Patent Publication Number: US-2007120897-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 droplet ejection direction.  
      2. Description of the Related Art  
      With progress of micromachining technologies, thermal bubble and piezoelectric actuations have been applied in microinjectors. Referring to  FIG. 1 , a conventional microinjector mechanism of an inkjet printer of EP 1116586 A1 primarily includes a thermally-actuated paddle  2 , a front substrate  3 , a back substrate  4 , and a heater  30 . The front and back substrates  3  and  4  form a channel with ink received therein, and a ink droplet D is ejected through the nozzle  3 ′ by the paddle  2 . Ejection of the droplet D is enhanced by the heater  30  disposed adjacent to the nozzle  3 ′. Another conventional inkjet printer, according to U.S. Pat. No. 6,536,882 B1, controls droplet ejection direction by a heater surrounding the nozzle outlet circumference.  
     BRIEF SUMMARY OF THE INVENTION  
      Microinjectors are provided. An embodiment of a microinjector includes a substrate, a channel, a nozzle formed at an end of the channel, and a deformable mechanism disposed on the substrate. A droplet is generated by ejecting fluid through the nozzle. The deformable mechanism comprises a piezoelectric layer and a flexible member. The flexible member connects the piezoelectric layer and the substrate, defining a part of the channel. When an electrical field is applied to the piezoelectric layer, the flexible member and the piezoelectric layer are deformed, altering the profile of the channel.  
    
    
     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 microinjector of an inkjet printer;  
       FIG. 2  is a top view of an embodiment of a microinjector;  
       FIG. 3  is a sectional view of  FIG. 2  along C-C′;  
       FIGS. 4   a ,  4   b ,  5   a , and  5   b  are perspective diagrams of the microinjector in  FIG. 3  when a piezoelectric layer thereof deforms;  
       FIGS. 6   a  and  6   b  are perspective diagrams of a microinjector comprising two nozzles;  
       FIGS. 7   a - 7   f  are perspective diagrams of a microinjector comprising two piezoelectric layers and two deformable members;  
       FIG. 8  is a perspective diagram of a microinjector comprising a plurality of piezoelectric layers and deformable members;  
       FIG. 9  is a perspective diagram of a microinjector comprising a plurality of embedded piezoelectric portions; and  
       FIGS. 10   a  and  10   b  are perspective diagrams of a microinjector comprising round nozzles. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      Referring to  FIG. 2 , an embodiment of a microinjector  5  comprises a piezoelectric layer  51 P disposed on an outer surface  50  thereof. The piezoelectric layer  51 P includes two piezoelectric portions  51 RP and  51 LP with a nozzle  53  formed therebetweeen. As shown in  FIG. 2 , the nozzle  53  has a width L 0  along X axis. Fluid can be ejected through the nozzle  53  by an actuator adjacent to the nozzle  53 , such as a heater (not shown).  
      Referring to  FIG. 3 , the microinjector  5  includes a substrate  52  and a deformable mechanism  51  disposed thereon. Here, the deformable mechanism  51  comprises a flexible member  51 E and the piezoelectric layer  51 P. The piezoelectric layer  51 P may comprise lead zirconate titanate (PZT), and the flexible member  51 E may comprise polymer composite, including a first flexible portion  51 RE and a second flexible portion  51 LE. As shown in  FIG. 3 , a channel  54  is connected to the nozzle  53  through the substrate  52  and the flexible member  51 E along Z axis, wherein fluid  55  in the channel  54  can be ejected from the nozzle  53 .  
      In this embodiment, the piezoelectric portions  51 RP and  51 LP are coated with electrodes on top and bottom surfaces thereof. When an electrical field is applied to the piezoelectric layer  51 P along Z axis per top and bottom electrodes, the piezoelectric portions  51 RP and  51 LP can contract or expand along X axis, and the first and second flexible portions  51 RE and  51 LE are deformed, to alter profile of the nozzle  53  or the channel  54 . As shown in  FIG. 4   a , when the piezoelectric portions  51 RP and  51 LP are expanded by an electrical field, the first and second flexible portions  51 RE and  51 LE are deformed, such that the nozzle  53  is narrowed from the width L 0  to L 1 , reducing discharge quantity of fluid  55  and increasing ejection speed of droplets.  
      Alternatively, as shown in  FIG. 4   b , when the piezoelectric portions  51 RP and  51 LP contract by an inverse electrical field, the first and second flexible portions  51 RE and  51 LE are deformed, such that the nozzle  53  is broadened from the width L 0  to L 2 , increasing discharge quantity of fluid  55  and reducing ejection speed of the droplets.  
      Referring to  FIG. 5   a , when the piezoelectric portion  51 RP contracts and the piezoelectric portion  51 LP expands by two opposite electrical fields, the channel  54  between the first and second flexible portions  51 RE and  51 LE is deflected to the right. Similarly, as shown in  FIG. 5   b , the channel  54  is deflected to the left when the piezoelectric portion  51 RP expands and the piezoelectric portion  51 LP contracts. According to this embodiment, profiles of the channel  54  can be appropriately altered to achieve deflected ejection of the droplet, wherein width of the nozzle  53  can remain the same by complementary deformations of the piezoelectric portions  51 RP and  51 LP.  
      Referring to  FIG. 6   a , another embodiment of a microinjector  6  primarily includes a substrate  62 , a deformable mechanism  61  disposed on the substrate  62 , two channels  64 L and  64 R through the deformable mechanism  61  and the substrate  62 , and two nozzles  63 L and  63 R connected to the channels  64 L and  64 R, respectively. As shown in  FIG. 6a , the deformable mechanism  61  comprises a flexible member  61 E and a piezoelectric layer  61 P disposed thereon. In this embodiment, the piezoelectric layer  61 P includes three piezoelectric portions  61 RP,  61 LP, and  61 CP coated with electrodes. The flexible member  61 E includes three flexible portions  61 RE,  61 LE, and  61 CE respectively connected to the piezoelectric portions  61 RP,  61 LP, and  61 CP. Profiles of the nozzles  63 L and  63 R and the channels  64 L and  64 R can be appropriately altered by expansion or contraction of the piezoelectric portions  61 RP,  61 LP, and  61 CP along X axis when an electrical field is applied thereto along Z axis.  
      Referring to  FIG. 6   b , when the piezoelectric portions  61 RP and  61 CP contract along X axis, the flexible portions  61  RE and  61  CE are deformed, such that the nozzle  63 R is broadened, increasing discharge quantity of fluid  65  through the nozzle  63 R and reducing ejection speed of droplets. Similarly, due to expansion of the piezoelectric portion  61 LP and contraction of the piezoelectric portion  61 CP, the channel  64 L is deflected rightward to alter ejection direction of droplet through the nozzle  63 L. According to this embodiment, ejection direction, speed and quantity of droplets through different nozzles can be appropriately controlled by altering profile of the deformable mechanism.  
      Referring to  FIG. 7   a , another embodiment of a microinjector  7  comprises a substrate  72 , a deformable mechanism  71  disposed on the substrate  72 , a channel  74 , and a nozzle  73  connected to the channel  74 . Specifically, the deformable mechanism  71  includes a first piezoelectric layer  711 P, a second piezoelectric layer  712 P, a first flexible member  711 E, and a second flexible member  712 E.  
      As shown in  FIG. 7   a , the first piezoelectric layer  711 P comprises two piezoelectric portions  711 RP and  711 LP, the second piezoelectric layer  712 P comprises two piezoelectric portions  712 RP and  712 LP, the first flexible member  711 E comprises two flexible portions  711 RE and  711 LE, and the second flexible member  712 E comprises two flexible portions  712 RE and  712 LE. In this embodiment, the first and second piezoelectric layers  711 P and  712 P are coated with electrodes on top and bottom surfaces thereof, expandable and contractible along X axis when an electrical field along Z axis is applied thereto.  
      Referring to  FIG. 7   b , when the piezoelectric portion  711 RP contracts and the piezoelectric portion  711 LP expands, the middle part of the channel  74  is deflected to the right, such that the second flexible member  712 E, the second piezoelectric layer  712 P and the nozzle  73  shift rightward along X axis. Similarly, as shown in  FIG. 7   c , when the piezoelectric portions  711 RP and  711 LP both expand along X axis, the nozzle  73  is narrowed.  
      Referring to  FIGS. 7   d  and  7   e , profiles of the nozzle  73  and the channel  74  can be altered when only the second piezoelectric layer  712 P deforms. In  FIG. 7   d , when the piezoelectric portion  712 LP expands and the piezoelectric portion  712 RP contracts, a part of the channel  74  is deflected to the right. In  FIG. 7e , the nozzle  73  is narrowed when the piezoelectric portions  712 RP and  712 LP both expand.  
      Referring to  FIG. 7   f , when applying electrical fields to the piezoelectric portion  711 RP,  711 LP,  712 RP, and  712 LP respectively, the nozzle  73  and the channel  74  can be deformed to a desired shape. Here, the piezoelectric portion  711 RP contracts, and the piezoelectric portions  711 LP,  712 RP, and  712 LP expand, such that the channel  74  is deflected to the right, and nozzle  73  is narrowed and shifted rightward. In this embodiment, the deformable mechanism  71  has two piezoelectric layers  711 P and  712 P and two flexible members  711 E and  712 E, such that profiles of the nozzle  73  and the channel  74  is highly alterable, facilitating control of ejection direction, speed and quantity of droplet.  
      As shown in  FIG. 8 , another embodiment of a microinjector  8  comprises a deformable mechanism  81  including a plurality of piezoelectric layers  81 P and flexible members  81 E alternatively stacked along Z axis, enhancing flexibility thereof. As shown in  FIG. 9 , another embodiment of a microinjector  9  comprises a flexible member  91 E and a plurality of piezoelectric portions  91 P embedded in the flexible member  91 E. As shown in  FIGS. 10   a  and  10   b , another embodiment of a microinjector comprises a plurality of round nozzles  103  formed between the piezoelectric portions  10 P disposed on the flexible member  10 E, rather than the rectangular nozzle  53  in  FIG. 2 .  
      Microinjectors having deformable mechanisms are provided according to the embodiments. Rather than conventional heating elements, ejection direction, speed and quantity of droplet are controlled by altering profiles of the nozzles and the channels, suitable for inkjet printers, biotechnologies, and micro jet propulsion systems.  
      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.