Abstract:
Micro-fluid jetting devices and methods for ejecting fluid mixtures on a substrate are disclosed. Embodiments of the invention show fluid-flow architecture whereby fluid channels direct a plurality of fluids from their respective reservoirs to be ejected through the nozzles of a nozzle plate.

Description:
TECHNICAL FIELD 
       [0001]    The invention relates to micro-fluid jetting devices and in particular to multi-fluid, handheld jetting devices having improved fluid ejection characteristics. 
       BACKGROUND AND SUMMARY 
       [0002]    Micro-fluid jetting devices are suitable for a wide variety of applications including, but not limited to, hand-held ink jet printers, ink jet highlighters, and ink jet air brushes. One of the challenges to providing such micro-fluid jetting devices on a large scale is to provide a manufacturing process that enables high yields of high quality jetting devices. Another challenge is to provide fluid jetting devices, such as handheld painting and printing devices that are capable of precisely reproducing any color at any time without color anomalies, which may include color halos. 
         [0003]    The use of handheld ink jet jetting devices for applying single colors to an object such as paper is a relatively simple operation. However, providing a mixture of color inks to an object using a micro-fluid jetting device presents significantly more challenges. For example, conventional handheld ink jet printing devices for printing multiple colors have a substantially linear nozzle arrangement as shown in  FIG. 1 . Nozzle holes  2  for cyan,  3  for magenta and  4  for yellow are illustrated. When the printhead having the foregoing substantially linear nozzle arrangement is used to produce a single solid color that is a mixture of two or more ink colors, unwanted color areas (hereafter referred to as “halos”) are deposited on the substrate as the printing device is moved. For example, when a conventional handheld ink jet printing device is moved in a perfectly linear direction, indicated by arrow  5 , across a substrate to provide a composite black bar  6 , unwanted cyan  7  and purple  8  halos appear on one side of the black bar  6  and unwanted orange  9  and yellow  11  halos appear on an opposite side of the black bar  6  along the linear direction the ink jet printing device is being moved, if the speed of movement is not perfectly linked to the timing of ink ejection. Additional halos may be formed if the printhead does not move in a perfectly linear direction. In order to produce the black bar  6 , the printhead must be moved substantially in the direction indicated by arrow  5 . If the printhead is moved perpendicular to the direction indicated by arrow  5 , composite colors cannot be printed because nozzle holes  2  for cyan,  3  for magenta, and  4  for yellow do not pass over the same point on the media. Accordingly, there is a need for improved handheld micro-fluid jetting devices that provide more uniform jetting of fluids when moved in a linear direction across a media. 
         [0004]    With regard to the foregoing and other objects and advantages exemplary embodiments of the disclosure provide a micro-fluid jetting device and a method of ejecting fluid mixtures onto a substrate. The micro-fluid jetting device includes a housing containing a logic circuit and fluid reservoirs for at least two different fluids. A micro-fluid ejection head is attached to a first end of the housing. The ejection head is in electrical communication with the logic circuit and the fluid reservoirs. At least two channel members are provided for directing fluid from the reservoirs to a plurality of fluid ejection nozzles in a nozzle plate member. The ejection nozzles for each of the at least two different fluids are arranged in the nozzle plate member so that adjacent ejection nozzles are in flow communication with different fluids. A power source in electrical connection with the micro-fluid ejection head is provided in the housing for activating the micro-fluid ejection head for jetting the fluids therefrom. 
         [0005]    In another embodiment, the disclosure provides a method for jetting different fluids to provide a mixture of different fluids deposited onto a substrate. The method includes providing a housing containing a logic circuit, fluid reservoirs for at least two different fluids, and a micro-fluid ejection head attached to a first end of the housing. The ejection head is in electrical communication with the logic circuit and the fluid reservoirs. At least two channel members are provided in the ejection head for directing fluid from the reservoirs to a plurality of fluid ejection nozzles in a nozzle plate member. The ejection nozzles for each of the at least two different fluids are arranged in the nozzle plate member so that adjacent ejection nozzles are in flow communication with different fluids. A power source in electrical connection with the micro-fluid ejection head is provided in the housing for activating the micro-fluid ejection head for jetting the fluids therefrom. Upon activation of the micro-fluid ejection head a mixture of fluids is ejected onto the substrate. 
         [0006]    An advantage of the exemplary embodiments described herein is that an essentially uniform mixture of fluids may be ejected onto a substrate regardless of the direction the printhead is being moved without causing the halo effect provided by conventional handheld fluid ejection devices. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Further advantages of the exemplary embodiments may become apparent by reference to the detailed description of preferred embodiments when considered in conjunction with the drawings, wherein like reference characters designate like or similar elements throughout the several drawings as follows: 
           [0008]      FIG. 1  is a schematic view of a prior art nozzle plate arrangement for an ink jet printhead and a resulting image having unwanted halos; 
           [0009]      FIG. 2  is a perspective view, not to scale, of a micro-fluid jetting device according to an exemplary embodiment; 
           [0010]      FIG. 3  is a partial exploded view, in perspective, of components of a micro-fluid jetting device according to the disclosure; 
           [0011]      FIG. 4  is a plan view, not to scale, of fluid openings for a fluid reservoir for a micro-fluid jetting device according to a first embodiment of the disclosure wherein the fluid reservoir contains four fluids; 
           [0012]      FIGS. 5-9  are plan views, not to scale, of fluid channel plates for a micro-fluid jetting device according to the disclosure; 
           [0013]      FIG. 10  is a plan view, not to scale, of a nozzle plate for a micro-fluid jetting device according to one exemplary embodiment of the disclosure; 
           [0014]      FIGS. 11-14  are schematic views of method for making and assembling channel plates for a micro-fluid jetting device according to the disclosure; 
           [0015]      FIG. 15  is a plan view, not to scale, of fluid openings for a fluid reservoir for a micro-fluid jetting device according to a second embodiment of the disclosure wherein the fluid reservoir contains six fluids; 
           [0016]      FIGS. 16-18  are plan views, not to scale, of fluid channel plates for a micro-fluid jetting device according to the second embodiment of the disclosure; 
           [0017]      FIG. 19  is a plan view, not to scale, of a nozzle plate for a micro-fluid jetting device according to the second embodiment of the disclosure; 
           [0018]      FIG. 20  is a perspective view, not to scale, of a jetting device and a docking station therefore according to one embodiment of the disclosure; and 
           [0019]      FIG. 21  is a schematic drawing of a control circuit for operation of a micro-fluid jetting device according to the disclosure. 
       
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0020]    With reference to  FIGS. 2-3 , aspects of embodiments described herein are illustrated.  FIG. 2  is a perspective view of a micro-fluid jetting device  10  jetting fluids  12  therefrom onto a substrate  14  such as paper. In the case of the fluids  12  being inks, a color detection device  16 , described in more detail below, may be fixedly or removably attached to an opposing end  18  of the device  10 . A housing component  20  of the jetting device  10  may include an activation switch  22  for selectively depositing the fluid  12  on the substrate  14 . 
         [0021]    The housing component  20  of the jetting device  10  may also include fluid ejection controls and/or a display. For jetting of inks, the controls may include line width, line shape, single color (such as an RGB setting) or dual colors (such as a slide switch allowing the user to dynamically adjust between two colors while writing). A color or monochrome LCD panel may be used to display color settings, line width and shape settings, battery level, and any additional information provided by the docking station and/or computer, such as a user-specified program that dynamically changes output ink colors, shapes, and/or line widths. The controls and/or displays may be included in the docking station  130  ( FIG. 20 ) in addition to, or instead of, on the housing component  20  of the jetting device  10 . 
         [0022]    As illustrated in more detail in  FIGS. 3-11 , the housing  20  is configured for containing at least two different fluids  12  in separate fluid reservoirs  24 . In  FIG. 3 , the jetting device  10  may include four separate fluid reservoirs  24 A,  24 B,  24 C, and  24 D. For example, the fluid reservoirs  24 A- 24 D may contain cyan, magenta, yellow, and black or white inks. Each of the fluids  12  in the reservoirs  24 A- 24 D is directed through a series of channel plates  26 - 34  to predetermined portions of a nozzle plate  36  for ejection onto the substrate  14 . Also included in the housing  20  are a power supply  38  and logic circuit for activating fluid ejector actuators in the device  10 . 
         [0023]    Each of the fluid reservoirs  24 A- 24 D may have one or more openings for flow of fluid therefrom toward the nozzle plate  36  through the series of channel plates  26 - 34 . In an embodiment wherein the jetting device  10  contains reservoirs  24  for four different fluids, reservoir  24 A contains one or more fluid exit ports  40 , reservoir  24 B contains one or more fluid exit ports  42 , reservoir  24 C contains one or more fluid exit ports  44  and reservoir  24 D contains one or more fluid exit ports  46  as shown in an exit side of the fluid reservoirs  24  in  FIG. 4 . Each of the exit ports  40 - 46  provides fluid from the corresponding reservoir  24 A- 24 D to the channel plate  26 . 
         [0024]    The channel plate  26 , viewed from a side thereof opposite the fluid reservoirs  24 A- 24 D in  FIG. 5 , contains a plurality of fluid inlet ports and a plurality of flow channels therein for distribution of fluid flowing from the corresponding fluid reservoirs. For example, channel plate  26  includes inlet ports  48 A- 48 C corresponding to exit ports  40  from fluid reservoir  24 A, inlet ports  50 A- 50 C corresponding to exit ports  42 , inlet ports  52 A- 52 C corresponding to exit ports  44 , and inlet ports  54 A- 54 B corresponding to exit ports  46 . Each of the inlet ports  48 - 54  is in fluid flow communication with a corresponding channel  56 - 62 . The channels  56 A- 56 C distribute fluid from reservoir  24 A to ejection actuators  63  ( FIG. 6 ) distributed in a predetermined pattern on channel plate  28 . 
         [0025]      FIG. 6  provides a plan view of fluid vias, such as vias  64 - 70 , in the channel plate  28  for flow of fluid to corresponding fluid ejection actuators  63  for each of the fluids. The fluid vias  64 - 70  are in fluid flow communication with the channels  56 - 62  described above. For example, fluid vias  64 A- 64 C are in flow communication with the channel  56 A, fluid vias  66 A- 66 D are flow communication with the channel  58 A, fluid vias  68 A- 68 B are in flow communication with the channel  60 A, and fluid vias  70 A- 70 C are in flow communication with the channel  62 A. Accordingly, each of the channels  56 - 62  provides fluid to at least two of the vias  64 - 70  in channel plate  28 . 
         [0026]    Two of the fluids, namely fluids from reservoirs  24 A and  24 C, are further distributed by channel plate  30  ( FIG. 7 ) for flow into individual fluid channels and fluid chambers for ejection by the fluid actuator devices  63 . Fluid vias  64 A- 64 C communicate with fluid openings, such as opening  72  for distribution to flow channels  74  and fluid chamber  76  corresponding to each of the fluid openings for fluids from reservoirs  24 A and  24 C. The channel plate  28  also contains flow through openings  78  and  80  for flow through channel plate  32  to channel plate  34  for fluids from reservoirs  24 B and  24 D. 
         [0027]    When four or more fluids are provided in the jetting device, a divider channel plate  32  ( FIG. 8 ) may be used between channel plates  30  and  34 . The divider channel plate  32  includes flow through openings  81  therein for flow to the channel plate  34  and the nozzle plate  36 . For jetting devices  10  containing from one to three fluids, the divider channel plate  32  may be eliminated. 
         [0028]      FIG. 9  provides the channel plate  34  having similar features to channel plate  30  ( FIG. 6 ), however, the channel plate  34  is configured for ejection of fluids from the reservoirs  24 B and  24 D. 
         [0029]      FIG. 10  provides a plan view of the nozzle plate  36  containing nozzle holes  82 . The nozzle holes  82  are distributed in a pattern that provides different fluid for closely adjacent nozzle holes  82 . Another pattern for nozzle holes  84  may include concentric circular patterns of the nozzle holes for different fluids as shown and described in more detail below. 
         [0030]    In  FIGS. 4-10 , the passage areas  84  and  86  are located between the housing  20  and the channel plates  26 - 34  and the nozzle plate  36  for electrical wiring or circuit components. 
         [0031]    The channel plates  26 - 34  and the nozzle plate  36  may be made from a wide variety of materials including, but not limited to, polymeric materials, ceramic materials, silicon materials, and the like. A particularly suitable material for the channel plates  26  and  30 - 34  is a photoimageable material such as a positive or negative photoresist material. For example, photoresist materials that may be spin coated onto or laminated to one another may be used to provide the channel plates  26  and  30 - 34  and the nozzle plate  36  by a process as described with reference to  FIGS. 11-14 . 
         [0032]    The channel plate  26  may be provided by a first layer  90  that is photoimaged and developed to provide the channel  60 A and the inlet port  52 A shown in outline in  FIG. 11 . In the alternative, the channel plate  26  may be formed by cutting, wet etching, dry etching or the like, a silicon wafer or other substrate used to form the first layer  90 . The channel plate  26  may then be applied, as by a lamination process, to a second layer  92 , as shown in  FIG. 12 , to provide the channel plate  28 . The second layer  92  may be made of a substrate material, such as silicon, ceramic, and the like, that may be deep reactive ion etched to provide the fluid vias  68 A and  68 B prior to laminating the channel plate  26  to the channel plate  28 . 
         [0033]    In  FIG. 13 , a third photoresist layer  94  is applied to the second layer  92 , as by a lamination process. Layer  94  is imaged to provide the flow channels  74  and the fluid chambers  76  for providing channel plate  30 . The layer  92  may be developed after imaging, or may be developed after imaging subsequent channel plates that are applied to the channel plates  26 - 30 . 
         [0034]      FIG. 14  illustrates the application of a layer  96  to the layer  94  to provide the divider channel plate  32  having the flow through openings  81  imaged therein. If the channel plate  30  is not developed before layer  96  is applied to layer  94 , then layer  96  may be spin coated onto layer  94 . Subsequently, the channel plate  34  may be spin coated and imaged as described above. 
         [0035]    Once all of the channel plates  32 - 34  have been imaged, they may be developed all at one by exposing the imaged channel plates  32 - 34  to a conventional developing fluid. In the alternative, for laminated layers  94 - 96 , each layer may be developed before a subsequent layer is laminated thereto. For example, in the case of the channel plates  26  and  30 - 34  being made of a polyimide or other polymeric material, each of the layers  90  and  94 - 96  may be laser ablated to provide the channels and flow features described above before subsequent layers are laminated thereto. Likewise, in the case of any of the channel plates  26 - 34  being made of silicon, ceramic, or composite materials, each layer may be dry etched, wet etched, mechanically machined, or laser cut before a subsequent layer is attached thereto. 
         [0036]    Depending on the number of different fluids in the fluid reservoirs of the jetting device, more or fewer channel plates may be used to provide selective flow of fluids to the nozzle plate  36 . For example, a jetting device for jetting two different fluid may only contain the channel plates  26 - 30  and the nozzle plate  36 . Also, both sides of one or more of the channel plates  26 - 34  may be imaged and developed to provide the various channels rather than providing individual channel plates  26 - 34  as shown. 
         [0037]    The nozzle plate  36  may be made of an electroformed metal or may be formed from a ceramic, composite, or silicon material. The nozzle plate  36  may likewise be made of a photoimageable material such as a positive or negative photoresist, or may be made of a polyimide or other polymeric material. In the case of a photoresist material, the nozzle plate  36  may be spin coated as a layer onto the layer  96  and imaged and developed as described above with reference to the layers  90 - 96  to provide the nozzle holes  82 . When the nozzle plate  36  is made of a polyimide or other polymeric material, the nozzle holes  82  may be laser ablated or molded into the nozzle plate material. 
         [0038]    Layers  90 ,  92 ,  94 , and  96  may be attached to one another and/or the housing component  20  and fluid reservoirs  24  using adhesives, laser welding, ultrasonic welding, solvent welding, thermal compression bonding, lamination, heat staking, or other conventional methods. 
         [0039]    The ejector actuators  63  for the fluids may be provided by thermal ejection actuators, piezoelectric actuators, electromagnetic actuators, and the like. A typical thermal type fluid ejection actuator is provided by multiple thin film insulative and conductive materials deposited on the substrate  92 . The substrate  92  may be provided by a silicon material containing a thermal barrier layer and a resistive material layer. The resistive layer may be made from a variety of materials including but not limited to tantalum/aluminum alloys. A first metal conductive layer such as aluminum, copper, or gold may provide anode and cathode connections to the resistive layer. In order to protect the ejection actuator from corrosion and erosion, a dual layer including a passivation layer made of silicon nitride, silicon carbide, or a combination of silicon nitride and silicon carbide, and a cavitation layer made of tantalum may be applied to the material resistive layer. A dielectric layer may be provided over the first metal conductive layer to insulate the first metal conductive layer from a second metal conductive layer. Like the first metal conductive layer, the second metal conductive layer may be made of aluminum, copper, gold and the like. 
         [0040]    In  FIGS. 15-19 , an alternate embodiment for channel plates and a nozzle plate is illustrated. Rather than a diagonal arrangement of alternating ejection nozzles for four fluids, the alternate embodiment illustrates a concentric alternating ejection nozzle arrangement. In  FIG. 15 , a housing component  98  for housing six separate fluid reservoirs  100 A- 100 F is illustrated. Each fluid reservoirs, such as reservoir  100 A has a one or more fluid outlet ports, such as outlet ports  102 . 
         [0041]    The outlet ports  102  are in fluid flow communication with corresponding concentric flow channels  104 A- 104 F which may be etched into a first side of channel plate  106  as shown in  FIG. 16 . Corresponding fluid vias  108  for providing fluid to ejection actuators  110  may be etched in a second side of the channel plate  106  or in a separate channel plate  112  ( FIG. 17 ). 
         [0042]    Channel plate  114  contains fluid flow channels  116  that are in flow communication with the fluid vias  108  for flow through channels  116  to ejection chambers  118 . Upon activation of the fluid ejection actuators, fluid is ejected through nozzle holes  120  in a nozzle plate  122 . In other respects, the channel plates  106 ,  112 , and  114  and the nozzle plate  122 , may be made and assembled as described above with reference to channel plates  26 - 34  and nozzle plate  36 . 
         [0043]    The battery  38 , included in the housing component  20 , may be a rechargeable battery or a disposable battery. In the alternative, power for the jetting device  10  may be provided by an electrical cable or wire connected to a separate power source. 
         [0044]    With reference to  FIG. 20 , an embodiment of the disclosure provides a docking station  130  for the micro-fluid jetting device  10 . The docking station  130  may include an ejector head cleaning and maintenance station, a battery charger, in the case of a rechargeable battery as the power source  38 , fluid selection and ejector width shape and control devices that are not included on the jetting device, and input and output connections that may interface with a personal computer system for programming memory in the micro-fluid jetting device  10 . Another optional feature that may be included with the docking station  130 , may include, but is not limited to, a scanner for input of information to the jetting device  10  or the personal computer. 
         [0045]    In embodiments wherein the jetting device  10  ejects inks, the jetting device  10  may also include the color detection deice  16  as shown in  FIGS. 1 and 20 . The color detection device  16  may be removably attached to the jetting device  10  for inputting colors to the jetting device  10 . Color detection devices  16  containing a three-element color sensor  132  such as a color sensor available from Laser Components Instrument Group, Inc. of Wilmington, Mass. under the trade name MCS3AT/BT. Such a color sensor  132  includes three Si-PIN photo diodes integrated on a chip. The photo diodes are provided as segments of a ring with a diameter of about 2 millimeters. A phototransistor is located near a red LED, a green LED, and a blue LED so that light reflected from each LED will strike the phototransistor. The LEDs are controlled by LED drivers in a digital ASIC. The phototransistor is connected to an analog to digital converter (ADC) in the digital ASIC. The phototransistor and LED&#39;s are mounted in an optical housing  114  so that the LED&#39;s in the sensor  132  will be at the proper operating distance when the housing  114  is pressed against a surface. The housing  114  is configured to block ambient light when the sensor  132  is pressed against a surface. 
         [0046]    The detection device  16  may be fixedly or removably attached to the end  18  of the housing  20  opposite the nozzle plate  36 . The color detection device  16  is operatively connected to a logic circuit to sample a color from a sample color source and provide an output for control of the jetting device  10  to provide ejection of ink therefrom corresponding to the sample color source. The color detection device  16  may be activated with a separate activation switch such as a plunger type switch integral with the color detection device  16 . 
         [0047]    A schematic illustration of a control system  134  for the color detector device  16  is illustrated in  FIG. 21 . According to the control system  134 , a sample switch such as a switch  136  may be located in the housing  114  in such a position that the switch  136  is depressed when the housing  114  is pressed against a surface. A state machine  138  controls the ADC  140  and an LED driver  142  for the LED&#39;s  144 ,  146 , and  148 , as well as an internal flash memory  150  comprising non-volatile RAM, a switch interface  152 , and an ejector head interface  154 . The state machine  138  may also be controlled externally through a manufacturing control interface  156 . 
         [0048]    In operation, a user presses the optical housing  114  against a surface to trigger color sampling. The surface may be a color palette containing sample color sources of different colors, or any colored object the user wishes to duplicate the color thereof. As the sample switch  136  is depressed, the switch  136  signals the state machine  138  to begin the sample process. Each LED  144 - 148  is turned on individually by the LED driver  142 , and a phototransistor  158  ADC reading provided by ADC  140  is stored by the state machine  138  in the non-volatile flash memory  150 . Thus, an RGB value is generated and stored in the flash memory  150  for later use. 
         [0049]    When the activation switch  22  is depressed by the user, the micro-fluid jetting device  10  will eject ink  12  through the nozzle plate  36  or  122 , toward the substrate  14 , as shown in  FIG. 1 , corresponding to the stored RGB value. As the button  22  is pushed, the state machine  138  loads the previously stored RGB value from flash memory  150 , and uses the RGB value as an index for input into a three-dimensional lookup table also stored in flash memory  150 . The lookup table contains CMY (or CMYK, CMYW, CcMmY, etc., depending on the ink colors available in the fluid reservoirs  24  or  100 ) values for output to the ejector head interface  154  for selective operation of ejection actuators. 
         [0050]    The manufacturing control interface  156  is used during manufacturing to calibrate the color sensor  132 . A manufacturing computer can turn on each LED  144 - 148 , read the ADC  140 , and write to the flash memory  150 , all through the manufacturing control interface  156 . Various calibration colors may be sampled by the color sensor  132 , and the resulting RGB values are used by the manufacturing computer to generate a custom lookup table for the sensor  132 . The lookup table may be stored in the flash memory  150 . 
         [0051]    In an alternative embodiment, one or more sensors  160  may be included on the jetting device  10  to detect media proximity, speed and direction of pen movement, and type of substrate  14 . The sensors  160  may have ADC signals input through a sensor interface  162  to the state machine  138 . In another embodiment, the sensors  160  may include a media detection sensor that disables the jetting device  10  from writing on surfaces other than a specified surface, such as white paper, to prevent unwanted ejection of fluids or inks onto fabrics, persons, or other surfaces. 
         [0052]    In a typical operation of a jetting device  10  for jetting different color inks, a first mixture of inks to provide a first color may be jetted. The jetting device  10  may then be inserted in the docking station  130  so that the nozzle plate  36  or  122  is wiped to remove any residual amount of the first color so that a second mixture of inks providing a second color may be jetted. In order to provide a desirable color ejected from the jetting device, typically only one color mixture is jetted at a time. However, control schemes may be devise for gradual dynamic color change during a jetting operating. 
         [0053]    Droplets  12  ejected from the jetting device  10  may have a size of from about 100 picoliters (pL) or less. In the case of ink droplets, mixing of colors on the media  14  or nozzle plate  36  or  122  may provide a wide variety of color variations. Ink droplets, about 2 pL or less in volume may be ejected from the nozzle holes  82  or  120  so that individual droplets are small enough to be imperceptible by the naked eye without substantial mixing of inks. 
         [0054]    It is contemplated, and will be apparent to those skilled in the art from the preceding description and the accompanying drawings, that modifications and changes may be made to the exemplary embodiments disclosed herein. Accordingly, it is expressly intended that the foregoing description and the accompanying drawings are illustrative of preferred embodiments only, not limiting thereto, and that the true spirit and scope of the disclosure be determined by reference to the appended claims.