Patent Publication Number: US-10780705-B2

Title: Fluid ejection device

Description:
BACKGROUND 
     Fluid ejection devices, such as printheads in inkjet printing systems, may use thermal resistors or piezoelectric material membranes as actuators within fluidic chambers to eject fluid drops (e.g., ink) from nozzles, such that properly sequenced ejection of ink drops from the nozzles causes characters or other images to be printed on a print medium as the printhead and the print medium move relative to each other. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram illustrating one example of an inkjet printing system including an example of a fluid ejection device. 
         FIG. 2  is a schematic plan view illustrating an example of a portion of a fluid ejection device. 
         FIG. 3  is a schematic plan view illustrating an example of a portion of a fluid ejection device. 
         FIGS. 4A, 4B, 4C  are schematic cross-sectional views illustrating an example of operation of the fluid ejection device of  FIG. 2 . 
         FIGS. 5A, 5B, 5C  are schematic cross-sectional views illustrating an example of operation of the fluid ejection device of  FIG. 3 . 
         FIG. 6  is a flow diagram illustrating an example of a method of operating a fluid ejection device. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific examples in which the disclosure may be practiced. It is to be understood that other examples may be utilized and structural or logical changes may be made without departing from the scope of the present disclosure. 
       FIG. 1  illustrates one example of an inkjet printing system as an example of a fluid ejection device with fluid circulation, as disclosed herein. Inkjet printing system  100  includes a printhead assembly  102 , an ink supply assembly  104 , a mounting assembly  106 , a media transport assembly  108 , an electronic controller  110 , and at least one power supply  112  that provides power to the various electrical components of inkjet printing system  100 . Printhead assembly  102  includes at least one fluid ejection assembly  114  (printhead  114 ) that ejects drops of ink through a plurality of orifices or nozzles  116  toward a print medium  118  so as to print on print media  118 . 
     Print media  118  can be any type of suitable sheet or roll material, such as paper, card stock, transparencies, Mylar, and the like, and may include rigid or semi-rigid material, such as cardboard or other panels. Nozzles  116  are typically arranged in one or more columns or arrays such that properly sequenced ejection of ink from nozzles  116  causes characters, symbols, and/or other graphics or images to be printed on print media  118  as printhead assembly  102  and print media  118  are moved relative to each other. 
     Ink supply assembly  104  supplies fluid ink to printhead assembly  102  and, in one example, includes a reservoir  120  for storing ink such that ink flows from reservoir  120  to printhead assembly  102 . Ink supply assembly  104  and printhead assembly  102  can form a one-way ink delivery system or a recirculating ink delivery system. In a one-way ink delivery system, substantially all of the ink supplied to printhead assembly  102  is consumed during printing. In a recirculating ink delivery system, only a portion of the ink supplied to printhead assembly  102  is consumed during printing. Ink not consumed during printing is returned to ink supply assembly  104 . 
     In one example, printhead assembly  102  and ink supply assembly  104  are housed together in an inkjet cartridge or pen. In another example, ink supply assembly  104  is separate from printhead assembly  102  and supplies ink to printhead assembly  102  through an interface connection, such as a supply tube. In either example, reservoir  120  of ink supply assembly  104  may be removed, replaced, and/or refilled. Where printhead assembly  102  and ink supply assembly  104  are housed together in an inkjet cartridge, reservoir  120  includes a local reservoir located within the cartridge as well as a larger reservoir located separately from the cartridge. The separate, larger reservoir serves to refill the local reservoir. Accordingly, the separate, larger reservoir and/or the local reservoir may be removed, replaced, and/or refilled. 
     Mounting assembly  106  positions printhead assembly  102  relative to media transport assembly  108 , and media transport assembly  108  positions print media  118  relative to printhead assembly  102 . Thus, a print zone  122  is defined adjacent to nozzles  116  in an area between printhead assembly  102  and print media  118 . In one example, printhead assembly  102  is a scanning type printhead assembly. As such, mounting assembly  106  includes a carriage for moving printhead assembly  102  relative to media transport assembly  108  to scan print media  118 . In another example, printhead assembly  102  is a non-scanning type printhead assembly. As such, mounting assembly  106  fixes printhead assembly  102  at a prescribed position relative to media transport assembly  108 . Thus, media transport assembly  108  positions print media  118  relative to printhead assembly  102 . 
     Electronic controller  110  typically includes a processor, firmware, software, one or more memory components including volatile and non-volatile memory components, and other printer electronics for communicating with and controlling printhead assembly  102 , mounting assembly  106 , and media transport assembly  108 . Electronic controller  110  receives data  124  from a host system, such as a computer, and temporarily stores data  124  in a memory. Typically, data  124  is sent to inkjet printing system  100  along an electronic, infrared, optical, or other information transfer path. Data  124  represents, for example, a document and/or file to be printed. As such, data  124  forms a print job for inkjet printing system  100  and includes one or more print job commands and/or command parameters. 
     In one example, electronic controller  110  controls printhead assembly  102  for ejection of ink drops from nozzles  116 . Thus, electronic controller  110  defines a pattern of ejected ink drops which form characters, symbols, and/or other graphics or images on print media  118 . The pattern of ejected ink drops is determined by the print job commands and/or command parameters. 
     Printhead assembly  102  includes one or more printheads  114 . In one example, printhead assembly  102  is a wide-array or multi-head printhead assembly. In one implementation of a wide-array assembly, printhead assembly  102  includes a carrier that carries a plurality of printheads  114 , provides electrical communication between printheads  114  and electronic controller  110 , and provides fluidic communication between printheads  114  and ink supply assembly  104 . 
     In one example, inkjet printing system  100  is a drop-on-demand thermal inkjet printing system wherein printhead  114  is a thermal inkjet (TIJ) printhead. The thermal inkjet printhead implements a thermal resistor ejection element in an ink chamber to vaporize ink and create bubbles that force ink or other fluid drops out of nozzles  116 . In another example, inkjet printing system  100  is a drop-on-demand piezoelectric inkjet printing system wherein printhead  114  is a piezoelectric inkjet (PIJ) printhead that implements a piezoelectric material actuator as an ejection element to generate pressure pulses that force ink drops out of nozzles  116 . 
     In one example, electronic controller  110  includes a flow circulation module  126  stored in a memory of controller  110 . Flow circulation module  126  executes on electronic controller  110  (i.e., a processor of controller  110 ) to control the operation of one or more fluid actuators integrated as pump elements within printhead assembly  102  to control circulation of fluid within printhead assembly  102 . 
       FIG. 2  is a schematic plan view illustrating an example of a portion of a fluid ejection device  200 . Fluid ejection device  200  includes a first fluid ejection chamber  202  and a corresponding drop ejecting element  204  formed in, provided within, or communicated with fluid ejection chamber  202 , and a second fluid ejection chamber  203  and a corresponding drop ejecting element  205  formed in, provided within, or communicated with fluid ejection chamber  203 . 
     In one example, fluid ejection chambers  202  and  203  and drop ejecting elements  204  and  205  are formed on a substrate  206  which has a fluid (or ink) feed slot  208  formed therein such that fluid feed slot  208  provides a supply of fluid (or ink) to fluid ejection chambers  202  and  203  and drop ejecting elements  204  and  205 . Fluid feed slot  208  includes, for example, a hole, passage, opening, convex geometry or other fluidic architecture formed in or through substrate  206  by which or through which fluid is supplied to fluid ejection chambers  202  and  203 . Fluid feed slot  208  may include one (i.e., a single) or more than one (e.g., a series of) such hole, passage, opening, convex geometry or other fluidic architecture that communicates fluid with one (i.e., a single) or more than one fluid ejection chamber, and may be of circular, non-circular, or other shape. Substrate  206  may be formed, for example, of silicon, glass, or a stable polymer. 
     In one example, fluid ejection chambers  202  and  203  are formed in or defined by a barrier layer (not shown) provided on substrate  206 , such that fluid ejection chambers  202  and  203  each provide a “well” in the barrier layer. The barrier layer may be formed, for example, of a photoimageable epoxy resin, such as SU8. In one example, a nozzle or orifice layer (not shown) is formed or extended over the barrier layer such that nozzle openings or orifices  212  and  213  formed in the orifice layer communicate with respective fluid ejection chambers  202  and  203 . 
     In one example, as illustrated in  FIG. 2 , nozzle openings or orifices  212  and  213  are of the same size and shape. Nozzle openings or orifices  212  and  213  may be of a circular, non-circular, or other shape. Although illustrated as being of the same size, nozzle openings or orifices  212  and  213  may be of different sizes (for example, different diameters, effective diameters, or maximum dimensions). Although illustrated as being of the same shape, nozzle openings or orifices  212  and  213  may be of different shapes (for example, one circular, one non-circular). In addition, although illustrated as being of the same shape and same size, drop ejecting elements  204  and  205  and corresponding fluid ejection chambers  202  and  203  may be of different shapes, and may be of different sizes. 
     Drop ejecting elements  204  and  205  can be any device capable of ejecting fluid drops through corresponding nozzle openings or orifices  212  and  213 . Examples of drop ejecting elements  204  and  205  include thermal resistors or piezoelectric actuators. A thermal resistor, as an example of a drop ejecting element, may be formed on a surface of a substrate (substrate  206 ), and may include a thin-film stack including an oxide layer, a metal layer, and a passivation layer such that, when activated, heat from the thermal resistor vaporizes fluid in corresponding fluid ejection chamber  202  or  203 , thereby causing a bubble that ejects a drop of fluid through corresponding nozzle opening or orifice  212  or  213 . A piezoelectric actuator, as an example of a drop ejecting element, generally includes a piezoelectric material provided on a moveable membrane communicated with corresponding fluid ejection chamber  202  or  203  such that, when activated, the piezoelectric material causes deflection of the membrane relative to corresponding fluid ejection chamber  202  or  203 , thereby generating a pressure pulse that ejects a drop of fluid through corresponding nozzle opening or orifice  212  or  213 . 
     As illustrated in the example of  FIG. 2 , fluid ejection device  200  includes a fluid circulation path or channel  220  and a fluid circulating element  222  formed in, provided within, or communicated with fluid circulation channel  220 . Fluid circulation channel  220  is open to and communicates at one end  224  with fluid feed slot  208  and is open to and communicates at another end  226  with fluid ejection chamber  202  and fluid ejection chamber  203 . In one example, end  226  of fluid circulation channel  220  communicates with fluid ejection chamber  202  at an end  202   a  of fluid ejection chamber  202  and communicates with fluid ejection chamber  203  at an end  203   a  of fluid ejection chamber  203 . 
     In one example, fluid circulating element  222  is provided in, provided along, or communicated with fluid circulation channel  220  between end  224  and end  226 . More specifically, in one example, fluid circulating element  222  is provided in, provided along, or communicated with fluid circulation channel  220  adjacent end  224 . In one example, and as further described below, fluid circulating element  222  is laterally adjacent fluid ejection chamber  202 , and fluid ejection chamber  202  is laterally adjacent fluid ejection chamber  203 . In other examples, a position of fluid circulating element  222  may vary along fluid circulation channel  220 . 
     Fluid circulating element  222  forms or represents an actuator to pump or circulate (or recirculate) fluid through fluid circulation channel  220 . As such, fluid from fluid feed slot  208  circulates (or recirculates) through fluid circulation channel  220  and fluid ejection chambers  202  and  203  based on flow induced by fluid circulating element  222 . In one example, circulating (or recirculating) fluid through fluid ejection chambers  202  and  203  helps to reduce ink blockage and/or clogging in fluid ejection device  200 . 
     In the example illustrated in  FIG. 2 , drop ejecting elements  204  and  205  and fluid circulating element  222  are each thermal resistors. Each of the thermal resistors may include, for example, a single resistor, a split resistor, a comb resistor, or multiple resistors. A variety of other devices, however, can also be used to implement drop ejecting elements  204  and  205  and fluid circulating element  222  including, for example, a piezoelectric actuator, an electrostatic (MEMS) membrane, a mechanical/impact driven membrane, a voice coil, a magneto-strictive drive, and so on. 
     In one example, fluid circulation channel  220  includes a path or channel portion  230  communicated with fluid feed slot  208 , and a path or channel portion  232  communicated with fluid ejection chamber  202  and fluid ejection chamber  203 . More specifically, in one example, path or channel portion  232  includes a section or segment  2321  communicated with fluid ejection chamber  202  and a section for segment  2322  communicated with fluid ejection chamber  203 . As such, in one example, fluid in fluid circulation channel  220  circulates (or recirculates) between fluid feed slot  208  and fluid ejection chambers  202  and  203  through channel portion  230  and channel portion  232 , including through segments  2321  and  2322 . 
     In one example, fluid circulation channel  220  forms a fluid circulation (or recirculation) loop between fluid feed slot  208  and fluid ejection chambers  202  and  203 . For example, fluid from fluid feed slot  208  circulates (or recirculates) through fluid ejection chamber  202  and through fluid ejection chamber  203  back to fluid feed slot  208 . More specifically, fluid from fluid feed slot  208  circulates (or recirculates) through channel portion  230 , through channel portion  232 , including through segments  2321  and  2322 , and through fluid ejection chamber  202  and fluid ejection chamber  203  back to fluid feed slot  208 . 
     As illustrated in the example of  FIG. 2 , fluid circulating element  222  is formed in, provided within, or communicated with channel portion  230  of fluid circulation channel  220 . As such, in one example, channel portion  230  directs fluid in a first direction, as indicated by arrow  230   a , and channel portion  232  directs fluid in a second direction opposite the first direction, as indicated by arrow  232   b . More specifically, in one example, fluid circulation channel  220  directs fluid in a first direction (arrow  230   a ) between fluid feed slot  208  and fluid ejection chambers  202  and  203 , and directs fluid in a second direction (arrow  232   b ) opposite the first direction between fluid feed slot  208  and fluid ejection chambers  202  and  203 . Thus, in one example, fluid circulating element  222  creates an average or net fluid flow in fluid circulation channel  220  between fluid feed slot  208  and fluid ejection chambers  202  and  203 . 
     In one example, to provide fluid flow in the first direction indicated by arrow  230   a  and the second, opposite direction indicated by arrow  232   b , fluid circulation channel  220  includes a channel loop  231 . As such, in one example, fluid circulation channel  220  directs fluid in the first direction (arrow  230   a ) between fluid feed slot  208  and channel loop  231 , and in the second direction (arrow  232   b ) between channel loop  231  and fluid ejection chambers  202  and  203 . In one example, channel loop  231  includes a U-shaped portion of fluid circulation channel  220  such that a length (or portion) of channel portion  230  and a length (or portion) of channel portion  232  are spaced from and oriented substantially parallel with each other. 
     In one example, as illustrated in  FIG. 2 , a width of segment  2321  of channel portion  232  and a width of segment  2322  of channel portion  232  are each less than a width of channel portion  230 . Furthermore, a width of segment  2321  is less than a width of fluid ejection chamber  202 , and a width of segment  2322  is less than a width of fluid ejection chamber  203 . In other examples, channel portions  230  and  232  (including sections, segments or regions thereof) may be of different widths, and may be of different lengths. 
     As illustrated in the example of  FIG. 2 , an array or series of fluid ejection devices  200  is provided along a length of fluid feed slot  208 . More specifically, one fluid ejection device  200  including fluid circulation path  220  with corresponding fluid circulating element  222 , fluid ejection chamber  202  with corresponding drop ejecting element  204 , and fluid ejection chamber  203  with corresponding drop ejecting element  205  is laterally adjacent another fluid ejection device  200  including fluid circulation path  220  with corresponding fluid circulating element  222 , fluid ejection chamber  202  with corresponding drop ejecting element  204 , and fluid ejection chamber  203  with corresponding drop ejecting element  205  along one side of fluid feed slot  208 . In one example, fluid ejection devices  200  are arranged on opposite sides of fluid feed slot  208  such that corresponding nozzle openings or orifices  212  and  213  of fluid ejection devices  200  are arranged in parallel (substantially parallel) columns (or arrays). 
       FIG. 3  is a schematic plan view illustrating an example of a portion of a fluid ejection device  300 . Similar to fluid ejection device  200 , fluid ejection device  300  includes a first fluid ejection chamber  302  with a corresponding drop ejecting element  304 , and a second fluid ejection chamber  303  with a corresponding drop ejecting element  305 , such that nozzle openings or orifices  312  and  313  communicate with respective fluid ejection chambers  302  and  303 . In one example, nozzle openings or orifices  312  and  313  are each of the same shape and size. In addition, drop ejecting elements  304  and  305  are each of the same shape and size. Although illustrated as being of the same shape and same size, nozzle openings or orifices  312  and  313 , and drop ejecting elements  304  and  305 , may be of different shapes, and may be of different sizes. 
     Similar to fluid ejection device  200 , fluid ejection device  300  includes a fluid circulation path or channel  320  with a corresponding fluid circulating element  322 . Similar to fluid circulating element  222 , fluid circulating element  322  is provided in, provided along, or communicated with fluid circulation channel  320 , and forms or represents an actuator to pump or circulate (or recirculate) fluid through fluid circulation channel  320 . In one example, and as further described below, fluid circulating element  322  is laterally adjacent and between fluid ejection chamber  302  and fluid ejection chamber  303 . In other examples, a position of fluid circulating element  322  may vary along fluid circulation channel  320 . 
     In one example, and as illustrated in  FIG. 3 , fluid circulation channel  320  includes a path or channel portion  330  communicated with fluid feed slot  308 , a path or channel portion  332  communicated with fluid ejection chamber  302 , and a path or channel portion  334  communicated with fluid ejection chamber  303 . As such, in one example, fluid in fluid circulation channel  320  circulates (or recirculates) between fluid feed slot  308  and fluid ejection chambers  302  and  303  through channel portion  330  and respective channel portions  332  and  334 . 
     Similar to fluid circulation channel  220  of fluid ejection device  200 , fluid circulation channel  320  of fluid ejection device  300  forms a fluid circulation (or recirculation) loop between fluid feed slot  308  and fluid ejection chambers  302  and  303 . For example, fluid from fluid feed slot  308  circulates (or recirculates) through fluid ejection chamber  302  and through fluid ejection chamber  303  back to fluid feed slot  308 . More specifically, fluid from fluid feed slot  308  circulates (or recirculates) through channel portion  330 , through channel portion  332  and channel portion  334 , and through fluid ejection chamber  302  and fluid ejection chamber  303  back to fluid feed slot  308 . 
     In addition, and similar to fluid circulating element  222  of fluid ejection device  200 , fluid circulating element  322  is formed in, provided within, or communicated with channel portion  330  of fluid circulation channel  320 . As such, in one example, channel portion  330  directs fluid in a first direction, as indicated by arrow  330   a , and channel portion  332  and channel portion  334  each direct fluid in a second direction opposite the first direction, as indicated by arrow  332   b  and arrow  334   b . Thus, in one example, fluid circulating element  322  creates an average or net fluid flow in fluid circulation channel  320  between fluid feed slot  308  and fluid ejection chambers  302  and  303 . 
     In one example, to provide fluid flow in the first direction indicated by arrow  330   a , and the second, opposite direction indicated by arrow  332   b  and arrow  334   b , fluid circulation channel  320  includes a channel loop  331  and a channel loop  333 . As such, in one example, fluid circulation channel  320  directs fluid in the first direction (arrow  330   a ) between fluid feed slot  308  and channel loops  331  and  333 , and in the second direction (arrow  332   b  and arrow  334   b ) between channel loop  331  and fluid ejection chamber  302  and between channel loop  333  end fluid ejection chamber  303 . In one example, channel loop  331  includes a U-shaped portion of fluid circulation channel  320 , and channel loop  333  includes a U-shaped portion of fluid circulation channel  320 . 
     As illustrated in the example of  FIG. 3 , an array or series of fluid ejection devices  300  is provided along a length of fluid feed slot  308 . More specifically, one fluid ejection device  300  including fluid circulation path  320  with corresponding fluid circulating element  322 , fluid ejection chamber  302  with corresponding drop ejecting element  304 , and fluid ejection chamber  303  with corresponding drop ejecting element  305  is laterally adjacent another fluid ejection device  300  including fluid circulation path  320  with corresponding fluid circulating element  322 , fluid ejection chamber  302  with corresponding drop ejecting element  304 , and fluid ejection chamber  303  with corresponding drop ejecting element  305  along one side of fluid feed slot  308 . In one example, fluid ejection devices  300  are arranged on opposite sides of fluid feed slot  308  such that corresponding nozzle openings or orifices  312  and  313  of fluid ejection devices  300  are arranged in parallel (substantially parallel) columns (or arrays). 
     As illustrated in the example of  FIG. 2 , fluid circulating element  222  is laterally adjacent fluid ejection chamber  202 , and fluid ejection chamber  202  is laterally adjacent fluid ejection chamber  203 . More specifically, fluid circulating element  222  is positioned to one side of fluid ejection chamber  202  along fluid feed slot  208 , and fluid ejection chamber  202  is positioned to one side of fluid ejection chamber  203  such that fluid ejection chamber  202  is positioned between fluid circulating element  222  and fluid ejection chamber  203  along fluid feed slot  208 . In addition, as illustrated in the example of  FIG. 3 , fluid circulating element  322  is laterally adjacent fluid ejection chamber  302  and laterally adjacent fluid ejection chamber  303 . More specifically, fluid circulating element  322  is positioned to one side of fluid ejection chamber  302  and positioned to one side of fluid ejection chamber  303  such that fluid circulating element  322  is positioned between fluid ejection chamber  302  and fluid ejection chamber  303  along fluid feed slot  308 . 
     As such, and as illustrated in the example of  FIG. 2 , fluid ejection chamber  202  and fluid ejection chamber  203  of fluid ejection device  200  are laterally adjacent to each other, and as illustrated in the example of  FIG. 3 , fluid ejection chamber  303  of one fluid ejection device  300  and fluid ejection chamber  302  of an adjacent fluid ejection device  300  are laterally adjacent to each other. Accordingly, drop ejecting element  204  and drop ejecting element  205  of fluid ejection device  200  may be operated separately or individually at different moments of time to produce drops of the same size (weight), or operated substantially simultaneously to produce a combined drop of a combined size (weight). In addition, drop ejecting element  304  of one fluid ejection device  300  and drop ejecting element  305  of an adjacent fluid ejection device  300  may be operated separately or individually at different moments of time to produce drops of the same size (weight), or operated substantially simultaneously to produce a combined drop of a combined size (weight). 
     More specifically, in one example, as illustrated in  FIGS. 4A, 4B, 4C , laterally adjacent drop ejecting elements  204  and  205  of fluid ejection device  200  (with laterally adjacent fluid circulating element  222  in fluid circulation channel  220 ) are operated substantially simultaneously to produce a combined drop of a combined size (weight). For example, as illustrated in  FIG. 4A , substantially simultaneous ejection of fluid from fluid ejection chambers  202  and  203  (through respective nozzles  212  and  213 ) results in individual drops  252  and  253  (with respective tails  254  and  255 ) being formed. Subsequently, as illustrated in  FIG. 4B , individual drops  252  and  253  begin to merge (and tails  254  and  255  break off). Thereafter, as illustrated in  FIG. 4C , a single, merged drop  256  is formed (with tails  254  and  255  dissipating). 
     In addition, in one example, as illustrated in  FIGS. 5A, 5B, 5C , drop ejecting element  305  of one fluid ejection device  300  (with laterally adjacent fluid circulating element  322  in fluid circulation channel  320 ) and laterally adjacent drop ejecting element  304  of an adjacent fluid ejection device  300  (with laterally adjacent fluid circulating element  322  in fluid circulation channel  320 ) are operated substantially simultaneously to produce a combined drop of a combined size (weight). For example, as illustrated in  FIG. 5A , substantially simultaneous ejection of fluid from fluid ejection chambers  303  and  302  (through respective nozzles  313  and  312 ) results in individual drops  353  and  352  (with respective tails  355  and  354 ) being formed. Subsequently, as illustrated in  FIG. 5B , individual drops  353  and  352  begin to merge (and tails  355  and  354  break off). Thereafter, as illustrated in  FIG. 5C , a single, merged drop  356  is formed (with tails  355  and  354  dissipating). 
       FIG. 6  is a flow diagram illustrating an example of a method  600  of operating a fluid ejection device, such as fluid ejection device  200 ,  300  as illustrated in the respective examples of  FIGS. 2, 3  and  FIGS. 4A, 4B, 4C and 5A, 5B, 5C . 
     At  602 , method  600  includes communicating two laterally adjacent fluid ejection chambers with a fluid slot, with each of the two laterally adjacent fluid ejection chambers including a drop ejecting element, such as fluid ejection chambers  202 / 203 ,  303 / 302  including respective drop ejecting elements  204 / 205 ,  305 / 304  communicating with respective fluid feed slots  208 ,  308 . 
     At  604 , method  600  includes circulating fluid from the fluid slot to the two laterally adjacent fluid ejection chambers through a fluid circulation path, with the fluid circulation path including a fluid circulating element, and the fluid circulating element positioned laterally adjacent at least one of the two laterally adjacent fluid ejection chambers, such as fluid from respective fluid feed slots  208 ,  308  circulating to respective fluid ejection chambers  202 / 203 ,  303 / 302  through respective fluid circulation paths or channels  220 ,  320  including respective fluid circulating elements  222 ,  322 . 
     At  606 , method  600  includes substantially simultaneously ejecting drops of fluid from the two laterally adjacent fluid ejection chambers, wherein the drops of fluid are to coalesce during flight, such as individual drops  252 / 253 ,  353 / 352  ejecting from respective fluid ejection chambers  202 / 203 ,  303 / 302  and combining as respective merged drops  256 ,  356 . 
     Although illustrated and described as separate and/or sequential steps, the method of forming the fluid ejection device may include a different order or sequence of steps, and may combine one or more steps or perform one or more steps concurrently, partially or wholly. 
     Although specific examples have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific examples shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific examples discussed herein.