METHOD AND SYSTEM FOR DETECTING MALFUNCTION OF A MEMS MICROPUMP

• US 20140147246A1
• Filed: 06/22/2012
• Published: 05/29/2014
• Est. Priority Date: 06/23/2011
• Status: Active Grant

• Current Assignee: Debiotech S.A.
• Original Assignee: Debiotech S.A.
• Inventors: Chappel, Eric, Neftel, Frdric, Proennecke, Stephan
• Granted Patent: US 10,286,144 B2
• Time in Patent Office: Days
• US Class Current: 415/1
• CPC Class Codes: A61M 5/14244 adapted to be carried by the patient, e.g. portable on the body
• CPC Class Codes: A61M 5/14593 the diaphragm being actuated by fluid pressure
• CPC Class Codes: A61M 5/16859 Evaluation of pressure response, e.g. to an applied pulse
• CPC Class Codes: A61M 5/16881 Regulating valves on-off valves, e.g. clamps A61M39/28
• CPC Class Codes: A61M 5/5086 for indicating if defective, used, tampered with or unsterile
• CPC Class Codes: F04D 15/0005 by using valves

Abstract

Method for detecting failure including possible under or over delivery of a micropump having at least an inlet valve, a pumping chamber with an inner pressure sensor and an outlet valve, said method comprising the determination of the pump tightness via the measurement of the pressure by said inner pressure sensor in said pumping chamber at least at certain intervals when the pump is inactive and the comparison with a value of reference.

Claims

1. Method for detecting failure including possible under or over delivery of a micropump having at least an inlet valve, a pumping chamber with an inner pressure sensor and an outlet valve, said method comprising the determination of the pump tightness via the measurement of the pressure by said inner pressure sensor in said pumping chamber at least at certain intervals when the pump is inactive and the comparison with a value of reference.

2. Method according to claim 1, wherein said reference value is obtained by measuring the pressure sensor in said pumping chamber during at least part of the pumping cycle when the pump is active.

3. Method according to claim 2, comprising furthermore the determination of an equivalent fluidic resistance as defined in the following equation:

1/R_eq=1/R_in+1/R_out

where

R_eq is the equivalent fluidic resistance

R_in the residual fluidic resistance of said inlet valve, when closed

R_out the residual fluidic resistance of said outlet valve, when closed,

said equivalent fluidic resistance being determined via the in-situ measurement, by said inner pressure sensor, of the pressure change in said pumping chamber when the pump is active.

4. Method according to claim 3, comprising furthermore the measurement of the pressure at the inlet and at the outlet of the pump when the pump is active, said possible under or over delivery being then characterized by a maximum leak rate Q_max which is determined according to the following relationship.

Q_max=Δ

P/4R_eq

Where Δ

P is the difference between said inlet and outlet pressures

5. Method according to claim 1 wherein the outlet valve is controlled externally and wherein said method comprises the actuation of the pump inducing a compression of a gas present in the pumping chamber while the outlet valve is closed by external means, said method comprising the measurement of the pressure of the gas in the pumping chamber before and after said compression, said method comprising furthermore the analysis of the pressure decay of said gas after the compression, said pressure decay being induced by the said residual fluidic resistances of inlet and outlet valves when closed.

6. Method according to claim 5, wherein the compression ratio of the pump, the opening thresholds of the inlet and outlet valves, respectively P_in and P_out, are determined by analyzing, during at least part of the pumping cycle, said inner pressure sensor when the pump is active.

7. Method according to claim 1, comprising the determination of a reservoir pressure with said inner detector when the pump is active, said method comprising the comparison between said equivalent fluidic resistance and said reservoir pressure with predetermined threshold values, said method comprising the triggering of an alarm when said fluidic resistance is smaller than said predefined threshold value of fluidic resistance and/or said reservoir pressure is larger than said predetermined threshold pressure value.

8. Method according to claim 3 furthermore comprising the measurement of the static relative pressure P in the pumping chamber by said inner pressure sensor when the pump is inactive, said under or over delivery being then characterized by a maximum leak rate Q which is determined according to the following relationship:

Q_max=1/(R_eq(1/P+1/P_{val in}))

Where P_{val in}, the opening threshold of the inlet valve, is equal to the difference of pressure upwardly and downwardly the inlet valve, the difference of pressure between respectively said pumping chamber pressure and said reservoir pressure, which is necessary to open the inlet valve.

9. Method according to claim 1, furthermore comprising the measurement of the pressure by said inner pressure sensor, when the functional pump is at rest and during the reservoir filling.

10. Method according to claim 9, wherein the pump is actuated at the end of the pump filling, said method comprising the measurement of said inner detector and the comparison between the measured pressure with a predefined threshold value, the pump being actuated until said pressure becomes smaller than said predefined threshold value.

11. Method according to claim 10, furthermore comprising a predefined number of additional actuation cycles.

12. Method according to claim 9, comprising the triggering of an alarm when the pressure measured by said inner detector during the filling exceeds a first predefined value, said alarm being stopped when said pressure decreases below a second predefined value.

13. Method according to claim 1, wherein the pump has a crack-guard onto at least one flexible part of the pump, said method comprising the electrical measurement of the crack-guard continuity.

14. Method according to claim 1, wherein the pump furthermore comprises an outer detector downward the outlet valve, said equivalent fluidic resistance being determined via the measurement, by said inner and outer pressure sensors, of the pressure decay in said pumping chamber when the pump is active.

15. Method according to claim 14, comprising the determination of the reservoir pressure with said inner and outer detectors when the pump is active, said method comprising the comparison between said equivalent fluidic resistance and said reservoir pressure with predetermined threshold values, said method comprising the triggering of an alarm when said fluidic resistance and/or said reservoir pressure are/is respectively smaller and larger than said predetermined threshold values.

16. Method according to claim 15, comprising furthermore the determination of the empty reservoir using said inner and outer detectors.

17. Method for detecting the under or over delivery of a micropump according to claim 14, furthermore comprising the measurement of the static relative pressure P and P₀ of the inner and outer detector respectively when the pump is inactive, said method comprising the determination of a minimum fluidic resistance of said outlet valve R_out, said value R_out being minimized in a first approximation by the equivalent fluidic resistance R_eq, said under or over delivery being then characterized by a maximum leak rate Q which is determined according to the following relationship:

Q_max=(P−

P₀)/R_eq

18. Method according to claim 14 furthermore comprising the measurement of the static relative pressure P and P₀ of the inner and outer detector respectively when the pump is inactive, said under or over delivery being then characterized by a maximum leak rate Q which is determined according to the following relationship:

Q_max=1/(R_eq(1/(P−

P₀)+1/P_{val in}))

Where P_{val in} is the opening threshold of the inlet valve.

19. Method according to claim 9, wherein the pump furthermore comprises an outer detector downward the outlet valve, said method comprising the pressure measurement with said inner and outer detectors and the comparison between the measured pressures with predefined threshold values, the pump being actuated until said pressure becomes smaller than said predefined threshold value.

20. Method according to claim 14, wherein the pump comprises a vent for the reference port of the pressure detectors, said method comprising the determination of the vent clogging by measuring and comparing the signals of both detectors according to predefined threshold values in presence of a gradient of pressure between the reference port of said detectors and outside.

21. Method according to claim 1, comprising furthermore a partial, a half or a full actuation of the membrane to determine the equivalent fluidic resistance of the valves.

22. Method according to claim 21, wherein the flow rate induced by said additional actuation is less than the usual flow rate when the pump is active.

23. Micropump having at least an inlet valve, a pumping chamber with an inner pressure sensor and an outlet valve, said micropump comprising under or over delivery detecting means which include a processing unit for determining the equivalent fluidic resistance according to the method as defined in claim 2.

24. Micropump according to claim 23 furthermore comprising an outer pressure detector located downward said outlet valve.

25. Micropump according to claim 23, furthermore comprising a crack-guard onto at least one flexible part and measuring means for electrical measurement of the crack-guard continuity.