Patent Publication Number: US-6902253-B2

Title: Fluid ejection

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This is a continuation of Application No. 10/218,935, filed on Aug. 14, 2002, now U.S. Pat. No. 6,729,715 issued May 4, 2004, which is incorporated by reference herein. 

   BACKGROUND OF THE INVENTION 
   A thermal inkjet printer typically includes one or more reciprocating print cartridges in which small drops of ink are formed and ejected towards a medium upon which it is desired to place alphanumeric characters, graphics, or images. Such cartridges include a printhead having an orifice plate that has a plurality of small nozzles through which the ink drops are ejected. Adjacent to the nozzles are ink firing chambers, in which ink resides prior to ejection through the nozzle. Ink is supplied to the ink-firing chambers through ink channels that are in fluid communication with an ink supply, which may be contained in a reservoir portion of the print cartridge or in a separate ink container spaced apart from the printhead. 
   Ejection of an ink drop through a nozzle employed in a thermal inkjet printer is accomplished by quickly heating a volume of ink within the adjacent ink firing chamber by applying an energizing electrical pulse to a heater resistor positioned in the ink firing chamber. The electrical pulse induces a temperature rise in the heater resistor, which heat energy is transferred to the ink to produce an ink vapor bubble. The rapid expansion of the ink vapor bubble forces ink through the nozzle. Once ink is ejected, the ink-firing chamber is refilled with ink from the ink channel and ink supply. The energy required to eject a drop of a given volume is referred to as turn-on energy. The turn-on energy is an amount of energy sufficient to form a vapor bubble having sufficient size to eject a predetermined amount of ink through the printhead nozzle. 
   The printhead includes a substrate, which is a conventional silicon wafer upon which has been grown a dielectric layer, such as silicon dioxide. The ink drops are ejected from small ink chambers carried on the substrate. The chambers (designated “firing chambers”) are formed in a component known as a barrier layer. The barrier layer is made from photosensitive material that is laminated onto the printhead substrate and then exposed, developed, and cured in a configuration that defines the firing chambers. 
   The heater resistor for ejecting a drop is a heat transducer, such as a thin-film resistor. The resistor is carried on the printhead substrate. The resistor is covered with suitable passivation and other layers and connected to conductive layers that transmit current pulses for heating the resistors. One resistor is located in each of the firing chambers. 
   In a typical printhead, the orifice plate covers most of the printhead. The orifice plate may be electroformed with nickel and coated with a precious metal for corrosion resistance. Alternatively, the orifice plate is made from a laser-ablated polyimide material. The orifice plate is bonded to the barrier layer and aligned so that each firing chamber is continuous with one of the orifices. 
   To refill the firing chambers after each drop is ejected, each chamber is continuous with an ink channel that is formed in the barrier layer. The channels extend toward an elongated ink feed slot that is formed through the substrate. The ink feed slot may be located in the center of the printhead with firing chambers located on opposite long sides of the feed slot. The slot is made after the ink-ejecting components (except for the orifice plate) are formed on the substrate. 
   The above-described components (barrier layer, resistors, etc) for ejecting the ink drops are mounted to the front side of the printhead substrate. The back side of the printhead is mounted to the body of the ink cartridge so that the ink slot is in fluid communication with an opening to the reservoir. Thus, refill ink flows through the ink feed slot from the back side of the substrate toward the front of the substrate and then across the front side through the channels (and beneath the orifice plate) to refill the chambers. 
   Significant effort has been expended in improving print quality. Since the image output of an inkjet printer is formed of individual ink drops, the image quality and contrasts, as well as variations in image hue and lightness, are dependent on ink drop volume and ink drop distribution on the printed medium. It is known that drop volumes vary with printhead substrate temperature because the properties that control them vary with temperature: the viscosity of the ink itself and the amount of ink vaporized by a heater resistor when driven by a given electrical printing pulse. One method of controlling drop volume is to vary the electrical pulse width supplied to the heater resistor. However, inkjet ink is chemically reactive, and prolonging exposure of the heater resistor and its electrical connections to the ink may result in a chemical attack upon the heater resistor and deterioration in the long-term performance of the heater resistor. Another method of controlling drop volume is to construct a protective layer having a thickness gradient over the heater resistor. However, varying the thickness of the protective layer is subject to the tolerances of the semiconductor manufacturing process and to the tolerances in the heat conduction gradients of the protective materials. 
   SUMMARY OF THE INVENTION 
   An arrangement or ejecting fluid includes at least one inner driver adapted to independently create a first drive bubble for ejecting a first drop of fluid, and at least one outer driver generally surrounding the inner driver, the inner driver and the outer driver together being adapted to create a second drive bubble for ejecting a second drop of fluid, the second drop of fluid being larger than the first drop of fluid, wherein the inner driver and the outer driver are electrically connected. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings illustrate embodiments of the present invention and together with the description serve to explain certain principles of the invention. Other embodiments of the present invention will be readily appreciated with reference to the drawings and the description, in which like reference numerals designate like parts and in which: 
       FIG. 1  is a block diagram of an inkjet printer according to an embodiment of the invention; 
       FIG. 2  is a perspective cutaway view of a portion of a printhead, showing components for ejecting ink, according to an embodiment of the invention; 
       FIG. 3  is a plan view of a resistor arrangement according to an embodiment of the invention; 
       FIG. 4  is a circuit diagram according to an embodiment of the invention; 
       FIG. 5  is a circuit diagram according to an embodiment of the invention; 
       FIG. 6  is a perspective view of a portion of a printhead, according to an embodiment of the invention; 
       FIG. 7  is a top view of the  FIG. 6  printhead in an alternative configuration, according to an embodiment of the invention; 
       FIG. 8  is a side cross-sectional view showing formation of a large drive bubble according to an embodiment of the invention; 
       FIG. 9  is a side cross-sectional view showing formation of a small drive bubble according to an embodiment of the invention; and 
       FIG. 10  is a perspective view of a print cartridge to which an inkjet printhead is attached, according to an embodiment of the invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  is a block diagram of inkjet printer  100  in accordance with an embodiment of the invention. Inkjet printer  100  includes power supply  102 , drop-firing controller  104  that includes a processor, for example a microcontroller or a microprocessor, platen motor  106 , at least one roller  108  coupled to platen motor  106  by roller bar  110 , memory  112 , position controller  114  coupled to memory  112  and platen motor  106 , and carriage motor  116  coupled to position controller  114 , all of which are optionally under the control of computer  140  that optionally includes a microprocessor. Inkjet printer  100  further includes carriage  118  coupled to power supply  102  and drop-firing controller  104 , which carriage  118  includes at least one print cartridge  122 . Carriage  118  is mounted on slide bar  120 , allowing carriage  118  to be reciprocated or scanned back and forth across print media  124 , such as paper, by carriage motor  116 . The scan axis, X, is indicated by arrow  130 . Platen motor  106  and carriage motor  116  are under the control of position controller  114 , which controller  114  optionally is implemented in a conventional hardware configuration and provided operating instructions from memory  112 . As carriage  118  scans, ink drops are selectively ejected from each print cartridge  122  onto media  124  in predetermined print swath patterns, forming images or alphanumeric characters using dot matrix manipulation. The ink drop trajectory axis, Z, is indicated by arrow  132 . The dot matrix manipulation is determined by computer  140 , which computer  140  transmits instructions to drop-firing controller  104  and power supply  102 . When a swath of print has been completed, media  124  is advanced an appropriate distance along the print media axis, Y, indicated by arrow  134 , by platen motor  106  and roller  108  in preparation for the printing of the next swath. 
   With reference to  FIG. 2 , components of printhead  150  according to an embodiment of the invention are formed on silicon wafer  152  upon which has been grown a dielectric layer, such as silicon dioxide layer  154 . The term substrate is optionally considered as including the wafer and dielectric layers. A number of printhead substrates optionally are made simultaneously on a single wafer, the dies of which each carry individual printheads. 
   Ink drops are ejected from small ink chambers carried on printhead substrate  155 . The chambers (designated “firing chambers”  156 ) are formed in barrier layer  158 , which is made from photosensitive material that is laminated onto printhead substrate  155  and then exposed, developed, and cured in a configuration that defines the firing chambers. The left portion of barrier layer  158  as illustrated in  FIG. 2  is broken away for clarity. 
   A mechanism for ejecting an ink drop from firing chamber  156  includes a plurality of drivers or heaters such as thin-film resistors  160 ,  161 . Resistors  160 ,  161  are carried on printhead substrate or base  155 . Resistors  160 ,  161  are covered with suitable passivation and other layers and are connected to conductive layers that transmit current pulses for heating the resistors. One set of resistors  160 ,  161  is located in each of the firing chambers  156 . Additional details regarding resistors  160 ,  161  are set forth below. 
   Ink drops are ejected through orifices  162  (one orifice is shown cut away in  FIG. 2 ) that are formed in orifice plate  164  that covers most of the printhead. Orifice plate  164  optionally is made from a laser-ablated polyimide material. Orifice plate  164  is bonded to barrier layer  158  and aligned so that each firing chamber  156  is continuous with one of the orifices  162  from which the ink drops are ejected. 
   Firing chambers  156  are refilled with ink after each drop is ejected. In this regard, each chamber is continuous with channel  166  that is formed in barrier layer  158 . Channels  166  extend toward elongated ink feed slot  170  that is formed through substrate  155 . Ink feed slot  170  optionally is centered between rows of firing chambers  156  that are located on opposite long sides of ink feed slot  170 . Slot  170  is made after the ink-ejecting components (except for orifice plate  164 ) are formed on substrate  155 , according to embodiments of the invention. 
   The above-described components (e.g. barrier layer  158 , resistors  160 ,  161 , etc.) for ejecting ink drops are mounted to front side  172  of substrate  155 . The back side of the printhead is mounted to the body of an ink cartridge so that ink slot  170  is in fluid communication with openings to a reservoir in the cartridge. Thus, refill ink flows through ink feed slot  170  from the back side of the printhead toward front side  172  of substrate  155 . The ink then flows across front side  172  (that is, to and through channels  166  and beneath orifice plate  164 ) to fill chambers  156 . 
   The portion of front side  172  of substrate  155  between slot  170  and ink channels  166  is shelf  176 . The portions of barrier layer  158  nearest ink slot  170  are shaped into lead-in lobes  178  that generally serve to separate one channel  166  from an adjacent channel. The left lobe  178  as illustrated in  FIG. 2  is partially broken away for clarity. Lobes  178  define surfaces that direct ink flowing from slot  170  across shelf  176  into channels  166 . Specific examples of lead-in lobes  178  and channel shapes are shown in the figures, but other lobes and shapes will be readily apparent to those of ordinary skill upon reading this disclosure. 
     FIG. 3  is a top plan view of inner and outer heater resistors  160 ,  161  in accordance with an embodiment of the invention. Orifice plate  164  and barrier layer  158  have been deleted for clarity here. Resistors  160 ,  161  are realized as thin-film, generally planar structures together defining a generally square geometric figure pattern. Other geometric figures, e.g. trapezoids, polygons and other useful geometric figures are optionally also used instead of or in addition to the illustrated generally square pattern. Resistors  160 ,  161  in the  FIG. 3  embodiment are segmented heater resistors including multiple inner heater resistor segments  200 ,  202  generally surrounded by multiple outer heater resistor segments  204 ,  206 ,  208 ,  210 . Multiple electrical conductors, e.g. thin-film metallic conductors, optionally are electrically and physically coupled to one or more of heater resistor segments  200 - 210 . Alternate fabrication techniques include resistor segments formed using vapor deposition, sputtering, or other techniques. 
   By selectively applying a voltage to predetermined heater resistors  160 ,  161 , current flow is induced in all or selected ones of the heater resistor segments. Inasmuch as current flow causes a temperature increase in the heater resistor segments, at least a portion of which heat is transferred to the ink or other fluid in firing chamber  156 , varying amounts of heat are transferred to the ink by varying the segments or heater resistors that are energized and hence heated. The dynamic selection of resistors  160 ,  161  and/or resistor segments  200 - 210  provides for the dynamic variation of an expelled ink drop volume as printer  100  is printing, which is highly desirable to obtain higher print quality. The dynamic selection and variation in ink drop volume also increases the number of shading combinations that are achievable, as will be described. 
     FIG. 4  is an electrical schematic diagram showing heater resistors  160 ,  161  connected in parallel and showing associated switching devices  250 ,  252 , in accordance with an embodiment of the invention. Switching device  250 ,  252  selectively apply a voltage to one or more of resistors  160 ,  161 . As shown in  FIG. 4 , resistor  160  is coupled to first switching device  250 , and resistor  161  is coupled to second switching device  252 . Each switching device  250 ,  252  includes a field effect transistor (FET), according to embodiments of the invention. Those of ordinary skill in the art will realize that many devices are optionally used to perform the switching functions of switching devices  250 ,  252 , such as bipolar junction transistors, MOSFETs, other field effect devices, and other devices, without departing from the spirit and scope of the present invention. 
   Switching device  250  is coupled to drop-firing controller  104  or another controller as well as to one or more of resistors  160 . Switching device  252  is coupled to drop-firing controller  104  or another controller as well as to one or more of resistors  161 . Switching devices  250 ,  252  are also connected to primitive line  254  and address line  256 , as illustrated, and to an appropriate power supply  102  or another power supply. As those of ordinary skill in the art will appreciate, specifying an address line and a primitive line uniquely identifies one particular set of resistors  160 ,  161 . Switching devices  250 ,  252  optionally are included in the circuitry of inkjet cartridge  122 . Alternatively, switching devices  250 ,  252  optionally are included in semiconductor substrate  155 , in the circuitry of carriage  118 , external to carriage  118  and in other circuitry of inkjet printer  100 , or elsewhere. 
   Each switching device  250 ,  252  is activated in response to the receipt of a control signal, for example a gate voltage that is equal to or greater than the turn-on voltage for the switching device, from drop-firing controller  104  or other controller or processor. In brief, when each switching device  250 ,  252  is activated, a voltage is sourced by power supply  102 , via the respective switching device, to each respective resistor  160 ,  161  via appropriate conductors or other connection devices. The application of a voltage in turn induces an electric current flow and the dissipation of thermal energy in each selected resistor  160 ,  161 , more specifically in each of the heater resistor segments  200 - 210  that are coupled to the conductor(s) activated by the switching devices. According to embodiments of the invention, the current flows through each heater resistor segment  200 ,  202  of resistor  160  and/or through each heater resistor segment  204 ,  206 ,  208 ,  210  of resistor  162 . At least a portion of the energy dissipated in each segment  200 - 210  is transferred to the ink or other fluid stored in firing chamber  156  to produce a drive bubble and the expulsion of fluid from chamber  156 . The activation of one or both switching devices  250 ,  252  results in the selective application of a voltage to, and induction of an electrical current flow in, heater resistor segments  200 - 210  and, ultimately, a controlled variation in the volume of ink expelled from chamber  156 . 
   According to embodiments of the invention, current flow through segments  200 ,  202  of heater resistor  160  as enabled by switching device  250  results in the nucleation of a drive bubble over resistor  160 . The drive bubble expands and forces an ink drop from chamber  156 . Current flow through all segments  200 ,  202 ,  204 ,  206 ,  208 ,  210  of heater resistors  160  and  161 , as enabled by switching devices  250 ,  252 , results in the nucleation of a drive bubble over both resistors  160 ,  161 . This drive bubble, which is larger than the drive bubble produced by activation of just switching device  250 , expands and forces a larger ink drop from chamber  156 . Current flow through segments  204 ,  206 ,  208 ,  210  of heater resistor  161  as enabled by switching device  252  results in the nucleation of a drive bubble over resistor  161 . By dynamically selecting activation of switching device  250 , switching device  252  or both switching devices  250 ,  252 , the size of the drop expelled by chamber  156  is dynamically adjusted. This dynamic adjustment allows for an additional level of control of variations of shading, hue and/or lightness, for example, of characters or print images on print media, without necessarily changing any electrical pulse widths or varying the thickness of the protective layer. Image quality is improved. 
   In terms of shading capabilities, the ability to provide two different drop sizes dramatically increases the number of available shadings. Assuming for example that up to five drops of ink can be fired, that the order of the drops is relevant, and that only one drop size is used by color, the following table indicates the significant increase in the number of color/shading possibilities that arise from having two drop sizes vs. just one drop size, without necessarily increasing dye loads or requiring additional drops. 
   
     
       
         
             
          
             
                 
             
             
               Five-ink color shadings 
             
          
         
         
             
             
          
             
                 
               Color Possibilities 
             
          
         
         
             
             
             
          
             
                 
               One Drop Size 
               Two Drop sizes 
             
             
                 
                 
             
          
         
         
             
             
             
             
          
             
                 
               5 Drops used 
               120 
               3840 
             
             
                 
               4 Drops used 
               120 
               1920 
             
             
                 
               3 Drops used 
               60 
               480 
             
             
                 
               2 Drops used 
               20 
               80 
             
             
                 
               1 Drop used 
               5 
               10 
             
             
                 
               Total Possible 
               325 
               6330 
             
             
                 
               combinations 
             
             
                 
                 
             
          
         
       
     
   
   In addition to selecting which of resistors  160 ,  161  to activate, embodiments of the invention provide ways to vary the size of firing chamber  156 , channel  166 , and/or other components, optionally in connection with the size of drop to be ejected. Particular embodiments control barrier  158  to adjust the shape and/or size of firing chamber  156  and/or channel  166 , for example. To that end, barrier  158  optionally is formed of a shape-change material according to this embodiment, e.g. a piezoelectric material that changes shape upon application of electric current. Drop-firing controller  104  controls application of electric current to barrier  158  to change its shape. More specifically, according to one example, application of electric current to barrier  158  causes barrier  158  to change the shape of firing chamber  156 . The change in shape of firing chamber is correlated, according to specific embodiments, to the size of the drop being fired, i.e. to the activation of switching devices  250  and/or  252  and resistors  160  and/or  161 . Embodiments of the invention provide a firing chamber size that is proportional to the size of the resistor(s) being fired. The bigger the resistor area being fired, the larger the size of firing chamber  156 . Thus, if just inner resistor  160  is being activated, a smaller firing chamber  156  is used, and if both inner resistor  160  and outer resistor  161  are being activated, a larger firing chamber  156  is used. Using a piezoelectric material allows the size of the firing chamber to be modified using an electrical pulse. Additionally, as will be described, embodiments of the invention change the size of channel  166  as well. 
   More particularly, the example of  FIG. 5  shows switching device  252  electrically connected to NOT gate  280 , which itself is electrically connected to barrier  158 . Accordingly, when switching device  252  is activated to energize outer resistor  161 , barrier  158  is not activated to contract and/or reduce the size of e.g. firing chamber  156 . When only switching device  250  is activated to energize only inner resistor  160 , on the other hand, switching device  252  is not activated. Barrier  158  therefore is activated, and reduces the size of e.g. firing chamber  156 . As will be described, barrier  158  optionally is activated to cover outer resistor  161  when outer resistor  161  is not being fired. The smaller corresponding shape of firing chamber  156  is better suited to the relatively small drop being created and fired by inner resistor  160 . Other control circuitry and/or logic control elements are contemplated as well, for example control by separate controllers or circuit components, other control components for activating barrier  158  instead of NOT gate  280 , etc. 
     FIGS. 6-7  are schematic diagrams showing a change in the size of firing chamber  156 , according to embodiments of the invention. In  FIG. 6 , barrier  158  defines firing chamber  156  such that both resistors  160 ,  161  are exposed. In  FIG. 7 , on the other hand, barrier  158  has decreased the size of firing chamber  156  such that only inner resistor  160  is exposed. Outer resistor  161  is covered. Thus, for a larger drive bubble and larger drop ejection, firing chamber  156  is larger (FIG.  6 ). For a smaller drive bubble and smaller drop ejection, firing chamber  156  is smaller (FIG.  7 ). Chamber size control according to embodiments of the invention generally tends to minimize problems associated with firing a relatively small drop from a relatively large chamber, because the size of the chamber is reduced to better fit the drop. Better drop-volume control and better drop-velocity control are achieved. 
     FIGS. 6-7  also illustrate that changing the shape of barrier  158  optionally changes the size of channel  166 . Channel  166  is wider when barrier  158  is not activated, as in  FIG. 6 , and is narrower when barrier  158  is activated, as in  FIG. 7 , according to this particular embodiment. Barrier  158  optionally is constructed and/or controlled to change the size of channel  166  either independently from or in conjunction with the changing size of firing chamber  156 . Controlling the size of channel  166 , especially at “pinch point”  290  thereof, effectively controls the fluid refill rate of chamber  156 . Improving or adjusting the refill rate of chamber  156  at desired times presents a number of advantages, according to certain embodiments of the invention. 
     FIGS. 8-9  are side cross-sectional views showing formation of large and small drive bubbles according to embodiments of the invention. In  FIG. 8 , chamber side wall  292  formed by barrier  158  is to the outside of resistor segments  206 ,  210  of outer resistor  161 . Both inner and outer resistors  160 ,  161  are activated such that large drive bubble  294  is formed across them. In  FIG. 9 , chamber side wall  292  formed by barrier  158  is to the inside of resistor segments  206 ,  210  of outer resistor  161 , but still is to the outside of resistor segments  200 ,  202  of inner resistor  160 . Just inner resistor  160  is activated, such that small drive bubble  296  is formed across segments  200 ,  202 . For clarity, orifice plate  164  is not illustrated in  FIGS. 8-9 , and  FIGS. 8-9  are not necessarily to scale. 
   Variations in the illustrated resistor layout are contemplated, according to embodiments of the invention. For example, segments  204 ,  206 ,  208  and  210  of outer resistor  161  optionally extend beyond the corners of segments  200 ,  202  of inner resistor  160 , as shown in  FIG. 1 , or remain within or adjacent the corners, as illustrated in FIG.  3 . The dimensions of the resistors illustrated in the drawings are not necessarily to scale; the relative sizes of the segments of resistors  160 ,  161  optionally are different than those shown. For example, the ratio of outer resistor area to inner resistor area depicted in e.g.  FIG. 3  optionally is smaller or larger than that illustrated. A smaller outer resistor  161  reduces the distance that barrier  158  traverses upon changing the size of firing chamber  156 . Additionally, resistors  160 ,  161  need not be segmented, according to embodiments of the invention, but can be unsegmented. Resistor sizes and/or values optionally are chosen in connection with the size of drive bubble desired, firing characteristics of the drops, size changes achieved with firing chamber  156 , and/or other factors, to e.g. reduce instabilities in firing and to improve fluid-ejection quality. Too large of a gap between barrier  158  and an associated resistor such as resistor  160  and/or  161  tends to increase the difficulty in maintaining acceptable print quality, for example. 
   Thus, embodiments of the invention provide a printing apparatus, comprising printhead substrate  155 , a plurality of heaters  160 ,  161  supported by printhead substrate  155  for firing drops of printing fluid, barrier  158  supported by printhead substrate  155  and defining a plurality of firing chambers  156 , disposed over heaters  160 ,  161 , barrier  158  being adapted to change shape, at least one controller  104  for activating the plurality of heaters  160 ,  161  and for controlling the shape of barrier  158  in association with activation of heaters  160 ,  161 , and orifice plate  164  defining a plurality of orifices  162  over firing chambers  156 , the drops being fired through orifices  162 . The barrier optionally is adapted to change the size of firing chambers  156  in association with activation of heaters  160 ,  161 . Barrier  158  also defines channels  166  for feeding printing fluid to firing chambers  156 , and barrier  158  optionally is adapted to change the size of channels  166  in association with activation of heaters  160 ,  161  to change refill rates of firing chambers  156 . Barrier  158  is formed of a shape-change material, according to specific embodiments, such as a piezoelectric material. Each heater  160 ,  161  comprises a plurality of individually controllable heating elements  200 - 210 . Controller  104  is adapted to control the size of firing chambers  156  based on control of the individually controllable heating elements. 
   Embodiments of the invention also provide a fluid ejection device, comprising base  155  and layer  158  supported by base  155 , the layer defining opening  156  and/or  166  of variable size for containing fluid to be ejected from the fluid ejection device. Fluid driver  160 ,  161  is supported by base  155  and is adapted to eject fluid drops of different sizes from the device. At least one controller  104  is operably coupled with layer  158  to adjust the size of the opening and is operably coupled with the fluid driver to adjust the size of the ejected drops. The opening defines firing chamber  156  for ejecting the fluid and/or channel  166  for feeding fluid into firing chamber  156  for ejection. 
   A method of controlling printhead  150 , according to an embodiment of the invention, includes creating a drive bubble in firing chamber  156  to eject a drop of printing fluid from printhead  150 , and changing the size of firing chamber  156  depending on the size of the drop and/or changing the size of refill channel  166  for the firing chamber  156 . A shape-change material, such as a piezoelectric material, in the form of barrier  158  or in barrier  158  is used to change the size of firing chamber  156 . According to more specific embodiments, the method includes creating a first drive bubble in firing chamber  156  with at least one first resistor  160 , creating a second drive bubble in firing chamber  156  with first resistor  160  and at least one second resistor  161 , the second drive bubble being larger than the first drive bubble, and changing the size of firing chamber  156  depending on whether the first drive bubble or the second drive bubble is created. 
   Embodiments of the invention also include one or more computer-readable media having stored thereon a computer program that, when executed by a processor, causes printhead control, printing, fluid ejection and/or the other features and capabilities described herein. 
     FIG. 10  is a perspective view of print cartridge body  122 . A lower side of substrate  155  includes structure or a surface for attachment to headland area  302  of print cartridge body  122 . More particularly, according to one example, headland area  302  of print cartridge body  122  includes flanges  304  that surround ink slots  306  and e.g. match an interface pattern on the lower side of substrate  155 . An adhesive bead is formed on flanges  304  of the headland area  302 , for example, and printhead  150  is then pressed onto headland area  302  with the interface pattern in alignment with flanges  304 . In this manner, ink slots  306  in print cartridge body  122 , the adhesive, and ink feed slots  170  in printhead  150  effectively form respective conduits for transporting ink from reservoirs in print cartridge body  122  to ink channels  166  of printhead  150 . 
   Although the present invention has been described with reference to certain embodiments, those skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. For example, the drawings associated with this disclosure are not necessarily to scale. Other shapes of chambers, heaters, heating elements and other components described herein are contemplated. Other applications besides printing (and fluids besides ink or other printing fluid) are contemplated. Finally, it should be understood that directional terminology, such as upper, lower, left, right, over, under, above, and below is used for purposes of illustration and description only, and is not intended necessarily to be limiting. Other aspects of the invention will be apparent to those of ordinary skill upon reading this disclosure.