Monolithic Cylinder Force Sensor for Microsurgery
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Solution Overview
Problem
Current 3-dimensional force sensing tools for microsurgical instruments, particularly for middle-ear and retinal surgery, are inadequate as they either measure forces only in one direction or are not suitable for detecting forces applied distant from the flexible zone, and existing designs are complex, costly, and difficult to manufacture for low-cost disposable medical instruments.
Innovation Solution
A monolithic cylinder structure with punch-like notches and optical fibers forming Fabry-Perot interferometric cavities, allowing for precise measurement of forces in three orthogonal directions without requiring rotation during manufacturing, thus reducing complexity and cost while maintaining high sensitivity and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing 3-dimensional force sensing tools are used, then force measurement capability is provided, but the device complexity and manufacturing cost increase
Solution Approach 1:
The sensing element is divided into multiple independent elastic zones separated by notches, with each zone containing optical fibres that can independently measure force components. This segmentation allows the complex 3D force measurement function to be distributed across simpler, modular zones, reducing overall device complexity while maintaining measurement precision.
Solution Approach 2:
The monolithic cylinder structure serves multiple functions simultaneously: it provides mechanical support, defines elastic zones for force sensing, guides optical fibres through integrated channels, and creates Fabry-Perot cavities for measurement. This multi-functionality eliminates the need for separate components, reducing device complexity while maintaining full 3D force measurement capability.
2Measurement precision
If existing force sensing elements are designed for close contact, then measurement accuracy is maintained, but the ability to detect forces applied at a distance is lost
Solution Approach 1:
The invention extends the sensing capability from lateral directions only to include the axial dimension by creating elastic zones that respond to forces applied at a distance along the z-axis. The notches and blade structures are configured to translate distant axial forces into measurable deformations within the elastic zones, adding dimensional versatility while maintaining measurement accuracy.
Solution Approach 2:
The elastic zones act as intermediaries that transmit forces applied at a distance through the structure to the measurement points. These zones amplify and translate distant forces into localized deformations that can be accurately measured by the optical fibres, enabling detection of forces applied far from the sensing element while maintaining precision.
3Measurement precision
If monolithic structures with multiple notches are used, then 3D force measurement is enabled, but manufacturing complexity and cost increase
Solution Approach 1:
Multiple functional elements are merged into a single monolithic cylinder structure: the support framework, elastic zones, notches, optical fibre channels, and Fabry-Perot cavity formations are all integrated into one piece. This merging eliminates the need for separate manufacturing and assembly steps for each component, significantly improving ease of manufacture while maintaining full 3D force measurement capability.
Solution Approach 2:
The invention uses parameter changes in the monolithic structure design, such as varying the thickness and positioning of notches and blades in different zones, to create the required elastic properties for 3D force sensing. These parameter variations are achieved through a single manufacturing process, making the complex sensing functionality manufacturable from a simple monolithic precursor.
4Measurement precision
If optical fibres are guided through channels to multiple notches, then comprehensive force sensing is achieved, but structural complexity increases
Solution Approach 1:
The channels serve multiple functions: they guide optical fibres to different notches, provide structural support, and define the boundaries of elastic zones. This multi-functionality reduces the need for additional guiding structures, maintaining comprehensive force sensing capability while minimizing structural complexity.
Solution Approach 2:
The optical fibres are nested within the monolithic structure's internal channels, with the channels themselves nested within the cylinder wall. This nested arrangement allows comprehensive force sensing across multiple notches while keeping the overall structure compact and simple, avoiding external routing complexity.
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
The solution enables accurate, low-cost, and sensitive measurement of 3-dimensional forces applied at a distance from the sensing element, suitable for microsurgical instruments, with a compact design suitable for middle-ear and retinal surgery, and is easy to manufacture, reducing the risk of infection by being simple and cost-effective.
Implementation Method 1
optical fibres (9), each fixed in one of the three channels (8), all entering the structure (2) from the bottom surface (3), crossing the first notch and ending at or near the top surface (5) while being interrupted in the first notch (6) so as to define two surfaces (10, 12) of each fibre that form Fabry-Perot interferometric cavities (13)
Data Source
AI summary
An optical force sensing element for microsurgical instruments and methods measures force F in three orthogonal directions and includes a monolithic cylinder structure, a cylindrical surface and a top surface that absorbs and transmits the force F. Three punch-like notches, all being parallel to the y-direction, are spaced apart along the z-axis and form two blades between the first and second notch and between the second and the third notch. Three channels parallel to the z-axis extend from the bottom surface to the top surface and cross the first notch while bypassing the other two notches. Three optical fibers, each fixed in one of the three channels, all entering the structure from the bottom surface, cross the first notch and end at or near the top surface while being interrupted in the first notch and forming two surfaces of each fiber that define a Fabry-Perot interferometric cavity.