Detection sensor and resonator

1. A detection sensor comprising:

a disc type mechanical resonator whose vibration characteristic is changed due to attachment or adsorption of a substance having a mass;

a driving unit that vibrates the resonator; and

a detection unit that detects the substance by detecting a change in vibrations of the resonator, wherein

the driving unit and the detection unit are spaced apart from the resonator,

the driving unit and the detection unit detect the vibration of the resonator and a change in vibrations of the resonator by electrostatically coupling with the resonator, and the resonator vibrates only in the in-disc-face direction of the resonator.

2. The detection sensor according to claim 1 , wherein

the substance is attached to the surface of the resonator.

3. The detection sensor according to claim 1 , wherein

the resonator has an adsorbing member that adsorbs the substance.

4. The detection sensor according to claim 1 , wherein

irregularity or a groove is formed on at least a part of the surface of the resonator.

5. The detection sensor according to claim 1 , wherein

the detection unit detects the quantity of the substance attached to the resonator.

6. The detection sensor according to claim 1 , wherein

the substance is a specific molecular or a plurality of types of molecules respectively having a specific characteristic or feature.

7. The detection sensor according to claim 1 , wherein

a plurality of the resonators are provided and one of the resonators and the other of the resonators are electrostatically coupled with each other, and

the detection unit detects attachment of the substance to the resonators by detecting a change in the difference between vibration frequencies when the substance attaches to the one-hand resonator and the other-hand resonator.

8. The detection sensor according to claim 1 , wherein the resonator is supported only at a peripheral portion of the resonator.

9. The detection sensor according to claim 1 , wherein the vibration generated in the resonator has the following three modes: (a) radial mode (mode in which it vibrates only in the diameter direction), (b) tangential mode (mode in which it vibrates only in θ direction), and (c) compound mode (mode in which diameter-directional vibration and θ-directional vibration are conjugated).

10. The detection sensor according to claim 1 , wherein the resonator uses single-crystal or polycrystalline Si as a structural material.

11. The detection sensor according to claim 1 , wherein

a reference resonator to which the substance does not attach is provided in parallel with the resonator, and

the detection unit detects attachment of the substance to the resonator by detecting a change in vibrations of the resonator on the basis of the vibration of the reference resonator when the substance attaches to the resonator.

12. The detection sensor according to claim 11 , wherein

reverse phase vibration is generated in the resonator and the reference resonator.

13. The detection sensor according to claim 1 , wherein

the detection unit detects a change in vibrations of the resonator due to the substance directly or indirectly attached or adsorbed to an area on the surface of the resonator.

14. The detection sensor according to claim 13 , wherein

the area is a portion where the vibration amplitude of the resonator becomes 50% or more with respect to the maximum vibration amplitude of the resonator.

15. The detection sensor according to claim 13 , wherein

the area includes a portion where the vibration amplitude of the resonator is maximized.

16. The detection sensor according to claim 13 , wherein

a plurality of the areas are set and substances different from each other are attached or adsorbed to the areas.

17. The detection sensor according to claim 1 , wherein

the resonator is annular in which the outside diameter is Ra and the inside diameter is Rb because an opening is formed at the central portion, and

the resonator is formed by the outside diameter Ra and the inside diameter Rb almost satisfying the radial-directional displacement U(r)=0 or tangential-directional displacement V(r)=0 when r=Ra or Rb, providing that the resonator vibrates on the positional coordinates (r, Θ), and the U(r) and V(r) at the position r are shown by expression (42).

U

⁡

(

r

)

=

∂

∂

r

⁢

J

n

⁡

(

hr

)

+

A

6

⁢

n

r

⁢

J

n

⁡

(

kr

)

+

A

7

⁢

∂

∂

r

⁢

Y

n

⁡

(

hr

)

+

A

8

⁢

n

r

⁢

Y

n

⁡

(

kr

)

V

⁡

(

r

)

=

n

r

⁢

J

n

⁡

(

hr

)

+

A

6

⁢

∂

∂

r

⁢

J

n

⁡

(

kr

)

+

A

7

⁢

n

r

⁢

Y

n

⁡

(

hr

)

+

A

8

⁢

∂

∂

r

⁢

Y

n

⁡

(

kr

)

(

42

)

In this case,

h

=

ω

⁢

ρ

⁡

(

1

-

σ

2

)

E

,

k

=

ω

⁢

ρ

⁡

(

2

+

2

⁢

σ

)

E

,

k

=

h

⁢

2

1

-

σ

σ: Poisson's ratio of resonator material, E: Young's modulus of resonator material, ρ: density of resonator material, ω: angular frequency, n: order of vibration mode, A6, A7, and A8: constants uniquely determined in accordance with specific vibration mode specified by outside diameter and inside diameter of resonator, Young's modulus, density and Poisson's ratio of resonator material, and boundary condition of resonator (in this case, free-free condition).

18. The detection sensor according to claim 17 , wherein

when r=Ra in the above expression (42) and U(r)=0 or V(r)=0 is almost satisfied, the resonator is supported by the outside diameter portion.

19. The detection sensor according to claim 17 , wherein

when r=Rb in the above expression (42) and U(r)=0 or V(r)=0 is almost satisfied, the resonator is supported by the inside diameter portion.

20. The detection sensor according to claim 18 or 19 , wherein

when r=Ra or Rb in the above expression (42) and U(r)=0 is almost satisfied, the resonator is supported at a position Θ of sin(nΘ)=0.

21. The detection sensor according to claim 18 or 19 , wherein

when r=Ra or Rb in the above expression (42) and V(r)=0 is almost satisfied, the resonator is supported at a position Θ of cos(nΘ)=0.