Patent Publication Number: US-2007122299-A1

Title: Valveless micro impedance pump

Description:
BACKGROUND OF THE INVENTION  
      The present invention is related to a valveless micro impedance pump in which the difference between impedances of materials results in difference between the impedances of the walls of the flow way for transmitting a medium.  
      The conventional micro-fluid elements are mainly developed and applied to control, detection, reaction and analysis of micro-fluid. The key elements include micropumps, microvalves, micro-flow ways, micromixers, etc. These elements can be integrated into intelligent micro-fluid chips with different functions. The intelligent micro-fluid chips are applicable to biotechnology, portable physiologic monitor, environmental analyzer, precision fluid control, fuel battery engineering, high-resolution nozzle, micro-power system, etc. The micropump is one of the most important key elements.  
      The micropumps can be mainly divided into valve-equipped type and valveless type. With respect to valveless micropumps, they can be powered by piezoelectric measure, pneumatic measure, static measure, profile-memorizing alloy, thermopneumatic measure, ultrasonic measure and bimetal.  
       FIG. 8  is a sectional view of a typical piezoelectric valveless micropump  6 .  FIG. 9  is a sectional view taken along line B-B of  FIG. 8 . The piezoelectric valveless micropump  6  is composed of a bottom layer  61 , a top layer  62 , a piezoelectric element  63  and two micro-flow ducts  64 . The piezoelectric valveless micropump  6  is operated in such a manner that a drive voltage is applied to the piezoelectric element  63 . The piezoelectric element  63  works to push a vibration membrane  621 . The vibration membrane  621  is deformed to cause change of the capacity of a middle flow way  65 . This leads to change of pressure. The water comes in from a water inlet  66  and flows through an expanded flow way  67  and the middle flow way  65 . The water then flows through another expanded flow way  68  to a water outlet  69 . The change of the capacity of the middle flow way  65  results in a pressure difference between the water inlet  66  and water outlet  69 . Therefore, the net flow of the water outlet  69  is larger than the net flow of the water inlet  66 . Accordingly, the water will flow from the water inlet  66  to the water outlet  69 .  
      The conventional piezoelectric valveless micropump is designed with a complicated expanded flow way. This increases the cost of the piezoelectric valveless micropump. In addition, the liquid can only one-way flow. This limits the application of the piezoelectric valveless micropump.  
     SUMMARY OF THE INVENTION  
      It is therefore a primary object of the present invention to provide a valveless micro impedance pump in which the materials are different in structure or hardness to lead to a difference between the impedances of the materials. Accordingly, the walls of the flow way have different impedances. Therefore, the medium within the flow way are waved along with the vibration membranes and thus transmitted to the water inlets/outlets.  
      According to the above object, the valveless micro impedance pump of the present invention includes:  
      a bottom layer formed with an opening;  
      a middle layer overlaid on the bottom layer, the middle layer being formed with an elongated recess in a position corresponding to the position of the opening of the bottom layer, the recess being slightly larger than a width of the opening and serving as a flow way, a bottom area of the middle layer between the flow way and the bottom layer being defined as a lower vibration membrane;  
      a top layer overlaid on the middle layer, the top layer having a fixing seat, a sink being formed on a nearly central portion of the fixing seat, a boss being disposed in the sink, a first water inlet/outlet being formed between left side of the sink and a left end of the top layer, a second water inlet/outlet being formed between right side of the sink and a right end of the top layer, the water inlets/outlets communicating with the flow way, a bottom area of the sink being defined as an upper vibration membrane; and  
      a piezoelectric element, a bottom face of the piezoelectric element being lengthwise fixed on top end of the boss and top face of the fixing seat.  
      The present invention can be best understood through the following description and accompanying drawings wherein: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a sectional view of the valveless micro impedance pump of the present invention;  
       FIG. 2  is a sectional view taken along line  2 - 2  of  FIG. 1 ;  
       FIG. 3  is a perspective sectional view of the valveless micro impedance pump of the present invention;  
       FIG. 4  is a flow chart of the manufacturing of the bottom layer of the valveless micro impedance pump of the present invention;  
       FIG. 5  is a flow chart of the manufacturing of the middle layer of the valveless micro impedance pump of the present invention;  
       FIG. 6  is a flow chart of the manufacturing of the top layer of the valveless micro impedance pump of the present invention;  
       FIG. 7  is a sectional view of a second embodiment of the valveless micro impedance pump of the present invention;  
       FIG. 8  is a sectional view of a conventional piezoelectric valveless micropump; and  
       FIG. 9  is a sectional view taken along line  9 - 9  of  FIG. 8 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Please refer to  FIGS. 1 and 2 . The valveless micro impedance pump  1  of the present invention includes a thin sheet-like bottom layer  10  formed with a central opening  101 .  
      The valveless micro impedance pump  1  of the present invention further includes a thin sheet-like middle layer  11  overlaid on the bottom layer  10 . The middle layer  11  is formed with an elongated recess in a position corresponding to the position of the opening  101  of the bottom layer  10 . The recess is slightly larger than the width of the opening  101  and serves as a flow way  113 . Amedium (which can be water or other liquid) can flow through the flow way  113 . A bottom area of the middle layer  11  between the flow way  113  and the bottom layer  10  is defined as a lower vibration membrane  114 .  
      The valveless micro impedance pump  1  of the present invention further includes a top layer  12  overlaid on the middle layer  11 . A bottom face of the top layer  12  serves as the top face of the flow way  113 . The top layer  12  has a fixing seat  121 . A sink  122  is formed on a nearly central portion of the fixing seat  121 . In this embodiment, the sink  122  is aligned with the opening  101  and has a width equal to the width of the opening  101 . A boss  123  is disposed on the bottom of the sink  122 . In this embodiment, the boss  123  is asymmetrically disposed on the bottom of the sink  122  proximal to lengthwise left side of the sink  122 . A first water inlet/outlet  124  is formed between lengthwise left side of the sink  122  and the left end of the top layer  12 . A second water inlet/outlet  124  is formed between lengthwise right side of the sink  122  and the right end of the top layer  12 . The water inlets/outlets  124  communicate with the flow way  113 . A bottom area of the sink  122  is defined as an upper vibration membrane  125 .  
      The valveless micro impedance pump  1  of the present invention further includes a piezoelectric element  2  fixedly bridged over the sink  122  of the fixing seat  121  between two sides thereof. The bottom face of the piezoelectric element  2  nearly attaches to the top end of the boss  123 . The piezoelectric element  2  works by way of uni-morph or bi-morph.  
      Referring to  FIG. 3 , the piezoelectric element  2  is fixed on the top face of the fixing seat  121  for driving the micropump. The upper vibration membrane connected with the boss  123  is pushed to produce vibration wave. The medium within the flow way  113  is squeezed by the upper and lower vibration membranes  125 ,  114  to wave to the water inlets/outlets  124  on two sides. The flow way  113  is defined between the upper vibration membrane  125  and the lower vibration membrane  114 . The fixing seat  121  and the bottom layer  10  have different structural designs. Therefore, the thickness of the wall of the flow way is varied and the impedance of the upper and lower vibration membranes,  115 ,  114  is varied. Accordingly, the hardness of the wall of the flow way is varied with sections of the flow way. In addition, the boss  123  is asymmetrically disposed on the bottom of the sink  122  proximal to one side of the fixing seat  121 . As a result, when the medium waves to collide a section of the fixing seat  121  more proximal to the boss  123 , the wave of the medium will be reflected in reverse direction. The wave is continuously collided and reflected so that the medium is transmitted to the water inlet/outlet  124  distal from the boss  123 . By means of changing the driving frequency of the piezoelectric element  2 , the flow can be otherwise controlled and the medium can flow in reverse direction.  
      The bottom layer  10 , middle layer  11  and top layer  12  of the present invention are made by means of photolithography in semiconductor manufacturing procedure. The bottom layer  10 , middle layer  11  and top layer  12  are mainly made of electrocasting nickel. The manufacturing procedure is described as follows:  
       FIG. 4  shows the manufacturing flow chart of the bottom layer  10  of the valveless micro impedance pump  1  of the present invention. In step (a) of  FIG. 4 , a stainless steel plate  21  is prepared. In step (b), a certain thickness of photoresistor  22  is painted on the stainless steel plate  21 . In step(c), through exposure, development and washing out photoresistor  22 , a desired pattern is left. In step (d), by means of micro-electrocasting technique, the desired structure is electrocast. The material of the structure is nickel. Finally, in step (e), the photoresistor  22  is removed and the structure is demolded to separate from the stainless steel plate  21  and form the bottom layer  10  of the valveless micro impedance pump  1  of the present invention.  
       FIG. 5  shows the manufacturing flow chart of the middle layer  11  of the valveless micro impedance pump  1  of the present invention. In step (a) of  FIG. 5 , a stainless steel plate  21  is prepared. In step (b), a layer of nickel is electrocast on the stainless steel plate  21  to form the lower vibration membrane  114 . In step (c), a certain thickness of photoresistor  22  is painted on the lower vibration membrane  114 . In step (d), through exposure, development and washing out photoresistor  22 , a desired pattern is left. In step (e), by means of micro-electrocasting technique, the desired structure is electrocast. The material of the structure is nickel. Finally, in step (f), the photoresistor  22  is removed and the structure is demolded to separate from the stainless steel plate  21  and form the middle layer  11  of the valveless micro impedance pump  1  of the present invention. The middle layer  11  includes the lower vibration membrane  114  and the flow way  113 .  
       FIG. 6  shows the manufacturing flow chart of the top layer  12  of the valveless micro impedance pump  1  of the present invention. In step (a) of  FIG. 6 , a stainless steel plate  21  is prepared. In step (b), a layer of photoresistor  22  is painted on the stainless steel plate  21 . In step (c), through exposure, development and washing out photoresistor  22 , a desired pattern is left. In step (d), a layer of nickel is electrocast to form the upper vibration membrane. In step (e) of a secondary photolithography, a certain thickness of photoresistor.  22  is painted on the upper vibration membrane  125 . In step (f), through exposure, development and washing out photoresistor  22 , a desired pattern is left. In step (g), again by means of micro-electrocasting technique, the fixing seat  121  is electrocast. The material of the fixing seat  121  is nickel. Finally, in step (h), the photoresistor  22  is removed and the structure is demolded to separate from the stainless steel plate  21  and form the top layer  12  of the valveless micro impedance pump  1  of the present invention. The top layer  12  includes the fixing seat  121 , the sink  122 , the boss  123 , the water inlets/outlets  124  and the upper vibration membrane  125 .  
       FIG. 7  shows a second embodiment of the present invention, in which two bosses  123 A are disposed in the sink  122 A of the top layer  12 A. In this embodiment, the bosses  123 A are symmetrically arranged. A piezoelectric element  2 A is disposed on each boss  123 A. The bottom face of the piezoelectric element  2 A is lengthwise fixed on top end of the boss  123 A and top face of the fixing seat  121 A.  
      According to the above arrangement, by means of the effect of the electric field, the upper and lower vibration membranes  125 A,  114 A are pushed by the piezoelectric elements through the bosses  123 A. The medium within the flow way  113 A is squeezed to flow toward the water inlets/outlets  124 A on two sides. The upper and lower vibration membranes  125 A,  114 A have different structures. Also, the hardness of the fixing seat  121 A is different from the hardness of the bottom layer  10 A. This leads to difference in impedance. Therefore, the wave of the medium can be transmitted.  
      The above embodiments are only used to illustrate the present invention, not intended to limit the scope thereof. Many modifications of the above embodiments can be made without departing from the spirit of the present invention.