GB2622862A

GB2622862A - An actuator component for a droplet ejection head and method of manufacture, a droplet ejection apparatus and method for operating the same

Info

Publication number: GB2622862A
Application number: GB2214375.4A
Authority: GB
Inventors: Brunahl Jurgen; Trip Renzo; Boltryk Peter; Nicholas Jackson Marc
Original assignee: Xaar Technology Ltd
Current assignee: Xaar Technology Ltd
Priority date: 2022-09-30
Filing date: 2022-09-30
Publication date: 2024-04-03
Also published as: GB202214375D0

Abstract

An actuator component 100 comprises an actuator assembly 80 and a nozzle plate 70. The actuator assembly comprises a plurality of liquid chambers 131 arranged to be fluidically connectable to a liquid supply 140. The actuator component further comprising a plurality of thermal control fluid channels 231 arranged to be fluidically connectable to a thermal control fluid supply 240. The liquid chambers and the thermal control fluid channels are fluidically independent from each other. The nozzle plate comprises a plurality of droplet ejection nozzles 121. The thermal control fluid channels and the liquid chambers are arranged in a repeating pattern. The actuator component is configured such that in use thermal control fluid flowing through the thermal control fluid channels controls the thermal properties of the liquid flowing through the liquid chambers to thereby control the thermal properties of the liquid ejected from the droplet ejection nozzles. The actuator assembly may comprise two or more liquid manifolds (101, 102, Fig.6E) arranged below the liquid chambers in a liquid chamber height direction; and arranged such that in use liquid flows from the first liquid manifold along the plurality of liquid chambers and into the second manifold.

Description

AN ACTUATOR COMPONENT FOR A DROPLET EJECTION HEAD AND METHOD OF MANUFACTURE, A DROPLET EJECTION APPARATUS AND METHOD FOR OPERATING THE SAME The present disclosure relates to an actuator component for a droplet ejection head. The actuator component may be particularly suitable for use in a dropleL ejection head that is a drop-on-demand inkjet printhead, or, more generally, for use in a droplet ejection apparatus and, specifically, a droplet ejection apparatus comprising one or more actuator components. The actuator component provides an array of liquid chambers, which each have an actuator, which may be a piezoelectric actuator element, and a nozzle. The piezoelectric element may, for example, comprise lead zirconate titanate (PZT), but any suitable material may be used. The actuator is operable to cause the release, in an ejection direction, of liquid droplets through the nozzle in response to electrical signals. The actuator component further provides an array of thermal control fluid channels, the actuator component being operable to enable a flow of thermal control fluid through said thermal control fluid channels so as to control the thermal properties of the liquid and hence the liquid droplets.

BACKGROUND

Droplet ejection heads are now in widespread usage, whether in more traditional applications, such as inkjet printing, or in 3D printing, or other rapid prototyping techniques. Accordingly, the liquids, e.g, inks, may have novel chemical properties to adhere to new substrates and increase the functionality of the deposited material. Droplet ejection heads have been developed that are capable of use in industrial applications, for example for printing directly onto substrates, such as ceramic tiles or textiles, or to form elements, such as colour filters, in LCD or OLED displays for flat-screen televisions. Such industrial printing techniques using droplet ejection heads allow for short production runs, customization of products and even printing of bespoke designs. It will therefore be appreciated that droplet ejection heads continue to evolve and specialise so as to be suitable for new and/or increasingly challenging applications. However, while a great many developments have been made in the field of droplet ejection heads, there remains room for improvements, In recent years, there has been increasing interest in printing higher viscosity liquids and other fluids whose properties require control to ensure that they are ejected at a suitable viscosity, or to maintain the liquid temperature in a desired range. For example, highly viscous inks may require heating above ambient temperatures to a sufficiently high temperature that their viscosity is reduced enough to enable droplets to be ejected from a nozzle. Other fluids may need to be kept within a certain temperature range and require heating/cooling dependent on ambient conditions or due to more or less heat being generated in a droplet ejection head due, for example, to the print duty.

SUMMARY

Traditional markets such as ceramics and new applications, such as direct-to-shape (DTS), demand increasing control of the thermal characteristics of the liquid being ejected, so as to control the droplets' properties. Such control may comprise controlling the temperature, such that the droplets' behaviour or performance is controlled, for example viscosity, or setting characteristics. For example the aim may be to control the liquid's behaviour in flight or when it is drying on a substrate by controlling the temperature at which it is ejected.

The present invention proposes an actuator component, an apparatus comprising the actuator component and a method to operate the apparatus to control the thermal characteristics of the liquid and hence of the droplets. Such control may comprise cooling or heating the liquid, depending on the operating conditions and desired liquid properties. The invention further proposes a method of manufacture of the actuator component.

Aspects of the invention are set out in the appended independent claims, while details of particular embodiments of the invention are set out in the appended dependent claims.

According to a first aspect of the invention there is provided an actuator component for a droplet ejection head comprising: an actuator assembly and a nozzle plate; wherein the actuator assembly comprises a plurality of liquid chambers arranged in a liquid chamber array extending in an array direction; and a plurality of thermal control fluid channels arranged in a thermal control fluid channel array extending in the array direction; wherein the plurality of liquid chambers and the plurality of thermal control fluid channels are fluidically independent; wherein the plurality of liquid chambers are arranged to be fluidically connectable to a liquid supply; wherein the plurality of thermal control fluid channels are arranged to be fluidically connectable to a thermal control fluid supply; wherein the nozzle plate comprises a plurality of droplet ejection nozzles arranged in a nozzle array extending in the array direction; wherein each liquid chamber is arranged to be fluidically connected to one or more of the droplet ejection nozzles and actuable for ejection of droplets of a liquid; wherein the plurality of thermal control fluid channels and the plurality of liquid chambers are arranged in a repeating pattern extending in the array direction; and wherein the actuator component is configured such that in use thermal control fluid flowing through the thermal control fluid channels controls the thermal properties of the liquid flowing through the liquid chambers to thereby control the thermal properties of the liquid ejected from the droplet ejection nozzles.

According to a second aspect of the invention there is provided a droplet ejection head comprising one or more actuator components according to die first aspect.

According to a third aspect of the invention there is provided a droplet ejection apparatus comprising one or more actuator components according to the first aspect or one or more droplet ejection heads according to the second aspect; and further comprising a liquid supply and a liquid path and a thermal control fluid path.

According to a fourth aspect of the invention there is provided a method of operating a droplet ejection apparatus according to the third aspect comprising: ejecting droplets of liquid from one or more of the droplet ejection nozzles in accordance with printing instructions; and flowing thermal control fluid through the thermal control fluid channels so as to control by thermal transfer the thermal properties of the liquid flowing through the liquid chambers and thereby to control the thermal properties of the liquid ejected from the droplet ejection nozzles.

According to a fifth aspect of the invention there is provided a method of manufacturing an actuator component according to the first aspect, wherein the method comprises the steps of -forming an actuator assembly, comprising: -forming one or more arrays of liquid chambers in one or more strips of piezoelectric material extending in an array direction, wherein each of the liquid chambers forms an open channel in the strip of piezoelectric material being open in a liquid chamber height direction and open at a first end and a second end in a liquid chamber extension direction; -forming one or more arrays of thermal control fluid channels in the one or more strips of piezoelectric material extending in the array direction, wherein each of the thermal control fluid channels forms an open channel in the strip of piezoelectric material being open in the liquid chamber height direction and open at a first end and a second end in the liquid chamber extension direction; wherein the liquid chamber array and the thermal control fluid channel array are fluidically independent from each other; arid -fixedly attaching a nozzle plate to the actuator assembly; -forming droplet ejection nozzles in the nozzle plate either before or after the step of fixedly attaching the nozzle plate to the actuator assembly such that when assembled the actuator component comprises droplet ejection nozzles fluidically connected to the liquid chambers.

According to a fifth aspect of the invention there is provided an actuator component for a droplet ejection head comprising: an actuator assembly and a nozzle plate; wherein the actuator assembly comprises a plurality of liquid chambers arranged in al quid chamber array extending in an array direction; wherein the plurality of liquid chambers are arranged to be fluidically connectable to a liquid supply; wherein the nozzle plate comprises a plurality of droplet ejection nozzles arranged in a nozzle array extending in the array direction; wherein each liquid chamber is arranged to be fluidically connected to one or more of die droplet ejection nozzles and actuable for ejection of droplets of a liquid; wherein the actuator assembly further comprises two or more liquid manifolds arranged below the liquid chambers in a liquid chamber height direction; wherein a first of the liquid manifolds is fluidically connected to one end of a plurality of liquid chambers in a liquid chamber extension direction; wherein a second one of said two or more liquid manifolds is fluidically connected to a second opposite end of the plurality of liquid chambers in the liquid chamber extension direction; and arranged such that in use liquid flows from the first liquid manifold along the plurality of liquid chambers from the first end to the second end and into the second manifold.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention and their variants will now be described with reference to the Figures.

Fig. IA depicts a schematic representation of an actuator component for a droplet ejection head according to an embodiment, with one side removed so as to show some of the fluid paths (liquid and thermal control fluid) therein; Fig. 1B depicts a schematic representation of a droplet ejection apparatus comprising an actuator component for a droplet ejection head according to die embodiment of Fig. 1A, with a further portion removed, the droplet ejection apparatus further comprising liquid and thermal control fluid supply paths and liquid and thermal control fluid supplies; Fig. 2A depicts a schematic representation of a droplet ejection apparatus comprising a part of an actuator component for a droplet ejection head according to another embodiment, with one side removed so as to show details of the fluid paths (liquid and thermal control fluid) therein, and liquid and thermal control fluid supply paths and liquid and thermal control fluid supplies; Fig. 2B depicts part of the schematic representation of Fig. 2A, with further portions removed, indicated by lines AA and BB in Fig. 2A, so as to provide further detail on the fluid paths therein; Fig. 2C depicts part of the schematic representation of Fig. 2B, with a further portion removed, indicated by line CC in Fig. 2A and Fig. 2B, so as to provide further detail on the fluid paths therein; Fig. 3 depicts a schematic representation of a section of an actuator component according to another embodiment, similar to that of Fig. 2C, comprising two thermal control fluid manifolds; Fig. 4 depicts a schematic representation of a section of an actuator component, similar to that of Fig. 3, comprising two liquid manifolds located below the liquid chambers in the liquid chamber height direction; Fig. 5 is a schematic drawing of a droplet ejection apparatus comprising an actuator component according to an embodiment and a movement device; Fig. 6A depicts a first step in a manufacturing process for an actuator component according to an embodiment, comprising forming a cut-out in one or more strips of piezoelectric material and fixedly attaching the strip(s) of piezoelectric material to a substrate so as to form a thermal control fluid manifold; Fig. 6B depicts a second step in a manufacturing process for an actuator component according to an embodiment, comprising forming one or more arrays of thermal control fluid channels in the one or more strips of piezoelectric material so as to create a plurality of open-ended thermal control fluid channels in said one or more strips of piezoelectric material, wherein the thermal control fluid channels are aligned in an array direction along the one or more strips of piezoelectric material; Fig. 6C depicts a third step in a manufacturing process for an actuator component according to an embodiment, comprising forming one or more cover parts that are conformal to at least some of said one or more strips of piezoelectric material and at least some of said substrate, and fixedly attaching them to said one or more strips of piezoelectric material and at least some of said substrate; Fig. 6D depicts a fourth step in a manufacturing process for an actuator component according to an embodiment, comprising forming the liquid chambers such that they are continuous through the cover part and the strips of piezoelectric material and form an open channel in the strip of piezoelectric material and in the cover part; Fig. GE depicts a fifth step in a manufacturing process for an actuator component according to an embodiment comprising attaching a nozzle plate to the actuator assembly to form the actuator component.

It should be noted that the drawings are not to scale and that certain features may be shown with exaggerated sizes so that these are more clearly visible.

DETAILED DESCRIPTION OF TFIE DRAWINGS

Embodiments and their various implementations will now be described with reference to the drawings. Throughout the following description, like reference numerals are used for like elements where appropriate.

Fig. IA and 1B depict a schematic representation of an actuator component 100 for a droplet ejection head according to an embodiment. In Fig. 1A, one side of the actuator component 100 has been removed so as to show some of the fluid paths (liquid and thermal control fluid) therein. Fig. 1B further depicts a droplet ejection apparatus 1 comprising the actuator component 100 of Fig. IA. The actuator component 100 of Fig. I B is shown schematically, with the top removed, as indicated by dotted lines XX in Fig. 1A, to allow more of the internal fluid paths to be seen. The droplet ejection apparatus 1 further comprises liquid and thermal control fluid supply paths 143,243 and liquid and thermal control fluid supplies 140,240.

The actuator component 100 comprises a nozzle plate 70 and an actuator assembly 80. The nozzle plate 70 has a thickness T. It can be seen from Fig. IA that the nozzle plate 70 comprises a plurality of droplet ejection nozzles 121 (hereinafter referred to as nozzles), through which liquid may be ejected in an ejection direction 16, arranged in a nozzle array 120. The nozzles 121 extend in a straight line in an array direction 10.

The actuator assembly 80 comprises a plurality of liquid chambers 131 arranged in a liquid chamber array 130, where respective liquid chambers 131 are fluidically connected to one or more nozzles 121. The actuator assembly 80 further comprises a plurality of thermal control fluid channels 231 arranged in a thermal control fluid channel array 230. The actuator assembly 80 may comprise one or more parts made from piezoelectric material. For example, one or more of the walls of the respective liquid chambers 131 may comprise piezoelectric material that is actuable, so as to eject liquid through a respective nozzle 121 in response to print instructions. It may be understood that this is by no means limiting and other devices or methods may be used to cause ejection of liquid through a respective nozzle 121.

The actuator component 100 of Fig. IA is a so-called end shooter actuator component where the nozzle plate 70 and the nozzles 121 are located at one end of the liquid chambers 131 in the liquid chamber extension direction 5. It can be seen that the nozzle plate 70 is located so as to fluidically seal the liquid chambers 131 and the thermal control fluid channels 231, in the liquid chamber extension direction 5. it can further be seen that, in this arrangement, the droplet ejection direction 16 is aligned with the liquid chamber extension direction 5 and the negative y-direction. It may be understood that, in general, in operation, the media facing surface 118 will be appropriately aligned with the media such that droplets ejected in the ejection direction 16 land in the desired location on the media.

The nozzles 121 are separated by a nozzle spacing ns in the array direction 10, which may be conveniently measured from the centre of a nozzle 121 to the centre of the adjacent nozzle. In the actuator component 100 the nozzles 121 have a circular exit, though it may be understood that this is not limiting. For clarity, it may be understood that the exits of the nozzles 121 are located in the media-facing surface 118 of the nozzle plate 70.

In the embodiment of Fig. 1A, the nozzle array 120 comprises three nozzles, 121 i-121-iii.It may be understood that this is by no means limiting and, in other arrangements, the nozzle array 120 may comprise one or more nozzles. The nozzle array 120 may comprise 12 l_i-121_n nozzles where n is any whole number.

For simplicity, the actuator assembly 80 is shown as a monolithic part, but the skilled person would understand that it may comprise several parts, joined together in any suitable manner. Alternatively, it may be understood that, for example, additive manufacturing techniques such as 3D printing may be used to manufacture some or all of the actuator assembly 80 or some or all of the actuator component 100 as a single piece. It can be seen that the actuator assembly 80 has a liquid manifold 101, which is fluidically connected to the liquid chambers 131 as shown in Fig. 1B and a thermal control fluid manifold 201, fluidically connected to the array of thermal control fluid channels 230 and hence to each respective thermal control fluid channel 231 (as seen from the cross-section through the first thermal control fluid channel 231_0, In this embodiment, the thermal control fluid manifold 201 is located below the liquid chambers 131 in the z-direction, the z-dircction being anti-parallel to the liquid chamber (and thermal control fluid channel) height direction 15. The thermal control fluid manifold 201 is also located at the base of the thermal control fluid channels 231, in the liquid chamber height direction 15, so that it intersects with and is fluidically connected to them, It may be generally understood that the above-described spatial arrangement is by no means essential and other arrangements of thermal control fluid manifold 201, relative to the liquid chambers 131 and the thermal control fluid channels 231, may be envisioned. Further, any suitable spatial arrangement of the thermal control fluid manifold 201, relative to the liquid manifold 101, may be utilised. It may be understood that such suitable spatial arrangements may be utilised providing that the thermal control fluid manifold 201 is fluidically connected to the thermal control fluid channel array 230, the liquid manifold 101 is fluidically connected to the liquid chamber array 130 and that the thermal control fluid path 243 and the liquid path 143 are kept fluidically separated from each other, such that there is no transfer of fluid from one path to the other.

The liquid chambers 131 and the thermal control fluid channels 231 may comprise one or more layers deposited on some or all of their internal surfaces, such as a metallic layer or layers to enable actuation of the piezoelectric material, for example, actuation of piezoelectric material in the shared walls 132. The liquid chambers I 3 1 and the thermal control fluid channels 231 may further comprise one or more protective coating layers to prevent the thermal control fluids from causing damage (e.g. corrosion) to the metallic layer(s) and/or to passivatc the electronics. Therefore the actuator component 100 comprises electrical traces and connections.

Turning now to Fig. 113, the nozzles 121 and nozzle array 120 are as described above with respect to Fig. IA. For simplicity, in Fig. 1B the actuator component 100 has been depicted as a single part, with the locations of the nozzle plate 70 and the actuator assembly 80 indicated, but it may be understood that the actuator component 100 in Fig. 1B comprises two separate parts as in Fig. 1A. The actuator component 100 comprises an array 130 of liquid chambers extending in the array direction 10. The army 130 of liquid chambers comprises a plurality of liquid chambers 131. The liquid chambers ( I 3 1 i-I31 iii) extend side-by-side in the array direction 10, said array direction 10 being generally perpendicular to a liquid chamber height HI in the negative z-direction. Each liquid chamber 131 is elongate in a liquid chamber extension direction 5 which is at an angle to the array direction 10. The liquid chambers 131 are also elongate in a direction non-parallel to the liquid chamber height H, and each liquid chamber 131 opens into the liquid manifold 10 I, at a first end, in the liquid chamber extension direction 5.

In this embodiment, the liquid chamber extension direction 5 is perpendicular to the array direction 10, but this is by no means essential and, in other arrangements, the liquid chamber extension direction 5 may be at a different angle, for instance so as to enable longer liquid chambers 131 within a given droplet ejection head footprint. Thus, more generally, the liquid chamber extension direction 5 may be at an angle other than 90° to the array direction 10.

The actuator component thrther comprises an army 230 of thermal control fluid channels 231 extending in the array direction 10. The plurality of thermal control fluid channels 231 i-231 extend side-by-side in the array direction 10. Each thermal control fluid channel 231 is elongate in the liquid chamber extension direction 5, which is at an angle to the array direction 10. The liquid chambers 131 and the thermal control fluid channels 231 extend side-by-side in the array direction such that they are arranged parallel to each other; but this is by no means essential and other arrangements may be envisaged. In this implementation, the array direction 10 is perpendicular to the liquid chamber extension direction 5, but it should be understood that this is by no means essential and, in other implementations, the liquid chambers 131 may be arranged at an angle other than 900 to the array direction, e.g. they may be elongate in a direction non-parallel to the array direction 10, as may the thermal control fluid channels 231. Further, it can be seen from Fig. IA and Fig. 1B that the liquid chambers 131 and the thermal control fluid channels 231 are arranged in a repeating pattern, in this case an alternating relationship extending in the array direction 10. Further, it can be seen that the liquid chambers 131 and the thermal control fluid channels 231 are regularly spaced such that the width W132 of the shared wall 132 separating a respective liquid chamber from a respective adjacent thermal control fluid channel is constant.

The liquid chambers 131 have a width Wlin the array direction 10 and a height HI in a liquid chamber height direction 15 (the negative z-direction). Similarly, the thermal control fluid channels 231 have a width Wtc in the array direction 10 and a height Htc in the liquid chamber height direction 15.

Each thermal control fluid channel 231 opens into the thermal control fluid manifold 201 at its base, in the liquid chamber height direction 15. So that the thennal control fluid channels 231 can fluidically connect to the thermal control fluid manifold 201 without the liquid chambers 131 impinging onto the thermal control fluid manifold 201, the height Htc is greater than the height HI (1-Itc>H1) e.g. in order to achieve fluidic independence the thermal control fluid channels 231 may have a have a greater height than the liquid chambers 131 in the liquid chamber height direction 15.

Further, because in this arrangement the thermal control fluid manifold 201 intersects the thermal control fluid channels 231 (see cross-section of 231_i for example) the thermal control fluid height Htc minus the thermal control fluid manifold height 1-im is greater than the liquid chamber height H1 (Htc-Hm>H1). Still further, in this arrangement, in order to prevent the thermal control fluid channels 231 impinging on the liquid manifold 101, the thermal control fluid channels 23! are shorter in the liquid chamber extension direction 5 than the liquid chambers 131 (Ltc<11).

The droplet ejection apparatus I of Fig. 1B may comprise one or more actuator components as described herein. More generally the droplet ejection apparatus 1 may comprise one or more droplet ejection heads comprising one or more actuator components as described herein. The droplet ejection apparatus I may further comprise a liquid supply 140, a liquid path 143, a thermal control fluid path 243 and a thermal control fluid supply 240. The liquid supply 140 is fluidically connectable to the nozzles 121 via the liquid path 143 and the thermal control fluid supply 240 is fluidically connectable to the thennal control fluid channels 231 via the thennal control fluid path 243.

It can be seen in Fig. 1B that, the liquid path 143 comprises an inlet liquid path 141 fluidically connecting the liquid supply 140 to a liquid inlet 144 in the actuator component 100. The liquid supply 140 may be fluidically connected to a liquid reservoir 146 (not shown), or it may comprise an integral reservoir. In the actuator component 100 the liquid path 143 comprises a liquid manifold 101 that is fluidically connected to the plurality of liquid chambers 131, arranged in a liquid chamber array 130, with each liquid chamber 131 being fluidically connected to a nozzle 121. The actuator component 100 of Fig. IA and Fig. 1B is a so-called end shooter actuator where the nozzles 121 are located at one end of the liquid chambers 131 in the liquid chamber extension direction 5. in the embodiment of Fig. IA and Fig. 1B the ejection direction 16 is in the negative-y-direction, further, it is aligned with the longitudinal liquid chamber extension direction 5 and perpendicular to the array direction 10. The liquid chambers 131 each comprise at least one actuator, which may be a piezoelectric actuator element, and at least one nozzle 121. The respective actuators for each liquid chamber 131 are operable to cause the release, in the ejection direction 16, of one or more liquid droplets, through the respective nozzle 121, in response to electrical signals (as indicated by droplet Dp 121 iii, ejected from nozzle 12 liii, in Fig. I B).

The thermal control fluid path 243 comprises a thermal control fluid path 241, which is fluidically connectable between the thermal control fluid supply 240 and the actuator component 100. In the actuator component 100, the thermal control fluid path 243 comprises a thermal control fluid manifold 201 that is fluidically connected to the plurality of thermal control fluid channels 231. In other words, the thermal control fluid channels 23! are fluidically connectable via the thermal control fluid manifold 201 to the thermal control fluid supply 240. As previously mentioned, the thermal control fluid supply 240 may be operable to cause a flow of thermal control fluid through the thermal control fluid channels 231.

There may be one or more thermal control fluid ports 244 (not shown) to connect the thermal control fluid path 243 to the actuator component 100 (or to a droplet ejection head comprising one or more actuator components 100) and enable supply of thermal control fluid to the thermal control fluid manifold 201, from the thermal control fluid path 241, Further, it can be seen that the thermal control fluid path 243 comprises a thermal control fluid path 242 to carry thermal control fluid away from the actuator component 100, similarly there may be a thermal control fluid port 245 (not shown) to connect the actuator component 100, or a droplet ejection head comprising one or more actuator components 100, to the thermal control fluid path 242. The thermal control fluid path 242 may connect to a thermal control fluid exhaust 246a or reservoir 246b. Alternatively, it may act as a return thermal control fluid path 242 that returns the thermal control fluid to the thermal control fluid supply 240. The thermal control fluid supply 240 may supply thermal control fluid at a suitable temperature, or it may be necessary to control the temperature of the thermal control fluid further using an optional thermal control device 247. The apparatus 1 may comprise one or more thermal control devices 247, which may be, for example, a heat exchanger, to heat or cool the thermal control fluid to the desired temperature. Alternatively, the thermal control device 247 may comprise a heater, which is utilised when the thermal control fluid is too cool, ancUor it may comprise a cooling device that is utilised when the thermal control fluid is too warm. By too cool and too warm it may be understood that the themml control fluid is respectively below or above the desired thermal control fluid temperature. Ttc(des red) More generally, the actuator components and apparatus described herein may be used, for example, to heat the liquid in high-viscosity liquid ejection applications where the liquid in the liquid chambers is a high-viscosity liquid, for example a high-viscosity ink, and requires heating above a threshold temperature to have flow properties suitable for printing. In some applications, the thermal control fluid in the thermal control fluid channels may be used to heat the ink, to keep it above a particular temperature threshold (such as a setting or solidification temperature). Alternatively, in some applications, the liquid in the liquid chambers may require cooling, for example if high levels of heat are being generated in the actuator component due to a high print duty, such that the liquid becomes too hot. This may be undesirable if the liquid is heated to a temperature where it's viscosity becomes too low, and, for example, it therefore doesn't have desired print qualities, or where the temperature reaches a point where volatile components in the liquid start to evaporate, or the liquid starts to degrade due to the temperatures reached. The thermal control fluid may be used to heat or cool the liquid, as required, by ensuring that there is an appropriate temperature difference between the liquid and the themml control fluid such that thermal energy transfers from one to other in the correct direction through the material structure of the actuator component 100, whilst keeping the fluid paths 143,243 separate.

It may be understood that, where the liquid chambers 131 and the thermal control fluid channels 231 extend side-by-side in the army direction 10, such that they are arranged parallel to each other, transfer of thermal energy between them may be readily achieved. The greater the overlap in cross-sectional area on a shared wall 132 between a respective liquid chamber 131 and a respective adjacent thermal control fluid channel 231 (see 132 ia and 132 ib to either side of liquid chamber 131_i in Fig. 1B), the greater the area through which thermal energy may transfer. Further improvements may be achieved by minimising the thickness of the actuator component structure between a respective liquid chamber 131 and the adjacent thermal control fluid channel 231, for example by reducing the width. W132, of the shared wall 132 between them. However, it may be understood that, where the actuator component design uses actuation of the shared walls 132 to cause the ejection of droplets from a respective liquid chamber 13 I, the minimum width W 132(min) of the shared wall 132 may be limited by the actuation requirements.

The droplet ejection apparatus 1 may further comprise one or more temperature sensors (not shown). The temperature sensors may be provided in the thermal control fluid path 243 and/or in the liquid path 143. They may be provided adjacent to the thermal control fluid supply 240 and/or adjacent to the liquid supply 140. They may be provided on the inlet thermal control fluid path 241 and the thermal control fluid return path 242. Additionally or instead, they may be provided on the liquid supply path 141. For example the thermal control fluid path 243 may comprise temperature sensors at the inlet and/or outlet to the actuator component 100 and/or at the inlet and/or outlet to the droplet ejection head. Likewise the liquid path 143 may comprise a temperature sensor on the liquid path 143 and/or at the inlet to the actuator component 100 and/or the inlet to the droplet ejection head.

Where the thermal control fluid path 243 comprises a thermal control device 247 and/or a reservoir 246b, there may be one or more temperature sensors adjacent to the thermal control device 247 and/or the reservoir 246b.

The temperature measurements may be provided to a controller (not shown). The controller may control the droplet ejection apparatus 1 so as to adjust the temperature of the liquid. For example, the controller may control the thermal control fluid supply 240 to alter the flow rate of the thermal control fluid. Further the controller may control a thermal control device 247 to heat or cool the thermal control fluid. The controller may, for example, use a look-up table or a calibration routine to determine the required temperature and/or flow rate of the thermal control fluid to give a desired liquid temperature.

The liquid path 143 and the thermal control fluid path 243 are fluidically separated from each other, ensuring that there is no mixing of the two fluids at any stage between the liquid supply 140 and the exits of the nozzles 121 or at any stage between the thermal control fluid supply 240 and thermal control fluid channels and the return thermal control fluid path 242. In other words the liquid path 143 and the thermal control fluid path 243 are both fluid tight and separate (or fluidically independent) from each other. As part of this as described in greater detail above, the heights H1 of the liquid chambers 131 and heights Htc of the thermal control fluid channels 231 are different, as are their respective lengths LI and Ltc. An additional advantage of keeping the two paths fluidically independent is that, for droplet ejection heads where the liquid is an aqueous (i.e, water-based) liquid, and the individual actuators are piezoelectric actuators comprised in the liquid chambers' shared (side) walls 132, each actuable through an electric field applied to drive electrodes provided on the walls, some or all of the drive electrodes/or and electrical traces for driving individual actuators may be located on the walls in the thermal control fluid channels 231. In this way, they are physically isolated from contact with the liquid, such as ink, in the liquid chambers 131, preventing electrical shorts. It may be understood that in such a design, the thermal control fluid in the thermal control fluid path 243 needs to be suitable for contact with the drive electrodes and/or the drive electrodes need coating with some form of passivation. For example, the thermal control fluid may be a non-aqueous liquid, or it may comprise additives with anti-corrosion properties. Alternatively, in such a desibm, the thermal control fluid may be a gas.

hi operation, the apparatus 1 may comprise liquid flowing from the liquid supply 140, via the liquid path 143 to the exits of the nozzles 121. Then, in accordance with printing instructions, the droplet ejection apparatus 1 may eject droplets of liquid from one or more of the nozzles 121 (in the ejection direction 16). At the same time, the droplet ejection apparatus 1 may cause thermal control fluid to flow through the thermal control fluid channels 231 so as to control by thermal transfer the thermal properties of the liquid flowing through the liquid chambers 131 and thereby to control the thermal properties of the liquid droplets ejected from the nozzles 121 and hence, for example, properties such as the viscosity, In somc applications, the thermal control fluid in thc thermal control fluid channels 231 may be a liquid, such as water or de-ionised water. The thermal control fluid may comprise additives, such as those with anti-corrosion or thermal control properties. in other applications, the thermal control fluid may be a gas.

The apparatus 1 may be arranged such that thermal control fluid flows from the thermal control fluid supply 240, via the thermal control fluid path 243 and through the thermal control fluid channels 231 so as to control the liquid temperature in the liquid chambers 131. The apparatus 1 is thither arranged such that the thermal control fluid supply 240 causes thermal control fluid to flow through the thermal control fluid channels 231 and to return to the thermal control fluid manifold 201 and thereafter to exit the actuator component 100. The thermal control fluid may return to the thermal control fluid supply 240 in a closed loop fluid path 243. Or it may be removed from the actuator component 100 and piped to thermal control fluid exhaust 246a, such as a drain or waste water pipework. For example, if the thennal control fluid is water, it may be piped to a drain connected to the public waste water systems. Alternatively the fluid path 243 may comprise a thermal control fluid reservoir 246b.

Turning now to Fig. 2A, this depicts a schematic representation of a droplet ejection apparatus 2 comprising an actuator component 200 for a droplet ejection head according to another embodiment. It can be seen that this actuator component 200 is a side shooter actuator component, where the ejection direction 16 is in the liquid chamber height direction 15, as compared to the end shooter actuator component of Fig, lA and Fig. 1B. As in the apparatus 1 of Fig. 1B, the apparatus 2 also comprises liquid mid thermal control fluid paths 143,243 and liquid and thermal control fluid supplies 140,240, respectively. The liquid supply 140 may be fluidically connected to a liquid reservoir 146 and the thennal control fluid supply may be fluidically connected to a thermal control fluid reservoir 246. One side of the actuator component 200 has been removed so as to show some details of the fluid paths. As in Fig. 1B, the actuator component 200 is shown as single part, with the locations of the nozzle plate 70 and the actuator assembly 80 indicated, but it may be understood that the actuator component 200 may comprise two separate parts as in Fig. 1A, or more separate parts, as described above.

As can be seen, the nozzles 121 i-iii are arranged part-way along their respective liquid chambers 13 1_i-iii in the liquid chamber extension direction 5, rather than at one end in the liquid chamber extension direction 5, as in the embodiment of Fig. IA and Fig. 1B. Accordingly, the nozzle plate 70 of Fig. 2A-fig. 2C is located on the top of the actuator component 200 (in the negative z-direction), ratherthan on one end as in Fig. IA and Fig. 1B. This is generally known as a side shooter actuator arrangement. It can further be seen that the nozzle plate 70 is located so as to fluidically seal the liquid chambers 131 and the thermal control fluid channels 231, in the liquid chamber height direction 15. In the embodiment of Fig. 2A-Fig. 2C, the ejection direction 16 is in the negative-zdirection, perpendicular to the longitudinal liquid chamber extension direction 5 and to the array direction 10. As previously described, in general, in operation, the media facing surface 118 will be appropriately aligned with the media such that droplets ejected in the ejection direction 16 land in the desired location on the media.

Further, the actuator component 200 has what is generally known as a recirculation or through-flow desibm, whereby, in operation, it is fluidically connected with a liquid path 143 such that liquid flows from the liquid supply 140 via the liquid path 143 to the actuator component 200 and then returns, via the liquid path 143, to the liquid supply 140 (as indicated by shaded arrows 148).

Parts of the liquid path 143 can be seen more clearly in Fig. 2B and Fig. 2C, which comprise details of the actuator component 200 of Fig. 2A where parts have been removed, as indicated by dash-dot lines AA. BB and CC. In operation, liquid travels from the liquid supply 140 via the liquid path 143, comprising the inlet liquid path 141, to the liquid inlet 144, from where it is supplied to the liquid manifold 101. It may be understood that the liquid path 143 may comprise further fluidic components within a droplet ejection head, as well as fluidic connections external to the droplet ejection head and further fluidic components to carry the liquid back to the liquid supply 140. From the liquid manifold 101, liquid is supplied to a first end of the plurality of liquid chambers 131, in the liquid chamber extension direction 5 (as shown by the arrows 148 in Fig. 2C), i.e. the liquid chambers 131 are fluidically connectable via the liquid manifold 101 to the liquid supply 140. The respective actuators for each liquid chamber 131 are operable to cause the release, in an ejection direction 16, of one or more liquid droplets, through a respective nozzle 121, in response to electrical signals. For example, a print command may cause an electrical signal to be sent to an actuator in chosen liquid chamber 13 l_ii, causing the actuator to actuate and eject liquid via the respective nozzle 12 1_h and form a droplet (as indicated by droplet Dp121 ii in Fig. 2C).

It may be understood that depending on the print instructions, at any given time there may be no nozzles 121 ejecting liquid, or one or more nozzles 121 may be caused to eject liquid, so as to form the required image on the medium. The remaining un-ejected liquid continues through the respective liquid chambers 131 in the liquid chamber extension direction 5 and exits the respective liquid chambers 131 at the second, opposite, end to which it entered, and hence enters into the liquid manifold 102. The liquid exits the liquid manifold 102 via one or more liquid outlets 145 (not shown, see Fig. 6E). The liquid outlets 145 may also be the point at which the liquid exits the actuator component 200 and returns to the liquid supply 140 via the return liquid path 142. Alternatively, the return liquid path 142 may comprise further fluidic components within the actuator component 200, and/or within a droplet ejection head, as well as fluidic connections external to the droplet ejection head and further fluidic components to carry the liquid back to the liquid supply 140.

It may be generally understood that in some arrangements, whereby the actuator component 200 is for use in a recirculation droplet ejection head, there may be one or more arrays of liquid chambers 131 and one or more liquid manifolds 101,102 whereby at least one of said one or more liquid manifolds is an inlet liquid manifold 101 and at least one of said one or more liquid manifolds is an outlet liquid manifold 102. Therefore, in operation, liquid flows from the liquid supply 141, through the inlet liquid manifold 101, through the liquid chamber array 130 and returns to the liquid supply 140, via the outlet liquid manifold 102.

In other words, the liquid chambers 131 are open at opposing ends in the liquid chamber extension direction 5 and fluidically connected, at a first end, to liquid manifold 101 and, at the second end, to liquid manifold 102. When operating in recirculation mode, liquid flows from inlet liquid manifold 101, via the respective first end of each liquid chamber 131, through the plurality of liquid chambers 131 and into the outlet liquid manifold 102, via the respective second end of each liquid chamber 131.1n accordance with print instructions, droplets may be ejected from one or more of the respective nozzles 121 in the array of nozzles 120 wherein said nozzles 121 are located part-way along the respective liquid chambers 131 in the liquid chamber extension direction 5. It may be understood that there may be times when none, some or all of the nozzles are ejection liquid droplets, depending on the print instructions.

Considering now the thermal control fluid path 243, as shown in Fig. 2A, this comprises a thermal control fluid path 241 that connects the thermal control fluid supply 240 to the actuator component 200. As seen in more detail in Fig. 2C, thennal control fluid path 243 of the droplet ejection apparatus 2 comprises a thermal control fluid path 241 and a thermal control fluid path 242, fluidically connected one to each end of the thermal control fluid manifold 201, such that the thermal control fluid path 243 is a recirculation flow path (as indicated by the arrows 248), such that the thermal control fluid path 241 is an inlet thermal control fluid path 241, and the thermal control fluid path 242 is a return thermal control fluid path 242. The thermal control fluid returns to the thermal control fluid supply 240, via the return thermal control fluid path 242. In use fluid flows from the thermal control fluid supply 240, via the inlet thermal control fluid path 241, which is fluidically connected to the thermal control fluid manifold 201. The thermal control fluid manifold 201 is fluidically connected to the plurality of thermal control fluid channels 231 such that thermal control fluid can enter and exit said thermal control fluid channels 231. The thermal control fluid manifold 201 is also fluidically connected to the return thermal control fluid path 242 so that, in use, fluid flows from the thermal control fluid manifold 201, via the return thermal control fluid path 242, to the thermal control fluid supply 240.

Various other features of the embodiment of Fig. 2A -Fig. 2C are as described above with respect to Fig. IA and Fig. 1B, for example, in order to prevent the thermal control fluid channels 231 impinging on the liquid manifolds 101,102, the thermal control fluid channels 231 are shorter, in the liquid chamber extension direction S, than the liquid chambers 131 (Ltc<L1). Similarly, the thermal control fluid channels 231 are deeper, such that their height Htc is greater than the height HI of the liquid chambers 131, and that, to prevent the liquid chambers impinging on the thermal control fluid manifold 201. Htc-1-lin>H1, where the thermal control fluid manifold 201 is located below the liquid chambers 131 in the z-clirection, or the negative liquid chamber (and thermal control fluid channel) height direction 15. The thermal control fluid manifold 201 is also located at the base of the thermal control fluid channels 231, in the liquid chamber height direction 15, so that it intersects with and is fluidically connected to them. However, other arrangements may be envisaged provided that the thermal control fluid manifold 201 is fluidically connected to the thermal control fluid channels 231 and is fluidically separated from (i.e. not fluidically connected to) the liquid chambers 131 or the liquid path 143. It can further be seen that, in this side shooter actuator arrangement, the thermal control fluid manifold 201 opposes the nozzle plate 70, i.e. it is located on the opposite side of the thermal control fluid channels 231, and liquid chambers 131, to the nozzle plate 70, in the liquid chamber height direction 15.

As described above, temperature sensors may be provided on the inlet thermal control fluid path 241 and the return thermal control fluid path 242. Additionally or instead, temperature sensors may be provided on the supply liquid path 141 and on the return liquid path 142. For example the thermal control fluid path 243 may comprise temperature sensors at the inlet and/or outlet to the actuator component 100 and/or at the inlet and/or outlet to the droplet ejection head. Likewise the liquid path 143 may comprise a temperature sensor at the liquid path 143 inlet and/or outlet to the actuator component 100 and/or the inlet and/or outlet to the droplet ejection head. Where the thermal control fluid path 243 comprises a thermal control device 247 and/or a reservoir 246b, there may be one or more temperature sensors adjacent to the thermal control device 247 and/or the reservoir 246b.

Considering Fig. 3, this is a schematic drawing of a section of an actuator component 300, similar to the section of Fig. 2C, according to another embodiment. The embodiment is similar to that of Fig. 2A-Fig. 2C but comprises two thermal control fluid manifolds 201,202, rather than one. The thermal control fluid manifolds 201,202 are located below the liquid chambers 131 in the z-direction, or the negative liquid chamber (and thermal control fluid channel) height direction 15. The thermal control fluid manifolds 201,202 are also located at the base of the thermal control fluid channels 231, in the liquid chamber height direction 15, so that they intersect with and are fluidically connected to them.

The actuator component 300, therefore, comprises two (or more) thermal control fluid manifolds (201,202) arranged such that a first of said thermal control fluid manifolds 201 is fluidically connected to a first end of a plurality of thermal control fluid channels 231 and such that a second one of said two or more thermal control fluid manifolds 202 is fluidically connected to a second opposite end of the plurality of thermal control fluid channels 231 such that in use thermal control fluid flows from said first thermal control fluid control manifold 201, along the plurality of thermal control fluid channels 231 from said first end to said second end and into said second thermal control fluid manifold 202.

The thermal control fluid channels 231 are fluidically connectable via the thermal control fluid manifold 201 to the thermal control fluid supply 240. It can be seen from Fig. 3 that there are a plurality of thermal control fluid ports 244 a-244 c to connect the thermal control fluid path 243 to the thermal control fluid manifold 201 of the actuator component 300. In operation, this enables supply of thermal control fluid from the thermal control fluid supply 240 to the thermal control fluid manifold 201 via the inlet thermal control fluid path 241, as indicated by the white arrows 248. The thermal control fluid channels 231 are fluidically connectable via the thermal control fluid manifold 202 to the return thermal control fluid path 242. The second thermal control fluid manifold 202 may comprise one or more thermal control fluid ports 245 (not shown in this view) to fluidically connect the thermal control fluid manifold 202 to the return thermal control fluid path 242.

Fig. 4 depicts a schematic representation of a section of an actuator component 400, similar to that of Fig. 3, comprising two liquid manifolds 101,102 located below the liquid chambers 131 in the liquid chamber height direction 15 and wherein said two or more liquid manifolds 101,102 are formed from two or more cut-outs 81 in the actuator assembly 80. Such an arrangement, with the liquid manifolds 101,102 below the liquid chambers 131 may be advantageous when a narrow droplet ejection head with a narrow actuator component is required. It will be understood that this design may be suitably combined with thermal control fluid paths 243 and channels 231 (not shown) similar to those described in connection with previously described embodiments. In this arrangement the actuator component 400 may comprise an actuator assembly 80 with a plurality of thermal control fluid channels 231 arranged in a thermal control fluid channel array 230 extending in an array direction 10 configured such that in use thermal control fluid flowing through said thermal control fluid channels 231 controls the thermal properties of the liquid flowing through the liquid chambers 131 to thereby control the thermal properties of the liquid ejected from the droplet ejection nozzles 121 Turning now to Fig. 5, this is a schematic drawing of a droplet ejection apparatus 7 comprising an actuator component 700 according to an embodiment, having an actuator assembly 80 and a nozzle plate 70, arranged in a droplet ejection head 702. The droplet ejection apparatus 7 also comprises a transport mechanism 105, for moving a deposition media 103, and a controller 104. The droplet ejection head 702 is mounted above the deposition media 103 such that there is a gap G between it and the deposition media 103. The deposition media 103 moves in a media movement direction 109.

The nozzle plate 70 has a media facing surface 118 in which the exits of the one or more nozzles 121 are located.

The actuator component 700 is arranged to eject droplets, via the one or more nozzles 121, toward the deposition media 103 in response to signals sent by the controller 104. The controller 104 may also control the transport mechanism 105. Alternatively there may be a master controller 112 to control all aspects of the droplet ejection apparatus 7. There may additionally be media encoder circuitry 107. The apparatus 7 further comprises a liquid supply 140, a liquid path 143, comprising inlet liquid path 141 and return liquid path 142, a thermal control fluid supply 240 and a thermal control fluid path 243, comprising thermal control fluid path 241 and a thermal control fluid path 242. Likewise, the actuator component 700 comprises one or more liquid chambers 131 and one or more thermal control fluid channels 231, etc. as described herein. The droplet ejection head 702 may comprise one or more actuator components 700. It may be generally understood that any of the actuator components 100-700 described herein may be used in the droplet ejection apparatus 7, and in the droplet ejection head 702.

METHOD OF OPERATION

A method of operation of the apparatus 7 may comprise ejecting droplets of liquid from one or more of the nozzles 121, in accordance with printing instructions, and flowing thermal control fluid from the thermal control fluid supply 240, via the thermal control fluid path 243 (via the inlet thermal control fluid path 24 I) to the actuator component 700, and through the thermal control fluid channels 231. This allows control of the temperature of the liquid, to be ejected from the droplet ejection nozzles 121, by transfer of thermal energy.

Where the liquid requires cooling, i.e. because the liquid rnmperature Tl is greater than the desired liquid temperature Tl(desired) (i.e. T1>T1(desired)), this may be via transfer of thermal energy from the liquid in the liquid chambers 131 to the thermal control fluid in the thermal control fluid channels 231. For example, the temperature Ttc of the thermal control fluid, as it enters the actuator component 700, may be cooler than the liquid in the actuator component 700 (i.e. Ttc<T1).

Where the liquid requires heating (i.e. T1cT1(desired)) this may be via transfer of thermal energy from the thermal control fluid, in the thermal control fluid channels 231, to the liquid in the liquid chambers 131. In this case, the thermal control fluid, as it enters the actuator component 700, may be hotter than the liquid in the actuator component 700 (e.g. Ttc>TI). Whether heating or cooling, the transfer of thermal energy may be via conduction through the structure of the actuator component 700, in particular, via the shared walls 132 separating the liquid chambers 131 from the thermal control fluid channels 231. it may be understood that control of the temperature of the liquid may control other properties of the liquid such as the viscosity.

The apparatus 7 may be arranged such that the thermal control fluid supply 240 causes thermal control fluid to flow to the thermal control fluid manifold 201, through the thermal control fluid channels 231, and hence back to the thermal control fluid manifold 201 (as in the embodiments of Fig. 1A-Fig. 1B, Fig. 2A-Fig. 2C and Fig. 6A-Fig. 6E). Alternatively the apparatus 7 may be arranged such that the thermal control fluid supply 240 causes thermal control fluid to flow to the thermal control fluid manifold 201, through the thermal control fluid channels 231, and hence to the thermal control fluid manifold 202 (as in the embodiment of Fig. 3). The method may then comprise removing the thermal control fluid from the actuator component 700, via the thermal control fluid path 243 (via the return thermal control fluid path 242). The thermal control fluid may return to the thermal control fluid supply 240 in a closed loop thermal control fluid path 243; it may additionally return to the thermal control fluid supply 240 via a thermal control fluid reservoir 246b. Alternatively, the thermal control fluid may be removed from the actuator component 700 and piped to thermal control fluid exhaust 246a, such as a drain or waste collector. For example, if the thermal control fluid is water, it may be supplied from the public fresh water system, being a thermal control fluid reservoir 246b, and piped to the public waste water systems being a thermal control fluid exhaust 246a.

The temperature of the thermal control fluid may require adjusting to a desired temperature Ttc(desired) before it reaches the actuator component 700, i.e. it may require heating or cooling, depending on the desired liquid temperature TI(desired) to be achieved. The method may therefore comprise heating or cooling the thermal control fluid using a thermal control device 247. The thermal control device 247 may be, for example, a heat exchanger, to heat or cool the thermal control fluid to the desired temperature Ttc(desired), located upstream of the actuator component 700 on the thermal control fluid path 243.

The method may further comprise measuring the temperature at one or more points in the thermal control fluid path 243 and/or the liquid path 143 using one or more temperature sensors, as described above with respect to Fig. 1A-Fig. 1B, and Fig. 2A-Fig. 2C. The measured temperatures may then be used to appropriately adjust the flow rate and/or temperature of the thermal control fluid so as to control the temperature of the liquid. For example, the temperature measurements may be provided to the controller 104. The controller 104 may control the droplet ejection apparatus 7 so as to adjust the temperature of the liquid. For example, the controller 104 may control the thermal control fluid supply 240 to alter the flow rate of the thermal control fluid. In some arrangements the flow rates may be controlled independently, for example, the method may comprise separately controlling the flow rates of the liquid (in the liquid path 143) and the thermal control fluid (in the thermal control fluid path 243) such that they flow through the actuator component 700 at different flow rates.

Further, the controller 104 may control a thermal control device 247 to heat or cool the thermal control fluid. The controller 104 may, for example, use a look-up table or a calibration routine to determine the desired temperature Ttc(desired), and/or flow rate of the thermal control fluid, to give a desired liquid temperature Tl(desired). it may generally be understood that the desired temperatures Ttc(desired) and Tl(desired) may comprise an acceptable range of operating temperatures rather than a single temperature. Still further, the method may comprise independently controlling the temperatures of the liquid and the thermal control fluid in the liquid path 143 and the thermal control fluid path 243. For example the two may be heated to desired temperatures prior to entering the one or more droplet ejection heads, and the transfer of thermal energy from one to the other within the droplet ejection head 702 may be to control fluctuations in the liquid temperature due to the printing duty cycle.

The method may thriller comprise flowing the thermal control fluid along the thermal control fluid channels 231 in a direction that is opposite to the direction of flow of the liquid in the liquid chambers 131. For example, if the liquid in the liquid chambers is flowing in the liquid chamber extension direction 5, the thermal control fluid may flow in the negative liquid chamber extension direction 5.

Where the liquid path 143 of the apparatus 1,2,7 comprises a return liquid path 142, the method may further comprise flowing unelected liquid from the liquid chambers 131 to the liquid supply 140, via the return liquid path 142. The liquid may, for example, flow from the plurality of liquid chambers 131 into a return liquid manifold 102 and from there to the return liquid path 142. The liquid path 143 may further comprise a liquid reservoir on the return liquid path 142 and the liquid may travel from the droplet ejection head(s) 702 to the liquid reservoir and hence to the liquid supply 140 in a recirculation loop.

The method may further comprise using the liquid for droplet ejection as the thermal control fluid, i.e. the same liquid is in both the liquid path 143 and in the thermal control fluid path 243. in such a case the method may comprise feeding said liquid path 143 and said thermal control fluid path 243 from a common liquid supply 140.

METHOD OF MANUFACTURE

Turning now to Fig. 6A-Fig. 6E, these summarise the main steps in a method of manufacturing an actuator assembly 80 for an actuator component 100-700 for a droplet ejection head as described herein. The main steps are as follows: Step 1 -forming one or more cut-outs 81 in one or more strips ofpiezoelectric material 82 and fixedly attaching the strip(s) of piezoelectric material 82 to a substrate 83, as depicted in Fig. 6A, so as to form one or more thermal control fluid manifolds 201 (and 202, where present). The strip of piezoelectric material 82 may, for example, comprise lead zirconate titanatc (PZT), but any suitable material may be used. This step may alternatively comprise fixedly attaching a larger piece of piezoelectric material to the substrate 83 and then cutting or forming or machining the larger piece so as to form one or more strips of piezoelectric material 82, where one or more cut-outs 81 have been pre-formed in the larger piece of piezoelectric material, so as to provide one or more thermal control fluid manifolds 201.

Alternatively the one or more thermal control fluid manifolds 201 may be formed as one or more cut-outs 81 (not shown) in the substrate 83, prior to attaching the one or more strips of piezoelectric material 82. in another implementation of the method, there may be one or more cut-outs 8 la in the substrate 83 and one or more cut-outs 8 lb in the one or more strips of piezoelectric material 82 (see Fig. 6E), such that, when the two parts are joined together, the one or more thermal control fluid manifolds 201 are formed by aligning the two cut-outs 8 la,8 lb. The cut-outs 81 may be arranged adjacent to, or at the interface or boundary between, the substrate 83 and the respective strip of piezoelectric material 82 in the liquid chamber height direction 15.

Step 2 -forming one or more arrays 230 of thermal control fluid channels 231 in the one or more strips of piezoelectric material 82, as shown in Fig. 6B, so as to create a plurality of open-ended themial control fluid channels 231 in said one or more strips of piezoelectric material 82, wherein the thermal control fluid channels 231 are aligned in an array direction 10 along the one or more strips of piezoelectric material 82.

Each thermal control fluid channel 231 is formed such that it comprises an open channel with an opening at both ends in the liquid chamber extension direction 5, and such that the thermal control fluid channels 231 are also open along their extent on the opposite side to the substrate 83 (i.e. in the liquid chamber height direction 15), and such that they open into and are fluidically connected to the thermal control fluid manifold 201, on the side of the piezoelectric strip 82 facing the substrate 83.

For example, they may be formed to be deep enough to intersect with the cut-outs 81 forming the thermal control fluid manifold 20E i.e. they may be partially or fully open on the side facing the substrate 83 so as to be fluidically connected to the thermal control fluid manifold 201. Any suitable method may be used to form the thermal control fluid channels 231, such as laser cutting, or cutting with a dicing blade or saw, or using a water jet cutter, or any other suitable cutting tool. As an example, dicing blades may be used that may be between 3pm and 160pm wide. Depending on the required design, the thermal control fluid channels 231 may be formed with any suitable width, Wtc, for example, they may be between 3pm and 160pm wide, preferably between 50pm and 100pm wide. The thermal control fluid channels 231 may be narrower than the liquid chambers 131 in the array direction 10 (Wtc<W1).

This step may also comprise forming the liquid chambers 131 such that each liquid chamber 131 may comprise an open channel in the strip of piezoelectric material 82, with an opening at both ends in the liquid chamber extension direction 5, and such that the liquid chambers 131 may also be open along their extent on the opposite side to the substrate 83 (i.e. in the liquid chamber height direction 15). Any suitable method may be used to form the liquid chambers 131, such as laser cutting, or cutting with a dicing blade or saw, or using a water jet cutter, or any other suitable cutting tool. Depending on the required design, the liquid chambers 131 may be formed with any suitable width, WI, for example, they may be between 3tun and 160pm wide, preferably between 50tun and 100pm wide. The liquid chambers 131 may be formed such that they are less tall than the thermal control fluid channels 231, so as not to impinge on the thermal control fluid manifold 201 (and 202, where present). Preferably, the same method may be used to form both the thermal control fluid channels 231 and the liquid chambers 131. Where the two are the same width (W1=Wtc) the same dicing blade may be used to form both the thermal control fluid channels 231 and the liquid chambers 131. Alternatively, the liquid chambers 131 may be formed later (see step 4 below).

The open design of the strip of piezoelectric material 82 mounted on the substrate 83 may allow a dicing blade, for example, to enter from the side and traverse the entire length of the liquid chambers 131, in the liquid chamber extension direction 5, from one end to the other to form said open channel, i.e. the liquid chambers may have a constant height H1 (and cross-sectional area) along their entire length in the liquid chamber extension direction 5. This may lead to more uniform flow along the liquid chambers 131. This is unlike other designs where, for example, the dicing blade must be lowered from above to cut the liquid chambers, and hence liquid chambers 131 may be obtained that are less tall at their ends, in the liquid chamber extension direction 5. Such unlike designs consequently have changes to the liquid flow velocities at the ends of the liquid chambers 13 I as the depth varies. The thermal control fluid channels 231 may be formed similarly to the liquid chambers 131 such that they too have a constant height Htc (and cross-sectional area) along their entire length in the liquid chamber extension direction 5.

Step 3 -fanning one or more cover parts 84_a,84_b that are conformal to at least some of said one or more strips of piezoelectric material 82 and at least some of said substrate 83, and fixedly attaching them to said one or more strips of piezoelectric material 82, and at least some of said substrate 83, as shown in Fig. 6C. The method may comprise fixedly attaching a first cover part 84_a to each of said one or more strips of piezoelectric material 82 at a first end in said liquid chamber extension direction 5 and fixedly attaching a second cover part 84_b to each of said one or more strips of piezoelectric material 82 at a second opposite end in the liquid chamber extension direction 5. Step 3 may further comprise fixedly attaching the one or more cover parts 84_a,84_b to at least some of said substrate 83, as shown in Fig. 6C. The cover part 84 a,84 b may comprise a single layer of material, or be formed from a number of layers of material fixedly attached together. Alternatively, it may comprise a number of parts that have been pre-shaped, to be conformal to a particular part of the strips of piezoelectric material 82 or the substrate 83, which are then fixedly attached together.

The cover part 84 a,84 b may be shaped by machining or moulding or any suitable manufacturing technique, such as cutting or grinding or laser ablating. The material of the cover part 84_a,84_b may be the same material as the strips of piezoelectric material 82, or a different material. The material of the cover part 84 a,84 b may comprise a material that is acoustically the same or similar to the strips of piezoelectric material 82 and/or the substrate 83. The cover part 84 a,84 b may be fixedly attached using any suitable method, for example, the attachment method may comprise bonding using any suitable bonding material. The bonding method may comprise depositing or 3D printing a bonding material in appropriate locations. The bonding material may be curable, e.g. a thermally curable material, or if the cover part is formed from a UV transparent material a UV curable material may be used. Epoxy resins -bonding materials that arc curable in a temperature range that doesn't damage or otherwise compromise the PZT performance -may be used; they may, for example, be curable below 140°C, more preferably below 120°C. Depending on the design of actuator component being made, whether with or without flow recirculation, whether an end shooter or a side shooter actuator component, there may be cover parts 84 on one side or both sides of the strips of piezoelectric material in the liquid chamber extension direction 5.

Where there is one cover part 84_a (as in the embodiment of Fig. 1A-Fig. 1B) the method may comprise fixedly attaching a first cover part 84_a to each of said one or more strips of piezoelectric material 82 at a first end in the liquid chamber extension direction 5. Where there are two cover parts 84_a,84_b (as in the embodiment of Fig. 2A-Fig. 2C, Fig. 3, Fig. 4 and as shown in Fig. 6C-Fig. 6E) the method may further comprise fixedly attaching a second cover part 84_b to each of said one or more strips of piezoelectric material 82 at a second opposite end in the liquid chamber extension direction 5.

Step 4 -Once the cover part(s) 84 a,84 b are attached, apertures 85 a,85 b may be formed in the cover parts 84 a,84 b. The method of manufacture may therefore comprise forming a plurality of apertures 85_a,85_b in the first and second cove r parts 84_a,84_b such that the first and second cover parts 84 a,84 b comprise at least one aperture 85 a,85 b per liquid chamber 131 over a substantial portion of the army of liquid chambers 130. The respective apertures 85a 85b per liquid chamber 13 I are paired such that for each liquid chamber 131 there is a continuous liquid path that passes through the first aperture 85_a in the first cover part 84_a at the first end of the liquid chamber 131, through the liquid chamber 131 and through the aperture 85_b in the second cover part 84_b at the second end of the liquid chamber 131. As described above, with respect to forming the liquid chambers, the apertures 85_a,85_13 may be formed using a cutting blade that enters from the side and traverses the entire length of each aperture so as to form each aperture 85 a,85 b with a constant height Ha, this height may be the same as that of the adjacent liquid chamber 131 (Ha=H1) or it may be less (Ha>HI), to allow a restrictor at the entrance and/or exit to the liquid chamber in the liquid chamber extension direction S. Forming the apertures 85 a,85 b may comprise running a dicing blade through the cover parts 84 a,84 b at appropriate positions in the array direction 10. If the liquid chambers were not formed as part of step 2 (see above) then this step may also comprise forming the liquid chambers 131, in which case this step may be performed by running a dicing blade through the one or more cover parts 84 a,84 b and the strip of piezoelectric material 82 in a single pass per liquid chamber 131 so as to form the continuous liquid path therethrough. The liquid chambers 131 and the apertures 85_a,85_b may be formed such that they are continuous through the cover part 84 a,84 b and the strips of piezoelectric material 82. The liquid chambers 131 and the apertures 85 rt85 b may be formed such that they are less tall than the thermal control fluid channels 231, so that they don't impinge on the thermal control fluid manifold 201 (202 where present). The liquid chambers 131 are also open along their extent on the opposite side to the substrate 83, in the liquid chamber height direction 15, as are the apertures 85 a,85 b.

To form the thermal control fluid channels 231 and/or the liquid chambers 131, a dicing blade may be lowered towards the substrate 110 to one side of the strip of piezoelectric material 82 and then moved across the strip of piezoelectric material 82 in the liquid chamber extension direction 5. Where there is more than one strip of piezoelectric material 82, the dicing blade may be moved so as to form all of the liquid chambers 131, at a given position in the array direction 10, at the same time as a row.

The dicing blade may then be lifted and returned to its original position, and the actuator assembly 80 may be incrementally moved in the array direction 10 so that the next row of liquid chamber(s) 131 and/or the thermal control fluid channels 231 may be formed. When forming the liquid chambers 131, the dicing blade may be lowered to a lesser extent than when forming the thermal control fluid channels 231, such that the liquid chamber height HI is less than the thermal control fluid channel height Htc (Hl<Htc). Depending on how and where the thermal control fluid manifold 201 (202 where present) was formed, the liquid chamber height HI may also be less than the thermal control fluid channel height Htc minus the thermal control fluid manifold height Hm (c.g.1-11<(Htc-Hm)).

Alternative methods of forming the thermal control fluid channels 231 and liquid chambers 131 may be envisioned. For example, both liquid chamber and thermal control fluid channel arrays 130,230 may be formed at the same time using a dicing blade to cut the open channels (or slots) in die one or more strips of piezoelectric material 82, as described above in Step 2. For example, the dicing blade may be used to cut alternate deeper slots, for the themml control fluid channels 23 I. and shallower slots, for the liquid chambers 131, by altering the depth settings appropriately as the blade is moved incrementally along the strip of piezoelectric material 82, in the array direction I 0. The one or more cover parts 84 a,84 b may then be attached and then the liquid chamber apertures 85 a,85 b, through the cover parts 84_a,84_b, may be formed in a second cutting operation. Alternatively, the liquid chamber apertures 85 a,85 b may be formed prior to attaching the one or more cover parts 84 a,84 b to the strip of piezoelectric material 82. Alternatively the liquid chamber apertures 85 a,85 b may be formed at the same time as the liquid chambers 131 in a single operation, for example using the same dicing blade to cut through both the one or more cover parts 84_a,84_b and the one or more strips of piezoelectric material 82.

In general, the method of manufacture comprises selectively forming a plurality of apertures %5a in the first cover parts 84 a, wherein said first cover parts 84_a comprise at least one aperture 85_a per liquid chamber 131 over a substantial portion of the array of liquid chambers 130 and, where present, selectively forming a plurality of apertures 85_b in said second cover parts 84_b wherein said second cover parts 84_b comprise at least one aperture 85_b per liquid chamber 131 over a substantial portion of the array of liquid chambers 130. It may be understood that where the embodiment comprises two cover parts 84 a,84 b per strip of piezoelectric material 82, the apertures 85 a,85 b may be aligned, e.g. at the first end and second ends of each respective liquid chamber 131 such that liquid can flow therethrough, entering at the first end and exiting at the second end.

Instead of cutting slots to form the apertures 85 a,85 b, alternatively they may be formed using a different method, such as laser etching, drilling, or boring, The apertures 85 a,85 b may not extend the full height of the liquid chambers 131. The apertures 85_a,85_b may be one or more holes or orifices in the one or more cover parts 84 a,84 b, connecting the liquid manifold 101 to the first end of the liquid chambers 131, and, where present, connecting the liquid manifold 102 to the second end of the liquid chambers 131. Where the thermal control fluid channels 231 are longer than the liquid chambers 131 in the liquid chamber extension direction 5, the above-described method steps may be altered appropriately so that thermal control fluid channel apertures are cut through the cover part 84 a,84 b.

Step 5 -Once the actuator assembly 80 has been formed as required, with any additional steps and stages that may be required incorporated (such as forming electrical traces and connections, or adding protective layers for chemical/electrical isolation of parts, or adding further parts to complete the formation of the liquid manifold(s) 101,102, then the nozzle plate 70 may be attached to the actuator assembly 80 to form the actuator component 100-700. The nozzles 121 may be formed prior to the attachment stage and/or after the nozzle plate 70 is in situ, as required. The nozzles 121 may be formed using any suitable method, such as laser ablation or etching.

It may be generally understood that the electrical traces, drive electrodes and connections may be deposited as continuous layers, built up one at a time, over some or all of the external surfaces of the actuator component 100-700, such as on the substrate 83 and the strip(s) of piezoelectric material 82, using any suitable method, such as electroless plating or metal sputtering/ evaporation. Cutting, or other removal techniques, may then be used to remove some of the metal layer or layers so as to form electrically isolated electrical traces and connections. if the electrical traces, drive electrodes and connections are formed using electroless plating, initially the thermal control fluid channels 231 may be formed using a shallow cut that doesn't connect them to the thermal control fluid manifold 201. The thermal control fluid channels 231 and the liquid chambers 131 may then be metalised, then another cut may be used to connect the thermal control fluid channels 231 to the thermal control fluid manifold(s) 201,202. These steps would prevent metalisation of the thermal control fluid manifold(s) 201,202, which could cause electrical shorts.

An alternative method would be to use line of sight plating of metal, which is a method that allows control of where and how deep into the thermal control fluid channels 231 any metal may be deposited. Still further, the thermal control fluid manifold(s) 201,202 could have a dissolvable/ removable block formed inside it, the thermal control fluid channels 23 I could be cut as normal, connecting to the thermal control fluid manifold(s) 201,202, and the block. Metalisation would then be performed and the block subsequently dissolved/removed, along with any metal deposited on the Mock, enabling fluidic connection between the thermal control fluid channels 23 I and the, now open, thermal control fluid manifold(s) 201,202.

if the actuator component is for an end shooter, as in Fig. IA-Fig. I B, the nozzle plate 70 may be fixedly attached to the strip of piezoelectric material 82 at the second end in the liquid chamber extension direction 5, opposite to the cover part 84_a, such that said nozzle plate 70 acts to fluidically seal the thermal control fluid channels 231 and the liquid chambers 131 in the liquid chamber extension direction S. If the actuator component is for a side shooter, as in Fig. 2A-Fig. 2C, Fig. 3, Fig. 4 and Fig. 6E the nozzle plate 70 may be fixedly attached to the strip of piezoelectric material 82 at one side in the liquid chamber height direction 15 (i.e. on the opposite side to the substrate 83) such that the nozzle plate 70 acts to fluidically seal the thermal control fluid channels 231 and the liquid chambers 131 in the liquid chamber height direction 15, as shown in Fig. 6E. It can further be seen that, in the arrangement of Fig. 6E, the nozzle plate 70 may further seal the apertures 85_a,85_b in the cover parts 84 a,84 b connecting the liquid manifolds 101,102 to the liquid chambers 131. The nozzle plate 70 may also seal the liquid manifolds 101,102 in the liquid chamber height direction 15, though this is not necessary and other arrangements may be used to form and/or seal the liquid manifolds 10 I, 102, it may be understood that the actuator component 100-700 may comprise further parts, for example, so as to seal the liquid manifolds 101,102 at either side in the liquid chamber extension direction 5 and at either end in the array direction 10.

Still thither, it may be understood that in other arrangements, such as the end-shooter actuator component of Fig. 1A-Fig. 1B, the nozzle plate 70 may be attached to the strip of piezoelectric material 82 at one side in the liquid chamber extension direction 5 so as to fluidically seal the liquid chambers 131 and the thermal control fluid channels 231 at a second end of the liquid chambers 131 in the liquid chamber extension direction 5. It may be understood that, in such a design, a cover part 84_a may be arranged on the opposite side of the strip of piezoelectric material 82 to the nozzle plate 70 in the liquid chamber extension direction 5, i.e. at the first end of the liquid chambers 131. Apertures 85_a may be formed in the cover part 84_a to connect to the plurality of liquid chambers 131 and fluidically connect them to the liquid manifold 101. For example, the method of manufacture may comprise fixedly attaching a first cover part 84_a to each of said one or more strips of piezoelectric material 82 at a first end in the liquid chamber extension direction 5 and selectively forming a plurality of apertures 85_a in said first cover parts 84_a such that the first cover parts 84_a comprise at least one aperture 85_a per liquid chamber 131 over a substantial portion of the array of liquid chambers 130.

It may further be understood that where the actuator component does not comprise a return liquid path 142 or a second liquid manifold 102 (i.e. it is not a recirculation actuator component for the liquid path 143) then only a first cover part 84_a with apertures 85_a at the first end of the liquid chambers 131 may be required, and that the above-described steps may be adjusted accordingly.

It may further be understood that an end shooter actuator component may further require a top part 86 (see Fig. 1A) that may be attached on the opposite side of the strip of piezoelectric material to the substrate 83 and the one or more thermal control fluid manifolds 201,202 so as to fluidically seal the thermal control fluid channels 231 and the liquid chambers 131 in the liquid chamber height direction 15. The top part 86 may be attached before or after the nozzle plate 70, It may be understood that, depending on the type of actuator component being made, the order of the above-described steps may be altered as required, and additional steps inserted as necessary to form other features of the actuator component and the droplet ejection head, for example, forming electrical traces and connections or providing insulating and protective coatings. It may be generally understood that the above methods of manufacture may be used, with appropriate adjustments, whether there is one cover part 84_a per respective strip of piezoelectric material 82 (i.e. for an end shooter actuator component) or two cover parts 84_a,84_b per respective strip of piezoelectric material (i.e. for a side shooter actuator component).

In general, the method of manufacture may comprise forming one or more cut-outs 81 in either the substrate 83 and/or the strip of piezoelectric material 82 -fixedly attaching the one or more strips of piezoelectric material 82 to the substrate 83 such that each of said one or more cut-outs R I is arranged adjacent to the interface between the substrate 83 and a respective strip of piezoelectric material 82 so as to form one or more thermal control fluid manifolds 201,202, wherein each of the one or more arrays 130 ofliquid chambers 131 arc fluidically separated from the one or more themal control fluid manifolds 201,202; and wherein each of said one or more arrays 230 of thermal control fluid channels 231 are fluidically connected to at least one of said one or more thermal control fluid manifolds 201,202.

GENERAL CONSIDERATIONS

It may be generally understood that as described herein, actuator components 100-700 for a droplet ejection head may comprise an actuator assembly RO and a nozzle plate 70. The actuator assembly 80 may comprise a plurality of liquid chambers 131 arranged in a liquid chamber array 130 extending in an array direction 10 and a plurality of thermal control fluid channels 231 arranged in a thermal control fluid channel array 230 and extending in the array direction 10. The plurality of liquid chambers 131 and the plurality of thermal control fluid channels 231 are fluidically independent. The plurality of liquid chambers 131 may be arranged to be fluidically connectable to a liquid supply 140 and the plurality of thermal control fluid channels 231 may be arranged to be fluidically connectable to a thermal control fluid supply 240. The nozzle plate 70 may comprise a plurality of droplet ejection nozzles 121 arranged in a nozzle array 120 extending in the array direction 10 and each liquid chamber 131 may be arranged to be fluidically connected to one or more of said droplet ejection nozzles 121 and actuable for ejection of droplets of a liquid. The plurality of thermal control fluid channels 231 and the plurality of liquid chambers 131 are arranged in a repeating pattern extending in the array direction 10. In use, the actuator component 100-700 is configured such that thermal control fluid flowing through the thermal control fluid channels 231 controls the thermal properties of the liquid flowing through the liquid chambers 131 to thereby control the thermal properties of the liquid ejected from the droplet ejection nozzles 121.

In some arrangements, the thermal control fluid channel army 230 may start before and finish after the liquid chamber array 130, such that there is a thermal control fluid channel 231 outermost in the positive and negative array direction 10. in such an arrangement, the total number of thermal control fluid channels 231 would be one more than the number of liquid chambers 131, e.g. m=n+1.

Further, it may be understood that the piezoelectric strip 82 may comprise buffer regions in the array direction 10. A buffer region may comprise dummy liquid chambers with no nozzles, and thermal control fluid channels. Dummy liquid chambers cannot eject liquid through nozzles 121, but, in use, allow liquid to travel therethrough. Buffer regions comprising these may, for example, be found at the outer ends of the actuator component 100-700 in the array direction 10. They may improve the flow uniformity along the actuator component 100-700, in the army direction 10, and may also aid in improving the stress profile along the actuator component 100-700, in the array direction 10, and therefore improve the droplet ejection performance and print quality (as stress in actuator components, such as those described herein, can lead to flow non-uniformity that 'prints through' into observable defects in the printed image or product). Buffer regions, may also be used to create gaps between nozzle clusters for control of, for example, the so-called woodgrain effect. In sonic instances, buffer regions may comprise regions without liquid chambers or thermal control fluid channels.

In some of the embodiments described herein, the exits of the nozzles 121 in the media-facing surface 118 are circular in cross-section, but it may be understood that this is by no means limiting and, in other arrangements, the nozzles may have other shapes at their exits.

The cross-sectional shape and area of the nozzles 121 may be the same through the nozzle plate 70 in the ejection direction 16, or they may vary (for example there may be a tapered hole such that the cross-sectional area increases (or alternatively decreases) through the nozzle plate 70 from inlet to exit, i.e. through the nozzle plate thickness T. Further, the nozzles 121 may be angled such that they pass through the nozzle plate 70 at an angle to the nozzle plate thickness T. The minimum diameter or width of any nozzles in the nozzle plate 70, depends in part on the material used and the manufacturing methods available. For example a minimum of 18iim is likely achievable with laser drilling, whilst for a silicon nozzle plate Deep Reactive Ion Etching (DRIE) may be used so that the nozzles may be smaller, for example I Own.

It may be understood that in arrangements where the nozzles 121 in a given array 120 are staggered from one or more adjacent nozzles 12 I such that they are offset from the array direction 10, then the nozzle spacing ns may be measured by projecting the centre-lines of the nozzles 121 onto a common line, parallel to the array direction 10.

It may further be understood that the actuator component 100-700 may comprise one or more liquid manifolds 101,102 and one or more thermal control fluid manifolds 201,202 where the one or more liquid manifolds 101,102 may be fluidically independent from the one or more thermal control fluid manifolds 201,202. Still further the one or more liquid manifolds 101,102 may be fluidi cal ly independent from the plurality of thermal control fluid channels 231 and the one or more thermal control fluid manifolds 201,202 may be fluidically independent from the plurality of liquid chambers 131.

It may be generally understood that, where the actuator component 100-700 is mounted in a droplet ejection head, or in an apparatus 1,2,7 comprising a plurality of actuator components 100-700 and/or one or more droplet ejection heads, wherein said droplet ejection heads comprise one or more actuator components 100-700 as described herein, the liquid path 143 and the thermal control fluid path 243 may be different to those described herein. They may be more complex, and may comprise further external sections to connect the fluid supplies 140,240 to the one or more droplet ejection heads. Further, there may be additional components to the fluid paths within the one or more droplet ejection heads to connect the fluid supplies (liquid and thermal control fluid, 140,240 respectively) to the one or more actuator components 100-700 located within the droplet ejection heads. There may also be additional components to the fluid paths to remove the fluids (liquid and/or thermal control fluid) from the actuator components 100-700. Still further, it may be understood that the fluid path layouts 143,243 may be different to those described herein, whilst still performing the essential tasks of supplying the fluids to the thermal control fluid channels 231 and the liquid chambers 131. It may further be generally understood that, whatever further components they may comprise, or different layouts they may have, the liquid path 143 and the thermal control fluid path 243 are fluidically separated from each other throughout at least the actuator assembly 80, preferably throughout the actuator component. They may be fluidically separated in their entirety.

It may be generally understood that where the method requires that thermal control fluid flows along the thermal control fluid channels 231 in a direction that is opposite to the direction of flow of the liquid in the liquid chambers 131 then the fluid paths 143,243 and the actuator components 100-700 may be appropriately arranged so as to enable this.

The actuator components 100-700 for a droplet ejection head described herein may comprise liquid chambers 131 with any suitable form of actuator, actuable so as to eject droplets via the respective one or more nozzles 121 associated with each liquid chamber 131. For example, the liquid chambers may comprise one or more walls that are actuable, for example one or more shared walls 132 may comprise PZT, or the liquid chambers 131 may be provided with an actuator in a roof mode arrangement. However, it may be understood that other forms of actuators may also be used, provided that they are suitable to cause the ejection of liquid via the respective nozzle 121 from an individual liquid chamber 131, in response to print instructions.

It may be generally understood that the liquid may be a liquid suitable for ejection as a droplet, i.e. a liquid for droplet ejection; such as a printing ink. it may be understood that printing inks vary greatly in their composition. This can depend on the colour being printed, the pigment if any in the printing ink, the desired properties on the print media (for example opacity, distribution, absorption, light reflection, etc.), and the type of media being printed onto, for example: paper, card, glass, cloth or fibre, metal, ceramic, etc. Additionally the liquid may be a functional fluid suitable for building up texture or for printing electronics components such as circuit boards, or for building three-dimensional objects (i.e. for 3D printing).

It may be understood that the thermal control fluid may be a gas. Where the thermal control fluid is a gas it may comprise one or more of the following: atmospheric air, air heated above or cooled below ambient temperatures, hum id air where the humidity is greater than ambient, dehumidified air where the humidity is less than ambient, inert gases, noble gases, or any other gas suitable for thermal control in the operating conditions being used. Alternatively the thermal control fluid may be a liquid. Where the thermal control fluid is a liquid it may comprise water, deionised water, or another suitable liquid, such as a refrigerant fluid. Where the thermal control fluid is a liquid, it may comprise additives to control or adjust the liquid's properties, such as anti-corrosion additives. In some circumstances the thermal control fluid may be the liquid for droplet ejection, for example ink, so as to avoid the costs of having two fluid types in the droplet ejection apparatus 1,2,7. In many applications, however, such liquid for droplet ejection may be expensive or otherwise undesirable or unsuitable to use in the thermal control fluid path 243 and another fluid type may be used for the thermal control.

Where the thermal control fluid is the liquid for droplet ejection (e.g. the printing ink), it may not be a requirement to keep the entirety of the thermal control fluid path 243 and the liquid path 143 separate; for example, the two paths may have some commonality, whilst keeping the main parts of the paths, such as the fluid paths in the actuator assembly 80, or preferably in the actuator component 100-700, fluidically separate. Alternatively, the fluid paths 143,243 may be kept separate in a droplet ejection head, which may comprise one or more actuator components 100-700, with the two paths splitting at, or before, the droplet ejection head on the inlet side, and rejoining at, or after, the droplet ejection head on the return side. in some cases the two paths may share a liquid for droplet ejection reservoir 146 and/or a liquid supply 140. For example, the liquid and the thermal control fluid may be fed from a common liquid supply 140. Where they share a liquid supply 140, the thermal control fluid path 243 may separate from the liquid path 143 downstream of the liquid supply 140. The thermal control fluid path 243 may comprise a thermal control fluid pump after the two paths have split. As a further example where the thermal control fluid is the liquid for droplet ejection, the fluid paths 143,243 may share part of a return liquid path 142, i.e. the two paths 143,243 may merge after the actuator component 100-700, or after the droplet ejection head.

It may be understood that for an embodiment such as that of Fig. 3, where there are two thermal control fluid manifolds 201,202 located below the liquid chambers 131, in the liquid chamber height direction 15, the method of manufacture may comprise forming two or more cut-outs 81 in the substrate 83 or in the one or more strips of piezoelectric material 82, or that two or more alignable cut-outs 8 la,8 lb may be formed in the substrate 83 and in the one or more strips of piezoelectric material 82 respectively. it may further be understood that, for an embodiment such as that of Fig. 4, where the liquid manifolds 101,102 are located below and in fluidic contact with the liquid chambers 131, where the actuator assembly 80 comprises one or more strips of piezoelectric material 82 and a substrate 83, the two or more liquid manifolds 101,102 may comprise cut-outs 81 in either the substrate 83 and/or the one or more strips of piezoelectric material 82, and the method of manufacture may comprise forming two or more cut-outs 81 in the substrate 83 or in the one or more strips of piezoelectric material 82, or that two or more alignable cut-outs 81a,81b may be formed in the substrate 83 and in the one or more strips of piezoelectric material 82, respectively.

It may be understood that, whilst the actuator components 100-700 described herein comprise an actuator assembly 80 formed from a substrate 83 and a strip of piezoelectric material 82, this is by no means limiting, and actuator assemblies 80 may comprise, for example, one or more substrates 83 and a plurality of strips of piezoelectric material 82, each strips of piezoelectric material 82 comprising one or more arrays 130 of liquid chambers 131 and one or more arrays 230 of thermal control fluid channels 231. Where appropriate, adjacent strips of piezoelectric material 82 may share liquid manifolds. For example, two strips of piezoelectric material 82 arranged on a substrate 83 may share a liquid manifold 101 arranged between them in the liquid chamber extension direction. Where the actuator component is a recirculation actuator component, the strips of piezoelectric material 82 may each further comprise a respective liquid manifold 102 on their outer edges in the liquid chamber extension direction 5.

Other arrangements of liquid manifolds for two or more strips of piezoelectric material 82 may be envisioned. It may further be understood that the embodiments described herein may be combined in any suitable manner, and more generally, it may further be understood that when any of the actuator components 100-700 described herein are incorporated into a droplet ejection head, said head may comprise additional parts, not shown such as liquid connections, head electronics, external electrical connections, etc. It may be generally understood that the liquid supply 140 and the thermal control fluid supply 240 may comprise a source of liquid and thermal control fluid respectively, or they may be connected to reservoirs 146,246 respectively. Additionally the liquid supply 140 and the thermal control fluid supply 240 may comprise pumps, degassers, and any other components required to supply the liquid and fluid.

It may be generally understood that one or more temperature sensors may be provided at suitable locations on the thermal control fluid path 243 and/or on the liquid path 143 as described herein.

The liquid and thermal control fluid circuits may further comprise thermally insulating layers or enclosures at one or more locations, It may be generally understood that methods of operation as described herein may suitably be used with any of the actuator components 100-700 and droplet ejection apparatus 1,2,7 described herein.

Claims

CLAIMS1. An actuator component for a droplet ejection head comprising: an actuator assembly and a nozzle plate; wherein said actuator assembly comprises a plurality of liquid chambers arranged in a liquid chamber array extending in an array direction; and a plurality of thermal control fluid channels arranged in a thermal control fluid channel array extending in said array direction; wherein said plurality of liquid chambers and said plurality of thermal control fluid chamois are fluidically independent; wherein said plurality of liquid chambers are arranged to be fluidically connectable to a liquid supply; wherein said plurality of thermal control fluid channels are arranged to be fluidically connectable to a thermal control fluid supply; wherein said nozzle plate comprises a plurality of droplet ejection nozzles arranged in a nozzle array extending in the array direction; wherein each liquid chamber is arranged to be fluidically connected to one or more of said droplet ejection nozzles and actuable for ejection of droplets of a liquid; wherein said plurality of thermal control fluid channels and said plurality of liquid chambers are arranged in a repeating pattern extending in the array direction; and wherein said actuator component is configured such that in use thermal control fluid flowing through said thermal control fluid channels controls the thermal properties of the liquid flowing through said liquid chambers to thereby control the thermal properties of the liquid ejected from said droplet ejection nozzles.
2. The actuator component according to Claim I, wherein said liquid chambers are elongate in a direction non-parallel to the array direction.
3. The actuator component according to Claim 1 or Claim 2, wherein said thermal control fluid channels are elongate in a direction non-parallel to the array direction.
4. The actuator component according to any preceding claim, wherein said thermal control fluid channels have a greater height than said liquid chambers in the liquid chamber height direction so as to achieve said fluidic independence.
5. The actuator component according to any preceding claim, further comprising one or more liquid manifolds and one or more thermal control fluid manifolds wherein said one or more liquid manifolds are fluidically independent from said one or more thermal control fluid manifolds.
6. The actuator component according to Claim 5, wherein said one or more liquid manifolds are fluidically independent from said plurality of thermal control fluid channels.
7. The actuator component according to Claim 5 or Claim 6, wherein said one or more thermal control fluid manifolds are fluidically independent from said plurality of liquid chambers.
8. The actuator component according to any of Claims 5 to 7, wherein said thermal control fluid channels are fluidically connectable via at least one of said one or more thermal control fluid manifolds to said thermal control fluid supply.
9. The actuator component according to any of Claims 5 to 8, comprising two or more thermal control fluid manifolds arranged such that a first of said thermal control fluid manifolds is fluidically connected to a first end of a plurality of thermal control fluid channels and such that a second one of said two or more thermal control fluid manifolds is fluidically connected to a second opposite end of the plurality of thermal control fluid channels such that in use thermal control fluid flows from said first thermal control fluid control manifold, along the plurality of thermal control fluid channels from said first end to said second end and into said second thermal control fluid manifold.
10. The actuator component head according to any preceding claim, wherein said liquid chambers and said thermal control fluid channels are arranged parallel to each other.
11. The actuator component according to any preceding claim, wherein said thermal control fluid channels and said liquid chambers are arranged in an alternating relationship extending in said array direction.
12. The actuator component according to any preceding claim, wherein said thermal control fluid channels are provided with drive electrodes and/or electrical traces.
13. The actuator component according to any preceding claim, wherein said thermal control fluid channels are narrower than said liquid chambers in the array direction.
14. A droplet ejection head comprising one or more actuator components according to any of Claims 1 to 13.
15. A droplet ejection apparatus comprising one or more actuator components according to any of claims Ito 13 or one or more droplet ejection heads according to Claim 14, and further comprising a liquid supply and a liquid path and a thermal control fluid path.
16. The droplet ejection apparatus according to Claim 15, further comprising a thermal control fluid supply.
17. The droplet ejection apparatus according to Claim 15 or Claim 16, wherein said thermal control fluid path comprises a return thermal control fluid path
18. The droplet ejection apparatus according to any of Claims 15 to Claim 17, wherein said liquid path comprises a return liquid path.
19. The droplet ejection apparatus according to any of Claims 15 to Claim 18, further comprising a thermal control fluid reservoir.
20. The droplet ejection apparatus according to any of Claims 15 to Claim 19, wherein the fluid paths are arranged such that in use thermal control fluid flows along the thermal control fluid channels in a direction that is opposite to the direction of flow of the liquid in the liquid chambers.
21. The droplet ejection apparatus according to any of Claims 15 to 20, further comprising one or more thermal control devices.
22. A method of operating a droplet ejection apparatus according to any of Claims 15 to 21, comprising: ejecting droplets of liquid from one or more of said droplet ejection nozzles in accordance with printing instructions; and flowing thermal control fluid through said thermal control fluid channels so as to control by thermal transfer the thermal properties of said liquid flowing through said liquid chambers and thereby to control the thermal properties of the liquid ejected from said droplet ejection nozzles.
23. The method according to Claim 22, wherein said liquid is a liquid for droplet ejection.
24. The method according to Claim 22 or Claim 23, wherein said thermal control fluid is a liquid.
25. The method according to Claim 22 or Claim 23, wherein said liquid and said thermal control fluid are fed from a common liquid supply.
26. The method according to any of Claims 22 to Claim 25, wherein the flow rates of said liquid and said thennal control fluid flowing through said droplet ejection apparatus are controlled 30 independently.
27. The method according to any of Claims 22 to Claim 26, wherein the temperatures of said liquid and said thermal control fluid flowing through said droplet ejection apparatus arc controlled independently.
28. The method according to any of Claims 22 to Claim 27, wherein said thermal control fluid comprises one or more of the following: atmospheric air, air heated above or cooled below ambient temperatures, humid air where the humidity is greater tinn ambient dehumidified air where the humidity is less than ambient, inert gases, noble gases.
29. The method according to any of Claims 22 to Claim 27 herein said thermal control fluid comprises a refrigerant fluid.
30. The method according to any of Claims 22 to Claim 27, wherein said thermal control fluid comprises water.
31. The method according to any of Claims 23 to Claim 27, when dependent on Claim 23, wherein said thermal control fluid comprises said liquid for droplet ejection.
32. A method of manufacturing an actuator component for a droplet ejection head, wherein said method comprises the steps of -forming an actuator assembly, comprising: -forming one or more arrays of liquid chambers in one or more strips of piezoelectric material extending in an array direction, wherein each of said liquid chambers forms an open channel in the strip of piezoelectric material being open in a liquid chamber height direction and open at a first end and a second end in a liquid chamber extension direction; -forming one or more arrays of thermal control fluid channels in said one or more strips of piezoelectric material extending in said array direction, wherein each of said thermal control fluid channels forms an open channel in the strip of piezoelectric material being open in the liquid chamber height direction and open at a first end and a second end in the liquid chamber extension direction; wherein said liquid chamber array and said thermal control fluid channel array are fluidically independent from each other; and -fixedly attaching a nozzle plate to the actuator assembly; -forming droplet ejection nozzles in said nozzle plate either before or after the step of fixedly attaching the nozzle plate to the actuator assembly such that when assembled said actuator component comprises droplet ejection nozzles fluidically connected to said liquid chambers.
33. The method according to Claim 32, further comprising -forming one or more cut-outs in either a substrate and/or said strip of piezoelectric material -fixedly attaching said one or more strips of piezoelectric material to said substrate such that each of said one or more cut-outs is arranged adjacent to the interface between the substrate and a respective strip of piezoelectric material so as to form one or more thermal control fluid manifolds, wherein each of said one or more arrays of liquid chambers are fluidically separated from said one or more thermal control fluid manifolds; and wherein each of said one or more arrays of thermal control fluid channels are fluidically connected to at least one of said one or more thermal control fluid manifolds.
34. The method according to Claim 32 or Claim 33, further comprising: -fixedly attaching a first cover part to each of said one or more strips of piezoelectric material at a first end in said liquid chamber extension direction.
The method according to Claim 34, further comprising: -selectively forming a plurality of apertures in said first cover parts wherein said first cover parts comprise at least one aperture per liquid chamber over a substantial portion of the array of liquid chambers.
36. The method according to Cairn 35, wherein fixedly attaching said nozzle plate comprises attaching it to the strip of piezoelectric material at a second end in the liquid chamber extension direction such that said nozzle plate acts to fluidically seal said thermal control fluid channels and said liquid chambers in said liquid chamber extension direction.
37. The method according to Claim 34, further comprising: -fixedly attaching a second cover part to each of said one or more strips of piezoelectric material at a second opposite end in the liquid chamber extension direction.
38. The method according to Claim 37, further comprising: -selectively forming a plurality of apertures in said first and second cover parts wherein said first and second cover parts comprise at least one aperture per liquid chamber over a substantial portion of the array of liquid chambers.
39. The method according to Claim 38, wherein fixedly attaching said nozzle plate comprises attaching it to the strip of piezoelectric material at one side in the liquid chamber height direction such that said nozzle plate acts to fluidically seal said thermal control fluid channels and said liquid chambers in said liquid chamber height direction
40. An actuator component for a droplet ejection head comprising: an actuator assembly and a nozzle plate; wherein said actuator assembly comprises a plurality of liquid chambers arranged in a liquid chamber array extending in an array direction; wherein said plurality of liquid chambers are arranged to be fluidically connectable to a liquid supply; wherein said nozzle plate comprises a plurality of droplet ejection nozzles arranged in a nozzle array extending in the array direction; wherein each liquid chamber is arranged to be fluidically connected to one or more of said droplet ejection nozzles and actuable for ejection of droplets of a liquid; wherein said actuator assembly further comprises two or more liquid manifolds arranged below said liquid chambers in a liquid chamber height direction; wherein a first of said liquid manifolds is fluidically connected to one end of a plurality of liquid chambers in a liquid chamber extension direction; wherein a second one of said two or more liquid manifolds is fluidically connected to a second opposite end of the plurality of liquid chambers in the liquid chamber extension direction; and arranged such that in use liquid flows from said first liquid manifold along the plurality of liquid chambers from said first end to said second end and into said second manifold.
41. The actuator component according to Claim 40, wherein said actuator assembly comprises one or more strips of piezoelectric material and a substrate and wherein said two or more liquid manifolds comprise one or more cut-outs in either the substrate and/or said one or more strips of piezoelectric material.
42. The actuator component according to Claim 40 or Claim 41, wherein said actuator assembly comprises a plurality of thermal control fluid channels arranged in a thermal control fluid channel array extending in an array direction configured such that in use thermal control fluid flowing through said thermal control fluid channels controls the thermal properties of the liquid flowing through said liquid chambers to thereby control the thermal properties of the liquid ejected from said droplet ejection nozzles.