Electrical elements

Abstract

An improved electric element is provided comprising a ceramic member, the ceramic member comprising at least one layer having a depth, and first and second electrodes disposed adjacent to the at least one layer of the ceramic member such that during operation, a potential difference may be established through at least a portion of the ceramic member, the electric element being disposed adjacent to a flexible membrane, the first electrode layer comprising a first electrode group comprising at least two fingers and a second electrode group comprising at least one finger, the fingers of the first and second electrode groups being alternately disposed in the first electrode layer in an interdigitating orientation, and the second electrode layer comprising a first electrode group comprising at least two fingers and a second electrode group comprising at least one finger, the fingers of the first and second electrode groups being alternately disposed in the second electrode layer in an interdigitating orientation. and for each electrode group, all fingers of the group are electrically connected to each other and to the group electrical contacts, the fingers of the first electrode group of the first electrode layer at least partially overlap in the interdigitated direction with corresponding fingers of the first electrode group of the second electrode layer, the fingers of the second electrode group of the first electrode layer at least partially overlap in the interdigitated direction with corresponding fingers of the second electrode group of the second electrode layer, and the group electrical contacts are arranged such that in the interdigitated direction, the fingers of the first and second electrode groups of the same electrode layer are at least partially overlapped in the interdigitated direction with corresponding fingers of the second electrode group of the second electrode layer, and the group electrical contacts are addressable to establish a potential difference between the fingers of the first and second electrode groups of the same electrode layer and a deformation of the ceramic member in the d33 mode, and in the depth direction, the potential difference between the at least partially overlapping fingers of the first and second electrode groups of the first and second electrode layers and a deformation of the ceramic member in the d31 mode. Suitable drive signals, switching circuits, controllers, and methods of driving the electric elements are also provided.

Description

[Technical field]

[0001] The present invention relates to electrical elements for Microelectromechanical Systems (MEMS) devices, in particular, but not exclusively, electromechanical actuators or sensors. Electromechanical actuators may find particularly advantageous application as actuator components in droplet ejection heads, such as inkjet printheads. [Background technology]

[0002] Droplet ejection heads are now widely used, whether for more traditional applications such as inkjet printing, advanced applications such as 3D printing, other material deposition, or rapid prototyping techniques. The fluids used may therefore have novel chemical properties that adhere to new substrates and / or increase the functionality of the deposited materials.

[0003] In recent years, inkjet printheads have been developed that can deposit ink directly onto ceramic tiles, textiles, or other substrates with high reliability and throughput, allowing the patterns on the substrate to be customized to a customer's exact specifications, and also reducing the need to inventory all printed products.

[0004] In yet other applications, MEMS actuator devices may be used to deposit fluids in chemical and biological applications, such as assays and tests, and MEMS sensing devices may be used to measure properties such as fluid pressure.

[0005] The electrical elements for MEMS devices, such as actuators and sensors, continue to evolve and specialize to suit new and / or increasingly challenging applications. However, despite much development, there remains room for improvement.

[0006] Electrical elements for MEMS devices are typically fabricated by deposition of a series of layers disposed on a substrate, for example through one or more techniques known in the thin film art. A typical electrical element may have a configuration such as that shown in FIG. 1A and FIG. 1B, in which a thin film of ceramic material exhibiting ferroelectric behavior, such as a piezoelectric material or a relaxor / ferroelectric crossover material, is interposed between two conductive layers of a bottom electrode and a top electrode. Such electrical elements are deposited layer by layer on a substrate, and typically a wafer contains a plurality of such arrays of electrical elements. The bottom electrode may be a common electrode or may be patterned to form an array of individual electrodes, each associated with an individual electrical element. The thin film of ceramic material may or may not be patterned in the same way. Thus, an individual electrical element may include an area of ​​a patterned thin film of ceramic material or an unpatterned thin film of a "common" ceramic material. The individually addressable area of ​​the electrical element may be defined by at least one of the patterned electrodes, such that it is individual for each electrical element. Electrical connection of the electrical elements to the drive circuitry can be ensured through the use of metal traces that are connected directly to the electrodes of the electrical elements.

[0007] Commonly used ceramic materials include lead-based ceramics with perovskite structure, especially lead zirconate titanate (PZT), doped PZT and PZT-based solid solutions. They can be deposited on a substrate through several deposition techniques known in the art, such as sputtering, chemical vapor deposition (CVD), and chemical solution deposition (CSD). In recent years, there has been a great deal of effort in developing lead-free alternative materials, such as (K,Na)NbO3-based materials, (Ba,Ca)(Zr,Ti)O3-based materials, and (Bi,Na,K)TiO3-based materials.

[0008] When configured as an actuator, one of the most important parameters of such an electric element is its efficiency: maximum displacement using the lowest possible voltage (or maximum displacement for higher sensitivity of the sensor). There are three main modes of operation for such an electric element: 33 d 15 , d 31 (referred to throughout as d33, d15, and d31 for simplicity). Many MEMS actuators operate in d31 mode. FIG. 1A is a schematic diagram of a MEMS actuator operable in d31 mode, depicting a cross-sectional view showing a schematic layout of a MEMS device 10 for a droplet ejection device, which may comprise an actuator element 102 comprising an electric element 120. The electric element 120 is mounted on a substrate 110, a portion of which is free to move as a flexible membrane. In this case, it is part of the roof of a fluid chamber 195. A fluid such as ink may be supplied to the fluid chamber 195 via a fluid port 198 cut or etched through the capping layer 103. The capping layer 103 may further comprise a cavity 106 above the electric element 120. Such a cavity may be sealed liquid-tight to prevent fluid from entering the cavity 106 from the fluid chamber 195 and the fluid port 198.

[0009] In some devices, only the inlet fluid port 198 may be required. Other MEMS devices may operate in a so-called through-flow mode, with a proportion of the fluid flowing through the fluid chamber 195 from the inlet fluid port 198 to the outlet fluid port 198 and ejected through the nozzle 197 as droplets when the electrical element 120 is appropriately actuated.

[0010] Figure 1B is a schematic diagram of a portion of the cross section of Figure 1A depicting a portion of the actuator component 102. It can be seen that an electrical element 120 is disposed on the substrate layer 110. The electrical element 120 comprises a ceramic member 123 and a lower electrode 121 and an upper electrode 122 disposed adjacent the ceramic member 123, respectively, such that during operation a potential difference is established across the ceramic member 123 between the lower electrode 121 and the upper electrode 122. The lower electrode is adjacent the substrate layer 110. An electrical trace 160 provides an electrical connection to the upper electrode 122. A further electrical trace (not shown in Figure 1B) is provided to electrically connect the lower electrode 121.

[0011] The actuator component 102 comprises several other layers, which may themselves be a single layer or may comprise a stack of sub-layers. Layers such as the insulating layer 170, the passivation layer 150 and the intermediate layer 140 may have various functions. The intermediate layer 140 may comprise, for example, a stress gradient reducing layer, a barrier layer to prevent diffusion of ions between the ceramic member and the substrate, and / or an adhesion layer to improve adhesion of the electrical element to the substrate. Such additional layers may include, for example, inorganic oxide or nitride layers, such as alumina, silica, silicon nitride, zirconia, tantala, hafnia, etc.

[0012] The ceramic member 123 extends in the XY plane and comprises any suitable type of thin film ceramic material that exhibits ferroelectric behavior, such as the materials described above. When an electric field is applied along the Z direction, establishing a potential difference between the top electrode 122 and the bottom electrode 121 and through the ceramic member 123, the ceramic material expands in the Z direction (d33) and contracts in the XY direction (d31). The electric element 120 is attached to the substrate 110 (with a portion that is a flexible membrane) so that as the ceramic material deforms, the flexible membrane bends down (in the negative Z direction) into the fluid chamber 195 (shown diagrammatically as a dashed line in FIG. 1A). When the electric field is removed, the ceramic material no longer experiences a potential difference and returns to a neutral (unformed) state and position, moving the flexible membrane with it. By applying suitable driving waveforms, electrical elements 120 such as those in Figures 1A and 1B can be used to eject droplets through nozzles 197 as and when desired, thereby, for example, printing onto a substrate. Typically, MEMS actuator devices used for droplet ejection comprise a plurality of such electrical elements and associated fluid chambers, which are generally arranged in an array comprising a single row or multiple rows, so that large areas of the substrate can be addressed. A droplet ejection head, for example, may comprise a plurality of actuators, which may itself be used alone or in conjunction with a number of other droplet ejection heads to form part of a droplet ejection device.

[0013] Rather than operating in d31 mode, some MEMS actuators operate in d33 mode, applying an electric field along the X direction using suitably positioned first and second electrodes to establish a potential difference across the ceramic member in the X direction. The ceramic material expands in the XY direction (d33) and contracts in the Z direction (d31). The actuator bends upwards (in the positive Z direction) and the flexible membrane moves as well. Again, when the electric field is removed the ceramic member returns to its neutral state and position, as does the flexible membrane.

[0014] It can be appreciated that MEMS devices similar to those described above operating in d33 or d31 mode can also be configured as sensors. For example, when an applied force (such as a fluid pressure) deflects a flexible membrane, which in turn deforms a ceramic member, electricity is generated in proportion to the movement. With suitable calibration data, the MEMS device can be used as a sensor to measure such forces.

[0015] A limitation of such MEMS actuators described above is that the maximum displacement for a given applied voltage is limited to that achievable by the deformation mode (d31 or d33) (for a sensor, the generated voltage is related to the maximum displacement achievable by the deformation mode.) It is desirable to have an electrical element that has a larger total displacement range available for a given applied voltage when used as an actuator, and a larger displacement when used as a sensor.

[0016] A further feature of actuator components 102 for droplet ejection heads such as that of FIG. 1A is that in some applications and drive schemes, the actuator element may be held in the deflection d31 position between jetting events by applying suitable voltages to electrodes 121, 122 to create an electric potential field across ceramic member 123. When a droplet ejection event is desired, a suitable drive waveform is supplied to the actuator and the following sequence of events occurs: the electric potential field is removed (e.g., d31 deflection is switched off), thus causing the actuator to return to a neutral position and moving the flexible membrane with it. This increases the volume of fluid chamber 195, thereby drawing fluid into fluid chamber 195. The drive waveform then applies suitable voltages to electrodes 121, 122 to re-establish the electric potential field across ceramic member 123 and deflect it once more in the d31 mode (e.g., d31 deflection mode is switched on), thereby moving the flexible membrane into fluid chamber 195 and ejecting a droplet of fluid via nozzle 197.

[0017] An advantage of such an operating method is that it provides higher performance stability since the first movement of the actuator causes a fluid chamber fill event, which may mitigate undesired droplet ejection events. A disadvantage of such a droplet ejection method is that the electric element 120 is held in the deformed d31 position with a holding voltage applied between droplet ejection events. This applied holding voltage results in higher power consumption, adding undesirable costs to the operation. Furthermore, this may cause excessive heat in the actuator component 102, which may need to be compensated for, for example, by long-term stresses in the boundary regions of the flexible membrane, which may result in accelerated degradation of the actuator performance. It is therefore desirable to be able to use a drive waveform in which the electric element 120 does not consume power between droplet ejection events unless actuated for other reasons (such as sensing purposes, nozzle clearance, or other functions that do not eject droplets, such as maintenance), so that the electric element 120 may be positioned in its neutral, undeformed state without significant power consumption between actuation events, while still being able to mitigate undesired droplet ejection events, for example, during start-up.

[0018] The present invention addresses the above requirements by providing electrical elements that deform in both d31 and d33 modes, and methods for driving or sensing such elements, with associated benefits for maximum achievable displacement and maximum achievable sensing sensitivity, respectively. Additionally, the present invention provides suitable drive waveforms for driving such electrical elements, including drive waveforms and methods of operation, such that, if desired, the electrical elements can be operated such that they can be held in a neutral position so as not to consume power except when the electrical elements are actuated (either for droplet ejection or for other purposes as described above). Summary of the Invention

[0019] Aspects of the invention are set out in the accompanying independent claims and particular embodiments of the invention are set out in the accompanying dependent claims.

[0020] The following disclosure relates in one aspect to an electrical device, comprising: a ceramic member, the ceramic member comprising at least one layer having a depth; first and second electrodes disposed adjacent at least one layer of the ceramic member such that, during operation, a potential difference can be established across at least a portion of the ceramic member; the electrical element is disposed adjacent to the flexible membrane; the first electrode layer comprises a first group of electrodes having at least two fingers and a second group of electrodes having at least one finger; the fingers of the first and second electrode groups are alternately arranged in the first electrode layer in an interdigitated direction; the second electrode layer comprises a first group of electrodes having at least two fingers and a second group of electrodes having at least one finger; the fingers of the first and second electrode groups are alternately arranged in the second electrode layer in an interdigitated orientation; For each electrode group, all the fingers of the group are electrical elements that are electrically connected to each other and to the group electrical contacts.

[0021] In a second aspect, a drive signal for driving an electrical element according to the first aspect is provided.

[0022] In a third aspect, there is provided a switching circuit for an electrical element according to the first aspect.

[0023] In a fourth aspect, there is provided a controller for a switching circuit according to the third aspect.

[0024] In a fifth aspect, there is provided a method of driving an electric element according to the first aspect. [Brief description of the drawings]

[0025] Reference is now made to the drawings.

[0026] [Figure 1A] 1 is a schematic cross-section through a known electrical component showing a schematic layout of known electrical elements for a droplet ejection head. [Figure 1B] 1B is a schematic cross-section through a portion of the electrical element of FIG. 1A. [Figure 2A] 1 depicts a top view of an electrical element according to one embodiment mounted on a flexible membrane. [Figure 2B] FIG. 2B is a side view of the embodiment of FIG. 2A. [Figure 2C] FIG. 2B is a perspective view of the embodiment depicted in FIG. 2A. [Figure 2D] 2B is a cross-section through the embodiment depicted in FIG. 2A along line AA. [Figure 2E] 2B is a cross-section through the embodiment of FIG. 2A along line BB. [Figure 3A] The electrodes are shaded to depict a cross section through an electrical element, such as that of FIG. 2A, that would deform the ceramic member in the d33 mode. [Figure 3B] 3B illustrates two electrode layers of the electrical element of FIG. 3A. [Figure 4A] The electrodes are shaded to depict a cross section through an electrical element, such as that of FIG. 2A, that would deform the ceramic member in the d31 mode. [Figure 4B] 4B depicts two electrode layers of an electrical element such as that of FIG. 4A. [Figure 5A] 1 is a top view of an electrical element according to another embodiment, the electrical element comprising a ceramic member having at least two layers, the electrical element also comprising a third electrode layer. [Figure 5B] FIG. 5B is a side view of the embodiment of FIG. 5A. [Figure 5C] FIG. 5B is a perspective view of the embodiment depicted in FIG. 5A. [Figure 5D] 5B is a cross-section through the embodiment taken along line AA shown in FIG. 5A. [Figure 5E] 5B is a cross-section through the embodiment taken along line BB shown in FIG. 5A. [Figure 6A]FIG. 5B is a top view of an electrical element according to another embodiment, similar to that of FIG. 5A, but where first electrode groups of the first and third electrode layers are electrically connected to each other and second electrode groups of the first and third electrode layers are electrically connected to each other. [Figure 6B] FIG. 6B is a side view of the embodiment of FIG. 6A. [Figure 6C] FIG. 6B is a perspective view of the embodiment depicted in FIG. 6A. [Figure 6D] 6B is a cross-section through the embodiment taken along line AA shown in FIG. 6A. [Figure 6E] 6B is a cross-section through the embodiment taken along line BB shown in FIG. 6A. [Figure 6F] FIG. 2 is a perspective view of the first, second and third electrode layers of the electrode and their electrical connections. [Figure 7A] 7 is a cross section through an electrical element such as that of FIG. 5 or FIG. 6 with electrodes shaded according to whether a first voltage V1 or a second voltage V2 is applied, the applied voltage causing the ceramic member to deform in the d33 mode. [Figure 7B] 7B depicts the three electrode layers of the electrical element of FIG. 7A. [Figure 8A] 7 is a cross section through an electrical element such as that of FIG. 5 or FIG. 6 with electrodes shaded as to whether a first voltage V1 or a second voltage V2 is applied, the applied voltage causing the ceramic member to deform in the d31 mode. [Figure 8B] 8B depicts the three electrode layers of the electrical element of FIG. 8A. [Figure 9A] 1 depicts a switching arrangement for an electronic element such as that of FIG. 6, in which a single finger in each group of each electrode layer is depicted such that an applied voltage causes the ceramic member to deflect in the d33 mode. [Figure 9B] 9B depicts a switching arrangement for an electrical element similar to that of FIG. 9A, such that an applied voltage causes the ceramic member to deflect in the d31 mode. [Figure 10A] 1 depicts a drive signal that causes a ceramic component to deform in a d31 mode. [Figure 10B]10B depicts the displacement of an electrical element in response to the drive signal of FIG. 10A. [Figure 10C] 10B illustrates the voltages applied to an electrical element such as that of FIG. 6 during first and third stages of the drive signal illustrated in FIG. 10A. [Figure 10D] 10B depicts the voltage applied to an electrical element such as that of FIG. 6 during a second stage of the drive signal depicted in FIG. 10A. [Figure 11A] 1 depicts a driving signal for an electric element that causes a ceramic member to deform in a d33 mode. [Figure 11B] 11B depicts the displacement of an electrical element in response to a drive signal in FIG. 11A starting from a neutral position, moving to a d33 deformation, and back again. [Figure 11C] 11B illustrates the voltages applied to an electrical element such as that of FIG. 6 during first and third stages of the drive signal illustrated in FIG. 11A. [Figure 11D] 11B depicts the voltage applied to an electrical element such as that of FIG. 6 during a second stage of the drive signal depicted in FIG. 11A. [Figure 12A] 1 depicts a drive signal for an electrical element that deforms a ceramic member in a first mode that includes movement from neutral to a d33 deformation, a d31 deformation, and back to neutral again. [Figure 12B] 12B depicts the displacement of an electrical element comprising a ceramic member in response to the drive signal of FIG. 12A. [Figure 12C] 12B depicts the voltages applied to an electrical element such as that of FIG. 6 during first and fourth stages of the drive signal depicted in FIG. 12A. [Figure 12D] 12B depicts the voltage applied to an electrical element such as that of FIG. 6 during a second stage of the drive signal depicted in FIG. 12A. [Figure 12E] 12B depicts the voltage applied to an electrical element such as that of FIG. 6 during a third stage of the drive signal depicted in FIG. 12A. [Figure 13A] 1 depicts a drive signal that deforms the electrical element in a second mode that involves moving from a d31 deformation to a d33 deformation and back to d31. [Figure 13B]13B depicts the displacement of an electrical element comprising a ceramic member in response to the drive signal of FIG. 13A. [Figure 13C] 13B illustrates the voltages applied to an electrical element such as that of FIG. 6 during first and third stages of the drive signal illustrated in FIG. 13A. [Figure 13D] 13B depicts the voltage applied to an electrical element such as that of FIG. 6 during a second stage of the drive signal depicted in FIG. 13A. [Figure 14A] 1 depicts a drive signal for the electric element that deforms the electric element in a third mode that includes movement from a neutral position to a d31 mode, to a d33 mode, back to the d31 mode, and then back to the neutral position. [Figure 14B] 14B depicts the displacement of an electrical element comprising a ceramic member in response to the drive signal of FIG. 14A. [Figure 14C] 14B illustrates the voltages applied to an electrical element such as that of FIG. 6 during first and fifth stages of the drive signal illustrated in FIG. 14A. [Figure 14D] 14B depicts the voltages applied to an electrical element such as that of FIG. 6 during second and fourth stages of the drive signal depicted in FIG. 14A. [Figure 14E] 14B depicts the voltage applied to an electrical element such as that of FIG. 6 during a third stage of the drive signal depicted in FIG. 14A. [Figure 15A] 1 depicts a drive signal for the electric element that distorts the electric element in a fourth mode that includes moving from a d31 deformation to a neutral position to a d33 deformation back to the neutral position and back to a d31 deformation. [Figure 15B] 15B depicts the displacement of an electrical element in response to the drive signal of FIG. 15A. [Figure 15C] 15B illustrates the voltages applied to an electrical element such as that of FIG. 6 during first and fifth stages of the drive signal illustrated in FIG. 15A. [Figure 15D] 15B depicts the voltages applied to an electrical element such as that of FIG. 6 during second and fourth stages of the drive signal depicted in FIG. 15A. [Figure 15E]15B depicts the voltage applied to an electrical element such as that of FIG. 6 during a third stage of the drive signal depicted in FIG. 15A. [Figure 16] Various electrical elements are depicted having alternative arrangements of electrodes.

[0027] In the drawings, like features are designated with like reference numerals throughout. It should be noted that the drawings are not to scale and that certain features may be shown in exaggerated size so that they can be more clearly seen. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] Here, embodiments of the present invention and their modifications will be described with reference to FIGS. 2 to 9, and a driving method and a driving signal will be described with reference to FIGS.

[0029] Two-tier device FIG 2A depicts a top view of an electrical element 20 according to one embodiment mounted to a flexible membrane 10. The electrical element 20 comprises a ceramic member 30 and first and second electrode layers 41, 42. The electrical element 20 is disposed adjacent to the flexible membrane 10 as part of a MEMS device 100. FIG 2B is a side view of the embodiment of FIG 2A, FIG 2C is a perspective view of the embodiment depicted in FIG 2A, FIG 2D is a cross section through the embodiment depicted in FIG 2A along line AA, and FIG 2E is a cross section through the embodiment depicted in FIG 2A along line BB.

[0030] From Figures 2A to 2E, it can be seen that the first and second electrode layers 41, 42 respectively include first and second electrode groups G1(41), G2(41), G1(42), and G2(42). Furthermore, for example, from Figure 2D, it can be seen that each electrode group includes a plurality of fingers G1(41)(i-ii), G2(41)(i-iii), G1(42)(i-ii), and G2(42)(i-iii). Furthermore, it can be seen that all the fingers of each electrode group G1(41), G2(41), G1(42), and G2(42) are electrically connected to each other by common connectors C1(41), C2(41), C1(42), and C2(42), respectively. The common connectors are then each electrically connected to a respective group electrical contact, i.e., C1 (41) to OL, C2 (41) to OR, C1 (42) to IL, and C2 (42) to IR. Electrical connection of the electrical elements to the drive circuitry can be ensured through the use of metal traces that are directly connected to the group electrical contacts OL, OR, IL, and IR of the electrical elements.

[0031] Although the ceramic member 30 is shown in FIGS. 2A-2E as comprising a single layer 31, this is by no means limiting, and the ceramic member 30 may comprise multiple layers 31(i-n), such that there is an electric element 20 comprising the ceramic member 30, the ceramic member 30 comprising at least one layer 31 having a depth (in a depth direction 80). The first and second electrode layers 41, 42 are disposed adjacent to at least one layer 31 of the ceramic member 30, so that during operation, a potential difference may be established across at least a portion of the ceramic member 30. The electric element 20 is disposed adjacent to the flexible membrane 10. In other words, as shown in FIG. 2, in this embodiment, the first and second electrode layers 41, 42 are disposed on opposing sides of the ceramic member 30, and while in this embodiment, the ceramic member 30 comprises a layer 31, it may be understood that this is not a limitation, and the ceramic member 30 may comprise multiple layers.

[0032] The first electrode layer 41 comprises a first electrode group G1(41) with two fingers G1(41)(i-ii) and a second electrode group G2(41) with three fingers G2(41)(i-iii). The fingers of the first and second electrode groups G1(41), G2(41) are arranged to interdigitate (interdigitate) in the first electrode layer 41 in an interdigitation direction 81. It can be seen that there is a gap y1 between the alternating fingers in the electrode layer, so that they do not contact each other. Similarly, the second electrode layer 42 comprises a first electrode group G1(42) with two fingers G1(42)(i-ii) and a second electrode group G2(42) with three fingers G2(42)(i-iii). The fingers of the first and second electrode groups G1(42), G2(42) are arranged alternately in the second electrode layer 42 in an interdigitated direction 81. From Figure 2D it can be seen that in this arrangement, each of the gaps y1 between alternating fingers of the second electrode layer 42 is filled with material that includes a portion of layer 31.

[0033] For each electrode group, all of the fingers in the group are electrically connected to each other (e.g., via common connectors C1(41), C2(41), C1(42), and C2(42) respectively) and electrically connected to group electrical contacts OL, OR, IL, and IR, respectively.

[0034] 2D , the fingers of the first electrode group G1(41) of the first electrode layer 41 are arranged such that they overlap, in the interdigitating direction 81, with corresponding fingers of the first electrode group G1(42) of the second electrode layer 42 on the other side of the ceramic member 30, such that finger G1(41)(i) overlaps with finger G1(42)(i), and similarly for the remaining fingers in electrode groups G1(41), G1(42). Similarly, the fingers of the second electrode group G2(41) of the first electrode layer 41 overlap, in the interdigitating direction 81, with corresponding fingers of the second electrode group G2(42) of the second electrode layer 42, such as finger G2(41)(i) overlapping with finger G2(42)(i).

[0035] Corresponding electrode group pairs may at least partially overlap, preferably they may overlap at least 50% in the interdigitating direction 81, more preferably they may overlap 50% or more, even more preferably they may overlap 90% or more. The center-to-center spacing Z1 (as depicted in FIG. 2D) may be substantially constant. Maintaining the center-to-center spacing Z1 constant may substantially align the electrodes and maximize the overlap area between corresponding fingers in the groups and layers. As can be seen from FIG. 2D and FIG. 2E, in this embodiment, the depth direction 80 and the interdigitating direction 81 are perpendicular to each other. As can be seen from FIG. 2D and FIG. 2E, the second electrode layer 42 is closer to the flexible membrane 10 than the first electrode layer 41.

[0036] It will be appreciated that layer 31 of ceramic member 30 may be formed by depositing multiple sub-layers, for example, by chemical vapor deposition (CVD), chemical solution deposition (CSD), sol-gel deposition, etc., to build up multiple layers to form a ceramic member of a desired thickness. It will be appreciated that ceramic materials, as used herein, include ceramic materials that exhibit ferroelectric behavior, examples of which are discussed above.

[0037] The flexible membrane 10 is fixedly attached to supports 50. Although supports 50 are shown along two sides of the flexible membrane 10, depending on the device in which the electrical element 20 is used and its location in the device, there may be continuous supports along the other two sides, or supports that are discontinuous or have openings to allow fluid to enter, for example, into spaces adjacent to the flexible membrane. For example, the electrical element 20 of Figures 2A-2E may be used as an actuator element of the droplet ejection head actuator component of Figure 1A in place of known arrangements. Furthermore, it will be understood that the supports 50 are shown only diagrammatically and that in practice any suitable arrangement may be used to support the flexible membrane 10 so that it can move as required.

[0038] Reference is now made to FIG. 3A, which depicts a cross section through an electric element 21 similar to that of FIGS. 2A-2E, except that the first electrode groups G1 (41), G1 (42) both comprise three fingers instead of two. FIGS. 3A-3B depict how a voltage may be applied to drive the electric element 21 as an actuator element. For simplicity, much of the detail of FIGS. 2A-2E has been omitted from FIGS. 3A-3B. In FIGS. 3A-3B, the electrode groups G1 (41), G2 (41), G1 (42), G2 (42) are shaded to indicate whether they are at a first voltage V1 (grey) or a second voltage V2 (black). Alternating rows 91, 92 of electrode fingers in the interdigitating direction 81 are either at a first voltage V1 or at a second voltage V2, e.g., a first row 91(i) includes G1(41)(i), G2(41)(i) at the second voltage V2, a second row 92(i) includes G2(41)(i) and G2(42)(i) at the first voltage V1, and the pattern repeats in the interdigitating direction 81.

[0039] In the example of FIG. 3A, electrode groups are selected and a voltage is applied to them such that the ceramic member 30 deforms in the d33 mode. FIG. 3B depicts an exploded top view of the first and second electrode layers 41, 42 of the electrical element 21 of FIG. 3A with the ceramic member 30 omitted. FIG. 3B also depicts the common connectors C1(41), C2(41), C1(42), C2(42), and the group electrical contacts OL, OR, IL, and IR. The electrode groups G1(41), G2(41), G1(42), G2(42), their respective connectors C1(41), C2(41), C1(42), C2(42), and the group electrical contacts OL, OR, IL, and IR are shaded to indicate whether a first voltage V1 (gray) or a second voltage V2 (black) has been applied to them, as in FIG. 3A.

[0040] From both Figures 3A and 3B, it can be seen that in each electrode layer 41, 42, the first electrode group G1 (41), G1 (42) is at the second voltage V2 (black) and the second electrode group G2 (41), G2 (42) is at the first voltage V1 (gray). When there is a voltage difference between the second voltage V2 and the first voltage V1 (e.g., V2>V1), such a configuration creates an effective electric potential field in the ceramic member 30 aligned with the interdigitation direction 81, causing the ceramic member 30 to deform and bend upward relative to the depth direction 80 in the d33 mode, as shown by the dashed line L33 in Figure 3A. It will be appreciated that, effectively, the effective electric potential field is the average of all the fields developed between each finger of the differently charged groups.

[0041] 3A or 3B, it will be appreciated that with the flexible membrane 10 adjacent to and fixedly connected to the electrical element 21 (e.g., as shown in FIG. 2), deformation of the ceramic member 30 in the d33 mode will similarly cause the flexible membrane 10 to move up in the depth direction 80. Because the flexible membrane 10 is fixedly attached to the support 50 and the electrical element 21, the support constrains the movement of the flexible membrane 10 such that the maximum displacement occurs furthest from the support 50, as shown by line L33 (e.g., generally in the middle).

[0042] Figure 4A depicts a cross section through an electrical element 21 like that of Figure 3A, except that the electrodes are selected such that the applied first and second voltages V1, V2 cause the ceramic member 30 to deform in the d31 mode. Figure 4B depicts an exploded top view of the first and second electrode layers 41, 42 of the electrical element 21 of Figure 4A. As with Figure 3, the electrodes, common connector, and group electrical contacts in Figure 4 are shaded to indicate whether the first voltage V1 or the second voltage V2 is applied to them.

[0043] 4A and 4B, it can be seen that in the first electrode layer 41, the first and second electrode groups G1(41), G2(41) are both at a first voltage V1, and in the second electrode layer 42, the first and second electrode groups G1(42), G2(42) are both at a second voltage V2. Stated differently, in FIG. 4A, all fingers in a given electrode layer 41, 42 are seen to be at the same voltage, whereas in FIG. 3A, the voltages applied to the fingers alternate in columns 91, 92 in the interdigitating direction 81.

[0044] When there is a voltage difference between the second voltage V2 and the first voltage V1 (e.g., V2>V1), such a configuration creates an effective electric potential field in the ceramic member 30, which in the case depicted in Figure 4 is aligned with the depth direction 80, causing the ceramic member 30 to deform and bend downward in the depth direction 80 in the d31 mode, as shown by dashed line L31. As shown in Figure 3, the flexible membrane 10 and support 50 are not depicted in Figure 4, but it will be understood that deformation of the ceramic member 30 in the d31 mode also causes the flexible membrane 10 to move downward in the depth direction 80.

[0045] By applying suitable drive signals to selected groups of electrode groups G1(41), G2(41), G1(42), G2(42) and addressing their respective groups electrical contacts OL, OR, IL, IR, the ceramic member 30 can be driven to deform in d33 and / or d31 modes, and when the electrical element 21 is attached to a flexible membrane this can create an electromechanical actuator for use, for example, in a droplet ejection head to eject droplets from a fluid chamber.

[0046] Alternatively, it will be appreciated that the electrical elements 20, 21 may be used as sensors, for example, when fluid pressure in the fluid adjacent to the flexible membrane 10 causes it to deflect and thus deform the ceramic member 30, as the deformation of the ceramic member 30 in d31 and / or d33 modes generates an electrical or (pressure varying) signal. The sensor may be used, for example, with suitable calibration data, to measure pressure in the fluid. As a further example, electromechanical actuators in fluidic devices, such as droplet ejection heads, may be used in idle times when not ejecting droplets to measure and monitor fluid properties, e.g., as sensors when not used as actuators. Still further, lower voltage signals may be sent to the electrical elements 20, 21 when idle to cause smaller deflections, insufficient to eject fluid droplets, to determine actuator properties, e.g., to track any changes (e.g., degradation) in actuator performance over time, or to check for actuator non-responsiveness.

[0047] method As an example, using the electric elements 20, 21 as electric actuator elements 20, 21, a method of driving the electric actuator elements 20, 21 may be as follows, where the electric actuator elements 20, 21 comprise a ceramic member 30. The ceramic member 30 comprises at least one ceramic layer 31 having a depth, and first and second electrode layers 41, 42 disposed adjacent the at least one ceramic layer 31 in a depth direction 80 such that, during operation, a potential difference can be established across at least a portion of the ceramic layer. The electric actuator element 20 is disposed adjacent to the flexible membrane 10.

[0048] The first electrode layer 41 includes a first electrode group G1(41) and a second electrode group G2(41), and the fingers of the first and second electrode groups G1(41), G2(41) are alternately arranged in the first electrode layer 41 in the interdigitating direction 81. The second electrode layer 42 includes a first electrode group G1(42) and a second electrode group G2(42). The fingers of the first and second electrode groups G1(42), G2(42) are alternately arranged in the second electrode layer 42 in the interdigitating direction 81.

[0049] For each electrode group G1(41), G2(41), G1(42), G2(42), all fingers in a given group are electrically connected to each other and to the group electrical contacts OL, OR, IL, IR, and the first electrode group G1(41) of the first electrode layer 41 at least partially overlaps with the first electrode group G1(42) of the second electrode layer 42 in the interdigitated direction 81. The second electrode group G2(41) of the first electrode layer 41 at least partially overlaps with the second electrode group G2(42) of the second electrode layer 42 in the interdigitated direction 81.

[0050] By selecting respective electrode groups to establish a potential difference across at least a portion of the ceramic member 30 (e.g., between respective selected electrode groups), the ceramic member 30 can be deformed in a d31 mode or a d33 mode. The method includes selecting a deformation mode, or a sequence of deformation modes, and providing at least two drive signals to the ceramic member 30 by addressing the respective group electrical contacts OL, OR, IL, IR to establish a potential difference between the respective selected electrode groups to deform the ceramic member 30 in the selected deformation mode or a sequence of selected d31 and / or d33 deformation modes, thereby moving the flexible membrane.

[0051] Because the ceramic member 30 can move both up and down relative to the depth direction 80, using an electric element capable of deformation in both d33 and d31 modes, and using a method of driving such an electric element to deform in d33 and / or d31 modes, can be used to increase the maximum displacement achievable for a given applied voltage. Increasing the maximum displacement of the ceramic member 30 increases the maximum actuation range of the electric actuator elements 20, 21. For example, in a droplet ejection device, this can increase the displacement volume of fluid achievable within the fluid chamber, and thus the maximum droplet size achievable. The larger maximum displacement volume achievable can also have the beneficial effect of allowing fluids with higher viscosities to be ejected more easily, extending the range of ejectable fluids.

[0052] Alternatively, a lower applied voltage may be used to achieve the same displacement as known electrical elements such as those of FIG. 1A, which may have a beneficial effect on the achievable lifetime for the electrical element and thus for fluidic MEMS devices such as droplet ejection heads incorporating such electrical elements 20, 21. Furthermore, operating the ceramic member 30 in d33 and d31 modes allows for the use of materials with lower overall performance by increasing the maximum displacement achievable with such materials. This may be beneficial if such materials are desirable for use due to other benefits such as reduced manufacturing costs or better environmental credentials (such as lead-free materials).

[0053] A method for deforming the electric actuator elements 20, 21 in d31 mode from an undeformed or neutral position (the neutral position being where the ceramic member 30 is not affected by a potential difference, e.g., because the applied voltage is a quiescent voltage or zero and therefore the ceramic member 30 is not otherwise subjected to any applied voltage) may include supplying a first voltage V1 to first and second electrode groups G1(41), G2(41) in the first electrode layer 41 and supplying a second voltage V2 to first and second electrode groups G1(42), G2(42) in the second electrode layer 42. This is shown in FIG. 4A, where in the first electrode layer 41, all electrodes in both groups G1(41), G2(41) are at voltage V1 (shaded grey), and in the second electrode layer 42, all electrodes in both groups G1(41), G2(41) are at voltage V2 (shaded black). As can be seen, the first electrode group G1(41) can be connected via the first group electrical contact OL and the first common connector C1(41), and the group of the second electrode group G2(41) can be connected via the second group electrical contact OR and the second common connector C2(41). Similarly, the first electrode group G1(42) can be connected via the third group electrical contact IL and the first common connector C1(42), and the second electrode group G2(42) can be connected via the fourth group electrical contact IR and the second common connector C2(42). The potential difference established by this arrangement is in the depth direction 80 .

[0054] When the second voltage V2 is greater than the first voltage V1, the application of the voltages described above may cause the ceramic member 30 to deform downward in the depth direction 80 in the d31 mode, as shown by the dotted line L31 in Fig. 4A. If the first and second voltages V1, V2 are maintained for a duration d, the ceramic member 30, and thus the electric actuator elements 20, 21, are held in the deformed d31 mode position for a duration d. For example, the first drive signal may be at the first voltage V1 and the second drive signal may be at the second voltage V2.

[0055] A method of deforming the electric actuator elements 20, 21 in d33 mode from a non-deformed or neutral position may include supplying a first voltage V1 to the first electrode group G1 (41) in the first electrode layer 41 and the first electrode group G1 (42) in the second electrode layer 42 [via the first group electrical contact OL and the third group electrical contact IL, respectively], and supplying a second voltage V2 to the second electrode group G2 (41) in the first electrode layer 41 and the second electrode group G2 (42) in the second electrode layer 42 [via the second group electrical contact OR and the fourth group electrical contact IR, respectively]. 3A where all electrodes in a first group G1 (41), G1 (42) of each first and second electrode layer 41, 42 are at voltage V2 (shaded black) and all electrodes in a second group G2 (41), G2 (42) of each first and second electrode layer 41, 42 are at voltage V1 (shaded grey), e.g., as explained above, the voltages V1, V2 applied to the fingers alternate in the interdigitated direction 81, e.g. 91, 92. Such an arrangement would create an effective electric potential field in the interdigitated direction 81.

[0056] When the second voltage V2 is greater than the first voltage V1, application of the voltages V1, V2 (e.g., as the first and second drive signals as described above) may cause the ceramic member 30 to deform upward in the d33 mode, as shown by the dotted line L33 in Fig. 3A. If the first and second voltages V1, V2 are maintained for a duration d, the ceramic member 30, and thus the electric actuator elements 20, 21, are held in the deformed d33 mode position for a duration d. The first voltage V1 may be a reference voltage, e.g., a ground voltage.

[0057] By selecting the respective electrode groups to establish a potential difference between the respective electrode groups, the ceramic member 30 may be deformed in a d31 mode or a d33 mode, or a sequence of selected d31 and / or d33 modes, providing greater operational flexibility for the use of the electric actuator elements 20, 21. It will be further appreciated that such a sequence may further include a stage in the sequence where the ceramic member 30 is in a neutral position.

[0058] As explained above, when the electric actuator elements 20, 21 are fixedly connected to the flexible membrane 10, they deform the ceramic member 30, thereby moving the flexible membrane 10 therewith. The electric actuator elements 20, 21 may be positioned adjacent to the flexible membrane 10 forming part of a fluid chamber wall in a fluidic MEMS device, such as a droplet ejection device, the fluid chamber further comprising a fluid inlet and nozzle.

[0059] In some embodiments, the fluid chamber may further comprise a fluid outlet so that the fluid chamber may be used in a so-called through-flow mode (e.g., in an arrangement similar to that of FIG. 1A). In such a droplet ejection device (whether through-flow or not), the method may include driving the electric actuator elements 20, 21 to deform in d33 mode or d31 mode, and / or in a sequence of d33 mode and / or d31 mode to move the flexible membrane 10 to eject droplets through the nozzle. The droplet ejection device may comprise a plurality of such fluid chambers, which may be arranged in an array such that individual electric actuator elements 20, 21 are activated as required using the above method to eject a selected sequence of droplets at a given location. Such a method may be used for printing on a substrate, where the droplet ejection device is configured as a droplet ejection head, such as an inkjet printhead.

[0060] It will be appreciated that in some applications it may be desirable to hold the electric actuator elements 20, 21 bent down in a deformed d31 mode position, for example in an electric actuator element for a droplet ejection device in which the flexible membrane 10 forms part of a wall of a fluid chamber, holding the electric actuator elements 20, 21 bent down in the d31 mode causes the flexible membrane 10 to move into the fluid chamber, reducing the fluid chamber volume.

[0061] The droplet ejection cycle may then include releasing the d31 deformation (e.g., by switching V1 and V2 off so that there is no potential difference across the ceramic member 30). The electrical actuator elements 20, 21 may then return to and pull the flexible membrane 10 therewith, increasing the fluid chamber volume and drawing in (DRAW) additional fluid, and then a subsequent reapplication of the d31 deformation may decrease the fluid chamber volume and eject (PUSH) some of the fluid from the nozzle. Thus, in some droplet ejection cycles, it may be desirable to apply a hold signal for a length of time before or after an actuation event to hold the ceramic member 30 in the d31 deformed position in preparation for an initial or subsequent actuation event, such as a droplet ejection event.

[0062] Thus, a method for deforming and holding a ceramic member in a deformed d31 mode may include supplying a first hold signal at a first voltage V1 and supplying a second hold signal at a second voltage V2, the method including supplying the first hold signal to the first and second electrode groups G1(41), G2(41) in the first electrode layer 41 [via the first group electrical contact OL and the second group electrical contact OR, respectively] and supplying a second hold signal to the first and second electrode groups G1(42), G2(42) in the second electrode layer 42 [via the third group electrical contact IL and the fourth group electrical contact IR, respectively] to deform the ceramic member 30 in the d31 mode and hold it in place, and similarly for the electrical elements 20, 21 and the flexible membrane 10.

[0063] In some implementations, it may be desirable to hold the ceramic member 30 in its neutral or undeformed position, where there is no potential difference across the ceramic member 30, before or during an actuation event. In such circumstances, the method may include providing a hold signal(s) to the first and second electrode groups G1(41), G2(41), G1(42), G2(42) of the first and second electrode layers 41, 42. For example, the hold signals may all be at the first voltage V1, so that all electrodes are at the first voltage V1. Alternatively, such a method may include providing no signal to any of the electrode groups G1(41), G2(41), G1(42), G2(42), for example, by switching off the voltage signal.

[0064] In an electrical actuator element for a droplet ejection device, where the flexible membrane 10 forms part of a wall of a fluid chamber, deforming the ceramic member upwards in d33 mode moves the flexible membrane 10 away from the fluid chamber, increasing the fluid chamber volume and drawing in additional fluid. Such a step may be used in preparation for a droplet ejection event, where a suitable hold signal may be used to deform the ceramic member 30 in d33 mode and hold it in place, in a similar manner as described for the d31 deformation above.

[0065] Such a method may include a first hold signal at a first voltage V1 and a second hold signal at a second voltage V2, the method including applying the first hold signal to second electrode groups G2(41), G2(42) in the first electrode layers 41, 42 and applying the second hold signal to first electrode groups G1(41), G1(42) in the first and second electrode layers 41, 42 to deform and hold the ceramic member 30 in the d33 mode.

[0066] Three-layer device, Figs. 5 and 6 Figure 5A shows a top view of an electric element 22 according to another embodiment similar to the embodiment of Figure 2A, and therefore like numerals have been used for like features where appropriate. In the embodiment of Figure 5A (more clearly seen in Figures 5B-5E), the electric element 22 comprises a ceramic member 30 further comprising at least a second layer 32 having a depth (in a depth direction 80). The electric element 22 further comprises a third electrode layer 43 and third electrode groups G1 (43), G2 (43).

[0067] Figure 5B is a side view of the embodiment of Figure 5A, Figure 5C is a perspective view of the embodiment depicted in Figure 5A, Figure 5D is a cross section through the embodiment depicted in Figure 5A along line AA, and Figure 5E is a cross section through the embodiment depicted in Figure 5A along line BB. Electrical element 22 comprises part of a MEMS device 101 which also comprises flexible membrane 10 and support 50.

[0068] As can be seen from Figures 5D and 5E, the third electrode layer 43 comprises a first electrode group G1(43) having two fingers and a second electrode group G2(43) having three fingers, the fingers of the first and second electrode groups G1(43), G2(43) being arranged alternately in the third electrode layer 43 in the interdigitating direction 81, and for each electrode group G1(43), G2(43), all the fingers in the respective group are electrically connected to each other (e.g., via common connectors C1(43), C2(43), respectively), and the common connectors C1(43), C2(43) are electrically connected to group electrical contacts OL2, OR2, where C1(43) is connected to OL2 and C2(43) is connected to OR2. As can be further seen in Figure 5D, in this embodiment, the third electrode layer 43 is closer to the flexible membrane 10 than the first electrode layer 41, and closer to the flexible membrane 10 than the second electrode layer 42. For clarity, as shown in Figure 5, the first and third electrode layers 41, 43 are disposed on opposite sides of the ceramic member 30, with a layer 31 of the ceramic member separating the first and second electrode layers 41, 42, and a second layer 32 of the ceramic member 30 separating the second and third electrode layers 42, 43. The third electrode layer 43 is disposed adjacent to the flexible membrane 10.

[0069] Such a three-layer arrangement may allow for greater complexity of the drive scheme, since all three electrode layers 41, 42, 43, or two of the three electrode layers may be driven in response to drive signals provided to the group electrical contacts OL, OR, IL, IR, OL2, OR2. For example, the electric element 22 may be configured such that all three electrode layers may be driven, for example, when the electric element 22 is being used to eject droplets from a fluid chamber, while two of the three electrode layers may be driven to test the performance of the electric element 22 (e.g., to check for aging effects or damage) without causing a sufficient displacement of the flexible membrane to eject droplets. Additionally, two of the three layers may be driven to provide a smaller displacement of the flexible membrane 10 that is insufficient to eject droplets, but that may be adjusted to generate pressure waves in the fluid chamber that cancel out reflected pressure waves in the fluid chamber or pressure waves coming from adjacent fluid chambers (such undesired pressure waves are referred to as fluidic crosstalk). Crosstalk can otherwise cause undesirable effects such as unwanted drop ejection events, or the emission of smaller sub-droplets, or the emission of droplets of larger or smaller volumes than desired.

[0070] Reference is now made to FIG. 6A, which shows a top view of an electrical element 23 according to another embodiment, similar to that of FIG. 5A, except that the first electrode group G1(41) of the first electrode layer 41 and the first electrode group G1(43) of the third electrode layer 43 are electrically connected to each other, i.e., the common connector C1(41) of G1(41) is electrically connected to the common connector C1(43) of G1(43) via a short 61, and the second electrode group G2(41) of the first electrode layer 41 and the second electrode group G2(43) of the third electrode layer 43 are electrically connected to each other, i.e., the common connector C2(41) of G2(41) is electrically connected to the common connector C2(43) of G2(43) via a short 62. This arrangement (seen, for example, more clearly in FIG. 6F) may reduce the complexity of the electrical connections to electrical element 23 because only four traces and four electrical contacts OL, OR, IL, IR (for the embodiment of FIG. 2A) are required, as opposed to the six electrical traces of electrical element 22 in FIG. 5A. This may be advantageous when space on a die or within a device is at a premium, or when close packing of multiple electrical elements is required.

[0071] 6B is a side view of the embodiment of FIG. 6A; FIG. 6C is a perspective view of the embodiment depicted in FIG. 6A; FIG. 6D is a cross-section through the embodiment depicted in FIG. 6A along line AA; FIG. 6E is a cross-section through the embodiment depicted in FIG. 6A along line BB; and FIG. 6F is a perspective view of the first, second and third electrode layers 41, 42, 43 and their electrical connections for the embodiment depicted in FIG. 6A (e.g., all other features are omitted).

[0072] 5A and 6A, in these embodiments, the third electrode layer 43 is disposed adjacent to the flexible membrane 10, the second electrode layer 42 is disposed adjacent to and between the first and second layers 31, 32 of the ceramic member 30, and the first electrode layer 41 is disposed adjacent to the first layer 31 of the ceramic member 30. As discussed above with reference to FIG. 2, the first layer 31 and the second layer 32 may comprise a single layer, but this is in no way limiting, and the ceramic member 30 may comprise multiple layers 31(i-n) and (if present) 32(i-n). For example, the layers 31, 32 may be formed by depositing multiple sub-layers, for example, by chemical vapor deposition (CVD), chemical solution deposition (CSD), sol-gel deposition, etc., to build up the multiple layers to form the ceramic member 30 of a desired thickness.

[0073] Reference is now made to Figures 7A, 7B and 8A, 8B, which depict an electrical element 24 similar to that of Figures 3A-3B and 4A-4B, but with three electrode layers 41, 42, 43. For simplicity, the ceramic member 30 is depicted as a continuous component in Figures 7A and 8A, but comprises two layers 31, 32 as depicted, for example, in Figures 5C and 6C.

[0074] FIG. 7A depicts a cross section through electrical element 24 with electrode groups G1(41), G2(41), G1(42), G2(42), G1(43), G2(43) shaded to indicate whether they have first voltage V1 or second voltage V2 applied to them and whether the selected group and the voltage applied to them will cause ceramic member 30 to deform in the d33 mode.

[0075] FIG. 7B depicts the three electrode layers 41, 42, 43 of the electrical element 24 of FIG. 7A, with the electrode groups G1(41), G2(41), G1(42), G2(42), G1(43), G2(43) and the respective components electrically connected thereto being shaded to indicate whether a first voltage V1 (grey) or a second voltage V2 (black) has been applied thereto.

[0076] 7A-7B are similar to FIGS. 3A-3B, in which alternating rows 91, 92 of electrode fingers in the interdigitating direction 81 are at voltage V1 or a second voltage V2. As in FIGS. 3A-3B, such an arrangement creates an effective potential field in the interdigitating direction 81 that will cause the ceramic member 30 to deform in the d33 mode and bend upward. The effect will be the same whether the relevant voltages are applied through six electrical contacts OL, IL, OL2, OR, IR, OR2 acting as electrical inputs for an arrangement such as that of FIGS. 5A-5E, or whether the voltages are applied through four electrical contacts OL, IL, OR, IR acting as electrical inputs for the arrangement of FIGS. 6A-6F.

[0077] For clarity, in FIG. 7B the arrangements of FIGS. 6A-6F are shown with black dotted lines for shorts 61 connecting the first electrode groups G1(41), G1(43) and grey dotted lines for shorts 62 connecting the second electrode groups G2(41), G2(43) of the first and third electrode layers 41, 43.

[0078] With respect to FIG. 7A, FIG. 8A depicts a cross section through the electrical element 24, with the electrodes shaded to indicate whether a first voltage V1 (grey) or a second voltage V2 (black) is applied to them. From FIG. 8A and FIG. 8B, it can be seen that in this implementation, the first and third electrode layers 41, 43 are at a first voltage V1, and the second electrode layer 42 is at a second voltage V2. With respect to FIG. 4A and FIG. 4B, the potential difference established by this arrangement is in a depth direction 80, and if the second voltage V2 is greater than the first voltage V1, the applied voltage will cause the ceramic member 30 to deform in d31 mode and move down in the depth direction 80. This movement can be achieved by applying appropriate voltages V1, V2 to the six electrical contacts OL, IL, OL2, OR, IR, OR2 for an arrangement such as that in FIG. 5A-5E. The same effect can also be achieved by applying appropriate voltages V1, V2 to four electrical contacts OL, IL, OR, IR acting as electrical inputs to an arrangement such as that in Figures 6A-6F, where the grey dotted lines indicate shorts 61 and 62. With reference to Figure 7B, short 61 connects first electrode groups G1(41), G1(43) of the first and third electrode layers 41, 43, and short 62 connects second electrode groups G2(41), G2(43).

[0079] There are two primary methods for applying appropriate voltages to selected electrode groups (one or more) using two or more driving voltages to deform the electrical element in a selected sequence of d31 and / or d33 modes.

[0080] Switching circuit method and apparatus A first such method includes controlling a switching circuit to connect and disconnect the first and / or second drive signals from the respective group electrical contacts according to a selected sequence. An arrangement including a switching circuit 85 is depicted in Figs. 9A and 9B. Fig. 9A depicts a switching arrangement for an electrical element such as that of Figs. 6A-6F. For simplicity, the ceramic layer 30 has been omitted so that only the electrode layers are shown, with each electrode layer 41, 42, 43 depicting a single finger (i) for each electrode group G1, G2 (one can imagine the image being slightly tilted to show two adjacent fingers in each electrode layer 41, 42, 43), e.g. Fig. 9A shows the same applied voltages as Fig. 7B, but each layer depicts a single finger in 41, 42, 43.

[0081] In the arrangement shown in FIG. 9A, switch 71 connects the first group electrical contact OL to the third group electrical contact IL, and a drive signal at the second voltage V2 is applied to both. Switch 72 connects the second and fourth group electrical contacts OR and IR to a drive signal at the first voltage V1. The result is that the first group of electrodes G1(41), G1(42), and G1(43) are at the second voltage V2, and the second group of electrodes G2(41), G2(42), and G2(43) are at the first voltage V1. When there is a voltage difference between the first voltage V1 and the second voltage V2, the applied voltages and the positions of switches 71, 72 are such that the ceramic member 30 deflects in the d33 mode.

[0082] Figure 9B depicts a similar switching arrangement for the electrical elements as in Figure 9A, but with the positions of switches 71, 72 changed. It will be noted that Figure 9B depicts the same applied voltages as Figure 8B, but only depicts a single finger in each electrode layer 41, 42, 43.

[0083] In the arrangement shown in FIG. 9B, the switch 71 connects the first group electrical contact OL to a drive signal at the first voltage V1. The third group electrical contact IL remains connected to a drive signal at the second voltage V2. The second group electrical contact OR remains connected to a drive signal at the first voltage V1, and the switch 72 moves to connect the fourth group electrical contact IR to a drive signal at the second voltage V2. The result is that the first and second electrode groups G1(41), G1(43), G2(41), G2(43) on the first and third electrode layers 41, 43 are at the first voltage V1, and the first and second electrode groups G1(42), G2(42) on the second electrode layer 42 are at the second voltage V2. The applied voltages and positions of switches 71, 72 are such that, for example, ceramic member 30 is deflected in d31 mode when there is a voltage difference between V1 and V2 (V2>V1). To return ceramic member 30 and flexible membrane to a neutral position, voltages V1 and V2 can be turned off so that there is no applied voltage and thus no potential difference applied to the ceramic member. Alternative methods such as an additional switch to connect to ground when desired can also be implemented.

[0084] 9A and 9B depict a MEMS device such as a droplet ejector incorporating switching circuitry 85 for electrical elements 21, 22, 23, 24 as described herein, or electrical elements, where electrical elements 21, 22, 23, 24 are configured as electrical actuator elements, and switching circuitry 85 includes at least two switches 71, 72 for connecting and / or disconnecting at least two drive signals from selected ones of electrical contacts OL, IL, OR, IR, [wherein the electrical contacts are configured as electrical inputs], whereby switching circuitry 85 enables electrical elements 21, 22, 23, 24 to be deformed in a selected sequence of d31 and / or d33 modes. When switching circuitry 85 is for a droplet ejector, it enables electrical elements to be deformed in a selected sequence of d31 and / or d33 modes, thereby moving flexible membrane 10 and ejecting droplets from a nozzle.

[0085] It can be understood that the switching circuit 85 as depicted in Figures 9A and 9B is for an electrical element such as that in Figures 6A-6F, but further that, due to the omission of the shorts 61, 62 and the third electrode layer 43, the switching circuit 85 works equally well for an electrical element such as that in Figure 2 comprising two electrode layers 41, 42. Furthermore, for an electrical element such as that in Figures 5A-5E, in the absence of the shorts 61, 62 connecting electrode groups in different layers, there would be a similar arrangement to that in Figures 9A-9B, but further comprising switches that can be used to apply appropriate voltages to the additional group electrical inputs OL2 and OR2, thereby comprising a switching circuit 85 comprising a plurality of switches.

[0086] 9A and 9B, it can be seen that there is a controller 86 for the switching circuitry 85 such that the controller 86 provides control signals to the switching circuitry 85 to implement the sequence of selected deformation modes. Such a controller 86 may be a pre-programmed controller 86 and may be located in close proximity to the electrical element(s) to provide control signals to the switches 71, 72. Additionally, the controller 86 may be mounted on the droplet ejection head.

[0087] Alternatively, the controller 86 may be fed information from an external controller 87, as shown in FIG. 9B. The external controller may be part of the droplet ejection device, but may be located outside the droplet ejection head. The controller may be a separate control board, or may be part of the control circuitry of the droplet ejection device, which may be configured to control the functions of various components of the droplet ejection device. The controller 86 may be a system-on-chip module, a computing device, a microprocessor, an application specific integrated circuit (ASIC), or any other suitable device for controlling the switches 71, 72. Furthermore, the controller 86 or the external controller 87 may be configured to be controlled by an external processor. The external processor may include a user interface for adjusting the printing process parameters, for example, the external processor may be a personal computer, or any other suitable device having a user interface.

[0088] It will further be appreciated that in some arrangements, the shorts 61, 62 connecting the electrodes of the first and third electrode layers 41, 43 may also comprise switches such that the electrical element may be connected and driven in a two-layer mode such as that depicted in Figures 2A-2E, 3A-3B and 4A-4B, or in a three-layer mode such as that depicted in Figures 6A-6F, 7A-7B and 8A-8B. Such changes in the number of layers in operation may be controlled by the controller 86 or in response to inputs received from an external processor, for example, if a user requires information regarding the state and operability of the actuators and wishes to implement a test program to determine this and change the mode of operation. It will further be appreciated that the switching circuitry may comprise switches such that any two of the three layers present in a three-layer arrangement may be driven to deform the electrical element in a two-layer mode. Such flexibility may be desirable, for example, when the objective is to provide a weaker deflection for testing or pressure pulse cancellation, as discussed above.

[0089] Drive signal method and drive signal A second method of applying appropriate voltages to selected electrode group(s) to deform an electric element, which may be understood to be used as an actuator in a selected sequence of d31 and / or d33 modes, includes providing up to four drive signals DOL, DOR, DIL, DIR to the electric element via respective group electrical contacts OL, OR, IL, IR, where the voltage in at least one of the four drive signals is varied to implement the selected sequence. For example, the method may include: providing a first drive signal DOL to a first electrode group G1 (41) in a first electrode layer 41 [by addressing the first group electrical contacts (OL)]; - supplying a second drive signal DOR to a second electrode group G2 (41) in the first electrode layer 41 [by addressing the second group electrical contacts (OR)]; - supplying a third drive signal DIL to the first electrode group G1 (42) in the second electrode layer 42 [by addressing the third group electrical contacts (IL)]; - supplying a fourth drive signal DIR to the second electrode group G2 (42) in the second electrode layer 42 [by addressing the fourth group electrical contacts (IR)].

[0090] Some non-limiting examples of such drive signals are depicted in Figures 10A-15E and described below. It will be appreciated that if there is a third electrode layer 43, an additional pair of drive signals may be used to drive the third layer. Alternatively, as shown in Figures 6A-6F, the electrodes in the three layers may be suitably electronically connected such that only four drive signals are required.

[0091] Generally, what is needed is a drive signal for an electric actuator element, the electric actuator element comprising a ceramic member 30 having a depth, the ceramic member 30 comprising at least one layer 31 and first and second electrode layers disposed adjacent the at least one layer 31 of the ceramic member 30 such that, during operation, a potential difference can be established through at least a portion of the ceramic member 30. The electric actuator elements 20, 21, 22, 23, 24 are arranged adjacent to the flexible membrane 10, and the first electrode layer 41 comprises a first electrode group G1(41) and a second electrode group G2(41), one of the first and second electrode groups G1(41), G2(41) comprises at least one finger and the other of the first and second electrode groups G1(41), G2(41) comprises at least two fingers, and the fingers of the first and second electrode groups G1(41), G2(41) are arranged alternately in the first electrode layer 41.

[0092] The second electrode layer 42 includes a first electrode group G1(42) and a second electrode group G2(42), where one of the first and second electrode groups G1(42), G2(42) includes at least one finger, and the other of the first and second electrode groups G1(42), G2(42) includes at least two fingers. The fingers of the first and second electrode groups G1(42), G2(42) are alternately arranged in the second electrode layer. Each electrode group G1(41), G2(41), G1(42), G2(42), all fingers in the group are electrically connected to each other and to group electrical inputs OL, OR, IL, IR, and by selecting each electrode group to establish a potential difference between the respective groups, the ceramic member can deform in d31 mode or d33 mode, and the drive signal comprises up to four drive signals DOL, DOR, DIL, DIR, whereby the drive signal is provided to one of the group electrical contacts OL, OR, IL, IR, and the voltage of at least one of the four drive signals is changed to establish a potential difference between the respective electrode groups, thereby deforming the ceramic member 30 in the selected d31 and d33 mode sequence, thereby moving the flexible membrane 10. Using multiple drive waveforms in this way, rather than switching circuits, can be advantageous in terms of space used on the die, since switching circuits and connections are no longer necessary. It also allows good design flexibility depending on the application, different combinations of drive signals can be used to create desired effects and fine-tune the actuator performance.

[0093] Considering first Fig. 10A, this depicts drive signals for the electric actuator elements, including a first drive signal DOL (supplied to group electrical contact OL and thus supplied to the first electrode group G1 (41) of the first electrode layer 41), a second drive signal DOR (supplied to group electrical contact OR and thus supplied to the second electrode G2 (41) of the first electrode layer 41), a third drive signal DIL (supplied to group electrical contact IL and thus supplied to the first electrode group G1 (42) of the second electrode layer 42), and a fourth drive signal DIR (supplied to group electrical contact IR and thus supplied to the electrode group G2 (42) of the second electrode layer 42). For clarity, the drive signals DOL, DOR, DIL, and DIR are depicted shifted on the vertical axis of Fig. 10A so that they can be distinguished from one another. In this example, the two voltages of the drive signals DIL and DIR vary over time such that they deform the ceramic member 30 in d31 mode, while the other two drive signals are maintained at a constant voltage, such as, for example, the first voltage V1.

[0094] Figure 10B depicts the displacement of the electrical element (displacement shown as a percentage of the total displacement achieved in response to the drive signal of Figure 10A) and Figure 10C depicts the applied voltages at three stages M, N, and O of the drive signal when applied to an electrical element such as that of Figures 6A-6F through group electrical contacts OL, OR, IL, IR. Figure 10C uses the same representation as Figures 9A and 9B, where a single finger (i) of each electrode group of each electrode layer 41, 42, 43 is shown and the shading indicates the applied voltage, a first voltage V1 (grey) or a second voltage V2 (black).

[0095] As discussed above, the flexible membrane 10 forms part of the fluid chamber, and when actuated in d31 mode to eject a droplet, it may be desirable to hold the deformed ceramic member 30 in d31 mode before the actuation event, so that the flexible membrane 10 deflects downwards into the fluid chamber. This is shown in stage M of Figures 10A and 10B, and in the schematic diagram of Figure 10C. Thus, the first drive signal DOL includes a first hold signal HOL, the second drive signal DOR includes a second hold signal HOR, the third drive signal DIL includes a third hold signal HIL, and the fourth drive signal DIR includes a fourth hold signal HIR. The hold signals HOL, HOR, HIL, HIR have a duration d. The first and second hold signals HOL, HOR are at a first voltage V1, and the third and fourth hold signals HIL, HIR are at a second voltage V2, where V2>V1, so that when the drive signals DOL, DOR, DIL, DIR are supplied to the ceramic member 30, it is deformed in d31 mode, for example, d31 on, for duration d.

[0096] The selected duration d is to hold the deformed ceramic member 30 in d31 mode until an actuation event or other movement of the ceramic member 30 is required. Depending on the operational requirements, the duration d may vary. It will be appreciated that if multiple actuation events follow each other in close succession, the duration d of the hold signal may be short or omitted, or a series of post-pulses after each initiation event may also / alternatively be used. It will further be appreciated that in some implementations, the ceramic member 30 may instead be held in a neutral position before and / or during the actuation event, and instead a pre-pulse or a series of pre-pulses may be used to deform the ceramic member 30 in d31 mode before the actuation event.

[0097] From FIG. 10A it can be seen that the drive sequence for operation in d31 mode may be as follows:

[0098] First stage M: the third and fourth drive signals DIL, DIR are at the second voltage V2, and the first drive signal DOL and the second drive signal DOR are at the first voltage V1, where V2>V1. These voltages are held for a length of time, and as a result, from FIG. 10B it can be seen that the ceramic member 30 is held in the d31 deformation (down) position (first stage M is at -100% displacement). Then, Second Stage N: At time t=t1, the third and fourth drive signals DIL, DIR are switched to voltage V1 for duration d1 such that all four drive signals DIL, DIR, DOL, DOR are at the first voltage V1, and in response, the ceramic member 30 moves to a neutral, undeformed position for duration d1 at t=t1 (0% displacement, see FIG. 10B).

[0099] Third stage O: Then, at t=t1+d1, the third and fourth drive signals DIL, DIR return to the second voltage V2 and the electric element returns to the deformed position d31.

[0100] The effect of this drive sequence on the electrodes is shown in FIG. 10C (first and third stages M, O) and FIG. 10D (second stage N).

[0101] In summary, when driving the piezoelectric member in d31 mode to eject a droplet, starting from the d31 deformation mode position, the drive signals are as follows: at a starting time t=t1, the third drive signal DIL and the fourth drive signal DIR simultaneously switch from the second voltage V2 to the first voltage V1 for duration d1, then the third drive signal DIL and the fourth drive signal DIR simultaneously return to the second voltage V2, for example, the ceramic member 30 moves to a neutral undeformed position for duration d1, and then experiences d31 on again.

[0102] If the electrical element of FIG. 10 is an electrical actuator element for a droplet ejection device, the flexible membrane will begin to deflect into the fluid chamber at stage M, then move to a neutral position at stage N, increasing the chamber volume and drawing in (drawing) fluid, and as it returns to the deflected position at stage O, reducing the chamber volume, and if the duration d1 and the voltage difference between V2 and V1 are sufficient, a droplet of fluid will be ejected (pushed) from the fluid chamber through the nozzle.

[0103] Reference is now made to FIG. 11, which includes a series of images similar to FIG. 10 of an electric element acting as an electric actuator element, but where a drive signal causes the ceramic member 30 to deform in d33 mode. FIG. 11A illustrates the drive signals, including first, second, third and fourth drive signals DOL, DOR, DIL, DIR, respectively. FIG. 11B illustrates the displacement rate of the electric element in response to the drive signals of FIG. 11A. FIG. 11C and FIG. 11D illustrate, using the same representation as FIG. 9A and FIG. 9B, the voltages applied to an electric element such as those of FIG. 6A-6F in response to the drive signals of FIG. 11A, where a single finger (i) of each electrode group of each electrode layer 41, 42, 43 is shown, and the shading indicates the applied voltage, the first voltage V1 (grey) or the second voltage V2 (black).

[0104] As can be seen from Figure 11, First Phase M: The electrical element starts in a neutral position with no potential difference across the ceramic member 30, e.g., the first, second, third and fourth drive signals DOL, DOR, DIL, DIR are all at the first voltage V1. Thereafter, Second stage N: At time t=t1, the first drive signal DOL and the third drive signal DIL simultaneously switch from the first voltage V1 to the second voltage V2 for duration d1 (deforming the ceramic component in d33 mode).

[0105] Third phase O: Then, after a duration d1, the first and third drive signals DOL, DIL return to the first voltage V1 (and the ceramic member 30 returns to the neutral position). 11B, a deformation cycle that starts in a neutral position of d33 off, switches to d33 on (draw), and then returns to d33 off (push). If an electric actuator element is being used for droplet ejection, this equates to drawing fluid into the fluid chamber as the ceramic member 30 deforms up, increasing its volume, and pushing fluid out of it as the ceramic member 30 moves down back to the neutral position, decreasing the chamber volume; if the voltage difference between V1 and V2 and duration d1 are sufficient, this drive signal will cause a droplet ejection event.

[0106] It will be appreciated that if the electrical elements are configured such that they can be driven in either the d33 mode or the d31 mode, this capability can be used to develop drive signals that will drive the ceramic member 30 in a combination of both deformation modes. There are multiple permutations that may be possible, and the drive signals illustrated in Figures 12A-15E and discussed below describe a limited set of drive signals that will cause the ceramic member 30 to move in a sequence of d31 and d33 deformations.

[0107] Mode 1: Consider now Fig. 12, which includes a series of figures similar to those of Figs. 10A-10D and 11A-11D, but where the ceramic member is deformed in a combination of d33 and d31 modes, referred to as Mode 1. As in the previous figures, Fig. 12C depicts the voltage at a single finger in each electrode group of each electrode layer 41, 42, 43 at stage M (and stage P), and similarly Fig. 12D shows the voltage at stage N, and Fig. 12E depicts the voltage at stage O. Fig. 12A depicts the drive signal for achieving Mode 1 deformation.

[0108] First Phase M: The first, second, third and fourth drive signals DOL, DOR, DIL, DIR all start at the first voltage V1, and from FIG. 12B it can also be seen that in the first phase M, the voltage is V1 for all fingers in all electrode groups, and the ceramic member is in its neutral, undeformed state. Thereafter, Second stage N: At time t=t1, the first drive signal DOL and the third drive signal DIL are simultaneously switched from the first voltage V1 to the second voltage V2 (d33 on), the voltages of all fingers in one electrode group in each electrode layer 41, 42, 43 are at the first voltage V1, and all fingers in the other electrode group in each electrode layer 41, 42, 43 are at the second voltage V2, and the ceramic member 30 is deformed in the d33 mode ( It does not matter which electrode groups are at the first voltage V1 and which electrode groups are at the second voltage V2, so long as the same electrode groups in each layer 41, 42 are at the same voltage, e.g., as shown in FIG. 7A , the electrode groups alternate between the first voltage V1 and the second voltage V2 to form a series of columns 91(i), 92(i), 91(ii), 92(ii), etc., with all electrode fingers in the same column being at the same voltage.

[0109] Third phase O: Then, after a duration d2, the first drive signal DOL returns to the first voltage V1, and at the same time the fourth drive signal DIR switches from the first voltage V1 to the second voltage V2 (d33 off and d31 on), so that the first and third electrode layers 41, 43 are at the first voltage V1 and the second electrode layer 42 is at the second voltage V2, whereby the ceramic component deforms in the d31 mode. Finally, Fourth stage P: After duration d3, the third drive signal DIL and the fourth drive signal DIR switch from the second voltage V2 to the first voltage V1 (d33 and d31 off), and from FIG. 12C it can be seen that in stage P, as stage M, the voltage for all fingers in all electrode groups is V1, and the ceramic member 30 is in its neutral undeformed state.

[0110] A method of deforming the ceramic member 30 in mode 1 using such drive signals includes starting with the ceramic member 30 in a neutral position with the d33 and d31 deformation modes off, and then supplying four drive signals to the group electrical contacts to switch the d33 deformation mode on for duration d2, then simultaneously switch the d33 deformation mode off and the d31 deformation mode on for duration d3, then switch the d31 deformation mode off, and return to the neutral position with both the d33 and d31 deformation modes off.

[0111] Mode 2: Considering Figures 13A-13D, which include a series of views similar to those of Figures 10A-12E, but unlike those of Figures 12A-12E, the ceramic member 30 is deformed in a combination of d33 and d31 modes, referred to as mode 2. Figure 13C shows the voltage at a single finger (i) in each electrode group in each electrode layer 41, 42, 43 at stage M (and stage O), and Figure 13D similarly shows the voltage at stage N. From Figure 13A, it can be seen that:

[0112] First stage M: The first and second drive signals DOL, DOR are at a first voltage V1, and the third and fourth drive signals, DIL, DIR are at a second voltage V2, so that the ceramic member 30 is deformed downward in the d31 mode, as shown by the negative displacement in FIG. 13B.

[0113] Second stage N: At time t=t1, as seen in FIG. 13B, the first drive signal DOL switches from the first voltage V1 to the second voltage V2 for duration d1, and simultaneously the fourth drive signal DIR switches from the second voltage V2 to the first voltage V1 (d31 off, d33 on) for duration d1, causing the ceramic member 30 to deform upwards in the d33 mode.

[0114] In the third stage O:t=t1+d1, the first drive signal DOL returns to the first voltage V1, the fourth drive signal DIR returns to the second voltage V2 (d33 off, d31 on), and the ceramic member 30 returns to its downward deformation in the d31 mode.

[0115] Thus, a method for deforming the ceramic member 30 in mode 2 includes starting with the ceramic member 30 deformed down in d31 mode, then switching the d31 deformation off and the d33 deformation on for duration d1, and then simultaneously switching the d33 deformation off and the d31 deformation on.

[0116] Mode 3: 14A-14E, which depict an arrangement in which ceramic member 30 deforms in a combination of d33 and d31 modes referred to as Mode 3.

[0117] First Phase M: From Fig. 14A, it can be seen that for Mode 1, the first, second, third and fourth drive signals DOL, DOR, DIL, DIR all start at the first voltage V1 and the ceramic member 30 is in a neutral position (see Fig. 14B). In a second phase N:t=t1, the third drive signal DIL and the fourth drive signal DIR simultaneously switch from the first voltage V1 to the second voltage V2 (D31 on, D33 off) for duration d4.

[0118] Third phase O: After a duration d4, the fourth drive signal DIR switches from the second voltage V2 to the first voltage V1, and at the same time the first drive signal DOL switches from the first voltage V1 to the second voltage V2 (d31 off, d33 on). Fourth phase P: After duration d5, the first drive signal DOL switches from the second voltage V2 to the first voltage V1, and at the same time the fourth drive signal DIR switches from the first voltage V1 to the second voltage V2 (d31 on, d33 off). Finally, Fifth phase Q: After duration d6, the third drive signal DIL and the fourth drive signal DIR simultaneously switch from the second voltage V2 to the first voltage V1 (d31 off, d33 off) and the ceramic member 30 returns to the neutral position.

[0119] Thus, a method of deforming the ceramic member 30 in mode 3 includes starting with the ceramic member 30 in the neutral position, then switching d31 on for duration d4, then simultaneously switching d31 off and d33 on for duration d5, then switching d31 on and d33 off for duration d6, then switching d31 off to return the ceramic member to the neutral position.

[0120] Mode 4: Finally, considering Figures 15A-15E, these depict Mode 4.

[0121] As for the first stage M:MODE2, MODE4 starts with the first and second drive signals DOL, DOR at the first voltage V1 and the third and fourth drive signals DIL, DIR at the second voltage V2 (e.g., so that the ceramic member 30 is deformed downwards in the d31 mode), and then In a second stage N:t=t1, the third drive signal DIL and the fourth drive signal DIR are simultaneously switched from the second voltage V2 to the first voltage V1 for a duration d4, whereby the ceramic member 30 moves to a neutral position for a duration d4, and then switched off d31. In a third phase O:t=t1+d4, the first drive signal DOL and the third drive signal DIL are simultaneously switched from the first voltage V1 to the second voltage V2 (d33 on, the ceramic member 30 deforms upwards) for a duration d5, and then: In a fourth phase P:t=t1+d4+d5, the first drive signal DOL and the third drive signal DIL then return to the first voltage V1, switch off d33, return to the neutral position for duration d6, and finally In the fifth stage Q:t=t1+d4+d5+d6, the third driving signal DIL and the fourth driving signal DIR simultaneously switch from the first voltage V1 to the second voltage V2, and deform the ceramic member 30 downward by switching on d31. As can be seen from Fig. 15A, the third driving signal DIL and the fourth driving signal DIR simultaneously switch from the second voltage V2 to the first voltage V1 for a duration d4, then after a duration d4, the first driving signal DOL and the third driving signal DIL simultaneously switch from the first voltage V1 to the second voltage V2 for a duration d5, then back to the first voltage V1, then after a duration d6, the third driving signal DIL and the fourth driving signal DIR simultaneously switch from the first voltage V1 to the second voltage V2.

[0122] It will be understood that the modes described herein are a small sub-selection of possible operating modes and their associated methods and drive signals. They provide flexibility in design and operational performance by providing a set of drive waveforms. Those skilled in the art can develop suitable drive signals and methods to deform the ceramic member in d31 and / or d33 modes, thereby using the electric element as an electric actuator element. If it is required that the ceramic member 30, and thus the flexible membrane 10, starts in a deformed position, the drive signals DOL, DOR, DIL, DIR can include appropriate hold signals HOL, HOR, HIL, HIR, respectively, at appropriate combinations of the first and second voltages V1, V2, as required, to deform the ceramic member 30 in d33 or d31 modes.

[0123] Further, the drive waveforms described herein may additionally include pre-pulses and post-pulses, for example to address crosstalk, provide additional fluid priming and functionality, or to move the ceramic member 30 from one position to another prior to an actuation event. A number of such drive waveforms may be chained together to form a series of deformation events, and thus an actuation event, as desired. It will be appreciated that a suitable hold signal may be used during a droplet ejection event to hold the ceramic member in a required position prior to the next deformation event in the sequence. It will be appreciated that any of the drive signals described herein may be provided to a droplet ejection device comprising at least one fluid chamber, the at least one fluid chamber comprising a fluid inlet, an electrical element, and a nozzle for droplet ejection therefrom, and movement of a flexible membrane in response to an appropriate drive signal causes ejection of a fluid droplet from the nozzle.

[0124] Sensor Mode As explained above, the electric elements 20, 21, 22, 23, 24 described herein may operate as electric sensor elements in idle times when not being used as electric actuator elements. Alternatively, there may be electric elements configured as electric sensor elements and MEMS devices configured such that the electric element is an electric sensor element and the group electrical contact(s) are configured as an electrical output. In both cases, there may be methods of sensing using the electric sensor element, the electric sensor element being: a) a ceramic member 30, the ceramic member 30 comprising at least one ceramic layer 31 having a depth; b) first and second electrode layers 41, 42 disposed adjacent to at least one ceramic layer 31 in a depth direction such that, during operation, a potential difference can be established across at least a portion of the ceramic layer 31; The electrical sensor elements 20, 21, 22, 23, 24 are disposed adjacent to the flexible membrane 10. The first electrode layer 41 comprises a first electrode group G1(41) and a second electrode group G2(41), one of the first and second electrode groups G1(41), G2(41) comprises at least one finger and the other of the first and second electrode groups comprises at least two fingers, and the first electrode groups G1(41), G2(41) are alternately disposed in the first electrode layer 41 in the interdigitating direction 81. The second electrode layer 42 comprises a first electrode group G1(42) and a second electrode group G2(42), one of the first and second electrode groups G1(42), G2(42) comprising at least one finger and the other of the first and second electrode groups comprising at least two fingers, the first electrode groups G1(42), G2(42) being alternately arranged in the second electrode layer 42 in an interdigitating direction 81, and for each electrode group G1(41), G2(41), G1(42), G2(42), all fingers in the group are electrically connected to each other (through a common connector) and to the group electrical contacts OL, OR, IL, IR.

[0125] The first electrode group G1 (41) of the first electrode layer 41 overlaps with the first electrode group G1 (42) of the second electrode layer 42 in the interdigitating direction 81, and the second electrode group G2 (41) of the first electrode layer 41 overlaps with the second electrode group G2 (42) of the second electrode layer 42 in the interdigitating direction 81. The ceramic member 30 can deform in a d31 mode or a d33 mode.

[0126] The sensing method includes the flexible membrane 10 moving in response to an external force and the ceramic member 30 thereby deforming in d31 and / or d33 modes to generate an electrical signal(s) that is / are provided to one or more of the group electrical contacts OL, OR, IL, IR, the group electrical contacts OL, OR, IL, IR configured as outputs. The sensing method may further include measuring the generated electrical signal(s) provided to one or more of the group electrical contacts OL, OR, IL, IR, and using the signal(s) to determine the deformation of the flexible membrane 10 and thus the strength of the external force(s). Such a method may include, for example, determining the force applied to the flexible membrane 10 using a pre-stored or look-up table of known signals, known deformations, and known forces.

[0127] Alternative Layouts 16A-16D depict various alternative arrangements for the electrodes. FIG. 16A shows an arrangement with an electric element 25 similar to that of FIG. 7A or FIG. 8A, but one of the layers, in this case the second electrode layer 42, comprises fingers G1 (42), G2 (42) that are longer in the interdigitating direction 81 than those in the other two electrode layers 41, 43, with the center-to-center spacing Z1 being substantially the same, such that the electrodes in the electrode layers 41, 42, 43 are aligned. It can thus be seen that the gap y2 between adjacent fingers of the layer of electrodes 42 is smaller than the gaps y1, y3 of the other two layers. Such an arrangement may ensure that the shorter electrode fingers in the two electrode layers 41, 43 are contained within the length of the longer fingers G1 (42) (i-iii), G2 (42) (i-iii) in the interdigitating direction 81, so as to ensure overlap even if there is misalignment between the layers. Such an arrangement may provide a more effective d31 deformation mode.

[0128] 16B, which depicts an arrangement having an electrical element 26 with first and second electrode layers 41, 42 and a third continuous electrode layer G(42a) located between the first and second electrode layers 41 and 42, where only the first and second electrode layers 41, 42 are interdigitated, and the first electrode group G1(41) of the first electrode layer 41 and the first electrode group G1(42) of the second electrode layer 42 are electrically connected to each other and may share a common group electrical connector, and similarly the second electrode groups G2(41) and G2(42) are electrically connected to each other and may share a common group electrical connector, while the third electrode layer G(42a) has a separate group electrical input. As can be further seen from FIG. 16B, in this embodiment the third electrode layer is closer to the flexible membrane than the first electrode layer, while the second electrode layer is closer to the flexible membrane than the third electrode layer. Such an arrangement may use the first and second electrode layers 41, 42 for deformation in d33 mode, so that, for example, alternating rows 91, 92 of electrode fingers in the interdigitated direction 81 are formed from first groups G1(41), G1(42) and second groups G2(41), G2(42) of the first and second electrode layers 41, 42, respectively, while the third electrode layer G(42a) remains neutral. Such an arrangement may use all three layers for deformation in d31 mode, for example, in a manner similar to that shown in FIG. 8A.

[0129] 16C and 16D depict top views of electrical elements 27 and 28 with the interdigitated fingers of the first electrode layer arranged in different orientations relative to the underlying fluid chamber (not shown) and thus the flexible membrane (in the case of an electrical actuator element), such that the interdigitating direction 81 is different in each case. In FIG. 16C, the interdigitating direction 81 is parallel to the chamber length direction y, and in FIG. 16D, the interdigitating direction 81 is perpendicular to the chamber length direction y. Either orientation is suitable for use in any of the embodiments and arrangements described herein, and it will be understood that in each case the second and (if present) third electrode layers 42, 43 (not shown) can be oriented in the same way as the first electrode layer 41 so as to overlap appropriately.

[0130] Modeling example The modeling work was carried out in COMSOL Multiphysics simulation software to investigate the effects of various configurations, and the results are shown in Tables 1 to 3.

[0131] In Table 1, the applied voltage, electric field, displacement and displacement area are shown and compared with a conventional d31 design (such as that in Figure 1) with two continuous electrodes on either side of the ceramic member. [Table 1]

[0132] Table 2 depicts the effect of varying the width in the interdigitating direction 81 of the electrode fingers in three layers of electrodes 41, 42, 43. The width is varied from 1 μm to 2.5 μm, maintaining a constant pitch (center-to-center spacing Z1) of 5 μm, and varying the applied voltage from 10 V to 40 V, giving the same applied field of 10 V / μm in all cases. In this table, all cases include three layers of electrodes 41, 42, 43, and the width of the electrode fingers in the first layer 41 and third layer 43 are the same. [Table 2]

[0133] The total displacement and total displacement area for different electrode widths for d33 and d31 modes of operation are plotted. In all cases the same voltage difference of 20V was applied. [Table 3]

[0134] In the above table, the pitch between the electrode fingers in each electrode layer is 5 μm for all cases.

[0135] Overview Any of the electrical elements 20, 21, 22, 23, 24, 25, 26 described herein, or any of the variations of these embodiments, can be incorporated into a MEMS device. In some MEMS devices, the electrical elements can be used as electrical actuator elements, for example, as described in the droplet ejection device, where the droplet ejection device includes at least one fluid chamber, the fluid chamber including a fluid inlet and a nozzle for droplet ejection therefrom, and at least one of the electrical elements 20, 21, 22, 23, 24, 25, 26 described herein. The droplet ejection device can be used in a variety of applications, including as a printing device. In such applications, the droplet ejection device can include multiple such fluid chambers, which can be arranged in an array to address a large area of ​​a substrate. Some droplet ejection devices can include multiple droplet ejection heads, each of which includes multiple such fluid chambers.

[0136] It will be understood that the number of fingers in each electrode group is not limited to those depicted herein, with a minimum requirement being that one of the first and second electrode groups comprises at least one finger and the other of the first and second electrode groups comprises at least two fingers. It will be further understood that there may be electrical elements 20, 21, 22, 23, 24, 25, 26 according to any of the embodiments described herein, with each electrode group comprising multiple fingers.

[0137] Further, it will be understood that there is no requirement for an even or odd number of fingers in any of the electrode groups, and that the first and second electrode groups may include the same or different numbers of fingers, provided that the fingers in the first and second electrode groups are arranged in an alternating manner. In some embodiments, the number of fingers in aligned groups may be the same, e.g., G1(41), G1(42), G1(43) have the same number of fingers as each other, and similarly, G2(41), G2(42), G2(43) have the same number of fingers as each other.

[0138] Furthermore, although the electrical elements 20, 21, 22, 23, 24, 25, 26 are described as being disposed adjacent to and fixedly connected to the flexible film 10, it will be understood that they may not be directly connected to the flexible film 10, as other layers may be interposed between portions of the electrical elements 20, 21, 22, 23, 24, 25, 26, etc., and the flexible film 10, as needed. It will be understood that such layers may comprise electrical and / or chemical passivation layers, adhesion layers, stress gradient mitigation layers, diffusion barriers, or any other additional layers between the electrical elements and the flexible film 10, similar to those described with reference to Figures 1A and 1B, that may be necessary for the construction and operation of the electrical elements. For example, if the electrode layer is made of platinum (Pt), a layer of zirconium dioxide (ZrO2) between the flexible film 10 and the adjacent electrode layer (42 or 43, depending on the embodiment) may support the growth of a ceramic, such as PZT, in the areas where the platinum electrodes are etched.

[0139] However, it will be appreciated that whether or not there is an intervening layer between the electrical elements 20, 21, 22, 23, 24, 25, 26 and the flexible membrane 10, the two are fixedly connected to one another such that the electrical elements 20, 21, 22, 23, 24, 25, 26 act as electrical actuator elements and the ceramic member 30 is driven to deform in the d33 and / or d31 modes, thereby moving the flexible membrane 10. Similarly, when the electrical elements 20, 21, 22, 23, 24, 25, 26 are configured or act as sensors, they move in response to a force applied to the flexible membrane, causing the ceramic member 30 to deform in the d33 and / or d31 modes and generate an electrical signal. Thus, adjacent and fixedly connected includes arrangements in which the electrical elements 20, 21, 22, 23, 24, 25, 26 and flexible membrane 10 have intervening layers as described herein, but still allow movement (e.g., deformation) of the electrical elements 20, 21, 22, 23, 24, 25, 26 to cause movement of the flexible membrane 10 (conversely relative to the electrical sensor element).

[0140] Furthermore, although layers 31 and 32 (if present) of the ceramic member are depicted as single layers, it will be understood that this is done for simplicity and that layers 31, 32 may comprise multiple layers or sub-layers (e.g., stacks of layers 31 (1-m) and 32 (1-n)). For example, such stacks of layers are typically formed from successive depositions, for example, depositing one thin film layer after another (e.g., 1, 2, 3 m / n) until a desired thickness of layers 31 and 32 (if present) is reached. Preparation of ceramic thin film layers for MEMS applications typically involves chemical solution deposition using chemical solution precursors or sputtering (e.g., RF magnetron sputtering) using solid sintered or hot pressed ceramic targets. Any other suitable preparation method may also be used.

[0141] The layers 31, 32 may preferably be formed through chemical solution deposition. For example, the multilayer thin film ceramic member 30 may be formed by multiple repetitions of deposition and drying of a precursor solution of the ceramic material, with crystallization between each set of deposition and drying steps, or by a crystallization step at the end of multiple repetitions of deposition and drying. As will be appreciated, the composition of each of the layers of the multilayer thin film ceramic member 30 may be substantially identical. Alternatively, the composition of the individual layers of the multilayer thin film ceramic member 30 may be optimized to meet specific operational requirements, for example, depending on whether one of the sublayers contacts the substrate and / or electrode of the electrical element. Thus, in such an embodiment, the composition of the individual layers of the multilayer thin film ceramic material 31(1-m), 32(1-n) may differ from one another, for example, they may include different dopants, different overall compositions, etc. Such design flexibility may allow fine tuning of the properties, and therefore performance, of the ceramic member 30. Furthermore, although the two layers 31, 32 are depicted herein as being of the same thickness in the depth direction 80, it will be understood that this is by no means necessary and the layers 31, 32 may have different thicknesses and may include different numbers of sub-layers. A typical thickness of the ceramic member 30 in the depth direction 80 may range from 0.5 to 3 μm, or may be 1 to 2 μm, with typical examples being 1.3 μm, 1.4 μm, or 1.5 μm. The thickness of the ceramic member 30 depends on the desired operating frequency, generally a higher operating frequency may require a thicker flexible membrane 10, and therefore a thicker ceramic member 30 is more powerful to be able to drive a thicker flexible membrane (designing ceramic members with higher piezo efficiency may also be utilized). Furthermore, it will be understood that, depending on their respective positions, the layers 31, 32 may include portions that form gaps y1, y2, y3 between adjacent fingers in the respective electrode layers adjacent thereto.

[0142] The electrodes 41, 42, 43 may be 100-200 nm thick, for example on the order of 150 nm thick in the depth direction 80. The thicknesses of the electrodes 41, 42 (and if present) 43 may be the same or different, they may comprise the same material, or they may all comprise different materials, with the electrodes 42 included in the ceramic member 30 being of a different material than the material on the outer edges 41, 43 of the three layer device. The material and thickness of the electrodes may be optimized for the design and purpose of the ceramic member 30. The electrodes 41, 42, 43 may be formed by any suitable method, for example any suitable deposition technique, such as sputtering.

[0143] As will be appreciated by those skilled in the art, if there are multiple electrical elements, the ceramic member 30 may be deposited first and then patterned and divided, for example, by etching, into multiple separate ceramic members 30, each associated with a respective one of the multiple electrical elements 20, 21, 22, 23, 24, 25, 26. Additionally, although not depicted herein, it will be appreciated that additional layers, such as passivation layers, may cover the electrical elements to protect against external damage, provide electrical and chemical passivation, and the like.

[0144] As used herein, "ceramic material" is understood to encompass any suitable material that exhibits ferroelectric behavior, such as, for example, piezoelectric materials or relaxor / ferroelectric crossover materials. As described above, examples of suitable ceramic materials include, but are not limited to, lead-based ceramics having a perovskite structure, such as lead zirconate titanate (PZT), doped PZT, and PZT-based solid solutions. Other suitable ceramic materials include lead-free alternative ceramic materials, such as (K,Na)NbO3-based materials, (Ba,Ca)(Zr,Ti)O3-based materials, and (Bi,Na,K)TiO3-based materials. These exemplary materials are in no way limiting, and other suitable materials may be used.

[0145] Where the first voltage V1 is a reference voltage, this voltage may be ground, although it will be appreciated that this is by no means required and the reference voltage may be a voltage other than ground.

[0146] Furthermore, it will be understood that the first and second voltages V1, V2 as described herein are not limited and different voltages may be used. Furthermore, when the second voltage V2 is greater than the first voltage V1, the difference (V2-V1) between the first and second voltages V1, V2 is not limited. For example, a smaller voltage difference may be used to provide a smaller deflection, or a larger voltage difference may be used with a more viscous fluid or to provide a larger deflection. Furthermore, different voltages or voltage sequences, or different voltage differences may be used to form pre-pulses and post-pulses for crosstalk suppression, etc.

[0147] Still further, within a given drive waveform, different steps and levels of voltages may be used rather than the binary first voltage V1, second voltage V2 used in the examples herein, e.g., the second voltage V2 may include a range of varying voltage levels, e.g., smaller voltages used for pre-pulses and post-pulses, for actuator sensing, or actuator evaluation, and stronger voltages used when a droplet ejection event is required. Still further, the length of the pulse (e.g., duration of change from one deformation mode to another, or to / from a neutral position) may be varied as needed. For example, a short duration pulse with a low voltage may be used to move the actuator and excite the membrane, e.g., to sense or test actuator performance while preventing droplet ejection. Similarly, a long duration pulse with a slow and gradual change in voltage may be used to move the ceramic member from one position to another (e.g., a holding position) without causing a droplet ejection event.

[0148] The voltage switching in Figures 10A-15A is depicted as occurring instantaneously, but is by no means limited, and there may be a slow rise and / or fall when switching from one voltage level to another. There may also be a delay during the switching from one voltage level to another, which may be predetermined or dynamic. Furthermore, the difference between the voltage level and the width of the pulse may be controlled as needed. As a result, depending on the delay, maximum voltage, minimum voltage and / or pulse width, the change in position of the ceramic member 30 (through steps M-P) depicted in Figures 10B-15B may be controlled as well.

[0149] It should be noted that the waveforms shown in Figures 10A-15A are for ease of understanding and are not limited to a particular waveform shape, but may take other forms and shapes, such as trapezoidal, sinusoidal, etc. Additionally, while the waveforms containing both d31 and d33 deflections are depicted symmetrically, it will be understood that a displacement split of 50%:50% is easier to present and allows for asymmetric deformations to either side of the neutral position. Additionally, for some applications, asymmetries can be designed to tailor the deflection of the flexible membrane for a particular application. This can be done by designing a ceramic member whose d33 and d31 responses are asymmetric and / or by using an asymmetric waveform.

Claims

1. An electric element comprising: a ceramic member, the ceramic member comprising at least one layer having a depth; first and second electrodes disposed adjacent the at least one layer of the ceramic member such that, during operation, a potential difference can be established through at least a portion of the ceramic member; the electrical element is disposed adjacent to the flexible membrane; the first electrode layer comprises a first group of electrodes having at least two fingers and a second group of electrodes having at least one finger; the fingers of the first and second electrode groups are alternately arranged in the first electrode layer in an interdigitated orientation; the second electrode layer comprises a first group of electrodes having at least two fingers and a second group of electrodes having at least one finger; the fingers of the first and second electrode groups are alternately arranged in the second electrode layer in an interdigitated orientation; for each electrode group, all of the fingers of the group are electrically connected to each other and to a group electrical contact; the fingers of the first set of electrodes of the first electrode layer at least partially overlap in the interdigitated orientation with corresponding fingers of the first set of electrodes of the second electrode layer; the fingers of the second set of electrodes of the first electrode layer at least partially overlap in the interdigitated orientation with corresponding fingers of the second set of electrodes of the second electrode layer; An electrical element, wherein the group electrical contacts are arranged such that they are addressable in the interdigitating direction to establish a potential difference between the fingers of the first and second electrode groups of the same electrode layer and a deformation of the ceramic member in a d33 mode, and in the depth direction to establish a potential difference between the at least partially overlapping fingers of the first and second electrode groups of the first and second electrode layers and a deformation of the ceramic member in a d31 mode.

2. 10. The electrical element of claim 1, wherein the ceramic member further comprises at least a second ceramic layer having a depth, and the electrical element further comprises a third electrode layer.

3. the third electrode layer comprises a first electrode group and a second electrode group, one of the electrode groups comprising at least one finger and the other of the electrode groups comprising at least two fingers, the fingers of the first and second electrode groups being alternately arranged on the third electrode layer in the interdigitated direction; 3. The electrical element of claim 2, wherein for each electrode group, all of the fingers of the group are electrically connected to each other and to a group electrical contact.

4. 3. The electrical element of claim 2, wherein the third electrode layer is disposed adjacent to the flexible membrane, the second electrode layer is disposed adjacent to and between the first and second layers of ceramic members, and the first electrode layer is disposed adjacent to the first layer of ceramic members.

5. 3. The electrical element of claim 2, wherein the third electrode layer is located between the first and second ceramic layers and the first and second electrode layers, the third electrode layer being continuous.

6. 3. The electrical element of claim 2, wherein the first group of one electrode layer and the first group of another electrode layer are electrically connected to each other and share a common group electrical input, and the second group of one electrode layer and the second group of another electrode layer are electrically connected to each other and share a common group electrical input, so that a potential difference can be established in the interdigitated orientation of at least a portion of the ceramic members during operation.

7. 3. The electrical element of claim 2, wherein the first group of one electrode layer and the second group of the same electrode layer are electrically connected to each other and share a common group electrical input, and the first group of another electrode layer and the second group of the another electrode layer are electrically connected to each other and share a common group electrical input, so that a potential difference can be established in a depth direction of at least a portion of the ceramic member during operation.

8. A droplet ejection device comprising at least one fluid chamber, the at least one fluid chamber comprising a fluid inlet and a nozzle for droplet ejection therefrom, and at least one electrical element according to any one of claims 1 to 7.

9. A MEMS device comprising the electric element according to any one of claims 1 to 7.

10. The electrical element is configured to be an electrical sensor element; deformation of the ceramic member in a d33 mode establishes a potential difference between the fingers of the first and second electrode groups of the same electrode layer to create an effective potential field aligned with the interdigitation direction; 10. The MEMS device of claim 9, wherein deformation of the ceramic member in a d31 mode establishes a potential difference between the at least partially overlapping fingers of the first and second electrode groups of the first and second electrode layers to create an effective potential field aligned with a depth direction.

11. The electrical element is configured to be an electrical actuator element; the establishment of a potential difference between the fingers of the first and second electrode groups of the same electrode layer creating an effective potential field aligned with the interdigitation direction, causing deformation of the ceramic member in a d33 mode; 10. The MEMS device of claim 9, wherein establishment of a potential difference between the at least partially overlapping fingers of the first and second electrode groups of the first and second electrode layers creating an effective potential field aligned with the depth direction causes deformation in a d31 mode.

12. 8. An electric element as claimed in any one of claims 1 to 7, wherein the switching circuit comprises at least two switches for connecting and disconnecting at least two drive signals from selected ones of the group electrical contacts to deform the electric element in a selected sequence of d31 and d33 modes.

13. 13. A controller for a switching circuit as claimed in claim 12, wherein the controller provides control signals to the switching circuit to implement a selected sequence of the d31 and d33 modes.

14. 1. A method of driving an electric actuator element, the method comprising: a ceramic member, the ceramic member comprising at least one ceramic layer having a depth; first and second electrode layers disposed adjacent the at least one ceramic layer in a depth direction such that, during operation, a potential difference can be established through at least a portion of the ceramic member; the electrical actuator element is disposed adjacent to a flexible membrane; the first electrode layer comprises a first electrode group and a second electrode group; the fingers of the first and second electrode groups are alternately arranged on the first electrode layer in an interdigitated orientation; the second electrode layer comprises a first electrode group and a second electrode group; the fingers of the first and second electrode groups are alternately arranged in the second electrode layer; for each electrode group of the first and second electrode layers, all fingers of the group are electrically connected to each other and to a group electrical contact; the first electrodes of the first electrode layer at least partially overlap with the first electrodes of the second electrode layer in the interdigitated orientation; the second group of electrodes of the first electrode layer at least partially overlapping the second group of electrodes of the second electrode layer in the interdigitated orientation; the electrical actuator elements are deformed by addressing selected respective electrodes and establishing a potential difference across at least a portion of the ceramic member, thereby deforming the ceramic member in a d31 mode or a d33 mode; The method further comprising: - selecting said d31 deformation mode or said d33 deformation mode or selecting a sequence of d31 and / or d33 deformation modes; - supplying at least two drive signals to the electric actuator element by addressing respective group electrical contacts of selected respective electrode groups, thereby establishing a potential difference between the selected respective electrode groups, thereby deforming the ceramic member in the selected deformation mode or in a sequence of the selected deformation modes, thereby moving the flexible membrane.

15. Deforming the ceramic member in a d31 mode, the at least two drive signals comprising: - providing a first voltage to the first electrodes of the first electrode layer and to the second electrodes of the first electrode layer; - providing a second voltage to the first electrodes in the second electrode layer and to the second electrodes in the second electrode layer, thereby establishing a potential difference between the selected respective electrodes.

16. The method for deforming the ceramic member in a d33 mode includes the step of: - providing a first voltage to the first electrodes of the first electrode layer and to the first electrodes of the second electrode layer; - providing a second voltage to the second group of electrodes in the first electrode layer and to the second group of electrodes in the second electrode layer, thereby establishing a potential difference between the selected respective groups of electrodes.

17. the ceramic member includes a neutral state in which no potential difference is established across the ceramic member; 15. The method of claim 14, further comprising holding the ceramic member in a neutral state before and / or after deforming the ceramic member in the selected deformation mode or in a selected sequence of the d31 and / or d33 deformation modes and / or as an intermediate step in the selected sequence of the d31 and / or d33 deformation modes.

18. the method further comprising the step of holding the ceramic component in a deformed state before and / or after deforming the ceramic component in the selected deformation mode or in a selected sequence of the d31 and / or d33 deformation modes and / or as an intermediate step in a selected sequence of the d31 and / or d33 deformation modes; The method of claim 14 , further comprising selecting whether to deform and hold in d33 mode or to deform and hold in d31 mode.

19. The method of claim 14 , wherein the second voltage is greater than the first voltage.

20. the method further comprising providing at least four drive signals to the electric actuator elements by addressing the respective group electrical contacts; 15. The method of claim 14, wherein the voltage in the at least one of the at least four drive signals is varied to implement a selected deformation mode or a selected sequence of d31 and / or d33 deformation modes.

21. The method further comprising: - supplying a first drive signal to the first electrodes of the first electrode layer; - supplying a second drive signal to the second set of electrodes in the first electrode layer; - supplying a third drive signal to the first electrodes of the second electrode layer; - supplying a fourth drive signal to the second group of electrodes in the second electrode layer.

22. the first drive signal includes a first hold signal, the second drive signal includes a second hold signal, the third drive signal includes a third hold signal, and the fourth drive signal includes a fourth hold signal; - to deform and hold the ceramic member in a d31 mode, the hold signal is at a voltage suitable to deform and hold the ceramic member in a d31 mode for a selected duration; - to deform and hold the ceramic member in a d33 mode, the hold signal is at a voltage suitable to deform and hold the ceramic member in a d33 mode for a selected duration; - to hold the ceramic member in an undeformed position, the first, second, third and fourth holding signals are all at the same voltage and remain so for a selected period of time, the method comprising: selecting a desired location for the ceramic member; and supplying appropriate drive signals to their respective electrodes so as to hold the ceramic member in the desired position.

23. 20. The method of any of claims 14 to 19, wherein the method comprises controlling a switching circuit to connect and disconnect a first drive signal and / or a second drive signal of the at least two drive signals from the respective group electrical contacts to implement the selected deformation mode or a selected sequence of the d31 and / or d33 deformation modes.

24. 24. The method of claim 23, wherein the first drive signal provides the first voltage and the second drive signal provides the second voltage.

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