System and method for detecting skin penetration

1. A system for detecting skin penetration, the system comprising:

an invasive component for penetrating the skin;

a dummy electrode for making contact with the surface of the skin;

at least one penetrating electrode disposed in the invasive component;

a Wheatstone bridge circuit;

wherein a resistance across the dummy electrode and the penetrating electrode constitutes one of the resistive legs of the Wheatstone bridge circuit, and

a first pair of reference electrodes for making contact with the surface of the skin, wherein a skin resistance across the first pair of reference electrodes constitutes the mirroring resistive leg, with respect to ground, of the Wheatstone bridge circuit;

wherein the system is configured to detect a depth of skin penetration of the invasive component based on a differential output voltage from the Wheatstone bridge circuit.

2. The system as claimed in claim 1 , wherein one of the reference electrodes is the dummy electrode.

3. The system as claimed in claim 1 , further comprising second and third pairs of reference electrodes, each for making contact with the surface of the skin, wherein respective skin resistances across the second and third pairs of reference electrodes constitute the remaining resistive legs of the Wheatstone bridge circuit respectively.

4. The system as claimed in claim 1 , wherein a plurality of penetrating electrodes are disposed in the invasive component.

5. The system as claimed in claim 4 , wherein resistances across the dummy electrode and the respective penetrating electrodes are multiplexed across one of the resistive legs of the Wheatstone bridge circuit connected to the respective penetrating electrodes, and the depth of skin penetration of the invasive component is detected based on differential output voltages from the Wheatstone bridge circuit induced by the respective resistances across the dummy electrode and the respective penetrating electrodes.

6. The system as claimed in claim 1 , wherein the invasive component comprises a microneedle disposed in a lancing device, and the dummy electrode for making contact with the surface of the skin is disposed on a skin-contact face of the lancing device.

7. The system as claimed in claim 1 , wherein the invasive component comprises a microneedle disposed in a lancing device, and the dummy electrode for making contact with the surface of the skin and the first pair of reference electrodes are disposed on a skin-contact face of the lancing device.

8. The system as claimed in claim 3 , wherein the invasive component comprises a microneedle disposed in a lancing device, and the dummy electrode for making contact with the surface of the skin and the first, second, and third pairs of reference electrodes are disposed on a skin-contact face of the lancing device.

9. The system as claimed in claim 1 , wherein the invasive component comprises a hollow or solid microneedle.

10. The system as claimed in claim 1 , wherein the invasive component comprises a conductive microneedle.

11. The system as claimed in claim 1 , wherein the invasive component comprises a non-conductive microneedle.

12. The system as claimed in claim 11 , wherein the invasive component comprises a plastic microneedle.

13. The system as claimed in claim 1 , further comprising means for indicating the depth of skin penetration of the invasive component based on the differential output voltage from the Wheatstone bridge circuit.

14. The system as claimed in claim 1 , further comprising means for displaying the depth of skin penetration of the invasive component based on the differential output voltages from the Wheatstone bridge circuit.

15. The system as claimed in claim 6 , wherein the reference and/or dummy electrodes are disposed around an opening of a distal end of the lancing device.

16. A method for detecting skin penetration, the method comprising the steps of:

penetrating the skin with an invasive component wherein at least one penetrating electrode is disposed in the invasive component;

making contact between a dummy electrode and the surface of the skin;

applying a resistance across the dummy electrode and the penetrating electrode as one of the resistive legs of a Wheatstone bridge circuit;

making contact with the surface of the skin with a first pair of reference electrodes;

applying a skin resistance across the first pair of reference electrodes as the mirroring resistive leg, with respect to ground, of the Wheatstone bridge circuit; and

detecting a depth of skin penetration of the invasive component based on a differential output voltage from the Wheatstone bridge circuit.

17. The method as claimed in claim 16 , wherein one of the reference electrodes is the dummy electrode.

18. The method as claimed in claim 16 , further comprising the steps of:

making contact with the surface of the skin with second and third pairs of reference electrodes, and

applying respective skin resistances across the second and third pairs of reference electrodes as the remaining resistive legs of the Wheatstone bridge circuit respectively.

19. The method as claimed in claim 16 , wherein a plurality of penetrating electrodes are disposed in the invasive component.

20. The method as claimed in claim 19 , wherein resistances across the dummy electrode and the respective penetrating electrodes are multiplexed to one of the resistive legs of the Wheatstone bridge circuit connected to the respective penetration electrodes and the depth of skin penetration of the invasive component is detected based on differential output voltages from the Wheatstone bridge circuit induced by the respective resistances across the dummy electrode and the respective penetrating electrodes.

21. The method as claimed in claim 16 , wherein the invasive component comprises a microneedle disposed in a lancing device, and the dummy electrode for making contact with the surface of the skin is disposed on a skin-contact face of the lancing device.

22. The method as claimed in claim 16 , wherein the invasive component comprises a microneedle disposed in a lancing device, and the dummy electrode for making contact with the surface of the skin and the first pair of reference electrodes are disposed on a skin-contact face of the lancing device.

23. The method as claimed in claim 18 , wherein the invasive component comprises a microneedle disposed in a lancing device, and the dummy electrode for making contact with the surface of the skin and the first, second, and third pairs of reference electrodes are disposed on a skin-contact face of the lancing device.

24. The method as claimed in claim 16 , wherein the invasive component comprises a hollow or solid microneedle.

25. The method as claimed in claim 16 , wherein the invasive component comprises a conductive microneedle.

26. The method as claimed in claim 16 , wherein the invasive component comprises a non-conductive microneedle.

27. The method as claimed in claim 26 , wherein the invasive component comprises a plastic microneedle.

28. The method as claimed in claim 16 , further comprising the step of:

indicating the depth of skin penetration of the invasive component based on the differential output voltage from the Wheatstone bridge circuit.

29. The method as claimed in claim 20 , further comprising the step of:

displaying the depth of skin penetration of the invasive component based on the differential output voltages from the Wheatstone bridge circuit.