Patent Publication Number: US-2007120894-A1

Title: Microinjectors

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The invention relates in general to microinjectors and in particular to microinjectors controlling ejection directions of droplets.  
      2. Description of the Related Art  
      Microinjection technologies are widely applied to inkjet printers. Two primary inkjet technologies are thermal bubble and piezoelectric. As shown in  FIG. 1 , U.S. Pat. No. 6,588,878 B2 discloses a thermal bubble inkjet print head comprising a plurality of jet units E. Ejection direction, speed and quantity of ink droplet depend on profiles, dimensions and arrangements of the reservoir  14 , the nozzle  18  and the heaters  20  of every jet unit E.  
      In  FIG. 1 , each jet unit E comprises two heaters  20  electrically connected in series. When the series heaters  20  are actuated, two bubbles are generated correspondingly, to eject fluid F through the nozzle  18  and generate a droplet D flying along Z axis. As the heaters  20  are symmetrically disposed on opposite sides of the nozzle  18 , droplet D flies along Z axis, substantially perpendicular to nozzle layer  12 .  
      According to prior art of U.S. Pat. No. 6,588,878 B2, structure of the jet unit E dominates fluid ejection through the nozzle  18 . When the jet unit E is determined, trajectory of droplet is invariable according thereto. Here, conventional droplet ejection trajectory is along Z axis, substantially perpendicular to nozzle layer  12 .  
     BRIEF SUMMARY OF THE INVENTION  
      Microinjectors are provided. A microinjector includes a substrate, a manifold formed on the substrate, and at least a jet unit. The jet unit includes a nozzle layer connected to the substrate, a nozzle disposed on the nozzle layer, a reservoir, a first heater disposed on a first side of the nozzle and a second heater disposed on a second side of the nozzle. The reservoir is formed between the nozzle layer and the substrate, connecting the nozzle and the manifold. Specifically, the first and second heaters are actuated by individual drive circuits, to heat the reservoir and eject droplets through the nozzle. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:  
       FIG. 1  is a perspective diagram of a conventional thermal bubble inkjet print head;  
       FIG. 2  is a perspective diagram of an embodiment of a microinjector with a first heater disposed on a side of a nozzle;  
       FIG. 3  is a perspective diagram of an embodiment of a microinjector with a first heater and a second heater disposed on adjacent sides of a nozzle;  
       FIGS. 4A, 4B  and  4 C are perspective diagrams illustrating contact positions of droplets on a medium;  
       FIGS. 5A and 5B  are perspective diagrams of an embodiment of a microinjector comprising a plurality of jet units, each unit comprising a first heater and a second heater disposed on adjacent sides of a nozzle;  
       FIGS. 6A and 6B  are perspective diagrams of an embodiment of a microinjector comprising a plurality of jet units, each jet unit comprising a first heater and a second heater disposed on opposite sides of a nozzle; and  
       FIG. 7  is a perspective diagram of an embodiment of a microinjector with four heaters surrounding a nozzle.  
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      An embodiment of a microinjector, such as a monolithic inkjet chip, comprises a substrate S, a manifold  16  formed on the substrate S and a plurality of jet units E, as shown in  FIG. 2 . Each of the jet units E comprises a nozzle layer  12  disposed on the substrate S, a reservoir  14  formed between the nozzle layer  12  and the substrate S, and a first heater H 1  disposed on an outer surface of the nozzle layer  12 . Specifically, the reservoir  14  connects the manifold  16  and a nozzle  18  on the nozzle layer  12 .  
      As shown in  FIG. 2 , the first heater H 1  is disposed close to the nozzle  18  to heat the reservoir  14 , and a bubble is thereby generated to eject a droplet D through the nozzle  18 . Here, since the first heater H 1  is asymmetrically disposed on a first side of the nozzle  18 , ejection direction of the droplet D deviates from Z axis by an angle a, as shown in  FIG. 2 . In some embodiments, a plurality of heaters can be disposed on different aspects around the nozzle  18 , to alter ejection trajectory of droplet D.  
      Referring to  FIG. 3 , another embodiment of a microinjector comprises a first heater H 1  and a second heater H 2  connected to individual drive circuits (not shown), disposed on first and second sides (left and upper sides) of the nozzle  18 . In this embodiment, the first and second heaters H 1  and H 2  are rectangular, extending along Y axis and X axis, respectively.  
       FIG. 4A  illustrates a contact position P on a medium of a droplet when the first heater H 1  in  FIG. 3  is actuated, and  FIG. 4B  illustrates a contact position P of a droplet when the second heater H 2  in  FIG. 3  is actuated. Here, since the first and second heaters H 1  and H 2  are disposed on adjacent sides (left and upper sides) of the nozzle  18  and actuated by independent drive circuits, when only the first heater H 1  is actuated to heat the reservoir  14 , the contact position P deviates from a center axis C 1  of the nozzle  18  and located in quadrant I or IV, as shown in  FIG. 4A . Similarly, when only the second heater H 2  is actuated to heat the reservoir  14 , contact position P deviates from another center axis C 2  and located in quadrant III or IV, as shown in  FIG. 4B . When both of the first and second heaters H 1  and H 2  are actuated to heat the reservoir  14 , as shown in  FIG. 4C , contact position P deviates from the center axes C 1  and C 2  and located in quadrant IV.  
      According to the embodiment, rectangular aspect ratios of the first and second heaters H 1  and H 2  can be appropriately designed, such as a square, to alter direction, quantity and speed of droplet ejection, wherein profiles of the first and second heaters H 1  and H 2  can be the same or different.  
      Referring to  FIGS. 5A and 5B , a microinjector comprises a manifold  16  and a plurality of jet units E, wherein fluid flows through the manifold  16  to the jet units E and exits the nozzles  18 . In this embodiment, each of the jet units E comprises a first heater H 1  and a second heater H 2  disposed on adjacent sides of the nozzle  18 .  
      In  FIG. 5A , the first and second heaters H 1  and H 2  in every jet unit E are disposed on left and upper sides of the nozzle  18 . As the first and second heaters H 1  and H 2  are actuated by individual drive circuits (not shown), ejection of droplet deviates rightward or downward from the nozzle  18 .  
      Referring to  FIG. 5B , each of the jet units E on the left side of the manifold  16  comprises a first heater H 1  and a second heater H 2  respectively disposed on left and upper sides of the nozzle  18 . Correspondingly, each of the jet units E on the right side of the manifold  16  comprises a first heater H 1  and a second heater H 2  respectively disposed on right and lower sides of the nozzle  18 . Comparing  FIG. 5A  with  FIG. 5B , the microinjector in  FIG. 5B  provides higher density of drop points on a medium. As the first and second heaters H 1  and H 2  in  FIGS. 5A and 5B  are actuated by individual drive circuits, rejection trajectories of droplets deviates from the nozzle  18  in X or Y directions, facilitating flexible and high printing efficiency of an inkjet printer.  
      Referring to  FIGS. 6A and 6B , the first and second heaters H 1  and H 2  can also be disposed on opposite sides of the nozzle  18  within every jet unit E. As shown in  FIG. 6A , the first and second heaters H 1  and H 2  are disposed on left and right sides of the nozzle  18 , to deviate contact positions of ejected droplets from the nozzle  18  along X axis. Similarly, as shown in  FIG. 6B , the first and second heaters H 1  and H 2  are disposed on upper and lower sides of the nozzle  18 , to deviate contact positions of ejected droplets from the nozzle  18  along Y axis.  
      Referring to  FIG. 7 , another embodiment of the nozzle  18  is surrounded by a first heater H 1 , a second heater H 2 , a third heater H 3  and a fourth heater H 4 , wherein profiles of the first, second third and fourth heaters H 1 , H 2 , H 3  and H 4  can be the same or different, such as squares or rectangles. Specifically, the first, second third and fourth heaters H 1 , H 2 , H 3  and H 4  are connected to individual drive circuits, to deviate contact positions of ejected droplets from the nozzle  18  along X axis or Y axis. In this embodiment, a control unit electrically connects every heater of the jet units E, to simultaneously control droplet ejection through every nozzles  18 . Thus, direction, quantity, speed, and contact position of ejected droplets can be appropriately altered, capable of high density printing and gray scale of high intensity resolution.  
      Microinjectors capable of controlling ejection direction, quantity and speed are provided according to the embodiments. The microinjectors can be applied in inkjet printers, micro jet propulsion system and Biomedical engineering, such as fuel/air ratio control systems and medical injections.  
      While the invention has been described by way of example and in terms of preferred embodiment, it is to be understood that the invention is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation to encompass all such modifications and similar arrangements.