Method for making micropumps

• US 6,227,809 B1
• Filed: 11/13/1998
• Issued: 05/08/2001
• Est. Priority Date: 03/09/1995
• Status: Expired due to Fees

• Current Assignee: Washington University In St Louis
• Original Assignee: University of Washington
• Inventors: Bardell, Ron L., Sharma, Nigel R., Forster, Fred K.
• Primary Examiner(s): FREAY, CHARLES GRANT
• Application Number:
  US09/192,078
• Time in Patent Office: 907 Days
• Field of Search: 417/53, 417/413.2, 417/322
• US Class Current: 417/53
• CPC Class Codes: F04B 43/046 with piezoelectric drive
• CPC Class Codes: F04B 53/1077 Flow resistance valves, e.g. without moving parts
• CPC Class Codes: F15C 5/00 Manufacture of fluid circuit elements; Manufacture of assemblages of such elements integrated circuits
• CPC Class Codes: F16K 2099/0074 using photolithography, e.g. etching
• CPC Class Codes: F16K 2099/0094 Micropumps
• CPC Class Codes: F16K 99/0001 Microvalves microdevices B81B1/00; manufacture or treatment of devices or systems in or on a substrate B81C1/00; microfluidic structures B01L3/5027; micropumps F04B19/006
• CPC Class Codes: F16K 99/0003 Constructional types of microvalves; Details of the cutting-off member
• CPC Class Codes: F16K 99/0021 No-moving-parts valves
• CPC Class Codes: F16K 99/0057 the fluid being the circulating fluid itself, e.g. check valves

Abstract

This invention provides a method by which the performance of reciprocating NMPV (No-Moving-Parts-Valve) micropumps can be optimized for a given choice of valve design, e.g. for diffuser/nozzle valves, rectifier valves etc. The method can more generally be used to design and produce NMPV micropumps with structures optimized for maximal pump performance. The method can further be used to design and construct NMPV pumps significantly smaller in size than those currently available to the art without significant loss in pump performance.

Claims

1. A method for making a micropump having no-moving-parts valves wherein the micropump comprises:

(1) a pump cavity of a selected diameter with at least one deformable cavity diaphragm of a selected thickness and which together define a cavity volume;

(2) one or more inlet valves and one or more outlet valves in fluid communication with the pump cavity, each inlet valve being a conduit with no moving parts shaped such that fluid flow in the conduit is restricted less in the direction toward the pump cavity than in the direction away from the pump cavity and each outlet valve being a conduit with no moving parts and shaped such that fluid flow in the conduit is restricted less in the direction away from the pump cavity than in the direction toward the pump cavity; and

(3) an actuator with a selected diameter which actuator is attached to the deformable cavity diaphragm to periodically change the cavity volume and to thereby pump fluid from each inlet valve through the pump cavity and through each outlet valve;

which comprises the steps of;

(a). selecting values for a geometric, materials, or other input parameter selected from the group consisting of valve geometry, pump cavity etch depth, diaphragm area, bubble volume, diaphragm diameter, diaphragm thickness, diaphragm density, diaphragm modulus of elasticity, Poisson'"'"'s ratio of the diaphragm, thickness of the actuator, diameter of the actuator, density of the actuator, modulus of elasticity of the actuator, and Poisson'"'"'s ratio of the actuator;

(b). calculating a first value of a pump performance parameter selected from the group consisting of pump cavity fluid pressure, diaphragm centerline deflection, the diaphragm swept volume flow rate, outlet volume flow rate and net volume flow rate using a linear systems model employing the selected input parameter values;

(c). varying the value of one or more of the input parameters;

(d). calculating the value of the selected pump performance parameter as a function of the varying input parameter or parameters;

(e). comparing the performance parameter calculated as a function of the varying input parameter or parameters to the first calculated value of the performance parameter to determine the values of the input parameter or parameters that result in optimized pump performance; and

(f). employing the values of the input parameter or parameters obtained in step (e) to make the micropump.

2. The method of claim 1 wherein the linear system model is represented by equations 1-3, 4A, 4B and 5 as follows:

$\begin{array}{cc}{\mathrm{kf}}_e<br><br>V=m<br><br>\frac{<br><br>{\stackrel{.}{W}}_c}{<br><br>t}+k<br><br>\int <br><br>{\stackrel{.}{W}}_c<br><br><br><br>t+\mathrm{\gamma <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{AP}& \left(1\right)\\ P=I_c<br><br>\frac{<br><br>Q_c}{<br><br>t}+P_c& \left(2\right)\\ P_c=\frac{1}{C_c}<br><br>\int <br><br>Q_c-Q_i-Q_o<br><br><br><br>t& \left(3\right)\\ P_c=\left(R_v+R_t\right)<br><br>Q_i+\left(I_v+I_t\right)<br><br>\frac{<br><br>Q_i}{<br><br>t}+\frac{1}{C_t}<br><br>\int <br><br>Q_i<br><br><br><br>t& \text{(4A)}\\ P_c=\left(R_v+R_t\right)<br><br>Q_o+\left(I_v+I_t\right)<br><br>\frac{<br><br>Q_o}{<br><br>t}+\frac{1}{C_t}<br><br>\int <br><br>Q_o<br><br><br><br>t<br><br><br><br>\mathrm{and}& \text{(4B)}\\ \mathrm{\gamma <br><br>}=\frac{2<br><br>\mathrm{\pi <br><br>}}{A}<br><br>\int <br><br>\frac{r_o}{2}<br><br>\left(1+\cos <br><br>\left(\frac{r<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\pi <br><br>}}{r_o}\right)\right)<br><br><br><br>r.& \left(5\right)\end{array}$

3. The method of claim 1 wherein the selected pump performance parameter is outlet flow volume or net volume of the pump.

4. The method of claim 3 wherein the input parameter that is varied is the diameter of the actuator.

5. The method of claim 4 wherein the actuator is a piezoelectric element.

6. The method of claim 4 wherein the value of the diameter of the piezoelectric element is varied between about 25% to about 95% of the diameter of the pump cavity.

7. The method of claim 1 wherein the input parameter that is varied is the thickness of the diaphragm to obtain a value that provides for optimal pump performance.

8. The method of claim 7 wherein the value of the pump cavity diameter is not varied.

9. The method of claim 8 wherein the actuator is a piezoelectric transducer and the value of the diameter of the piezoelectric transducer is also varied to obtain a value for the diameter of the piezoelectric transducer that provides for optimal pump performance.

10. A method for making a micropump having no-moving-parts valves wherein the micropump comprises:

(1) a pump cavity of a selected diameter with at least one deformable cavity diaphragm of a selected thickness which together define a cavity volume;

(2) one or more inlet valves and one or more outlet valves in fluid communication with the pump cavity, each inlet valve being a conduit with no moving parts shaped such that fluid flow in the conduit is restricted less in the direction toward the pump cavity than in the direction away from the pump cavity and each outlet valve being a conduit with no moving parts and shaped such that fluid flow in the conduit is restricted less in the direction away from the pump cavity than in the direction toward the pump cavity; and

(3) an actuator with a diameter ranging from about 25% to about 90% of that of the pump cavity diameter which actuator is attached to the deformable cavity diaphragm to periodically deform the diaphragm and as a result to periodically change the cavity volume and to thereby pump fluid from each inlet valve through the pump cavity and through each outlet valve;

which method comprises the step of selecting the pump cavity diameter, the thickness of the diaphragm and the diameter of the diaphragm to maximize pump outlet flow.

11. The method of claim 10 wherein the actuator is a piezoelectric element.

12. The method of claim 10 wherein the micropump is fabricated in silicon by micromaching techniques.

13. The method of claim 10 wherein the inlet and outlet valves are rectifier valves.

14. A method for operating a micropump to pump an incompressible fluid wherein the micropump has a pump cavity of a selected diameter with at least one deformable cavity diaphragm of a selected thickness which together define a cavity volume;

one or more inlet valves and one or more outlet valves in fluid communication with the pump cavity, each inlet valve being a conduit with no moving parts and shaped such that fluid flow in the conduit is restricted less in the direction toward the pump cavity than in the direction away from the pump cavity and each outlet valve being a conduit with no moving parts and shaped such that fluid flow in the conduit is restricted less in the direction away from the pump cavity than in the direction toward the pump cavity; and

an actuator with diameter ranging from about 25% to about 90% of the diameter of the pump cavity and which is attached to the deformable cavity diaphragm to periodically change the cavity volume and to thereby pump fluid from each inlet valve through the pump cavity and through each outlet valve;

which comprises the step of applying a periodic voltage change to said actuator at the diaphragm resonance frequency to operate the pump.

15. The method of claim 14 wherein the actuator is a piezoelectric element.

16. The method of claim 14 wherein the inlet and outlet valves are rectifier valves.

17. The method of claim 14 wherein the micropump has one deformable diaphragm.

18. An improved micropump of the type having a pump cavity of a selected diameter with at least one deformable cavity diaphragm of a selected thickness which together define a cavity volume;

one or more inlet and outlet valves in fluid communication with the pump cavity, the inlet valve being a conduit with no moving parts and shaped such that fluid flow in the conduit is restricted less in the direction toward the pump cavity than in the direction away from the pump cavity and the outlet valve being a conduit with no moving parts and shaped such that fluid flow in the conduit is restricted less in the direction away from the pump cavity than in the direction toward the pump cavity; and

an actuator with a diameter about 50% to about 95% of that of the pump cavity attached to the deformable cavity diaphragm to periodically change the cavity volume and to thereby pump fluid from the inlet valve through the pump cavity and through the outlet valve;

wherein the improvement is that the diaphragm thickness and the pump chamber diameter are selected such that a maximal outlet flow rate is obtained.

19. A micropump which comprises a pump cavity of a selected diameter less than 6 mm with at least one deformable cavity diaphragm of a selected thickness which together define a cavity volume;

one or more inlet and outlet valves in fluid communication with the pump cavity, each inlet valve being a conduit with no moving parts and shaped such that fluid flow in the conduit is restricted less in the direction toward the pump cavity than in the direction away from the pump cavity and each outlet valve being a conduit with no moving parts and shaped such that fluid flow in the conduit is restricted less in the direction away from the pump cavity than in the direction toward the pump cavity; and

an actuator with a diameter about 50% to about 95% of that of the pump cavity attached to the deformable cavity diaphragm to periodically change the cavity volume and to thereby pump fluid from the inlet valve through the pump cavity and through the outlet valve;

wherein the diaphragm thickness, piezoelectric transducer thickness and piezoelectric transducer diameter are selected such that a maximal outlet flow rate is obtained.

20. A micropump of claim 19 wherein the pump cavity diameter is about 3 mm or less.

21. A micropump of claim 19 wherein the pump cavity diameter is about 1.5 mm to about 0.5 mm.

22. A micropump of claim 19 which is fabricated in silicon by micromaching techniques.

23. A micropump of claim 19 which is fabricated using micromolding techniques.

24. A micropump of claim 19 which is optimized for pumping an incompressible fluid.

25. The micropump of claim 19 wherein the actuator is a piezoelectric element.

26. The micropump of claim 19 wherein the inlet and outlet valves are rectifier valves.

27. A method for making a micropump wherein the micropump comprises:

(1) a pump cavity of a selected breadth and selected depth with at least one deformable cavity diaphragm made of a selected material and having a selected thickness and which together define a cavity volume;

(2) one or more inlet valves and one or more outlet valves of known inertence and resistance;

(3) an actuator shaped for use with the selected pump cavity shape made of a selected material and having a selected breadth ranging from about 25% to about 90% of that of the pump cavity which actuator is attached to the deformable cavity diaphragm to periodically change the cavity volume and to thereby pump fluid from each inlet valve through the pump cavity and through each outlet valve;

which comprises the steps of;

setting a value for one of the input geometric or material parameters selected from the group consisting of pump cavity breadth, pump cavity depth, deformable pump cavity diaphragm material, deformable pump cavity diaphragm thickness, actuator breadth, and actuator thickness;

calculating a pump performance parameter selected from the group consisting of cavity fluid pressure, diaphragm centerline velocity, diaphragm swept volume flow rate, net volume flow rate and outlet volume flow rate as a function of varying each of the values of the input geometric or material parameters, except the value of the one set input geometric or material parameter;

comparing the calculated performance parameters as a function of varying input geometric or material parameters to determine optimized values of the varying input parameters; and

selecting values for pump cavity breadth, pump cavity depth, deformable pump cavity diaphragm material, deformable pump cavity diaphragm thickness, actuator breadth, and actuator thickness of the micropump that provide desired pump performance as indicated by the comparison of calculated pump performance parameter;

and making the micropump such that the input geometric or materials parameters provide for desired pump performance.

28. The method of claim 27 wherein the pump performance parameter is calculated using a linear systems model.

29. The method of claim 27 wherein the inlet and outlet valves are no-moving-parts valves.

30. The method of claim 27 wherein the pump performance parameter is outlet volume flow rate.

31. The method of claim 27 wherein the pump performance parameter is calculated using the equations 1-3, 4A, 4B and 5 as follows:

$\begin{array}{cc}{\mathrm{kf}}_e<br><br>V=m<br><br>\frac{<br><br>{\stackrel{.}{W}}_c}{<br><br>t}+k<br><br>\int <br><br>{\stackrel{.}{W}}_c<br><br><br><br>t+\mathrm{\gamma <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{AP}& \left(1\right)\\ P=I_c<br><br>\frac{<br><br>Q_c}{<br><br>t}+P_c& \left(2\right)\\ P_c=\frac{1}{C_c}<br><br>\int <br><br>Q_c-Q_i-Q_o<br><br><br><br>t& \left(3\right)\\ P_c=\left(R_v+R_t\right)<br><br>Q_i+\left(I_v+I_t\right)<br><br>\frac{<br><br>Q_i}{<br><br>t}+\frac{1}{C_t}<br><br>\int <br><br>Q_i<br><br><br><br>t& \text{(4A)}\\ P_c=\left(R_v+R_t\right)<br><br>Q_o+\left(I_v+I_t\right)<br><br>\frac{<br><br>Q_o}{<br><br>t}+\frac{1}{C_t}<br><br>\int <br><br>Q_o<br><br><br><br>t<br><br><br><br>\mathrm{and}& \text{(4B)}\\ \mathrm{\gamma <br><br>}=\frac{2<br><br>\mathrm{\pi <br><br>}}{A}<br><br>\int <br><br>\frac{r_o}{2}<br><br>\left(1+\cos <br><br>\left(\frac{r<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\pi <br><br>}}{r_o}\right)\right)<br><br><br><br>r.& \left(5\right)\end{array}$