Patent Publication Number: US-9889670-B1

Title: Fluidic dispensing device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is related to U.S. patent application Ser. No. 15/183,666, now U.S. Pat. No. 9,744,771; Ser. No. 15/183,693, now U.S. Pat. No. 9,707,767; Ser. No. 15/183,705, now U.S. Pat. No. 9,751,315; Ser. No. 15/183,722, now U.S. Pat. No. 9,751,316; Ser. Nos. 15/183,736; 15/193,476; 15/216,104; 15/239,113; 15/256,065, now U.S. Pat. No. 9,688,074; Ser. Nos. 15/278,369; 15/373,123; 15/373,243; 15/373,635; and Ser. No. 15/435,983. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to fluidic dispensing devices, and, more particularly, to a fluidic dispensing device, such as a microfluidic dispensing device, having a lid-body split design. 
     2. Description of the Related Art 
     One type of microfluidic dispensing device, such as an ink jet printhead, is designed to include a capillary member, such as foam or felt, to control backpressure. In this type of printhead, the only free fluid is present between a filter and the ejection device. If settling or separation of the fluid occurs, it is almost impossible to re-mix the fluid contained in the capillary member. 
     Another type of printhead is referred to in the art as a free fluid style printhead, which has a movable wall that is spring loaded to maintain backpressure at the nozzles of the printhead. One type of spring loaded movable wall uses a deformable deflection bladder to create the spring and wall in a single piece. An early printhead design by Hewlett-Packard Company used a circular/cylindrical deformable rubber part in the form of a thimble shaped bladder positioned between a container lid and a body. The thimble shaped bladder maintained backpressure in the ink enclosure defined by the thimble shaped bladder by deforming the bladder material as ink was delivered to the printhead chip. More particularly, in this design, the body is relatively planar, and a printhead chip is attached to an exterior of the relatively planar body on an opposite side of the body from the thimble shaped bladder. The thimble shaped bladder is an elongate cylindrical-like structure having a distal sealing rim that engages the planar body to form the ink enclosure. Thus, in this design, the sealing rim of the thimble shaped bladder is parallel to the printhead chip. A central longitudinal axis of the container lid and thimble shaped bladder extends though the location of the printhead chip and the corresponding chip pocket of the body. The deflection of the thimble shaped bladder collapses on itself, i.e., around and inwardly toward the central longitudinal axis. 
     What is needed in the art is a fluidic dispensing device having a lid-body split design that has a fluid chamber defined by an interior perimetrical wall of a body and has a diaphragm that engages an end surface of the interior perimetrical wall of the body. 
     SUMMARY OF THE INVENTION 
     The present invention provides a fluidic dispensing device having a lid-body split design that has a fluid chamber defined by an interior perimetrical wall of a body and has a diaphragm that engages an end surface of the interior perimetrical wall of the body. 
     The invention in one form is directed to a fluidic dispensing device having a body that includes a base wall having an exterior base surface, and an interior perimetrical wall that extends from the base wall to define a chamber. The interior perimetrical wall has a perimetrical end surface. The body has an exterior wall extending away from the base wall. The exterior wall has a chip mounting surface defining a first plane, the base wall being oriented along a second plane, the first plane being orthogonal to the second plane. An ejection chip is mounted to the chip mounting surface of the body. A diaphragm is engaged with the perimetrical end surface of the chamber to define a fluid reservoir. A lid is attached to the body, with the diaphragm interposed between the lid and the body. The body and the lid define a split at a juncture of the lid and the body. 
     In one implementation, a ratio of a distance A from the exterior base surface of the base wall of the body to a center of the ejection chip and a distance C from the exterior base surface of the base wall of the body to a top of the exterior wall of the body at the location of the split is in a range of 20 percent to 80 percent, and the distance A is less than the distance C. 
     The invention in another form is directed to a fluidic dispensing device having a body that includes a base wall having an exterior base surface, and an interior perimetrical wall that extends from the base wall to define a chamber. The interior perimetrical wall has a perimetrical end surface. The body has an exterior wall extending away from the base wall. The exterior wall has a chip mounting surface defining a first plane. The base wall is oriented along a second plane. The first plane is orthogonal to the second plane. An ejection chip is mounted to the chip mounting surface of the body. A diaphragm is engaged with the perimetrical end surface of the chamber to define a fluid reservoir. The diaphragm has a dome portion. A lid is attached to the body, with the diaphragm interposed between the lid and the body. The lid has a lid portion that accommodates the dome portion of the diaphragm. The body and the lid define a split at a juncture of the lid and the body. A ratio of a distance A from the exterior base surface of the base wall of the body to a center of the ejection chip and a distance B from the exterior base surface of the base wall of the body to the perimetrical end surface of the interior perimetrical wall of the chamber of the body is in a range of 20 percent to 80 percent, and the distance A is less than the distance B. 
     The invention in another form is directed to a fluidic dispensing device having a body including a base wall having an exterior base surface, and an interior perimetrical wall that extends from the base wall to define a chamber. The interior perimetrical wall has a perimetrical end surface. The body has an exterior wall extending away from the base wall. The exterior wall has a chip mounting surface defining a first plane. The base wall is oriented along a second plane, with the first plane being orthogonal to the second plane. An ejection chip is mounted to the chip mounting surface of the body. A diaphragm is engaged with the perimetrical end surface of the chamber to define a fluid reservoir. The diaphragm has a dome portion. A lid is attached to the body, with the diaphragm interposed between the lid and the body. The lid has a lid portion that accommodates the dome portion of the diaphragm. The body and the lid define a split at a juncture of the lid and the body. A ratio of the distance B from the exterior base surface of the base wall of the body to the perimetrical end surface of the interior perimetrical wall of the chamber of the body and a distance D from the exterior base surface of the base wall of the body to a top of the lid portion of the lid that accommodates the dome portion of the diaphragm is in a range of 40 percent to 95 percent, and the distance B is less than the distance D. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is a perspective view of an embodiment of a microfluidic dispensing device in accordance with the present invention, in an environment that includes an external magnetic field generator. 
         FIG. 2  is another perspective view of the microfluidic dispensing device of  FIG. 1 . 
         FIG. 3  is a top orthogonal view of the microfluidic dispensing device of  FIGS. 1 and 2 . 
         FIG. 4  is a side orthogonal view of the microfluidic dispensing device of  FIGS. 1 and 2 . 
         FIG. 5  is an end orthogonal view of the microfluidic dispensing device of  FIGS. 1 and 2 . 
         FIG. 6  is an exploded perspective view of the microfluidic dispensing device of  FIGS. 1 and 2 , oriented for viewing into the chamber of the body in a direction toward the ejection chip. 
         FIG. 7  is another exploded perspective view of the microfluidic dispensing device of  FIGS. 1 and 2 , oriented for viewing in a direction away from the ejection chip. 
         FIG. 8  is a section view of the microfluidic dispensing device of  FIG. 1 , taken along line  8 - 8  of  FIG. 5 . 
         FIG. 9  is a section view of the microfluidic dispensing device of  FIG. 1 , taken along line  9 - 9  of  FIG. 5 . 
         FIG. 10  is a perspective view of the microfluidic dispensing device of  FIG. 1 , with the end cap and lid removed to expose the body/diaphragm assembly. 
         FIG. 11  is a perspective view of the depiction of  FIG. 10 , with the diaphragm removed to expose the guide portion and stir bar contained in the body, in relation to first and second planes and to the fluid ejection direction. 
         FIG. 12  is an orthogonal view of the body/guide portion/stir bar arrangement of  FIG. 11 , as viewed in a direction into the body of the chamber toward the base wall of the body. 
         FIG. 13  is an orthogonal end view of the body of  FIG. 11 , which contains the guide portion and stir bar, as viewed in a direction toward the exterior wall and fluid opening of the body. 
         FIG. 14  is a section view of the body/guide portion/stir bar arrangement of  FIGS. 12 and 13 , taken along line  14 - 14  of  FIG. 13 . 
         FIG. 15  is an enlarged section view of the body/guide portion/stir bar arrangement of  FIGS. 12 and 13 , taken along line  15 - 15  of  FIG. 13 . 
         FIG. 16  is an enlarged view of the depiction of  FIG. 12 , with the guide portion removed to expose the stir bar residing in the chamber of the body. 
         FIG. 17  is a top view of the microfluidic dispensing device of  FIG. 1 , corresponding to the perspective view of  FIG. 10 , having the end cap and lid removed to show a top view of the diaphragm that is positioned on the body. 
         FIG. 18  is a bottom perspective view of the diaphragm of  FIG. 17 . 
         FIG. 19  is a bottom view of the diaphragm of  FIGS. 17 and 18 . 
         FIG. 20  is a bottom perspective view of the lid of  FIGS. 6-9 . 
         FIG. 21  is a bottom view of the lid of  FIGS. 6-9 and 20 . 
         FIG. 22  is an enlarged section view of the microfluidic dispensing device of  FIG. 1 , taken along line  9 - 9  of  FIG. 5 , which identifies distance ranges for the location of certain components of one preferred design of the microfluidic dispensing device of  FIG. 1 . 
         FIG. 23  is a further enlarged section view corresponding to a portion of  FIG. 22 , showing component positions of the microfluidic dispensing device prior to welding the lid to the body. 
         FIG. 24  is a further enlarged section view corresponding to a portion of  FIG. 22 , showing component positions of the microfluidic dispensing device during an initial intermediate stage of welding the lid to the body. 
         FIG. 25  is a further enlarged section view corresponding to a portion of  FIG. 22 , showing component positions of the microfluidic dispensing device during a later intermediate stage of welding the lid to the body. 
         FIG. 26  is a further enlarged section view corresponding to a portion of  FIG. 22 , showing component positions of the microfluidic dispensing device at the end of the welding process, with the lid securely attached to the body. 
         FIG. 27  is a section view that shows a modification to the design depicted in  FIGS. 23-26 , wherein the diaphragm pressing surface of the lid has a downwardly facing perimetrical protrusion that engages the exterior perimetrical rim of the diaphragm. 
         FIG. 28  is a graph showing an ideal backpressure range for the microfluidic dispensing device of  FIGS. 1-26 , and plotting pressure versus deliverable fluid for two diaphragm designs. 
         FIG. 29A  is a top view of the diaphragm of the microfluidic dispensing device of  FIGS. 1-26 . 
         FIG. 29B  is a section view of the diaphragm of  FIG. 29A , taken along line  29 B- 29 B of  FIG. 29A . 
         FIG. 29C  is an enlargement of a portion of the section view of  FIG. 29B . 
         FIG. 30A  is a top view of an alternative diaphragm for use with the microfluidic dispensing device of  FIGS. 1-26 . 
         FIG. 30B  is a section view of the diaphragm of  FIG. 30A , taken along line  30 B- 30 B of  FIG. 30A . 
         FIG. 30C  is an enlargement of a portion of the section view of  FIG. 30B . 
         FIG. 31A  is a top view of another alternative diaphragm for use with the microfluidic dispensing device of  FIGS. 1-26 . 
         FIG. 31B  is a section view of the diaphragm of  FIG. 31A , taken along line  31 B- 31 B of  FIG. 31A . 
         FIG. 31C  is an enlargement of a portion of the section view of  FIG. 31B . 
     
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate embodiments of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any manner. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings, and more particularly to  FIGS. 1-16 , there is shown a fluidic dispensing device, which in the present example is a microfluidic dispensing device  110  in accordance with an embodiment of the present invention. 
     Referring to  FIGS. 1-5 , microfluidic dispensing device  110  generally includes a housing  112  and a tape automated bonding (TAB) circuit  114 . Microfluidic dispensing device  110  is configured to contain a supply of a fluid, such as a fluid containing particulate material, and TAB circuit  114  is configured to facilitate the ejection of the fluid from housing  112 . The fluid may be, for example, cosmetics, lubricants, paint, ink, etc. 
     Referring also to  FIGS. 6 and 7 , TAB circuit  114  includes a flex circuit  116  to which an ejection chip  118  is mechanically and electrically connected. Flex circuit  116  provides electrical connection to an electrical driver device (not shown), such as an ink jet printer, configured to operate ejection chip  118  to eject the fluid that is contained within housing  112 . In the present embodiment, ejection chip  118  is configured as a plate-like structure having a planar extent formed generally as a nozzle plate layer and a silicon layer, as is well known in the art. The nozzle plate layer of ejection chip  118  has a plurality of ejection nozzles  120  oriented such that a fluid ejection direction  120 - 1  is substantially orthogonal to the planar extent of ejection chip  118 . Associated with each of the ejection nozzles  120 , at the silicon layer of ejection chip  118 , is an ejection mechanism, such as an electrical heater (thermal) or piezoelectric (electromechanical) device. The operation of such an ejection chip  118  and driver is well known in the micro-fluid ejection arts, such as in ink jet printing. 
     As used herein, each of the terms substantially orthogonal and substantially perpendicular is defined to mean an angular relationship between two elements of 90 degrees, plus or minus 10 degrees. The term substantially parallel is defined to mean an angular relationship between two elements of zero degrees, plus or minus 10 degrees. 
     As best shown in  FIGS. 6 and 7 , housing  112  includes a body  122 , a lid  124 , an end cap  126 , and a fill plug  128  (e.g., ball). Contained within housing  112  is a diaphragm  130 , a stir bar  132 , and a guide portion  134 . Each of the housing  112  components, stir bar  132 , and guide portion  134  may be made of plastic, using a molding process. Diaphragm  130  is made of elastomeric material, such as rubber or a thermoplastic elastomer (TPE), using an appropriate molding process. Also, in the present embodiment, fill plug  128  may be in the form of a stainless steel ball bearing. 
     Referring also to  FIGS. 8 and 9 , in general, a fluid (not shown) is loaded through a fill hole  122 - 1  in body  122  (see also  FIG. 6 ) into a sealed region, i.e., a fluid reservoir  136 , between body  122  and diaphragm  130 . Back pressure in fluid reservoir  136  is set and then maintained by inserting, e.g., pressing, fill plug  128  into fill hole  122 - 1  to prevent air from leaking into fluid reservoir  136  or fluid from leaking out of fluid reservoir  136 . End cap  126  is then placed onto an end of the body  122 /lid  124  combination, opposite to ejection chip  118 . Stir bar  132  resides in the sealed fluid reservoir  136  between body  122  and diaphragm  130  that contains the fluid. An internal fluid flow may be generated within fluid reservoir  136  by rotating stir bar  132  so as to provide fluid mixing and redistribution of particulate in the fluid within the sealed region of fluid reservoir  136 . 
     Referring now also to  FIGS. 10-16 , body  122  of housing  112  has a base wall  138  and an exterior perimeter wall  140  contiguous with base wall  138 . Exterior perimeter wall  140  is oriented to extend from base wall  138  in a direction that is substantially orthogonal to base wall  138 . Lid  124  is configured to engage exterior perimeter wall  140 . Thus, exterior perimeter wall  140  is interposed between base wall  138  and lid  124 , with lid  124  being attached to the open free end of exterior perimeter wall  140  by weld, adhesive, or other fastening mechanism, such as a snap fit or threaded union. Attachment of lid  124  to body  122  occurs after installation of diaphragm  130 , stir bar  132 , and guide portion  134  in body  122 . 
     Exterior perimeter wall  140  of body  122  includes an exterior wall  140 - 1 , which is a contiguous portion of exterior perimeter wall  140 . Exterior wall  140 - 1  has a chip mounting surface  140 - 2  that defines a plane  142  (see  FIGS. 11 and 12 ), and has a fluid opening  140 - 3  adjacent to chip mounting surface  140 - 2  that passes through the thickness of exterior wall  140 - 1 . Ejection chip  118  is mounted, e.g., by an adhesive sealing strip  144  (see  FIGS. 6 and 7 ), to chip mounting surface  140 - 2  and is in fluid communication with fluid opening  140 - 3  (see  FIG. 13 ) of exterior wall  140 - 1 . Thus, the planar extent of ejection chip  118  is oriented along plane  142 , with the plurality of ejection nozzles  120  oriented such that the fluid ejection direction  120 - 1  is substantially orthogonal to plane  142 . Base wall  138  is oriented along a plane  146  (see  FIG. 11 ) that is substantially orthogonal to plane  142  of exterior wall  140 - 1 . As best shown in  FIGS. 6, 15 and 16 , base wall  138  may include a circular recessed region  138 - 1  in the vicinity of the desired location of stir bar  132 . 
     Referring to  FIGS. 11-16 , body  122  of housing  112  also includes a chamber  148  located within a boundary defined by exterior perimeter wall  140 . Chamber  148  forms a portion of fluid reservoir  136 , and is configured to define an interior space, and in particular, includes base wall  138  and has an interior perimetrical wall  150  configured to have rounded corners, so as to promote fluid flow in chamber  148 . Interior perimetrical wall  150  of chamber  148  has an extent bounded by a proximal end  150 - 1  and a distal end  150 - 2 . Proximal end  150 - 1  is contiguous with, and may form a transition radius with, base wall  138 . Such an edge radius may help in mixing effectiveness by reducing the number of sharp corners. Distal end  150 - 2  is configured to define a perimetrical end surface  150 - 3  at a lateral opening  148 - 1  of chamber  148 . Perimetrical end surface  150 - 3  may include a single perimetrical rib, or a plurality of perimetrical ribs or undulations as shown, to provide an effective sealing surface for engagement with diaphragm  130 . The extent of interior perimetrical wall  150  of chamber  148  is substantially orthogonal to base wall  138 , and is substantially parallel to the corresponding extent of exterior perimeter wall  140  (see  FIG. 6 ). 
     As best shown in  FIGS. 15 and 16 , chamber  148  has an inlet fluid port  152  and an outlet fluid port  154 , each of which is formed in a portion of interior perimetrical wall  150 . The terms “inlet” and “outlet” are terms of convenience that are used in distinguishing between the multiple ports of the present embodiment, and are correlated with a particular rotational direction of stir bar  132 . However, it is to be understood that it is the rotational direction of stir bar  132  that dictates whether a particular port functions as an inlet port or an outlet port, and it is within the scope of this invention to reverse the rotational direction of stir bar  132 , and thus reverse the roles of the respective ports within chamber  148 . 
     Inlet fluid port  152  is separated a distance from outlet fluid port  154  along a portion of interior perimetrical wall  150 . As best shown in  FIGS. 15 and 16 , considered together, body  122  of housing  112  includes a fluid channel  156  interposed between the portion of interior perimetrical wall  150  of chamber  148  and exterior wall  140 - 1  of exterior perimeter wall  140  that carries ejection chip  118 . 
     Fluid channel  156  is configured to minimize particulate settling in a region of ejection chip  118 . Fluid channel  156  is sized, e.g., using empirical data, to provide a desired flow rate while also maintaining an acceptable fluid velocity for fluid mixing through fluid channel  156 . 
     In the present embodiment, referring to  FIG. 15 , fluid channel  156  is configured as a U-shaped elongated passage having a channel inlet  156 - 1  and a channel outlet  156 - 2 . Fluid channel  156  dimensions, e.g., height and width, and shape are selected to provide a desired combination of fluid flow and fluid velocity for facilitating intra-channel stirring. 
     Fluid channel  156  is configured to connect inlet fluid port  152  of chamber  148  in fluid communication with outlet fluid port  154  of chamber  148 , and also connects fluid opening  140 - 3  of exterior wall  140 - 1  of exterior perimeter wall  140  in fluid communication with both inlet fluid port  152  and outlet fluid port  154  of chamber  148 . In particular, channel inlet  156 - 1  of fluid channel  156  is located adjacent to inlet fluid port  152  of chamber  148  and channel outlet  156 - 2  of fluid channel  156  is located adjacent to outlet fluid port  154  of chamber  148 . In the present embodiment, the structure of inlet fluid port  152  and outlet fluid port  154  of chamber  148  is symmetrical. 
     Fluid channel  156  has a convexly arcuate wall  156 - 3  that is positioned between channel inlet  156 - 1  and channel outlet  156 - 2 , with fluid channel  156  being symmetrical about a channel mid-point  158 . In turn, convexly arcuate wall  156 - 3  of fluid channel  156  is positioned between inlet fluid port  152  and outlet fluid port  154  of chamber  148  on the opposite side of interior perimetrical wall  150  from the interior space of chamber  148 , with convexly arcuate wall  156 - 3  positioned to face fluid opening  140 - 3  of exterior wall  140 - 1  and ejection chip  118 . 
     Convexly arcuate wall  156 - 3  is configured to create a fluid flow through fluid channel  156  that is substantially parallel to ejection chip  118 . In the present embodiment, a longitudinal extent of convexly arcuate wall  156 - 3  has a radius that faces fluid opening  140 - 3  and that is substantially parallel to ejection chip  118 , and has transition radii  156 - 4 ,  156 - 5  located adjacent to channel inlet  156 - 1  and channel outlet  156 - 2 , respectively. The radius and transition radii  156 - 4 ,  156 - 5  of convexly arcuate wall  156 - 3  help with fluid flow efficiency. A distance between convexly arcuate wall  156 - 3  and fluid ejection chip  118  is narrowest at the channel mid-point  158 , which coincides with a mid-point of the longitudinal extent of ejection chip  118 , and in turn, with a mid-point of the longitudinal extent of fluid opening  140 - 3  of exterior wall  140 - 1 . 
     Each of inlet fluid port  152  and outlet fluid port  154  of chamber  148  has a beveled ramp structure configured such that each of inlet fluid port  152  and outlet fluid port  154  converges in a respective direction toward fluid channel  156 . In particular, inlet fluid port  152  of chamber  148  has a beveled inlet ramp  152 - 1  configured such that inlet fluid port  152  converges, i.e., narrows, in a direction toward channel inlet  156 - 1  of fluid channel  156 , and outlet fluid port  154  of chamber  148  has a beveled outlet ramp  154 - 1  that diverges, i.e., widens, in a direction away from channel outlet  156 - 2  of fluid channel  156 . 
     Referring again to  FIGS. 6-10 , diaphragm  130  is positioned between lid  124  and perimetrical end surface  150 - 3  of interior perimetrical wall  150  of chamber  148 . The attachment of lid  124  to body  122  compresses a perimeter of diaphragm  130  thereby creating a continuous seal between diaphragm  130  and body  122 . More particularly, diaphragm  130  is configured for sealing engagement with perimetrical end surface  150 - 3  of interior perimetrical wall  150  of chamber  148  in forming fluid reservoir  136 . Thus, in combination, chamber  148  and diaphragm  130  cooperate to define fluid reservoir  136  having a variable volume. 
     Referring particularly to  FIGS. 6, 8 and 9 , an exterior surface of diaphragm  130  is vented to the atmosphere external to microfluidic dispensing device  110  through a vent hole  124 - 1  located in lid  124  so that a controlled negative pressure can be maintained in fluid reservoir  136 . Diaphragm  130  is made of elastomeric material, and includes a dome portion  130 - 1  configured to progressively collapse toward base wall  138  as fluid is depleted from microfluidic dispensing device  110 , so as to maintain a desired negative pressure (i.e., backpressure) in chamber  148 , and thus changing the effective volume of the variable volume of fluid reservoir  136 . As used herein, the term “collapse” means to fall in, as to buckle, sag, or deflect. 
     Referring to  FIGS. 8 and 9 , for sake of further explanation, below, the variable volume of fluid reservoir  136 , also referred to herein as a bulk region, may be considered to have a proximal continuous ⅓ volume portion  136 - 1 , and a continuous ⅔ volume portion  136 - 4  that is formed from a central continuous ⅓ volume portion  136 - 2  and a distal continuous ⅓ volume portion  136 - 3 , with the central continuous ⅓ volume portion  136 - 2  separating the proximal continuous ⅓ volume portion  136 - 1  from the distal continuous ⅓ volume portion  136 - 3 . The proximal continuous ⅓ volume portion  136 - 1  is located closer to ejection chip  118  than the continuous ⅔ volume portion  136 - 4  that is formed from the central continuous ⅓ volume portion  136 - 2  and the distal continuous ⅓ volume portion  136 - 3 . 
     Referring to  FIGS. 6-9 and 16 , stir bar  132  resides in the variable volume of fluid reservoir  136  and chamber  148 , and is located within a boundary defined by the interior perimetrical wall  150  of chamber  148 . Stir bar  132  has a rotational axis  160  and a plurality of paddles  132 - 1 ,  132 - 2 ,  132 - 3 ,  132 - 4  that radially extend away from the rotational axis  160 . Stir bar  132  has a magnet  162  (see  FIG. 8 ), e.g., a permanent magnet, configured for interaction with an external magnetic field generator  164  (see  FIG. 1 ) to drive stir bar  132  to rotate around the rotational axis  160 . The principle of stir bar  132  operation is that as magnet  162  is aligned to a strong enough external magnetic field generated by external magnetic field generator  164 , then rotating the external magnetic field generated by external magnetic field generator  164  in a controlled manner will rotate stir bar  132 . The external magnetic field generated by external magnetic field generator  164  may be rotated electronically, akin to operation of a stepper motor, or may be rotated via a rotating shaft. Thus, stir bar  132  is effective to provide fluid mixing in fluid reservoir  136  by the rotation of stir bar  132  around the rotational axis  160 . 
     Fluid mixing in the bulk region relies on a flow velocity caused by rotation of stir bar  132  to create a shear stress at the settled boundary layer of the particulate. When the shear stress is greater than the critical shear stress (empirically determined) to start particle movement, remixing occurs because the settled particles are now distributed in the moving fluid. The shear stress is dependent on both the fluid parameters such as: viscosity, particle size, and density; and mechanical design factors such as: container shape, stir bar  132  geometry, fluid thickness between moving and stationary surfaces, and rotational speed. 
     Also, a fluid flow is generated by rotating stir bar  132  in a fluid region, e.g., the proximal continuous ⅓ volume portion  136 - 1  and fluid channel  156 , associated with ejection chip  118 , so as to ensure that mixed bulk fluid is presented to ejection chip  118  for nozzle ejection and to move fluid adjacent to ejection chip  118  to the bulk region of fluid reservoir  136  to ensure that the channel fluid flowing through fluid channel  156  mixes with the bulk fluid of fluid reservoir  136 , so as to produce a more uniform mixture. Although this flow is primarily distribution in nature, some mixing will occur if the flow velocity is sufficient to create a shear stress above the critical value. 
     Stir bar  132  primarily causes rotation flow of the fluid about a central region associated with the rotational axis  160  of stir bar  132 , with some axial flow with a central return path as in a partial toroidal flow pattern. 
     Referring to  FIG. 16 , each paddle of the plurality of paddles  132 - 1 ,  132 - 2 ,  132 - 3 ,  132 - 4  of stir bar  132  has a respective free end tip  132 - 5 . To reduce rotational drag, each paddle may include upper and lower symmetrical pairs of chamfered surfaces, forming leading beveled surfaces  132 - 6  and trailing beveled surfaces  132 - 7  relative to a rotational direction  160 - 1  of stir bar  132 . It is also contemplated that each of the plurality of paddles  132 - 1 ,  132 - 2 ,  132 - 3 ,  132 - 4  of stir bar  132  may have a pill or cylindrical shape. In the present embodiment, stir bar  132  has two pairs of diametrically opposed paddles, wherein a first paddle of the diametrically opposed paddles has a first free end tip  132 - 5  and a second paddle of the diametrically opposed paddles has a second free end tip  132 - 5 . 
     In the present embodiment, the four paddles forming the two pairs of diametrically opposed paddles are equally spaced at 90 degree increments around the rotational axis  160 . However, the actual number of paddles of stir bar  132  may be two or more, and preferably three or four, but more preferably four, with each adjacent pair of paddles having the same angular spacing around the rotational axis  160 . For example, a stir bar  132  configuration having three paddles may have a paddle spacing of 120 degrees, having four paddles may have a paddle spacing of 90 degrees, etc. 
     In the present embodiment, and with the variable volume of fluid reservoir  136  being divided as the proximal continuous ⅓ volume portion  136 - 1  and the continuous ⅔ volume portion  136 - 4  described above, with the proximal continuous ⅓ volume portion  136 - 1  being located closer to ejection chip  118  than the continuous ⅔ volume portion  136 - 4 , the rotational axis  160  of stir bar  132  may be located in the proximal continuous ⅓ volume portion  136 - 1  that is closer to ejection chip  118 . Stated differently, guide portion  134  is configured to position the rotational axis  160  of stir bar  132  in a portion of the interior space of chamber  148  that constitutes a ⅓ of the volume of the interior space of chamber  148  that is closest to fluid opening  140 - 3 . 
     Referring again also to  FIG. 11 , the rotational axis  160  of stir bar  132  may be oriented in an angular range of perpendicular, plus or minus 45 degrees, relative to the fluid ejection direction  120 - 1 . Stated differently, the rotational axis  160  of stir bar  132  may be oriented in an angular range of parallel, plus or minus 45 degrees, relative to the planar extent (e.g., plane  142 ) of ejection chip  118 . In combination, the rotational axis  160  of stir bar  132  may be oriented in both an angular range of perpendicular, plus or minus 45 degrees, relative to the fluid ejection direction  120 - 1 , and an angular range of parallel, plus or minus 45 degrees, relative to the planar extent of ejection chip  118 . 
     More preferably, the rotational axis  160  has an orientation substantially perpendicular to the fluid ejection direction  120 - 1 , and thus, the rotational axis  160  of stir bar  132  has an orientation that is substantially parallel to plane  142 , i.e., planar extent, of ejection chip  118  and that is substantially perpendicular to plane  146  of base wall  138 . Also, in the present embodiment, the rotational axis  160  of stir bar  132  has an orientation that is substantially perpendicular to plane  146  of base wall  138  in all orientations around rotational axis  160  and is substantially perpendicular to the fluid ejection direction  120 - 1 . 
     Referring to  FIGS. 6-9, 11, and 12 , the orientations of stir bar  132 , described above, may be achieved by guide portion  134 , with guide portion  134  also being located within chamber  148  in the variable volume of fluid reservoir  136  (see  FIGS. 8 and 9 ), and more particularly, within the boundary defined by interior perimetrical wall  150  of chamber  148 . Guide portion  134  is configured to confine stir bar  132  in a predetermined portion of the interior space of chamber  148  at a predefined orientation, as well as to split and redirect the rotational fluid flow from stir bar  132  towards channel inlet  156 - 1  of fluid channel  156 . On the return flow side, guide portion  134  helps to recombine the rotational flow received from channel outlet  156 - 2  of fluid channel  156  in the bulk region of fluid reservoir  136 . 
     For example, guide portion  134  may be configured to position the rotational axis  160  of stir bar  132  in an angular range of parallel, plus or minus 45 degrees, relative to the planar extent of ejection chip  118 , and more preferably, guide portion  134  is configured to position the rotational axis  160  of stir bar  132  substantially parallel to the planar extent of ejection chip  118 . In the present embodiment, guide portion  134  is configured to position and maintain an orientation of the rotational axis  160  of stir bar  132  to be substantially parallel to the planar extent of ejection chip  118  and to be substantially perpendicular to plane  146  of base wall  138  in all orientations around rotational axis  160 . 
     Guide portion  134  includes an annular member  166 , a plurality of locating features  168 - 1 ,  168 - 2 , offset members  170 ,  172 , and a cage structure  174 . The plurality of locating features  168 - 1 ,  168 - 2  are positioned on the opposite side of annular member  166  from offset members  170 ,  172 , and are positioned to be engaged by diaphragm  130 , which keeps offset members  170 ,  172  in contact with base wall  138 . Offset members  170 ,  172  maintain an axial position (relative to the rotational axis  160  of stir bar  132 ) of guide portion  134  in fluid reservoir  136 . Offset member  172  includes a retention feature  172 - 1  that engages body  122  to prevent a lateral translation of guide portion  134  in fluid reservoir  136 . 
     Referring again to  FIGS. 6 and 7 , annular member  166  of guide portion  134  has a first annular surface  166 - 1 , a second annular surface  166 - 2 , and an opening  166 - 3  that defines an annular confining surface  166 - 4 . Opening  166 - 3  of annular member  166  has a central axis  176 . Annular confining surface  166 - 4  is configured to limit radial movement of stir bar  132  relative to the central axis  176 . Second annular surface  166 - 2  is opposite first annular surface  166 - 1 , with first annular surface  166 - 1  being separated from second annular surface  166 - 2  by annular confining surface  166 - 4 . Referring also to  FIG. 9 , first annular surface  166 - 1  of annular member  166  also serves as a continuous ceiling over, and between, inlet fluid port  152  and outlet fluid port  154 . The plurality of offset members  170 ,  172  are coupled to annular member  166 , and more particularly, the plurality of offset members  170 ,  172  are connected to first annular surface  166 - 1  of annular member  166 . The plurality of offset members  170 ,  172  are positioned to extend from annular member  166  in a first axial direction relative to the central axis  176 . Each of the plurality of offset members  170 ,  172  has a free end configured to engage base wall  138  of chamber  148  to establish an axial offset of annular member  166  from base wall  138 . Offset member  172  also is positioned and configured to aid in preventing a flow bypass of fluid channel  156 . 
     The plurality of offset members  170 ,  172  are coupled to annular member  166 , and more particularly, the plurality of offset members  170 ,  172  are connected to second annular surface  166 - 2  of annular member  166 . The plurality of offset members  170 ,  172  are positioned to extend from annular member  166  in a second axial direction relative to the central axis  176 , opposite to the first axial direction. 
     Thus, when assembled, each of locating features  168 - 1 ,  168 - 2  has a free end that engages a perimetrical portion of diaphragm  130 , and each of the plurality of offset members  170 ,  172  has a free end that engages base wall  138 , with base wall  138  facing diaphragm  130 . 
     Cage structure  174  of guide portion  134  is coupled to annular member  166  opposite to the plurality of offset members  170 ,  172 , and more particularly, the cage structure  174  has a plurality of offset legs  178  connected to second annular surface  166 - 2  of annular member  166 . Cage structure  174  has an axial restraint portion  180  that is axially displaced by the plurality of offset legs  178  (three, as shown) from annular member  166  in the second axial direction opposite to the first axial direction. As shown in  FIG. 12 , axial restraint portion  180  is positioned over at least a portion of the opening  166 - 3  in annular member  166  to limit axial movement of stir bar  132  relative to the central axis  176  in the second axial direction. Cage structure  174  also serves to prevent diaphragm  130  from contacting stir bar  132  as diaphragm displacement (collapse) occurs during fluid depletion from fluid reservoir  136 . 
     As such, in the present embodiment, stir bar  132  is confined within the region defined by opening  166 - 3  and annular confining surface  166 - 4  of annular member  166 , and between axial restraint portion  180  of the cage structure  174  and base wall  138  of chamber  148 . The extent to which stir bar  132  is movable within fluid reservoir  136  is determined by the radial tolerances provided between annular confining surface  166 - 4  and stir bar  132  in the radial direction, and by the axial tolerances between stir bar  132  and the axial limit provided by the combination of base wall  138  and axial restraint portion  180 . For example, the tighter the radial and axial tolerances provided by guide portion  134 , the less variation of the rotational axis  160  of stir bar  132  from perpendicular relative to base wall  138 , and the less side-to-side motion of stir bar  132  within fluid reservoir  136 . 
     In the present embodiment, guide portion  134  is configured as a unitary insert member that is removably attached to housing  112 . Guide portion  134  includes retention feature  172 - 1  and body  122  of housing  112  includes a second retention feature  182 . First retention feature  172 - 1  is engaged with second retention feature  182  to attach guide portion  134  to body  122  of housing  112  in a fixed relationship with housing  112 . The first retention feature  172 - 1 /second retention feature  182  may be, for example, in the form of a tab/slot arrangement, or alternatively, a slot/tab arrangement, respectively. 
     Referring to  FIGS. 7 and 15 , guide portion  134  may further include a flow control portion  184 , which in the present embodiment, also serves as offset member  172 . Referring to  FIG. 15 , flow control portion  184  has a flow separator feature  184 - 1 , a flow rejoining feature  184 - 2 , and a concavely arcuate surface  184 - 3 . Concavely arcuate surface  184 - 3  is coextensive with, and extends between, each of flow separator feature  184 - 1  and flow rejoining feature  184 - 2 . Each of flow separator feature  184 - 1  and flow rejoining feature  184 - 2  is defined by a respective angled, i.e., beveled, wall. Flow separator feature  184 - 1  is positioned adjacent inlet fluid port  152  and flow rejoining feature  184 - 2  is positioned adjacent outlet fluid port  154 . 
     The beveled wall of flow separator feature  184 - 1  positioned adjacent to inlet fluid port  152  of chamber  148  cooperates with beveled inlet ramp  152 - 1  of inlet fluid port  152  of chamber  148  to guide fluid toward channel inlet  156 - 1  of fluid channel  156 . Flow separator feature  184 - 1  is configured such that the rotational flow is directed toward channel inlet  156 - 1  instead of allowing a direct bypass of fluid into the outlet fluid that exits channel outlet  156 - 2 . Referring also to  FIGS. 9 and 14 , positioned opposite beveled inlet ramp  152 - 1  is the fluid ceiling provided by first annular surface  166 - 1  of annular member  166 . Flow separator feature  184 - 1  in combination with the continuous ceiling of annular member  166  and beveled ramp wall provided by beveled inlet ramp  152 - 1  of inlet fluid port  152  of chamber  148  aids in directing a fluid flow into channel inlet  156 - 1  of fluid channel  156 . 
     Likewise, referring to  FIGS. 9, 14 and 15 , the beveled wall of flow rejoining feature  184 - 2  positioned adjacent to outlet fluid port  154  of chamber  148  cooperates with beveled outlet ramp  154 - 1  of outlet fluid port  154  to guide fluid away from channel outlet  156 - 2  of fluid channel  156 . Positioned opposite beveled outlet ramp  154 - 1  is the fluid ceiling provided by first annular surface  166 - 1  of annular member  166 . 
     In the present embodiment, flow control portion  184  is a unitary structure formed as offset member  172  of guide portion  134 . Alternatively, all or a portion of flow control portion  184  may be incorporated into interior perimetrical wall  150  of chamber  148  of body  122  of housing  112 . 
     In the present embodiment, as best shown in  FIG. 15 , stir bar  132  is oriented such that the plurality of paddles  132 - 1 ,  132 - 2 ,  132 - 3 ,  132 - 4  periodically face the concavely arcuate surface  184 - 3  of the flow control portion  184  as stir bar  132  is rotated about the rotational axis  160 . Stir bar  132  has a stir bar radius from rotational axis  160  to the free end tip  132 - 5  of a respective paddle. A ratio of the stir bar radius and a clearance distance between the free end tip  132 - 5  and flow control portion  184  may be 5:2 to 5:0.025. More particularly, guide portion  134  is configured to confine stir bar  132  in a predetermined portion of the interior space of chamber  148 . In the present example, a distance between the respective free end tip  132 - 5  of each of the plurality of paddles  132 - 1 ,  132 - 2 ,  132 - 3 ,  132 - 4  and concavely arcuate surface  184 - 3  of flow control portion  184  is in a range of 2.0 millimeters to 0.1 millimeters, and more preferably, is in a range of 1.0 millimeters to 0.1 millimeters, as the respective free end tip  132 - 5  faces concavely arcuate surface  184 - 3 . Also, it has been found that it is preferred to position stir bar  132  as close to ejection chip  118  as possible so as to maximize flow through fluid channel  156 . 
     Also, guide portion  134  is configured to position the rotational axis  160  of stir bar  132  in a portion of fluid reservoir  136  such that the free end tip  132 - 5  of each of the plurality of paddles  132 - 1 ,  132 - 2 ,  132 - 3 ,  132 - 4  of stir bar  132  rotationally ingresses and egresses a proximal continuous ⅓ volume portion  136 - 1  that is closer to ejection chip  118 . Stated differently, guide portion  134  is configured to position the rotational axis  160  of stir bar  132  in a portion of the interior space such that the free end tip  132 - 5  of each of the plurality of paddles  132 - 1 ,  132 - 2 ,  132 - 3 ,  132 - 4  rotationally ingresses and egresses the proximal continuous ⅓ volume portion  136 - 1  of the interior space of chamber  148  that includes inlet fluid port  152  and outlet fluid port  154 . 
     More particularly, in the present embodiment, wherein stir bar  132  has four paddles, guide portion  134  is configured to position the rotational axis  160  of stir bar  132  in a portion of the interior space such that the first and second free end tips  132 - 5  of each the two pairs of diametrically opposed paddles  132 - 1 ,  132 - 3  and  132 - 2 ,  132 - 4  alternatingly and respectively are positioned in the proximal continuous ⅓ portion  136 - 1  of the volume of the interior space of chamber  148  that includes inlet fluid port  152  and outlet fluid port  154  and in the continuous ⅔ volume portion  136 - 4  having the distal continuous ⅓ portion  136 - 3  of the interior space that is furthest from ejection chip  118 . 
     Referring again to  FIGS. 6-10 , diaphragm  130  is positioned between lid  124  and perimetrical end surface  150 - 3  of interior perimetrical wall  150  of chamber  148 . Referring also to  FIGS. 16 and 17 , diaphragm  130  is configured for sealing engagement with perimetrical end surface  150 - 3  of interior perimetrical wall  150  of chamber  148  in forming fluid reservoir  136  (see  FIGS. 8 and 9 ). 
     Referring to  FIGS. 10 and 17 , diaphragm  130  includes dome portion  130 - 1  and an exterior perimetrical rim  130 - 2 . Dome portion  130 - 1  includes a dome deflection portion  130 - 3 , a dome side wall  130 - 4 , a dome transition portion  130 - 5 , a dome crown  130 - 6 , and four web portions, individually identified as central corner web  130 - 7 , central corner web  130 - 8 , central corner web  130 - 9 , and central corner web  130 - 10 . Dome deflection portion  130 - 3  and the four web portions  130 - 7 ,  130 - 8 ,  130 - 9 ,  130 - 10  join dome portion  130 - 1  to exterior perimetrical rim  130 - 2 . In the orientation shown in  FIG. 10 , dome crown  130 - 6  includes a slight circular depression  130 - 11  in the right-most portion of dome crown  130 - 6  that is a manufacturing feature created during the molding of diaphragm  130 , and does not affect the operation of diaphragm  130 . 
     As will be described in more detail below, in the present embodiment, diaphragm  130  is configured such that during the collapse of diaphragm  130  during fluid depletion from fluid reservoir  136 , the displacement of dome portion  130 - 1  is uniform with dome crown  130 - 6  of diaphragm  130  becoming concave, as viewed from the outside of diaphragm  130 , and the direction of collapse, i.e., displacement, of dome portion  130 - 1  is along a deflection axis  188  that is substantially perpendicular to the fluid ejection direction  120 - 1  (see also  FIG. 11 ), is substantially perpendicular to plane  146  of base wall  138 , and is substantially parallel to plane  142  of chip mounting surface  140 - 2 . In the present embodiment, a position of deflection axis  188  substantially corresponds to a central region of dome portion  130 - 1 . Stated differently, during the collapse of diaphragm  130  during fluid depletion from fluid reservoir  136 , the direction of the movement of dome crown  130 - 6  of dome portion  130 - 1  of diaphragm  130  is along deflection axis  188  toward base wall  138 , and is substantially perpendicular to the fluid ejection direction  120 - 1 , is substantially perpendicular to plane  146  of base wall  138 , and is substantially parallel to plane  142  of chip mounting surface  140 - 2 . 
     Also, as shown in  FIGS. 6-10 and 17 , microfluidic dispensing device  110  is configured such that diaphragm  130  is oriented to extend across the largest surface area of chamber  148  in forming fluid reservoir  136 . As such, advantageously, an amount of movement of dome crown  130 - 6  of diaphragm  130  required to maintain the desired backpressure in fluid reservoir  136  is less than would be required if a diaphragm were somehow installed at a side wall location of body  122 . 
       FIGS. 18 and 19  show a bottom, i.e., interior, view of diaphragm  130 , wherein there is shown an interior perimetrical positioning rim  131 - 2 , an interior of dome deflection portion  130 - 3 , and an intermediate interior depressed region  131 - 4  interposed between interior perimetrical positioning rim  131 - 2  and dome deflection portion  130 - 3 . Interior perimetrical positioning rim  131 - 2  aids in locating diaphragm  130  relative to body  122 . A base of the intermediate interior depressed region  131 - 4  defines a continuous perimeter sealing surface  131 - 6 . Referring to  FIGS. 16-19 , continuous perimeter sealing surface  131 - 6  has a planar extent that surrounds chamber  148 , and with the planar extent being substantially parallel to plane  146  of base wall  138  and substantially perpendicular to plane  142  (see  FIG. 11 ). As such, during the collapse of diaphragm  130  during fluid depletion from fluid reservoir  136 , the direction of the movement of dome crown  130 - 6  of diaphragm  130  is substantially perpendicular to the planar extent of continuous perimeter sealing surface  131 - 6 . Dome deflection portion  130 - 3  defines an undulated transition between dome side wall  130 - 4  and continuous perimeter sealing surface  131 - 6 , as will be described in further detail below. 
     In the present embodiment, for example, interior perimetrical positioning rim  131 - 2 , intermediate interior depressed region  131 - 4 /continuous perimeter sealing surface  131 - 6 , and dome deflection portion  130 - 3  may be concentrically arranged relative to each other. In the present embodiment, referring to  FIG. 19 , an outer perimetrical shape of an outer perimeter OP 1  of continuous perimeter sealing surface  131 - 6  coincides with the outer perimetrical shape of interior perimetrical positioning rim  131 - 2 . Referring to  FIGS. 17 and 19 , an inner perimetrical shape of an inner perimeter IP 1  of exterior perimetrical rim  130 - 2  corresponds to the inner shape of continuous perimeter sealing surface  131 - 6  ( FIG. 19 ), but inner perimeter IP 1  does not coincide with the outer perimetrical shape of the outer perimeter OP 2  of dome deflection portion  130 - 3  because the respective curved corners have different curved shapes, e.g., by having different radii. As such, and referring to  FIG. 17 , at each respective curved corner between the inner perimetrical shape of the inner perimeter of continuous perimeter sealing surface  131 - 6  and the outer perimetrical shape of the outer perimeter of dome deflection portion  130 - 3 , there is defined a respective one of central corner webs  130 - 7 ,  130 - 8 ,  130 - 9 , and  130 - 10  of diaphragm  130 . 
     Referring also to  FIGS. 16 and 23-26 , body  122  includes a stepped arrangement that includes a lower channel  122 - 2 , an interior recessed surface  122 - 3 , and an exterior rim  122 - 4 . Exterior rim  122 - 4  has an upper inner side wall  122 - 5  that extends downwardly, in the orientation as shown, and vertically terminates at an outer edge of the interior recessed surface  122 - 3 . Channel  122 - 2  has a lower inner side wall  122 - 6  that extends upwardly, in the orientation as shown, to vertically terminate at an inner edge of the interior recessed surface  122 - 3 . As such, each of upper inner side wall  122 - 5  and lower inner side wall  122 - 6  is substantially perpendicular to the interior recessed surface  122 - 3 , with upper inner side wall  122 - 5  being laterally offset from lower inner side wall  122 - 6  by a width of interior recessed surface  122 - 3 , and with upper inner side wall  122 - 5  and lower inner side wall  122 - 6  being vertically offset by interior recessed surface  122 - 3 . 
     Channel  122 - 2  further includes an inner perimetrical side wall  122 - 7 , that also forms an outer perimeter surface portion of interior perimetrical wall  150 , and that is laterally spaced inwardly from the lower inner side wall  122 - 6 , such that inner perimetrical side wall  122 - 7  is the innermost side wall of channel  122 - 2  and lower inner side wall  122 - 6  is the outermost side wall of channel  122 - 2 . In particular, channel  122 - 2  having lower inner side wall  122 - 6  and inner perimetrical side wall  122 - 7  defines a recessed path in body  122  around perimetrical end surface  150 - 3  of body  122 , with the inner perimetrical side wall  122 - 7  vertically terminating at an outer edge of perimetrical end surface  150 - 3  of body  122 . 
     Referring to  FIGS. 23-26 , channel  122 - 2  of body  122  is sized and shaped to receive and guide interior perimetrical positioning rim  131 - 2  of diaphragm  130 , with interior perimetrical positioning rim  131 - 2  contacting inner perimetrical side wall  122 - 7 , and with lower inner side wall  122 - 6  of channel  122 - 2  of body  122  being intermittently engaged by a perimeter of exterior perimetrical rim  130 - 2  of diaphragm  130 , so as to guide diaphragm  130  into a proper position with body  122 . Also, the continuous perimeter sealing surface  131 - 6  of diaphragm  130  is sized and shaped to engage perimetrical end surface  150 - 3  of body  122  so as to facilitate a closed sealing engagement of diaphragm  130  with body  122 . Thus, when diaphragm  130  is properly positioned relative to body  122  by interior perimetrical positioning rim  131 - 2  and channel  122 - 2 , continuous perimeter sealing surface  131 - 6  of diaphragm  130  is positioned to engage perimetrical end surface  150 - 3  of body  122  around an entirety of perimetrical end surface  150 - 3 . In the present embodiment, perimetrical end surface  150 - 3  may include a single perimetrical rib, or a plurality of perimetrical ribs or undulations as shown, to provide an effective sealing surface for engagement with continuous perimeter sealing surface  131 - 6  of diaphragm  130 . 
       FIGS. 20 and 21  show an interior, or underside, of lid  124  having a recessed interior ceiling  124 - 2  that defines a recessed region  124 - 3  that is configured to accommodate a full (non-collapsed) height of dome portion  130 - 1  of diaphragm  130 . Referring also to  FIGS. 23-26 , lid  124  further includes an interior positioning lip  190 , a diaphragm pressing surface  192 , and an exterior positioning lip  194 , each of which laterally surrounds recessed region  124 - 3 , as best shown in  FIGS. 20 and 21 . Diaphragm pressing surface  192  is recessed between interior positioning lip  190  and exterior positioning lip  194 . 
     Exterior positioning lip  194  is used to position lid  124  relative to body  122 . In particular, during assembly, exterior positioning lip  194  is received and guided by upper inner side wall  122 - 5  of exterior rim  122 - 4  into contact with interior recessed surface  122 - 3  of body  122  (see also  FIG. 16 ). Also, the apex rim (sacrificial material  218 ; see  FIGS. 23-26 ) of exterior positioning lip  194  will be melted and joined to body  122  at interior recessed surface  122 - 3  during an ultrasonic welding process to attached lid  124  to body  122 . While ultrasonic welding is a current preferred method for attachment of lid  124  to body  122  in the present embodiment, it is contemplated that in some applications, another attachment method may be desired, such as for example, laser welding, mechanical attachment, adhesive attachment, etc. 
     Referring again to  FIGS. 20, 21, and 23-26 , interior positioning lip  190  of lid  124  is used to position diaphragm  130  relative to lid  124 , and interior perimetrical positioning rim  131 - 2  of diaphragm  130  is used to position diaphragm  130  relative to body  122 . In particular, referring also to  FIG. 17 , interior positioning lip  190  of lid  124  is sized and shaped to receive thereover the inner perimeter IP 1  of exterior perimetrical rim  130 - 2 , so as to position exterior perimetrical rim  130 - 2  of diaphragm  130  in opposition to diaphragm pressing surface  192  of lid  124 . 
     In addition, referring again to  FIGS. 20 and 21 , the present embodiment may include a plurality of diaphragm positioning features  194 - 1  that extend inwardly from exterior positioning lip  194 . The plurality of diaphragm positioning features  194 - 1  are located to engage an external perimeter of exterior perimetrical rim  130 - 2  of diaphragm  130  to help position diaphragm  130  relative to lid  124 . More particularly, in the present embodiment, exterior perimetrical rim  130 - 2  of diaphragm  130  is received in the region between interior positioning lip  190  of lid  124  and the plurality of diaphragm positioning features  194 - 1  of lid  124 , and interior perimetrical positioning rim  131 - 2  of diaphragm  130  is positioned in channel  122 - 2  of body  122 , and thereby together help to prevent the dome bending features, such as dome deflection portion  130 - 3 , and continuous perimeter sealing surface  131 - 6 , from being unduly distorted, or continuous perimeter sealing surface  131 - 6  from leaking, during assembly or negative pressure dome deflections of dome portion  130 - 1 . Also, interior positioning lip  190  of lid  124  and interior perimetrical positioning rim  131 - 2  of diaphragm  130  collectively limit an amount of seal distortion during collapse of diaphragm  130  when vacuum is generated in fluid reservoir  136  of microfluidic dispensing device  110  during assembly. 
     Referring again to  FIGS. 20 and 21 , diaphragm pressing surface  192  of lid  124  is planar, having a uniform height, so as to provide substantially uniform perimeter compression of diaphragm  130  (see also  FIGS. 17, 19, and 23-26 ) at continuous perimeter sealing surface  131 - 6  around dome portion  130 - 1 . In particular, diaphragm pressing surface  192  of lid  124  is sized and shaped to force continuous perimeter sealing surface  131 - 6  of diaphragm  130  into sealing engagement with perimetrical end surface  150 - 3  of body  122  around an entirety of perimetrical end surface  150 - 3  of body  122 , when lid  124  is attached to body  122 . 
     Referring also to  FIG. 22 , a dome vent chamber  196  having a variable volume is defined in the region between dome portion  130 - 1  of diaphragm  130  and lid  124 . As fluid is depleted from fluid reservoir  136 , dome portion  130 - 1  of diaphragm  130  collapses accordingly, thus increasing the volume of dome vent chamber  196 , while decreasing the volume of fluid reservoir  136 , so as to maintain the desired backpressure in fluid reservoir  136 . 
     Referring again to  FIGS. 20 and 21 , located on interior ceiling  124 - 2  of lid  124  is a rib  198  and a rib  200 , with rib  198  being spaced apart from rib  200 . Vent hole  124 - 1  is located in lid  124  between ribs  198 ,  200 . Ribs  198 ,  200  provide a spacing between interior ceiling  124 - 2  of lid  124  and dome portion  130 - 1  of diaphragm  130  in a region around vent hole  124 - 1  (see also  FIGS. 17 and 22 ). As such, ribs  198 ,  200  help to avoid a sticking contact between dome portion  130 - 1  of diaphragm  130  and interior ceiling  124 - 2  of lid  124 , which could result in an undesirable de-priming of ejection chip  118  because the sticking would prevent a collapse of dome portion  130 - 1  as ink is depleted from chamber  148 . 
     As shown in  FIGS. 20 and 21 , included on opposite sides of, and laterally extending through, interior positioning lip  190  is a dome vent path  124 - 4  and a dome vent path  124 - 5 , which supplement vent hole  124 - 1  formed in a central portion of lid  124  in venting the region between dome portion  130 - 1  of diaphragm  130  and lid  124 . Lid  124  further includes a side vent opening  124 - 6  and a side vent opening  124 - 7 , which are in fluid communication with the atmosphere external to microfluidic dispensing device  110 . Each of dome vent paths  124 - 4 ,  124 - 5  is in fluid communication with one or both of side vent openings  124 - 6 ,  124 - 7 . 
     Vent hole  124 - 1 , and the combination of one or more of dome vent path  124 - 4  and a dome vent path  124 - 5  with one or more of side vent openings  124 - 6  and  124 - 7 , facilitate communication of the exterior of dome portion  130 - 1  with the atmosphere external to microfluidic dispensing device  110  when microfluidic dispensing device  110  is fully assembled, i.e., when lid  124  is attached to body  122 . 
     Vent hole  124 - 1 , dome vent path  124 - 4 , and a dome vent path  124 - 5  provide venting redundancy to the region between dome portion  130 - 1  of diaphragm  130  and the interior ceiling  124 - 2  of lid  124 , so as to facilitate a collapse of dome portion  130 - 1  as fluid is depleted from microfluidic dispensing device  110 , even if one or more, but not all, of the vent hole  124 - 1  and side vent openings  124 - 6 ,  124 - 7  is blocked. For example, even if vent hole  124 - 1  was blocked, such as by product labeling, venting of the region between dome portion  130 - 1  and lid  124  is maintained by one or more of dome vent path  124 - 4  and a dome vent path  124 - 5  via one or more of side vent openings  124 - 6 ,  124 - 7 . 
     Referring again to  FIG. 22 , microfluidic dispensing device  110  is configured with an external split  202  (depicted by a dashed horizontal line) at a juncture of body  122  and lid  124 . During ultrasonic welding of lid  124  to body  122 , an external perimetrical gap  204  between body  122  and lid  124  at split  202  is reduced as material is melted and reformed at the junction of lid  124  and body  122 . 
     Split  202  is perpendicular to the chip mounting surface  140 - 2  and the orientation of ejection chip  118 . The location of split  202  is designed such that body  122 , and not lid  124 , defines the chip mounting surface  140 - 2 , fluid channel  156 , fluid reservoir  136 , and the perimetrical end surface  150 - 3  (that contacts the continuous perimeter sealing surface  131 - 6  of diaphragm  130 ). Split  202  is positioned away from chip mounting surface  140 - 2  and fluid channel  156  to minimize distortion issues in the chip pocket and fluid channel areas during the processes such as welding or chip attachment. Also, split  202  is positioned away from chip mounting surface  140 - 2  and fluid channel  156  to minimize post manufacturing issues, such as sensitivity to handling or chip stress. 
     The location of split  202  also is positioned so that lid  124  has sufficient structure to allow uniform compression of the continuous perimeter sealing surface  131 - 6  of diaphragm  130 . Diaphragm  130  has sufficient material thickness in the region of continuous perimeter sealing surface  131 - 6  to prevent loss of seal compression during the life of microfluidic dispensing device  110 . Lid  124  defines a raised section (recessed region  124 - 3 ; see  FIGS. 20 and 21 ) that accommodates dome vent chamber  196  and dome portion  130 - 1  of diaphragm  130 , so that there is displaceable volume (i.e., a portion of fluid reservoir  136 ) that is located above the perimetrical end surface  150 - 3  of body  122 , that contacts the continuous perimeter sealing surface  131 - 6  of diaphragm  130 . 
     To achieve the advantages set forth above, in one preferred design of microfluidic dispensing device  110 , design criteria has been established that defines distance ranges for the location of certain components of the design. 
     Referring to  FIG. 22 , in conjunction with  FIGS. 17-21 , four distance ranges are defined, as follows: distance  206 , distance  208 , distance  210 , and distance  212 . 
     Distance  206  is the distance (length, e.g., height) from exterior base surface  214  of base wall  138  of body  122  to the vertical center of ejection chip  118 , which corresponds to the center of the chip mounting surface  140 - 2 , i.e., the chip pocket, (see  FIG. 7 ) which holds ejection chip  118 . As alternatively defined, distance  206  is the distance from exterior base surface  214  of base wall  138  of body  122  to the vertical center of fluid channel  156 . 
     Distance  208  is the distance (length, e.g., height) from exterior base surface  214  of base wall  138  of body  122  to the perimetrical end surface  150 - 3  of interior perimetrical wall  150  of body  122 , wherein interior perimetrical wall  150  defines a portion of fluid reservoir  136  and the height of chamber  148 . 
     Distance  210  is the distance (length, e.g., height) from exterior base surface  214  of base wall  138  of body  122  to the top of exterior wall  140 - 1  of body  122  at the location of split  202 . 
     Distance  212  is the distance (length, e.g., height) from exterior base surface  214  of base wall  138  of body  122  to the top of a portion  216  of lid  124  around recessed region  124 - 3  that accommodates dome portion  130 - 1  of diaphragm  130 , e.g., portion  216  of lid  124  that internally is variably spaced from adjacent dome crown  130 - 6  of diaphragm  130  by a displacement of dome crown  130 - 6  of diaphragm  130 . 
     The relationship between the distances  206 ,  208 ,  210 ,  212  are defined by the following mathematical expressions:
 
 A&lt;B&lt;D;A&lt;C&lt;D;  
 
20%&lt;( A/C )&lt;80%;20%&lt;( A/B )&lt;80%;
 
40%&lt;( C/D )&lt;95%; and 40%&lt;( B/D )&lt;95%, wherein:
 
     A=distance  206 ; B=distance  208 ; C=distance  210 ; and D=distance  212 . 
     Stated differently, referring to  FIG. 22 , the ratio of the distance  206  and distance  210  is in a range of 20 percent to 80 percent, the ratio of the distance  206  and distance  208  is in a range of 20 percent to 80 percent, the ratio of the distance  210  and distance  212  is in a range of 40 percent to 95 percent, and the ratio of the distance  208  and distance  212  is in a range of 40 percent to 95 percent, and wherein distance  206  is less than distance  208  and distance  208  is less than distance  212 ; and, distance  206  is less than distance  210  and distance  210  is less than distance  212 . 
     Referring to  FIGS. 23-26 , the attachment of lid  124  to body  122  compresses a perimeter of diaphragm  130  thereby creating a continuous seal between diaphragm  130  and body  122 .  FIGS. 23-26 , for example, respectively illustrate four example stages of compression of the perimeter of diaphragm  130  as lid  124  is attached to body  122  via ultrasonic welding, wherein  FIG. 23  depicts component positions prior to welding lid  124  to body  122 , and  FIG. 26  depicts component positions at the end of the welding process, with lid  124  securely attached to body  122 . 
     Referring to  FIGS. 23-26 , during the ultrasonic welding process, the perimetrical gap  204  is progressively reduced as sacrificial material  218  is melted from exterior positioning lip  194  of lid  124  and redistributed in joining lid  124  to body  122 . In doing so, a compressive force is applied to exterior perimetrical rim  130 - 2  of diaphragm  130  by diaphragm pressing surface  192  of lid  124 . Stated differently, exterior perimetrical rim  130 - 2  of diaphragm  130  is compressed between diaphragm pressing surface  192  of lid  124  and perimetrical end surface  150 - 3  of body  122  so as to engage continuous perimeter sealing surface  131 - 6  of diaphragm  130  in sealing engagement with perimetrical end surface  150 - 3  of body  122 . 
     During the welding process, interior positioning lip  190  and exterior positioning lip  194  (including diaphragm positioning features  194 - 1  shown in  FIGS. 20 and 21 ) of lid  124 , and interior perimetrical positioning rim  131 - 2  of diaphragm  130 , together help to prevent the dome bending features, such as dome deflection portion  130 - 3 , and continuous perimeter sealing surface  131 - 6 , from being unduly distorted, or continuous perimeter sealing surface  131 - 6  from leaking. 
     Again, by way of example,  FIGS. 23-26  respectively illustrate four example stages within the progressive compression of exterior perimetrical rim  130 - 2  of diaphragm  130  as lid  124  is attached to body  122  via ultrasonic welding.  FIG. 23  depicts component positions prior to welding lid  124  to body  122 , and in this example, perimetrical gap  204  is 850 microns, wherein the weld distance is 0.0 microns and the elastomeric material compression of exterior perimetrical rim  130 - 2  of diaphragm  130  is −312 microns. The negative value for elastomeric material compression means that there is a gap between diaphragm pressing surface  192  of lid  124  and exterior perimetrical rim  130 - 2  of diaphragm  130 .  FIG. 24  depicts component positions during an initial intermediate stage of welding lid  124  to body  122 , with perimetrical gap  204  at 538 microns, wherein the weld distance is 312 microns and the elastomeric material compression of exterior perimetrical rim  130 - 2  of diaphragm  130  is 0.0 microns, i.e., initial contact of diaphragm pressing surface  192  of lid  124  with exterior perimetrical rim  130 - 2  of diaphragm  130 .  FIG. 25  depicts component positions during a later intermediate stage of welding lid  124  to body  122 , with perimetrical gap  204  at 388 microns, wherein the weld distance is 462 microns and the elastomeric material compression of exterior perimetrical rim  130 - 2  of diaphragm  130  is 150 microns, i.e., diaphragm pressing surface  192  of lid  124  is engaged with and compressing exterior perimetrical rim  130 - 2  of diaphragm  130  against perimetrical end surface  150 - 3  of body  122 .  FIG. 26  depicts component positions at the completion of welding lid  124  to body  122 , with perimetrical gap  204  at 238 microns, wherein the weld distance is 612 microns and the elastomeric material compression of exterior perimetrical rim  130 - 2  of diaphragm  130  is 300 microns, i.e., diaphragm pressing surface  192  of lid  124  is at maximum compression of exterior perimetrical rim  130 - 2  of diaphragm  130 . 
       FIG. 27  shows a modification to the design depicted in  FIGS. 23-26 , wherein the diaphragm pressing surface  192  of lid  124  of  FIGS. 23-26  is modified to form a lid  220  having a downwardly facing perimetrical protrusion  222  that is cone-like in cross-section, and engages exterior perimetrical rim  130 - 2  of diaphragm  130 , to force exterior perimetrical rim  130 - 2  into sealing engagement with perimetrical end surface  150 - 3  of body  122 . In the present embodiment, perimetrical end surface  150 - 3  of body  122  may be flat, or may include one or more upwardly facing perimetrical ribs or undulations, to provide an effective sealing surface for engagement with diaphragm  130 . 
     As mentioned above, it is desirable to maintain some backpressure in fluid reservoir  136  so as to prevent weeping of fluid from ejection chip  118 . However, if the backpressure becomes too high, thus causing air ingestion through the nozzles, then an inadequate amount of fluid may be delivered to ejection chip  118 , thus resulting in erratic fluid expulsion, if any, from ejection chip  118 . 
     In the examples provided above, backpressure (negative pressure) is generated in fluid reservoir  136 , with diaphragm  130  being configured to balance forces and active areas to achieve the desired backpressure. 
     Diaphragm  130  is made of elastomeric material, and thus the force generated by diaphragm  130  is through deformation of the elastomeric material, e.g., bending and/or stretching of the elastomeric material, in the regions of dome portion  130 - 1  and/or dome deflection portion  130 - 3 . Deformation of the elastomeric material forming diaphragm  130  may be dependent on such factors as the wall thickness of regions of diaphragm  130 , the cross-section profile shape (e.g., undulations, straight vs. curved, etc.) of regions of diaphragm  130 , and/or durometer of the elastomeric material. The effective area over which this force is applied is the movable portion of the elastomeric material i.e., dome portion  130 - 1  and/or dome deflection portion  130 - 3  of diaphragm  130 , that is located laterally inwardly away from the stationary support provided by perimetrical end surface  150 - 3  of body  122 . 
       FIG. 28  is a graph showing an ideal backpressure range  230  for microfluidic dispensing device  110  having a stir bar guide, such as guide portion  134  (see also  FIGS. 1 and 6 ). In the present example, the ideal backpressure range  230  is a range of −5 to −15 inches H 2 O through the range of deliverable fluid, i.e., to the end of the lifetime  232  of microfluidic dispensing device  110 , as represented on the graph of  FIG. 28  by the vertical dashed line. Those skilled in the art will recognize that the ideal backpressure range  230  for a given fluidic dispensing device design may differ from the range identified above, depending on such factors as variations in the size of the fluidic dispensing device, the capacity of the fluid reservoir, and/or the amount of fluid in the reservoir. 
     In  FIG. 28 , curve  234  represents an initial design for a diaphragm for use in microfluidic dispensing device  110 , and curve  236  represents a refinement of the diaphragm design from the initial design to achieve the ideal backpressure range  230  for the lifetime  232  of microfluidic dispensing device  110 . In the general configuration of the diaphragm, e.g., diaphragm  130 , dome backpressure increases and starts to become more constant (e.g., at fluid depletion of 0.5 cubic centimeters (cc) in this example) as the rolling of the elastomeric material occurs at dome deflection portion  130 - 3  and/or dome side wall  130 - 4  of dome portion  130 - 1 . 
     Each of curves  234  and  236  illustrate the end of the useful life of a respective microfluidic dispensing device at lifetime  232 , which in the present example occurs at 1.25 cc of fluid depletion, that is characterized by a sharp increase in backpressure (a sharp decrease in pressure). For example, referring also to  FIG. 22 , it has been observed that when diaphragm  130  has collapsed to the point where dome portion  130 - 1 , e.g., dome crown  130 - 6 , starts to contact features (e.g., a stir bar guide or stir bar) internal to fluid reservoir  136 , the rate of backpressure change increases, since the design of diaphragm  130  can no longer adequately counteract the backpressure increase due to further fluid depletion (fluid expulsion) from fluid reservoir  136 . 
     While it may be possible to extend the lifetime  232  somewhat by removal of the stir bar guide, it is noted that the stir bar guide, such as guide portion  134 , advantageously prevents dome portion  130 - 1 , e.g., dome crown  130 - 6 , from contacting the stir bar, e.g., stir bar  132 , thereby preventing the collapse of diaphragm  130  from impeding rotation of stir bar  132 , resulting in a loss of mixing capability. Stated differently, in the present example having guide portion  134 , the effective range of deflection of dome portion  130 - 1  along deflection axis  188  that corresponds to the lifetime  232  is the distance from the maximum height of dome crown  130 - 6  over base wall  138  to the height of guide portion  134  over base wall  138 , i.e., the position where dome portion  130 - 1  contacts guide portion  134 . 
     In  FIG. 28 , curve  234  represents an initial design for a diaphragm for use in microfluidic dispensing device  110 , which is shown to provide undesirable results relative to the ideal backpressure range  230 , since after 0.25 cc fluid depletion the backpressure exceeds the maximum backpressure of the ideal backpressure range  230 , e.g., a backpressure greater than −15 inches H 2 O in this example. In practice, it is desirable for microfluidic dispensing device  110  to enter the ideal backpressure range  230  as quickly as possible, and then remain in the ideal backpressure range  230  throughout the lifetime  232  of microfluidic dispensing device  110 , as generally depicted by curve  236 . Thus, for an initial design that does not achieve the desired backpressure criteria, as represented by curve  234 , diaphragm design refinements are desirable such that the backpressure versus fluid depletion characteristics of microfluidic dispensing device  110  of the present design more closely emulate the curve  236  during the lifetime  232 . 
     While the construction of fluidic dispensing devices in accordance with the present invention may vary in size and fluid capacity, the general construction and operating principles remain the same throughout. As such, one skilled in the art will recognize that the ideal backpressure range  230  and curve  236  depicted by example in  FIG. 28  is specific to a microfluidic dispensing device, such as microfluidic dispensing device  110 , and that other ideal backpressure ranges and/or operation curves may be established to take into account the size and fluid capacity differences of various fluidic dispensing devices. 
     Referring now to  FIGS. 29A-C ,  30 A-C, and  31 A-C, there is shown three examples of variations on the diaphragm design that may be used to approximate operation curve  236 , which during its lifetime  232  does not have a backpressure that exceeds the maximum backpressure, e.g., a backpressure less than −15 inches H 2 O in this example, of the ideal backpressure range  230 , depicted in  FIG. 28 . Each of  FIGS. 29A-C ,  30 A-C, and  31 A-C show the respective diaphragm  130 ,  260 ,  280  in its rest state, i.e., under no backpressure. 
     Each of diaphragms  130 ,  260 ,  280  is configured to collapse along deflection axis  188  in a direction that is initially toward, and then away from, the plane of continuous perimeter sealing surface  131 - 6 , wherein the deflection axis  188  is substantially perpendicular to the plane of continuous perimeter sealing surface  131 - 6 . Also, each of diaphragms  130 ,  260 ,  280  has a cross-section profile (e.g., shape and/or taper and/or thickness) that is selected to control the deflection, i.e., collapse, of the respective dome portion  130 - 1 ,  260 - 1 ,  280 - 1  at a given backpressure represented by the graph of  FIG. 28 . 
       FIGS. 29A-29C  show diaphragm  130 , as described above, in a horizontal orientation, i.e., a planar extent of continuous perimeter sealing surface  131 - 6  is horizontal, as shown. As best shown in  FIGS. 29B and 29C , the portions of diaphragm  130  that have an influence on the collapse characteristics of diaphragm  130  during fluid depletion are dome deflection portion  130 - 3 , dome side wall  130 - 4 , dome transition portion  130 - 5 , and dome crown  130 - 6 . 
     Dome deflection portion  130 - 3  has a curved S-shaped configuration in cross-section having a curved extent  240 . Dome side wall  130 - 4  has a tapered cross-section profile, i.e., the wall thickness increases in a direction from the dome deflection portion  130 - 3  to dome transition portion  130 - 5 , and has a straight extent  242  at an off-vertical angle  244  of 22±3 degrees relative to the vertical axis at the juncture of dome transition portion  130 - 5  and dome crown  130 - 6 . Dome transition portion  130 - 5  has substantially uniform thickness (i.e., ±5 percent uniform thickness) in cross-section, having a straight extent  246  at an off-vertical angle  248  of 72±3 degrees. Dome crown  130 - 6  has substantially uniform thickness in cross-section, having a straight extent  250  and is horizontal, i.e., with an off-vertical angle of 90 degrees, such that a planar extent of dome crown  130 - 6  is substantially perpendicular to a plane of continuous perimeter sealing surface  131 - 6 . The hardness of the elastomeric material constituting diaphragm  130  is 40±3 durometer. This configuration was found to achieve the pressure versus deliverable fluid curve  236  of  FIG. 28 , with a backpressure variation range of plus or minus five percent. 
       FIGS. 30A-30C  show a diaphragm  260 , which is designed as a suitable replacement for diaphragm described above. Diaphragm  260  has in common with diaphragm  130  the exterior perimetrical rim  130 - 2 ; dome deflection portion  130 - 3 ; four web portions  130 - 7 ,  130 - 8 ,  130 - 9 ,  130 - 10 ; interior perimetrical positioning rim  131 - 2 , intermediate interior depressed region  131 - 4 ; and continuous perimeter sealing surface  131 - 6 . For purposes of discussion, diaphragm  260  is in a horizontal orientation, i.e., the planar extent of continuous perimeter sealing surface  131 - 6  is horizontal, as shown. As best shown in  FIGS. 30B and 30C , the portions of diaphragm  260  that have an influence on the collapse characteristics of diaphragm  260  during fluid depletion are dome deflection portion  130 - 3  and dome portion  260 - 1  having dome side wall  260 - 4 , dome transition portion  260 - 5 , and dome crown  260 - 6 . 
     Dome deflection portion  130 - 3  has a curved S-shaped configuration in cross-section having a curved extent  240 , and is identical to the corresponding cross-section of diaphragm  130 . 
     Dome side wall  260 - 4  has a tapered cross-section profile, i.e., the wall thickness increases in a direction from the dome deflection portion  130 - 3  to dome transition portion  260 - 5 , and has a straight extent  262  at an off-vertical angle  264  of 17±3 degrees relative to the vertical axis at the juncture of dome transition portion  260 - 5  and dome crown  260 - 6 . While dome side wall  260 - 4  is similar in cross-section profile to dome side wall  130 - 4  of diaphragm  130 , it is noted that the amount of taper of dome side wall  260 - 4  is less than dome side wall  130 - 4  of diaphragm  130 . As such, dome side wall  260 - 4  has a thinner cross-section profile than dome side wall  130 - 4  of diaphragm  130 . It has been found that changing the thickness of the dome side wall of the dome portion has an effect of changing the elasticity, i.e., stretchiness, of the dome side wall along its length, e.g., height, and thus having an effect on the deflection of the respective dome portion along deflection axis  188 . 
     Dome transition portion  260 - 5  has non-uniform thickness in cross-section, having a curved extent  266  having a bell-like flared portion  268  in cross-section that flares in thickness to join with dome crown  260 - 6 . Curved extent  266  is oriented at an off-vertical angle  270  of 80±3 degrees. 
     Dome crown  260 - 6  has substantially uniform thickness, having a straight extent  272  and is horizontal, i.e., with an off-vertical angle of 90 degrees. The hardness of the elastomeric material constituting diaphragm  260  is 50±3 durometer. This configuration was found to achieve the pressure versus deliverable fluid curve  236  of  FIG. 28 , with a backpressure variation range of plus or minus five percent. 
     Thus, each of diaphragm  130  and diaphragm  260  was able to achieve the pressure versus deliverable fluid curve  236  of  FIG. 28 . However, in comparison to diaphragm  130 , diaphragm  260  was able to do so using a higher durometer elastomeric material by reducing the amount of wall thickness of dome side wall  260 - 4 , and by reducing the thickness and adopting a curved bell-like shape for dome transition portion  260 - 5 . However, the more complex shape of diaphragm  260  may increase manufacturing complexity over that of diaphragm  130 . 
     Thus, changes in the cross-section profile of a respective diaphragm are effected by at least one of changing a shape of the dome transition portion, and changing an amount of a taper of the dome side wall in a direction toward the dome transition portion, thereby changing a thickness of the dome side wall. Further, at least one of a cross-section profile taper/thickness of the dome side wall and a shape of the dome transition portion may be selected based at least in part on the durometer of the elastomeric material selected for use for manufacturing the respective diaphragm. It is further noted that differences in the angular relationships of the dome side wall and the dome transition portion may be realized to accommodate the change in taper/thickness and/or shape of the cross-section profile. 
       FIGS. 31A-31C  show a diaphragm  280 , which is designed as a suitable replacement for diaphragms  130  and/or  260  described above. Diaphragm  280  is similar in many respects to diaphragm  130 , except for the use of a higher durometer elastomeric material and the use of a dome portion  280 - 1  having a thinner dome side wall  280 - 4 . For purposes of discussion, diaphragm  280  is in a horizontal orientation, i.e., the planar extent of continuous perimeter sealing surface  131 - 6  is horizontal, as shown. As best shown in  FIGS. 31B and 31C , the portions of diaphragm  280  that have an influence on the collapse characteristics of diaphragm  280  during fluid depletion are dome deflection portion  130 - 3 , and dome portion  280 - 1  having dome side wall  280 - 4 , dome transition portion  280 - 5 , and dome crown  280 - 6 . 
     Dome deflection portion  130 - 3  has a curved S-shaped configuration in cross-section having a curved extent  240 . 
     Dome side wall  280 - 4  has a tapered cross-section profile, i.e., the wall thickness increases in a direction from the dome deflection portion  130 - 3  to dome transition portion  280 - 5 , and has a straight extent  282  at an off-vertical angle  284  of 17±3 degrees relative to the vertical axis at the juncture of dome transition portion  280 - 5  and dome crown  280 - 6 . While dome side wall  280 - 4  is similar in cross-section profile to dome side wall  130 - 4  of diaphragm  130  or dome side wall  260 - 4  of diaphragm  260 , it is noted that the amount of taper of dome side wall  280 - 4  is less than either of dome side wall  130 - 4  of diaphragm  130  or dome side wall  260 - 4  of diaphragm  260 . As such, dome side wall  260 - 4  has a thinner cross-section profile than dome side wall  130 - 4  of diaphragm  130  or dome side wall  260 - 4  of diaphragm  260 . 
     Dome transition portion  280 - 5  has substantially uniform thickness in cross-section, having a straight extent  286  at an off-vertical angle  288  of 77±3 degrees. 
     Dome crown  280 - 6  has substantially uniform thickness in cross-section, having a straight extent  290  and is horizontal, i.e., with an off-vertical angle of 90 degrees. 
     The hardness of the elastomeric material constituting diaphragm  280  is 50±3 durometer. This configuration was found to achieve the pressure versus deliverable fluid curve  236  of  FIG. 28 , with a backpressure variation range of plus or minus five percent. 
     Thus, each of diaphragm  130 , diaphragm  260 , and diaphragm  280  was able to achieve the pressure versus deliverable fluid curve  236  of  FIG. 28 . However, in comparison to diaphragm  130 , diaphragm  280  was able to do so using a higher durometer elastomeric material by reducing the amount of wall thickness of dome side wall  280 - 4 . Accordingly, the configuration of diaphragm  280  retains the manufacturing simplicity of the design of diaphragm  130 , while permitting the use of a higher durometer material than that of diaphragm  130 . 
     While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.