of electrical element 120. . FIG. 3 shows a top view of two regions at opposite ends of the actuator unit 200 in a first direction 510. Ceramic member 123 and passivation layer 150 have been omitted for clarity.

In some known constructions (not shown), the second electrode is designed to extend away from the ceramic member and onto the top of the substrate where the electrical connection is established.

The structures of FIGS. 2 and 3 save space on the substrate 110 and reduce the overall size of the electrical components by establishing electrical connection points 161 on top of the electrical element 120 rather than on the top of the substrate 110. can do. This means that the electrical elements 120 can be packed more tightly, thereby increasing the number of electrical elements 120 that can be formed on the substrate 110. For droplet ejecting heads, this will result in higher resolution.

On the other hand, as shown in FIG. 2 and FIG. The region is more stressed as a result of the additional stiffness provided by the electrical connection point 161 and is more likely to fail with respect to its opposite region in the first direction 510.

In order to ensure good reliability of the electrical element 120, the stresses to which the electrical element 120 is subjected should be managed to reduce the risk of delamination, and the stresses experienced by regions of the electrical element that are approximately symmetrical to each other should be as similar as possible. This is very important. In this way, stress is distributed more evenly and the occurrence of weak points that are prone to failure is reduced.

As mentioned above, the presence of electrical connections can also affect the distribution of heat. A hot spot may be formed corresponding to the electrical connection point 161, and the electrical element 120 may be susceptible to thermal damage. Therefore, it is also important that the heat distribution be as uniform as possible throughout the electrical element 120.

The present invention provides an improved design of an actuator unit with an electrical element, a design that reduces the uneven distribution of stress and heat within the electrical element, minimizes the occurrence of weak spots, and increases the reliability of the electrical element. I will provide a.

Aspects of the invention are set out in the accompanying independent claims, and certain variants of the invention are set out in the accompanying dependent claims.

In one aspect, the present invention provides an actuator unit for a MEMS device, the actuator unit comprising: a base material having a first surface; a membrane provided at least partially on the first surface of the base material; a flow path comprising a fluid chamber formed within the flow path, the membrane providing one of the walls of the fluid chamber; and disposed on the membrane and at least partially over the fluid chamber; An electrical element, the electrical element comprising: a first electrode disposed on the membrane for connection to the first electrical wiring; a ceramic member disposed on the first electrode; and a ceramic member disposed on the ceramic member. a second electrode for connecting to a second electrical wiring, the electrical element deforms when a predetermined electric field is applied, and the electrical element is elongated in the first direction and is elongated in the first direction. an electrical element having two spaced apart opposing ends, each end disposed partially over the substrate and partially above the fluid chamber; and respective opposing ends of the electrical element. a peripheral structure positioned relative to the fluid chamber, wherein both peripheral structures have substantially the same elastic properties and are positioned relative to the fluid chamber such that both ends of the electrical element experience substantially the same stress upon application of a predetermined electric field. An actuator unit includes a peripheral structure for receiving the actuator unit.

A second aspect of the present invention provides a droplet ejection head including the actuator unit according to the first aspect.

Furthermore, a droplet ejection device including a droplet ejection head according to a second aspect is provided.

Reference is now made to the drawings.

FIG. 1 is a schematic cross-sectional view of an actuator unit that is not part of the invention. FIG. 2 is a schematic cross-sectional view of a portion of the actuator unit indicated by the circle in FIG. 1. FIG. 3 is a schematic diagram of a top view of the actuator unit of FIG. 1; FIG. FIG. 4 is a schematic cross-sectional view of an actuator unit according to an embodiment of the invention. FIG. 5 is a schematic cross-sectional view of a portion of the actuator unit indicated by the circle in FIG. 4. FIG. 6A-C are schematic illustrations of top views of actuator units according to different embodiments of the invention. FIG. 7 is a schematic cross-sectional view of a droplet ejection head according to an embodiment of the present invention.

In the drawings, like elements are designated with like reference numerals throughout. It is noted that the drawings are not to scale, and certain features may be shown in exaggerated size to be more clearly seen.

Exemplary embodiments of the invention and variations thereof will now be described with reference to FIGS. 4, 5, 6A, 6B, and 6C.

FIG. 4 shows a cross section of an actuator unit 100 according to the first aspect of the invention. 5 shows a cross-sectional view of the part indicated in one of the circles of FIG. 4, and FIGS. 6A, B, and C are arranged at opposite ends of the actuator unit of FIG. 4 according to different embodiments of the invention. A top view of the part to be used is shown.

An actuator unit 100 for a MEMS device is formed within the base material 110, including a base material 110 having a first surface 110A, a membrane 140 provided at least partially on the first surface 110A of the base material 110. a flow path comprising a fluid chamber 195, the membrane 140 providing one of the walls of the fluid chamber 195; An electric element 120 is provided. The electric element 120 includes a first electrode 121 disposed on the membrane 140 and for connecting to a first electrical wiring (not shown), and a ceramic member 123 disposed on the first electrode 121. A second electrode 122 is arranged on the ceramic member 123 and connected to the second electric wiring 160, and the electric element 120 deforms when a predetermined electric field is applied. The electrical element 120 is elongated in a first direction 510 and has two opposite ends spaced apart in the first direction 510 (circled in FIG. 4, in more detail in FIG. 5, and in top view in FIGS. 6A-C). ). Each end is positioned partially over the substrate 110 and partially over the fluid chamber 195. Peripheral structures 168 are each disposed at opposite ends of the electrical element 120 in the first direction 510 , both peripheral structures 168 having substantially the same elastic properties and disposed relative to the fluid chamber 195 and disposed at opposite ends of the electrical element 120 in the first direction 510 . Both ends experience substantially the same stress when a predetermined electric field is applied.

5, the end of the actuator unit 100 of the embodiment of FIG. 4 is shown in more detail. FIG. 5 shows a substrate 110 having a first surface 110A and a fluid chamber 195 having a membrane 140 as one of its walls. Although the material of the base material is not particularly limited, for example, the base material 110 may be a silicon wafer. Membrane 140 may be formed from sublayers 141 and 142 deposited on top of each other in thickness direction 505. Sublayer 141 may include, for example, silica (SiO ₂ ) formed by thermal oxidation of a silicon wafer. Sublayer 142 may include, for example, alumina (Al ₂ O ₃ ) deposited by atomic layer deposition (ALD). Any other materials and/or deposition methods known in the art may be used to form membrane 140.

Electrical element 120 is formed on membrane 140 and partially overlies fluid chamber 195 and partially over substrate 110 . The first electrode 121 may be made of platinum (Pt), for example. Ceramic member 123 can include, for example, Nb-doped PZT (PNZT) deposited by sol-gel deposition. The second electrode 122 may be another Pt electrode. Alternatively, the second electrode 122 may have a different composition from the first electrode 121, for example, may be a combination of an iridium (Ir) layer and an iridium oxide (IrO ₂ ) layer. One or more passivation layers 150 are provided over electrical element 120. The passivation layer 152 may be, for example, an alumina layer deposited by ALD. Passivation layer 153 may be, for example, a silica layer deposited by plasma enhanced chemical vapor deposition (PE-CVD).

Electrical element 120 includes two peripheral structures 168 disposed at opposite ends of electric element 120 in first direction 510 . Both peripheral structures 168 have essentially the same elastic properties, so that both ends of the electrical element 120 experience the same stress upon application of a given electric field.

A peripheral structure 168 is symmetrically positioned over the electrical element. They extend partly over fluid chamber 195 and partly over substrate 110.

FIG. 6A shows a top view of the flow path of the embodiment of FIG. 4 with fluid chamber 195 and optionally restrictor 194, bottom electrode 121, top electrode 122 and surrounding structure 168. Ceramic member 123 and passivation 150 have been omitted for clarity. As shown in FIG. 6A, the peripheral structure 168 has a trilobal shape, but this shape is not limited and other shapes may be selected. The shape of each peripheral structure 168 is symmetrical with respect to the line of symmetry a of the electrical element 120 along the first direction 510. The peripheral structure 168 is also arranged symmetrically about a line of symmetry b in the same plane rotated 90 degrees (ie, perpendicular) to the line of symmetry a.

The shape of the surrounding structure 168 provides sufficient and evenly distributed stiffness at each end of the electrical element 120 to provide sufficient and evenly distributed stiffness to the regions of the electrical element that are subject to higher stress, i.e., the interface between the fluid chamber 195 and the substrate 110. By reinforcing the regions, the occurrence of delamination during deformation of the electrical element 120 is reduced. This is accomplished by ensuring that the peripheral structure 168 extends symmetrically over such interface area. Each peripheral structure 168 preferably extends above the substrate 110 to an extent that ensures sufficient strength enhancement of the ends of the electrical element 120 by effectively securing the ends to the substrate 110. . Those skilled in the art will appreciate that the expansion of the peripheral structure 168 on the substrate 110 depends on the overall shape of the electrical element 120 and the degree of deformation of the ceramic member 123 when a predetermined electric field is applied. will understand the impact it has on

Both peripheral structures 168 in FIG. 6A are preferably formed of the same material or materials. Each peripheral structure 168 may be formed of multiple layers, preferably of different materials, to fine tune the elastic properties. They may include at least one layer made of electrically conductive material. A conductive material can provide an electrical connection between the electrical trace 160 and the second electrode 122. A material that is also thermally conductive would further aid in thermal management by providing a path for dissipating heat generated by electrical element 120 during operation. This may help by reducing the occurrence of hot spots at the ends of the electrical elements 120 where stress is highest. The surrounding structure 168 may also include a layer of insulating material that can assist in fine-tuning the elastic and/or thermal properties.

In some embodiments, at least one of the peripheral structures 168 includes a conductive material that forms an electrical connection at a connection point 161 between the second electrode 122 and the second electrical trace 160. Preferably, the second electrical wiring 160 connects the second electrode 122 to a drive circuit (not shown) through a via 161_a formed in the passivation layer 150, for example by etching, as shown in FIGS. 5 and 6A. Connecting. Passivation layer 150 is interposed between electrical element 120 and peripheral structure 168 at least around via 161_a. In the illustrated example, passivation layer 150 is a stack of layers 151-152 that protects electrical element 120 and electrical interconnect 160 and insulates second electrical interconnect 160 from bottom electrode 121.

If the peripheral structure 168 and the second electrical trace 160 are directly connected (formed of the same material) at only one end of the electrical element (as shown, for example, in FIGS. 6A and 6C), the peripheral structure 168 itself It will be appreciated that it still has the same shape as the surrounding structure 168 at the opposite end of the actuator 120 near the element. Because the electrical wiring material is located away from the area of the interface between fluid chamber 195 and substrate 110, the presence of connected electrical wiring 160 is critical to the stresses experienced at certain ends of electrical element 120. It will not have any significant impact. In a preferred embodiment, peripheral structure 168 is made of the same material as electrical interconnect 160, so that they are formed in the same process step and do not require adding another process step to the manufacturing process. Suitable materials are aluminum (Al), gold (Au), copper (Cu), platinum (Pt), nickel (Ni), etc., or combinations thereof. A thin adhesive layer may be deposited before and/or after the formation of the electrical wiring. The second electrical interconnect 160 and peripheral structure 168 can be formed by sputtering and subsequently patterning the metal layer into the desired shape using standard photolithography and etching processes.

Another passivation layer 151 may be deposited over the entire electrical element 120. Passivation layer 151 can be made of silica deposited by PE-CVD, for example. A passivation layer 151 is also deposited on the second electrical interconnect 160.

Passivation layers 151-153 may be etched over electrical element 120, for example by lithography. This is particularly advantageous in reducing any suppressive effect of the passivation layer 150 on the displacement of the electrical element 120 during operation.

A continuous insulating layer 170 may also be deposited over the electrical element 120. The insulating layer 170 may be, for example, a stack of silica and tantala layers deposited on top of each other in the thickness direction 505 by atomic layer deposition (ALD). Insulating layer 170 can further protect electrical element 120 from the external environment and can improve the robustness of passivation layer 150 by plugging pinholes and other defects.

Some embodiments of the invention, an example of which is shown in FIG. 6A. The second electrode 122 can be formed of a material with high electrical conductivity, such as, but not limited to, platinum (Pt) and/or gold (Au).

In another embodiment, an example of which is shown in FIGS. 6B and 6C, the second electrode 122 is formed from a bilayer of a relatively low conductivity material, such as iridium (Ir) and iridium oxide (IrO ₂ ). may be done.

The choice of material forming the electrodes may be determined by the material's ability to achieve particular requirements, such as good adhesion to ceramic components, etc., in part at the expense of electrical conductivity. In such a case, a method for reducing the contribution of the second electrode to the resistance of the electrical connection is to create two or more electrical connection points 161 between each second electrode 122 and the corresponding second electrical trace 160. It is to establish. In these embodiments, both peripheral structures 168 may include a conductive material that forms an electrical connection at an electrical connection point 161 between the second electrode 122 and the second electrical trace 160. In a preferred embodiment, both peripheral structures 168 are made of the same material as the second electrical interconnect 160.

When two electrical connection points 161 are provided at both ends of the second electrode 122, the second electrical wiring 160 may be provided with a connection portion 162 between the two electrical connection points 161. In the embodiment of FIG. 6B, the connection 162 is provided on the substrate 110 in a first direction 510 along the electrical element 120. In another embodiment, as shown in FIG. 6C, the second electrical wiring 160 includes a connection 162 that overlaps the electrical element 120 and extends between the electrical connection points 161.

In the example shown in FIG. 6B, as described above, the electrical interconnect material is located away from the region of the interface between the fluid chamber 195 and the substrate 110, which is subject to high stress if the electrical element 120 deforms. It will be appreciated that the presence of the electrical wiring material connecting the peripheral structure 168 to the second electrical wiring 160 does not affect the stress experienced by the ends of the electrical element 120 because of the presence of the electrical wiring material connecting the peripheral structure 168 to the second electrical wiring 160.

As previously discussed, the surrounding structure 168 may also be useful in assisting in managing heat generated by the electrical elements when a predetermined electric field is applied. Accordingly, in some embodiments, the surrounding structure 168 includes a material having a higher thermal conductivity than that of the ceramic member 123, such as a metal, a combination of metals, an alloy, a polymer, a resin, etc. but not limited to.

To further strengthen the ends of the electrical element 120, an additional layer (not shown) is provided on the peripheral structure 168 on a side of the peripheral structure 168 opposite the side of the peripheral structure 168 facing the electrical element; The ends of electrical element 120 can be sealed.

In a preferred embodiment, the additional layer comprises a material that provides sufficient stiffness to minimize stress experienced by the area of the interface between fluid chamber 195 and substrate 110. Additional layers may include, for example, curable polymeric materials. In one embodiment, the additional layer comprises a polymerizable alkene that exhibits ring strain, such as cyclobutene. Cyclic alkenes may specifically include benzocyclobutene or bisbenzocyclobutene, such as those available under the trademark Cyclotene (BCB). In another embodiment, the additional layer comprises a partially curable polymerizable epoxide. Suitable partially curable epoxides include novolak epoxides, such as those known as SU8 negative photoresists. In yet another embodiment, the additional layer comprises a partially cured polyimide, such as a partially cured aliphatic polyimide or an aromatic polyimide. Suitable polyimides include those available under the trademark HD Microsystems (eg, PI-5878G). In preferred embodiments, the additional layer comprises a patternable polymeric material, such as, but not limited to, BCB.

The additional layer of material can be applied locally onto the end region of the electrical element 120 by any method known in the art, such as printing, lithography, and stamping, and then cured.

Alternatively, an additional layer of material can be provided as a layer over the entire first surface 110A and within the electrical element or element 120 and partially or fully cured and patterned to remove unwanted areas, e.g. It can be removed from the area above the second electrode 122.

In some embodiments, the additional layer is also a tie layer used to bond the first substrate to the capping layer. In these embodiments, the thickness of the additional layer is such that upon bonding, if the additional layer or the bonding layer is deformed by the application of a bonding force, the material of the additional layer covers the surrounding structure 168 but the passivation 150 is removed. It is important to control the area of the upper electrode 122 so as not to cover it.

A second aspect of the present invention provides a droplet ejection head including the actuator unit as described above.

FIG. 7 shows a droplet ejection head 400 according to an embodiment of the present invention, in which a nozzle plate 196 is provided in a thickness direction 505 on the surface of the fluid chamber 195 opposite to the surface on which the electrical element 120 is formed. It will be done. Nozzles 197 are formed within nozzle plate 196 for ejecting fluid droplets from fluid chamber 195 . The second substrate 103 defines a recess 106 for the electrical element 120. Such a recess 106 is sealed liquid-tight to prevent fluid in the fluid chamber 195 and the inlet passage 131 and outlet passage 132 at each end of the fluid chamber 195 in the first direction 510 from entering the recess 106. can be done.

Furthermore, a droplet ejection device including a droplet ejection head according to a second aspect of the present invention is provided.

The embodiments described above and their variations can be used alone or in combination, depending on the specific application requirements, to achieve an improved electrical component according to the invention.

Claims (14)

An actuator unit for a MEMS device, the actuator unit comprising:
- a substrate having a first surface;
- a membrane provided at least partially on the first surface of the substrate;
- a flow path comprising a fluid chamber formed in the substrate, the membrane providing one of the walls of the fluid chamber;
- an electrical element provided on the membrane and at least partially on the fluid chamber, the electrical element comprising:
i) a first electrode disposed on the membrane and connected to a first electrical wiring;
ii) a ceramic member disposed on the first electrode;
iii) a second electrode disposed on the ceramic member and connected to a second electrical wiring;
The electric element is deformed when a predetermined electric field is applied, and the electric element is elongated in a first direction and has two opposing ends spaced apart in the first direction, each end being an electrical element disposed partially on the substrate and partially on the fluid chamber;
- peripheral structures arranged at opposite ends of each of said electrical elements,
both peripheral structures have substantially the same elastic properties and are positioned relative to the fluid chamber such that both ends of the electrical element experience substantially the same stress upon application of a predetermined electric field. , actuator unit. 2. The actuator unit of claim 1, wherein the peripheral structure is arranged in a symmetrical overlapping relationship with respect to the electrical element. 3. An actuator unit according to claim 1 or claim 2, wherein each peripheral structure is symmetrical about a centerline of the electrical element extending in the first direction. 4. The peripheral structure according to any one of claims 1 to 3, wherein the peripheral structure is symmetrical about a centerline of the electrical element extending across the electrical element perpendicular to the first direction. actuator unit. 5. The method according to claim 1, wherein at least one of the peripheral structures comprises an electrically conductive material forming an electrical connection between the second electrode and the second electrical wiring. actuator unit. The actuator unit according to any one of claims 1 to 5, wherein the actuator unit further comprises a passivation layer interposed between the electrical element and the surrounding structure. An actuator unit according to any one of the preceding claims, wherein both peripheral structures comprise electrically conductive material forming an electrical connection between the second electrode and the second electrical wiring. 8. The actuator unit of claim 7, wherein the wiring comprises a connection overlapping the electrical element and extending between the electrical connections. An actuator unit according to any one of the preceding claims, wherein the peripheral structure comprises a material having a higher thermal conductivity than the thermal conductivity of the ceramic member. Actuator unit according to any one of the preceding claims, wherein the peripheral structure is formed from a plurality of layers. Actuator unit according to any one of claims 1 to 10, wherein an additional layer is provided on the peripheral structure on the side of the peripheral structure opposite the side of the peripheral structure facing the electrical element. . 12. The actuator unit of claim 11, wherein the additional layer comprises a patternable polymeric material. A droplet ejection head comprising the actuator unit according to any one of claims 1 to 12. A droplet ejection device comprising the droplet ejection head according to claim 13.

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