Triaxial fiber optic force sensing catheter
A fiber optic force sensing assembly for detecting forces imparted at a distal end of a catheter assembly. The structural member may include segments adjacent each other in a serial arrangement, with gaps located between adjacent segments that are bridged by flexures. Fiber optics are coupled to the structural member. In one embodiment, each fiber optic has a distal end disposed adjacent one of the gaps and oriented for emission of light onto and for collection of light reflected from a segment adjacent the gap. The optical fibers cooperate with the deformable structure to provide a change in the intensity of the reflected light, or alternatively to provide a variable gap interferometer for sensing deformation of the structural member. In another embodiment, the gaps are bridged by fiber Bragg gratings that reflect light back through the fiber optic at central wavelengths that vary with the strain imposed on the grating.
1. A fiber optic force sensing assembly, comprising:
a structural member defining a longitudinal axis and including a plurality of segments that are adjacent each other along the longitudinal axis, each of adjacent ones of the plurality of segments defining a gap therebetween;
a flexure bridging each gap, wherein the flexure defines a cross-section on a plane orthogonal to the longitudinal axis, the cross-section defining an area centroid, a first inertial axis and a second inertial axis being defined as passing through the area centroid, the second inertial axis being normal to the first inertial axis and intersecting the longitudinal axis of the structural member; and
a fiber optic coupled to the structural member.
2. The fiber optic force sensing assembly of claim 1 , wherein an area moment of inertia about the second inertial axis being at least ten times greater than an area moment of inertia about the first inertial axis.
3. The fiber optic force sensing assembly of claim 1 , wherein the area moment of inertia about the first inertial axis of the fiber optic force sensing assembly is the minimum area moment of inertia of the cross-section of the flexure.
4. The fiber optic force sensing assembly of claim 1 , further comprising a plurality of fiber optics coupled to the structural member.
5. The fiber optic force sensing assembly of claim 4 , wherein the fiber optic is a first fiber optic, and the fiber optic force sensing assembly further comprises a second fiber optic arranged on an opposing side of the gap from the first fiber optic.
6. The fiber optic force sensing assembly of claim 5 , wherein the first fiber optic and the second fiber optic are configured to define an interferometric gap.
7. The fiber optic force sensing assembly of claim 5 , wherein at least one of the first fiber optic and the second fiber optic include one of a Fabry-Perot resonator and a fiber Bragg grating.
8. The fiber optic force sensing assembly of claim 7 , wherein the Fabry-Perot resonator comprises an intrinsic Fabry-Perot interferometer.
9. The fiber optic force sensing assembly of claim 1 , wherein a portion of the cross-section of the flexure of the fiber optic force sensing assembly defines a circular segment.
10. The fiber optic force sensing assembly of claim 1 , wherein the fiber optic force sensing assembly includes a plurality of gaps and a plurality of flexures corresponding to a number of the plurality of gaps.
11. The fiber optic force sensing assembly of claim 10 , wherein the fiber optic force sensing assembly includes three gaps and at least one flexure bridges each gap.
12. The fiber optic force sensing assembly of claim 10 , wherein at least one of the gaps is reduced and at least one of the gaps is increased when the structural member is subjected to a lateral force.
13. The fiber optic force sensing assembly of claim 10 , wherein each of the gaps is reduced when the structural member is subjected to an axial force.
14. The fiber optic force sensing assembly of claim 10 , wherein each of the flexures are located at a circumferential position about the longitudinal axis that is different from the circumferential position of the other flexures.
15. The fiber optic force sensing assembly of claim 10 , wherein the flexures are centered at 120-degree intervals about the longitudinal axis.
16. The fiber optic force sensing assembly of claim 1 , wherein the plurality of segments are adjacent one another in a serial arrangement along the longitudinal axis.
17. The fiber optic force sensing assembly of claim 1 , wherein the fiber optic is disposed within a groove along an outer surface of one or more of the plurality of segments.
18. The fiber optic force sensing assembly of claim 17 , wherein an end of the fiber optic is located at or within the groove.
19. The fiber optic force sensing assembly of claim 1 , wherein the flexure is configured to transfer torsional force about the longitudinal axis between the plurality of segments.
20. The fiber optic force sensing assembly of claim 1 , wherein the flexure is configured to bend about the first inertial axis.