Patent Publication Number: US-9902166-B2

Title: Maintenance valve for fluid ejection head

Description:
RELATED APPLICATION 
     This application is a Continuation of U.S. patent application Ser. No. 14/427,267, filed Mar. 10, 2015 which is a 371 National Stage Application of International Patent Application Serial No. PCT/IB2013/002980, filed Sep. 12, 2013 which claims the benefit of Provisional Application Ser. No. 61/700,013, filed Sep. 12, 2012, the contents of which are incorporated herein by reference in their entirety. 
    
    
     FIELD 
     The present invention is directed to apparatuses and methods for controlling fluid flow through ejection chips. 
     SUMMARY 
     According to an exemplary embodiment of the present invention, an ejection chip comprises a substrate, a flow feature layer, a nozzle plate, and one or more valves. The substrate includes one or more fluid channels and one or more fluid ports each in communication with at least one of the one or more fluid channels. The flow feature layer is disposed over the substrate, and the flow feature layer includes one or more flow features each in communication with at least one of the one or more fluid ports. The nozzle layer is disposed over the flow feature layer, and the nozzle layer includes one or more nozzles each in communication with at least one of the one or more flow features so that one or more fluid paths are defined by the one or more fluid channels, the one or more fluid ports, the one or more flow features, and the one or more nozzles. The one or more valves selectively impede flow of fluid through the one or more fluid paths. 
     In exemplary embodiments, the one or more valves are disposed within the substrate. 
     In exemplary embodiments, the one or more valves are disposed under the substrate. 
     In exemplary embodiments, the one or more valves impede flow of fluid through select fluid paths of the one or more fluid paths during a maintenance operation. 
     In exemplary embodiments, the one or more valves impede flow of fluid flow through select fluid paths of the one or more fluid paths during a jetting operation. 
     In exemplary embodiments, the ejection chip further comprises one or more ejector elements disposed on the substrate. 
     In exemplary embodiments, the one or more valves comprise a bubble disposed along at least one of the one or more fluid paths. 
     In exemplary embodiments, the one or more valves selectively impede the flow of fluid through at least one of the one or more fluid ports. 
     In exemplary embodiments, the one or more valves comprise flexible membranes that selectively impede flow of fluid through at least one of the one or more fluid paths. 
     In exemplary embodiments, the flexible membranes are formed of an elastomer. 
     In exemplary embodiments, the ejection chip further comprises a pneumatic channel configured to create a pressure differential along at least one of the one or more fluid paths so that the flexible membrane deflects toward a region of lower pressure. 
     In exemplary embodiments, the flexible membranes are configured to engage a wall to selectively impede the flow of fluid through at least one of the one or more fluid paths. 
     In exemplary embodiments, the one or more valves comprise a bimetallic valve. 
     In exemplary embodiments, the bimetallic valve comprises a plurality of materials each having a different coefficient of thermal expansion. 
     In exemplary embodiments, the bimetallic valve is configured to be heated such that the bimetallic valve deflects in the direction of the material of the plurality of materials having the lowest coefficient of thermal expansion. 
     In exemplary embodiments, the bimetallic valve extends substantially across at least one of the one or more fluid ports. 
     In exemplary embodiments, the bimetallic valve extends entirely across at least one of the one or more fluid ports. 
     In exemplary embodiments, the bimetallic valve is spaced away from at least one of the one or more fluid ports by one or more mounts. 
     In exemplary embodiments, at least one of the one or more valves may be a piezoelectric valve or an electrostatic valve. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features and advantages of the present invention will be more fully understood with reference to the following, detailed description of illustrative embodiments of the present invention when taken in conjunction with the accompanying figures, wherein: 
         FIG. 1A  is a side cross-sectional view of an ejection chip according to an exemplary embodiment of the present disclosure; 
         FIG. 1B  is a side cross-sectional view of the ejection chip of  FIG. 1A  having a bubble formed therein; 
         FIG. 1C  is an enlarged view of the area of detail identified in  FIG. 1B ; 
         FIG. 2A  is a first sequential view of the fabrication of an ejection chip according to an exemplary embodiment of the present disclosure, shown in side cross-section; 
         FIG. 2B  is a second sequential view of the fabrication of an ejection chip, shown in side cross-section; 
         FIG. 2C  is a third sequential view of the fabrication of an ejection chip, shown in side cross-section; 
         FIG. 2D  is a fourth sequential view of the fabrication of an ejection chip, shown in side cross-section; 
         FIG. 2E  is a fifth sequential view of the fabrication of an ejection chip, shown in side cross-section; 
         FIG. 2F  is a sixth sequential view of the fabrication of an ejection chip, shown in side cross-section; 
         FIG. 2G  is a seventh sequential view of the fabrication of an ejection chip, shown in side cross-section; 
         FIG. 2H  is a eighth sequential view of the fabrication of an ejection chip, shown in side cross-section; 
         FIG. 2I  is a side cross-sectional view of the ejection chip formed in  FIGS. 2A-2H , with a valve thereof being actuated; 
         FIG. 3A  is a side cross-sectional view of an ejection chip having a valve according to an exemplary embodiment of the present disclosure; 
         FIG. 3B  is a side cross-sectional view of the ejection chip of  FIG. 3A , with the valve being actuated; 
         FIG. 4A  is a first sequential view of the fabrication of an ejection chip according to an exemplary embodiment of the present disclosure, shown in side cross-section; 
         FIG. 4B  is a second sequential view of the fabrication of an ejection chip, shown in side cross-section; 
         FIG. 4C  is a third sequential view of the fabrication of an ejection chip, shown in side cross-section; 
         FIG. 4D  is a side cross-sectional view of the ejection chip formed in  FIGS. 4A-4C , with a value thereof being in a resting condition; 
         FIG. 4E  is a side cross-sectional view of the ejection chip formed in  FIGS. 4A-4C , with a valve thereof being actuated; 
         FIG. 5A  is a side cross-sectional view of an ejection chip according to an exemplary embodiment of the present disclosure; and 
         FIG. 5B  is a side cross-sectional view of the ejection chip of  FIG. 5B , with a valve thereof being actuated. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Exemplary embodiments of the present disclosure are directed to apparatuses and methods for controlling fluid flow through ejection chips, for example, micro-fluid ejection heads. Ejection chips may be configured to store and/or eject and/or direct fluids, such as ink, therefrom. Ejection chips may be utilized, for example, in inkjet printers. 
     Ejection chips may be arranged in a variety of configurations to suit particular needs of use. In embodiments, a plurality of ejection chips may be arranged to form a printhead that is movable across a length and/or width of a surface of a medium, such as a sheet of paper, to project fluids sequentially into sections thereon. In such embodiments, a plurality of ejection chips may form a scanning printhead. In embodiments, a plurality of ejection chips may be arranged to form a printhead that may extend substantially the width of a medium. In such embodiments, a plurality of ejection chips may form a pagewide printhead. In pagewide printheads, a substantially greater, for example twenty-fold, number of ejection chips may be present. Accordingly, pagewide printheads may be configured to utilize a greater amount of ink, for example, during maintenance operations. 
     In embodiments, to facilitate proper and/or continuous performance of the ejection chips that form a printhead, maintenance operations may include passing a wiping member along a portion of ejection chip to draw out contaminated, improper, or otherwise undesirable fluids, to clear debris, and/or to prime such printheads. Exemplary embodiments of such operations are described in U.S. Patent Application Publication No. 2013/0215191. In such embodiments, the wiping member may have the effect of wicking ink through the ejection chip, thus depleting ink from a reserve within or associated with an ejection chip. In embodiments where a wiping operation is performed on a pagewide printhead, a substantial volume of ink may be depleted in this manner, for example, a twenty-fold increase in ink depletion as compared to a scanning printhead. In embodiments, all ejection chips associated with a given printhead may not necessarily require maintenance during a given maintenance operation. Thus, it may be impracticable to selectively wipe certain printheads while isolating others due to close tolerances and/or geometries within a printhead. Accordingly, it may be desirable to provide a micro-electromechanical system (MEMS) to inhibit, e.g., reduce, minimize, and/or prevent, unintended and/or unnecessary loss of ink during maintenance operations. 
     Referring to  FIG. 1A , an exemplary embodiment of an ejection chip is shown in cross-sectional view and is generally designated as  100 . Ejection chip  100  may include a substrate  110 , a plurality of fluid ejector elements  120 , a flow feature layer  130 , and/or a nozzle layer  140 . In embodiments, ejection chip  100  may have a different configuration. 
     Substrate  110  may be formed of a semiconductor material, such as a silicon wafer. One or more fluid ports  112  may be apertures formed along the top surface of the substrate  110  by processing portions of the substrate  110 . As described herein, processing portions of an ejection chip may include, for example, mechanical deformation such as grinding, chemical etching, or patterning desired structures with photoresist, to name a few. A back side of the substrate  110  may be processed to form one or more fluid channels  114  in fluid communication with respective fluid ports  112 . Fluid channels  114  may be in fluid communication with a supply of ink, such as an ink reservoir. 
     One or more ejector elements  120  may be disposed on the substrate  110 . Ejector elements  120  may be comprised of one or more conductive and/or resistive materials so that when electrical power is supplied to the ejector elements  120 , heat is caused to accumulate on and/or near the ejector elements  120 . In embodiments, ejector elements  120  may be formed of more than one layered material, such as a heater stack that may include a resistive element, dielectric, and protective layer. The amount of heat generated by ejector elements  120  may be directly proportional to the amount of power supplied to the ejector elements  120 . In embodiments, power may be supplied to ejector elements  120  so that a predetermined thermal profile is generated by ejector elements  120 , for example, a series of power pulses of constant or variable amplitude and/or duration to achieve intended performance. 
     A flow feature layer  130  may be disposed over the substrate  110 . Flow feature layer  130  may be disposed in a layered or otherwise generally planar abutting, relationship with respect to substrate  110 . Flow feature layer  130  may be formed of, for example, a polymeric material. Flow feature layer  130  may be processed such that one or more flow features  132  are formed along and/or within flow feature layer  130 . In embodiments, flow features  132  may have geometry and/or dimensioning so that flow features  132  are configured to direct the flow of ink through ejection chip  100 . 
     A nozzle layer  140  may be disposed over the flow feature layer  130 . In embodiments, nozzle layer  140  may be disposed in a layered relationship with flow feature layer  130 . In embodiments, nozzle layer  140  may be formed of, for example, a polymeric material. Nozzle layer  140  may be processed such that one or more nozzles  142  are formed along a top surface of the nozzle layer  140 . Nozzles  142  may be configured as exit apertures for ink being ejected from the ejection chip  100 . Accordingly, nozzles  142  may have geometry and/or dimensioning configured to direct the trajectory of ink exiting the ejection chip  100 . Respective fluid ports  112 , fluid channels  114 , flow features  132 , and/or nozzles  142  may collectively form fluid paths  148  within the ejector chip  100 . 
     Referring additionally to  FIGS. 1B and 1C , in use, fluid channels  114  may be at least partially filled with ink. Ink may be any fluid suitable for use in an inkjet printing operation. Power may be supplied to the ejector elements  120  such that ejector elements  120  heat the surrounding ink. Power may be supplied to ejector elements  120  such that a portion of ink  150  is caused to quickly vaporize, such as by flash vaporization, so that one or more vapor bubbles  152  are formed within the fluid channel  114 . The vapor comprising bubbles  152  may be formed from the vaporization of an aqueous component of the ink. A high-powered electrical pulse may be provided to form bubbles  152 . In embodiments, a series of electrical pulses may be provided to form bubbles  152 . Following formation of bubbles  152 , electrical power may continue to be supplied to ejector elements  120  at an equal or lesser level than the initial amount of electrical power to form bubbles  152  in order to sustain bubbles  152  within the fluid channel  114 . Bubbles  152  tend to expand, e.g., hydraulically, due to their higher energy state within the liquid ink, but are restricted from expanding beyond a given dimension by the walls of the surrounding fluid path  148 . Accordingly, bubbles  152  are configured as a pressurized region within fluid path  148  that forms a discontinuity of the liquid ink. In this manner, bubbles  152  may be provided to selectively impede the passage of ink through select fluid paths  148 . In embodiments, the relatively lower temperature of the walls of fluid channel  114  compared to bubble  152  may inhibit the expansion of bubble  152  into a fluid-tight seal with the walls of fluid path  148 . In such embodiments, bubble  152  may permit some ink to flow through the fluid path  148 . In embodiments, bubble  152  may be formed along a different portion of fluid path  148 , e.g. a fluid port  112 . 
     When it is desired to permit ink flow through the fluid channel  114 , electrical power may be disengaged from ejector elements  120 . A reduction in electrical power to ejector elements may cause a reduction in heat near the ejection elements  120  so that bubbles  152  may dissipate, collapse, and/or return to a lower energy state so that the vapor comprising bubbles  152  are absorbed back into the surrounding ink. 
     In embodiments, electrical power may be supplied to ejector elements  120  to form one or more bubbles  152  during maintenance operations, for example, to inhibit the loss of ink through an ejector chip  100  due to wiping of the ejection chip  100 . In such embodiments, a fluid flow controlling member, such as a valve, of the ejection chip  100  may comprise one or more bubbles  152 . In such embodiments, one or more valves comprising bubbles  152  have a normally open configuration. In such embodiments, bubbles  152  are normally absent from select fluid paths  148  and are selectively formed along select fluid paths  148 , for example, during maintenance operations. 
     In embodiments, power may be supplied to ejector elements  120  to form bubble  152  within fluid channels  114  in a substantially constant state except for during use of the ejector chip  100  to eject ink onto a medium, such as a jetting operation. In such embodiments, one or more valves of the ejection chip  100  may comprise bubbles  152  having a normally closed configuration. In such embodiments, bubbles  152  are normally present within select fluid paths  148  and are absent during jetting operations. In such embodiments, bubbles  152  may normally be present within select fluid paths  148  so that ink is impeded from entering fluid paths  148  from a location external of an ejection chip, for example, ink that has been splashed or misfired from a nozzle not associated with select fluid paths  148 . In this manner, bubbles  152  may be formed to selectively impede contamination of select fluid paths  148 . 
     Turning to  FIGS. 2A, 2B, 2C, 2D, 2E, 2F, 2G, and 2H , the fabrication of an exemplary embodiment of an ejection chip, generally designated  200 , is shown. 
     A substrate  210 , such as a silicon wafer, may be provided in a first step of a fabrication process. A sacrificial material  220 , e.g., a silicon dioxide layer, may be deposited over the substrate  210 . The sacrificial material  220  may be processed so that the sacrificial material is patterned over the substrate  210  to correspond to a location of a fluid port  212 . A heater metal  230  and a conductor metal  240  may then be deposited over the substrate  210  and sacrificial material  220 . Heater metal  230  and conductor metal  240  may be deposited on substrate  210  in a layered configuration. Heater metal  230  and conductor metal  240  may be configured to generate heat upon receiving electrical power. In embodiments, heater metal  230  and/or conductor metal  240  have conductive and/or electrical resistive properties such that electrical power may be transmitted therealong to cause a buildup of heat within and/or around heater metal  230  and/or conductor metal  240 . In embodiments, heater metal  230  and conductor metal  240  may be formed from one or more of Si, Al, Ta, W, Hf, Ti, poly-Si, Ni, TiN, and/or TaC, to name a few. The heater metal  230  and conductor metal  240  may be patterned along the surface of substrate  210  so that at least one coextensive region of heater metal  230  and conductor metal  240  is present over the substrate  210 . In embodiments, the conductor metal  240  may be etched away in a region of desired heat generation. 
     As shown in  FIG. 2E , a heater passivation layer  250  is then deposited on the substrate  210 . Heater passivation layer  250  may be formed of, for example, silicon dioxide and/or silicon nitride. Heater passivation layer  250  may be disposed in a layered relationship with at least a portion of the conductor metal  240 . Heater passivation layer  250  may be processed so that heater passivation layer  250  is patterned over the conductor layer  240 . 
     As shown in  FIG. 2F , sacrificial layer  220  may then be processed, for example, etched away using a tetramethylammonium hydroxide (TMAH) etching process. In embodiments, a portion of the substrate  210  is also removed during this process. Processing of the sacrificial layer  220  may cause the formation of one or more fluid ports  212  along the substrate  210 . 
     As shown in  FIG. 2G , a bottom surface of the substrate  210  may then be processed so that one or more fluid channels  214  are formed in the substrate  210 . Fluid channels  214  may be in fluid communication with one or more respective fluid ports  212 . 
     In embodiments, a flow feature layer including a plurality of flow features may be deposited over the heater passivation layer  150 . Such a flow feature layer may be substantially similar to flow feature layer  130  described above. Such a flow feature layer may be processed to form one or more flow features therealong. Such flow features may be in fluid communication with one or more respective fluid ports  212 . 
     In embodiments, a nozzle layer may be deposited over a flow feature layer. Such a nozzle layer may be substantially similar to nozzle layer  280  described above. Such a nozzle layer may be processed so that one or more nozzles are formed therealong. Such nozzles may be in fluid communication with one or more respective flow features of a flow feature layer. In embodiments, nozzles, flow features, fluid channels  214  and/or fluid ports  212  may collectively form fluid paths  216  within ejection chip  200 . 
     As shown in  FIG. 2H , following the fabrication of ejection chip  200 , a portion of heater metal  230  and a portion of passivation layer  250  may extend substantially across a fluid port  214 . The portions of heater metal  230  and passivation layer  250  may be spaced away from the surface of the substrate  210 , e.g., by one or more mounts  232 . In embodiments, mounts  232  may be an unprocessed portion of sacrificial layer  220 . In embodiments, mounts  232  may be unetched sidewalls of resistive film and/or dielectric material. Mounts  232  may provide a clearance C between the portions of heater metal  230  and passivation layer  250  and the substrate  210  so that ink may pass through the clearance C. In embodiments, clearance C may be dimensioned to permit a negligible amount of ink to pass therethrough. 
     Heater metal  230  and passivation layer  250  may have a coextensive arrangement to together form a bimetallic valve  290 . In embodiments, conductor metal  240  may alternatively or additionally form a part of bimetallic valve  290 . Bimetallic valve  290  may configured such that heater metal  230  and passivation layer  250  are formed of materials having a different coefficient of thermal expansion (CTE) when placed in a substantially similar environment. In embodiments, Si may have a CTE of about 2.5 ppm/° C., Si 3 N 4  may have a CTE of about 2.8 ppm/° C., TiO 2  may have a CTE of about 7.2 to about 7.10 ppm/° C., Al may have a CTE of about 24 to about 27 ppm/° C., Ta may have a CTE of about 6.5 ppm/° C., W may have a CTE of about 4 ppm/° C., Hf may have a CTE of about 5.9 ppm/° C., Ti may have a CTE of about 9.5 ppm/° C., poly-Si may have a CTE of about 9.4 ppm/° C., SiO 2  may have a CTE of about 0.5 ppm/° C., SiC may have a CTE of about 2.5 to about 5.5 ppm/° C., Ni may have a CTE of about 13.3 ppm/° C., TiN may have a CTE of about 9.4 ppm/° C., and TaC may have a CTE of about 6.3 ppm/° C., to name a few. 
     In use, electrical power may be supplied to the ejection chip  200  such that the heater metal  230  and passivation layer  250  are caused to increase in thermal energy so that temperature increases. Due to the different CTEs comprising heater metal  230  and passivation layer  250 , increased thermal energy across the bimetallic valve  290  will cause the valve  290  to deflect, such as bend, flex, and/or warp, in the direction of the material having the lower of the two CTEs. Accordingly, the bimetallic valve  290  will deflect away from the fluid port  212 . In embodiments, bimetallic valve  290  may define one or more peripheral edges that are not attached to mounts  232 . In such embodiments, the bimetallic valve  290  may deflect or bow such that a gap G is formed between an apex of the deflected bimetallic valve  290  and the fluid portion  212 . In embodiments, gap G may define a greater space than clearance C measured between bimetallic valve  290  and fluid port  212  when bimetallic valve  290  is in an unactuated, e.g., non-powered state. In embodiments, gap G may permit an increased amount of ink to flow through fluid port  212 . In this manner, bimetallic valve  290  may be configured to selectively impede the flow of ink through select fluid channels  216  in the ejection chip  200 . 
     In embodiments, bimetallic valve  290  may substantially impede the flow of ink through select fluid paths  216  in an unactuated state. In such embodiments, bimetallic valve  290  may comprise a normally-closed valve. In this manner, bimetallic valve  290  may be powered, for example, during a jetting operation of the ejection chip  200 , to selectively permit the flow of ink through select fluid paths  216  through the ejection chip  200 . In such embodiments, the bimetallic valve  290  may be normally closed to inhibit cross-contamination of select fluid paths  216  by impeding the flow of ink or other substances into select fluid paths  216  from an external environment. In embodiments, an ejection chip may utilize a valve having a different actuatable configuration, such as a piezoelectric valve and/or an electrostatic valve. 
     In embodiments, bimetallic valve  290  may allow the flow of ink through select fluid paths  216  in an unactuated, e.g., resting or unpowered state. In such embodiments, bimetallic valve  290  may comprise a normally-open valve. In this manner, bimetallic valve  290  may be powered, e.g., during a maintenance operation, to selectively impede select fluid paths through the ejection chip  200 . 
     Turning to  FIG. 3A , an ejector chip  300  according to an exemplary embodiment of the present disclosure is shown. Ejector chip  300  may be formed in a substantially similar manner to ejector chip  200  described above, and may comprise substantially similar components. In embodiments, heater metal  230  and passivation layer  250  may be processed such that the heater metal  230  and passivation layer  250  together form a flapper valve  390  that extends substantially across the fluid port  212 . In embodiments, flapper valve  390  may be configured as a strip of bimetallic material. Flapper valve  390  may have a cantilevered configuration, e.g., flapper valve may be attached to one side of a fluid port  212  and have a free end extending across the fluid port  212 . Flapper valve  390  may be positioned in a layered relationship with the substrate  210  and may extend between or beyond the edges of fluid port  212 . Accordingly, ejection chip  300  may be devoid of mounts  232  for flapper valve  390 . In embodiments, flapper valve  390  may extend partially across the fluid port  212  so flapper valve  390  may have a terminus spaced between the edges of fluid port  212 . The generally planar abutting relationship of the flapper valve  390  and the fluid port  212  may provide a substantially fluid-tight seal between the flapper valve  390  and the fluid port  212  so that ink is substantially inhibited from flowing through fluid port  212  when flapper valve  390  is in place in a resting position. 
     Similar to ejection chip  200  above, heater metal  230  and passivation layer  250  may each have a different CTE. Accordingly, heater metal  230  and passivation layer  250  may be powered such that thermal energy increases across flapper valve  390  such that the flapper valve  390  deflects in the direction of the material having the lower CTE. Because the flapper valve  390  includes a free end that is not attached at one end of the fluid port  212 , the flapper valve  390  may deflect away from the fluid port  212  such that a gap G 2  is formed between an end of the flapper valve  390  and the fluid port  212 . Accordingly, the flapper valve  390  may be actuated to permit the flow of ink through the fluid port  212 . 
     In embodiments, flapper valve  390  may substantially impede the flow of ink through select fluid paths  216  in an unactuated state. In such embodiments, flapper valve  390  may comprise a normally-closed valve. In this manner, flapper valve  390  may be powered, e.g., during a jetting operation of the ejection chip  300 , to selectively open select fluid paths  216  through the ejection chip  300  during jetting, and flapper valve  390  may be configured to selectively impede select fluid paths  216  through the ejection chip  300  in other states. In embodiments, an ejection chip may utilize a valve having a different actuatable configuration, such as a piezoelectric valve and/or an electrostatic valve. 
     In embodiments, flapper valve  390  may allow the flow of ink through select fluid paths  216  in an unactuated state. In such embodiments, flapper valve  390  may comprise a normally-open valve. In this manner, flapper valve  390  may be powered, for example, during a maintenance operation, to selectively impede select fluid paths  216  through the ejection chip  300 . 
     Referring to  FIGS. 4A, 4B, 4C, 4D, and 4E , fabrication of an ejection chip assembly  400  according to an exemplary embodiment of the present disclosure is shown. Ejection chip assembly  400  includes a substrate  410 . Substrate  410  may be substantially similar to substrates  110  and  210  described above, for example, substrate  410  may be a silicon wafer. Substrate  410  may be processed to define one or more fluid ports  412  and one or more fluid channels  414 . The one or more fluid ports  412  may be in fluid communication with the one or more fluid channels  414 . Substrate  410  may also include a restrictor  416 , as will be described further herein. In embodiments, restrictor  416  may form a partition between one or more fluid channels  414  and a respective fluid chamber  418 . 
     A valve substrate  420  may be affixed to a bottom portion of the substrate  410 . Valve substrate  420  may be formed from a variety of materials, such as silicon, glass, liquid crystal polymer, or plastic, to name a few. Valve substrate  420  may be positioned along one or more fluid channels  414  of substrate  410  so that valve substrate  420  at least partially encloses one or more of the fluid channels  414 . Valve substrate  420  may be processed to form a displacement chamber  422  thereon. A flexible membrane  424  may be laminated on top of the valve substrate  420  such that a portion of flexible membrane  424  covers displacement chamber  422  to form a flexible valve  426  disposed under the substrate  410 . One or more flexible valves  426  may be disposed across the displacement chamber  414 . Flexible valve  426  may be formed of a polymeric material, such as polydimethylsiloxane, perfluoropolyether, polytetrafluoroethylene, or fluorinated ethylene-propylene, to name a few. In embodiments, flexible valve  426  may be an elastomer. 
     Restrictor  416  may be a portion, such as a wall, of substrate  410  that extends toward the displacement chamber  422 . Restrictor  416  may be positioned such that the restrictor  416  engages to contact and/or substantially abut the flexible valve  426 . Restrictor  416  may extend toward the flexible valve  426  in a substantially transverse manner. In embodiments, restrictor  416  may contact or substantially abut the flexible valve  426  such that the flexible valve  426  is maintained in a substantially planar configuration by the presence of restrictor  416 . In this manner, restrictor  416  may fluidly isolate an ink chamber  418  from a fluid channel  414 . 
     A flow feature layer  430  may be disposed over the substrate  410 . Flow feature layer  430  may be substantially similar to flow feature layer  130  described herein. Flow feature layer  430  may be processed such that flow feature layer  430  includes one or more flow features  432 . Flow features  432  may be in selective fluid communication with one or more respective fluid ports  412 , as will be described further herein. Flow features  432  may be in fluid communication with one or more fluid ports  412  and one or more fluid channels  414  and one or more fluid chambers  418 . 
     A nozzle layer  440  may be disposed over the flow feature layer  430 . Nozzle layer  440  may be substantially similar to nozzle layer  140  described above. Nozzle layer  440  may be processed such that nozzle layer  440  includes one or more nozzle  442  formed therealong. Each nozzle  442  may be in fluid communication with one or more respective flow feature  432 . In embodiments, nozzles  442 , flow features  432 , fluid ports  412 , fluid channels  414  and/or fluid chamber  418  may collectively form a fluid path  419  within ejection chip assembly  400 . 
     Displacement chamber  422  may be fluidly coupled with a pneumatic channel  423 , such as a source of vacuum. Accordingly, pneumatic channel  423  may be configured to change a pressure P of fluids, such as air, within the displacement chamber  423 . In an initial or valve closed state, a fluid pressure P between the substrate  410  and flow feature layer  430 , for example, along a fluid channel  414 , may be substantially similar to fluid pressure P in the displacement chamber  422 . 
     In use, pneumatic channel  423  may be actuated, e.g., powered by a pump or other source of vacuum, such that fluids are withdrawn from displacement chamber  422 . As fluid pressure within the displacement chamber  422  decreases, an at least partial vacuum is formed such that a fluid pressure P′ is formed in the displacement chamber  422 . Fluid pressure P′ may be different, e.g., lower, than fluid pressure P between the substrate  410  and the valve substrate  420 . Accordingly, a pressure differential on either side of the flexible valve  426  may cause the flexible valve  426  to deflect away from the restrictor  416  toward the region of lower pressure P′ such that a gap G 3  is formed between the restrictor  416  and the flexible valve  426 . In this manner, gap G 3  permits ink to flow between the fluid port  412  and the flow features  432  along the fluid channel  414 . The deflected flexible valve  426  may comprise a valve open condition of the ejection chip assembly  400 . 
     To return the flexible valve  426  to the closed condition, pneumatic channel  423  may be disengaged, for example, removed or shut down, from the displacement chamber  422  so that the fluid pressure in the displacement chamber  422  and the fluid pressure between the substrate  410  and valve substrate  420  substantially equalizes. In the absence of a pressure differential, flexible valve  426  may return to its resting, generally planar condition, such that the flexible valve  426  contacts or abuts the restrictor  416  so that ink is inhibited from flowing between the fluid chamber  418  and fluid channel  414 . In embodiments, flexible valve  426  may have a resilient configuration such that flexible valve  426  is maintained under a bias to return to its resting condition. In embodiments, pneumatic channel  423  may be configured to deliver fluid pressure to create a positive pressure environment to facilitate the return of flexible valve  426  to its resting condition. In this manner, flexible valve  426  may be configured to selectively impede fluid flow through select fluid paths  419  through ejection chip assembly  400  in a resting condition, such as a normally closed valve. 
     Turning to  FIG. 5A , an ejection chip assembly according to an embodiment of the present disclosure is generally designated as  500 . Ejection chip assembly  500  may include substantially similar components to ejection chip assembly  400  described above, such as nozzle layer  440 , flow feature layer  430  and/or valve substrate  420 . 
     Ejection chip assembly  500  may include a substrate  510  that is similar to substrate  410 . Substrate  510  may include a restrictor  516  that extends toward displacement chamber  422 . Restrictor  516  may be positioned with respect to flexible valve  426  such that a gap G 4  is present between the restrictor  516  and the flexible valve  426  in a resting condition of the flexible valve  426 . 
     Referring additionally to  FIG. 5B , to actuate flexible valve  426 , pneumatic channel  423  may supply fluid pressure, e.g., positive air pressure, to displacement chamber  422  such that a pressure P 2  is formed within displacement chamber  422 . Pressure P 2  may be different, e.g., greater than a pressure P formed along the fluid channel  414  so that a pressure differential is present within ejection chip assembly  500 . The pressure differential may cause the flexible valve  426  to deflect toward the region of lower pressure P so that the flexible valve  426  is urged into contact to form a substantially fluid tight seal with restrictor  516  so that ink is inhibited from flowing past the restrictor  516 . 
     In this manner, a flexible valve  426  may be provided so that the flexible valve  426  is normally positioned to allow ink flow through the ejection chip assembly  500  and may be actuated to substantially impede ink flow through select fluid paths  519  of the ejection chip assembly  500 , such as a normally open valve. 
     While this invention has been described in conjunction with the embodiments outlined above, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, the exemplary embodiments of the invention, as set forth above, are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the invention.