Folded Nitinol Sheet Coils for Compact Catheter Force Sensing
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Solution Overview
Problem
Conventional contact force sensors in medical catheters are costly and difficult to mass-produce, particularly due to the need for individually prepared springs, which limits their availability for small spaces and increases production complexity.
Innovation Solution
The development of catheters with contact force sensors using spring designs cut from planar sheet metal and shape-set into final form, featuring resilient members with central rings, sinusoidal configurations, and multiple sectors, allowing for deformation-based displacement measurement without the need for welding, enabling mass production and compact design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If springs are individually prepared by cutting from nitinol tubing, then the contact force sensor can be assembled, but the production cost increases and mass production becomes difficult
Solution Approach 1:
The spring is segmented into multiple identical units that can be simultaneously cut from a single planar sheet of nitinol material. This allows multiple springs to be prepared in parallel rather than individually, enabling mass production while maintaining the required spring properties.
Solution Approach 2:
The spring design transitions from a three-dimensional tubular structure to a two-dimensional planar sheet configuration. This dimensional change allows the springs to be cut and prepared in a plane, making them suitable for mass production techniques such as laser cutting or stamping, while the subsequent folding creates the necessary three-dimensional spring structure.
2Reliability
If conventional spring designs are used, then the contact force sensor can function, but the space required increases
Solution Approach 1:
The spring is designed as a planar structure that can be folded into a compact three-dimensional configuration. This allows the spring to maintain its functional length and deformation capability while occupying minimal space when not in use, fitting the compact requirements of modern catheter sensors.
Solution Approach 2:
The planar spring structure can be folded and nested within the catheter body, allowing the sensor to be compact when retracted and extend only when needed for measurement. This nesting capability reduces the overall volume requirement while maintaining full sensor functionality.
3Strength
If welding is used to assemble spring components, then the structure can be joined, but the production complexity and cost increase
Solution Approach 1:
Multiple spring components are designed to be interconnected through folding rather than separate welding operations. The planar sheet structure allows adjacent spring elements to be joined by simple folding and bending, merging multiple components into a single integrated structure that maintains structural integrity without requiring welding.
Solution Approach 2:
The spring structure is designed to self-assemble through elastic deformation and geometric interlocking. The folded planar configuration allows the spring to maintain its shape and structural strength through its own elastic properties rather than requiring external welding or fastening operations.
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
This approach reduces production costs and allows for the creation of reliable, compact contact force sensors suitable for medical catheters, enhancing their availability and performance in verifying electrode contact with cardiac tissue during ablation procedures.
Implementation Method 1
a resilient member interposed between two contacting elements... a force applied to at least one of the elements causes a deformation of the spring that correlates with a displacement of the elements relative to one another
Implementation Method 2
The resilient member is formed of shape-set elastic material and has proximal and distal extensions in contact with the proximal portion and the distal portion of the insertion tube
Data Source
AI summary
A contact force sensor is constructed using a spring in which a resilient member is interposed between two contacting elements. Extensions connected to the resilient member are in contact with the elements. A force applied to at least one of the elements causes a deformation of the spring that correlates with a displacement of the elements relative to one another.