Multicore Fiber Force Sensor with Bragg Gratings
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Solution Overview
Problem
Current force sensing technologies are inadequate for accurately measuring forces applied to medical devices, particularly in terms of sensitivity and direction independence, and are sensitive to temperature variations and structural changes.
Innovation Solution
A system comprising a multicore fiber with Fiber Bragg Gratings and a force transducing element, such as a compressive spring, that is fixed to the fiber to induce bending, compression, or tension, allowing for optical measurement of force characteristics, with the fiber under pretension to prevent buckling and enhance sensitivity, and capable of independent directional force measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a force transducing element is integrated into a host material with structural elements, then the system can measure force, but the measurement is sensitive to temperature variations and structural changes
Solution Approach 1:
The system separates the force transducing element from the host material's structural elements. The force transducing element is integrated into the catheter shaft independently, allowing it to transduce force to the optical fiber without being influenced by temperature-induced changes in surrounding structural elements like the catheter tube
Solution Approach 2:
The optical fiber acts as an intermediary between the force transducing element and the measurement system. The fiber transduces force mechanically while being insensitive to temperature variations, thereby isolating the measurement from temperature effects that would otherwise affect structural elements of the host material
2Measurement precision
If the force transducing element is made stiff to dominate host material stiffness, then temperature sensitivity is reduced, but the force required to compress the fiber increases
Solution Approach 1:
The stiffness of the force transducing element is optimized to a specific range that is sufficient to dominate the stiffness of the host material at the location of the transducer, ensuring temperature independence, while not being excessively stiff. This allows the element to remain compliant enough to be compressed by physiological forces while maintaining structural dominance for temperature compensation
3Ease of manufacture
If the multicore fiber is not under pretension, then the system is easier to manufacture, but buckling of the fiber can occur in the force transducing element
Solution Approach 1:
The multicore fiber is pre-tensioned during assembly to a specific tensioning force that places it under initial tension. This preliminary action prevents the fiber from buckling when compressive forces are later applied during operation, while the tensioning mechanism allows for controlled application and release of this pretension
4Measurement precision
If conventional force sensing technologies are used, then the system can detect force, but the sensitivity and direction independence are inadequate
Solution Approach 1:
The force transducing element is designed with symmetric geometry and uniform stiffness in all lateral directions, making it universally responsive to forces from any direction. This multi-directional capability allows the same element to accurately sense forces regardless of their orientation, providing direction independence while maintaining high sensitivity
Solution Approach 2:
The force transducing element employs asymmetric design features strategically positioned to compensate for directional variations. By introducing controlled asymmetries in the placement of structural features or the orientation of the optical fiber relative to the element, the system achieves uniform sensitivity across different force directions
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate, direction-independent force sensing with reduced temperature sensitivity and lower required force for compression, suitable for medical devices like catheters, with the ability to differentiate between force and temperature influences.
Implementation Method 1
each core comprises at least one Fiber Bragg Grating
Implementation Method 2
multicore fiber comprising at least two cores of which each core comprises at least one Fiber Bragg Grating
Implementation Method 3
transduce force applied to the force transducing element to the multicore fiber, resulting into a bending and/or compression and/or tension of the multicore fiber
Data Source
AI summary
An optical system comprises a multicore fiber comprising at least two cores of which each core comprises at least one Fiber Bragg Grating. The optical system also comprises a force transducing element being bendable in one or more directions and being fixed to the multicore fiber so as to transduce force applied to the force transducing element to the multicore fiber, resulting into a bending and/or compression and/or tension of the multicore fiber. The multicore fiber is connectable or connected to a measurement system for optically measuring the response of at least one Fiber Bragg Grating, for each of at least 2 cores of the multicore fiber, as a result of the multicore fiber bending and/or compression and/or tension for deriving a characteristic of the force acting on the position of the force transducing element of the optical system.