Flexible Catheter Drive Shaft Alloy Structure for High-RPM Durability
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Solution Overview
Problem
Existing flexible catheters with pliable drive shafts face challenges in maintaining reliability and durability during high-speed, long-term operations, particularly in applications like blood pumping, where material fatigue and risk of shaft breakage are significant concerns.
Innovation Solution
The catheter design incorporates a drive shaft made from an alloy with a high content of chromium, nickel, and cobalt, along with a hollow shaft design and coaxial windings to enhance flexibility and torsional stiffness. Additionally, the use of a biocompatible lubricant and a bearing coil with a specific geometric design helps reduce wear and improve operational reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the drive shaft is made flexible and pliable to navigate through blood vessels, then the catheter can be positioned at desired locations, but the drive shaft becomes susceptible to material fatigue and breakage during high-speed, long-term operation
Solution Approach 1:
The drive shaft is constructed from a composite structure consisting of multiple fine wires (e.g., 7x0.005 inches or 7x0.003 inches) bundled together. This composite wire construction provides both the necessary flexibility to navigate vascular paths and enhanced durability through distributed stress across multiple strands, preventing catastrophic failure from material fatigue during high-speed operation
Solution Approach 2:
The drive shaft is divided into multiple discrete wire segments bundled together rather than a single solid rod. This segmentation allows each individual wire to flex independently, maintaining overall flexibility while distributing mechanical stresses across numerous smaller elements, thereby reducing the risk of complete shaft failure during prolonged high-speed operation
2Productivity
If the drive shaft is operated at high rotation speeds (more than 10,000, 20,000 or even 30,000 revolutions per minute) to deliver blood, then the productivity increases, but material fatigue and damaging processes on the drive shaft progress more rapidly
Solution Approach 1:
The composite wire construction with multiple fine strands distributed the centrifugal and torsional stresses generated during high-speed rotation across numerous individual wires. This composite structure enables the drive shaft to sustain rotation speeds exceeding 10,000, 20,000, or even 30,000 RPM while delaying material fatigue through stress distribution and redundancy
Solution Approach 2:
The drive shaft parameters were optimized by selecting wire diameter (e.g., 0.005 inches or 0.003 inches), wire material properties, and bundle configuration to achieve the necessary balance between flexibility and high-speed durability, enabling sustained operation at rotation speeds greater than 10,000 RPM with reduced material fatigue
3Strength
If a hard sheath is used to protect the drive shaft, then the shaft is protected from external damage, but the sheath wears the shaft and accelerates damaging processes
Solution Approach 1:
The sheath material parameters were specifically selected to have a softer hardness than the drive shaft wires, reversing the traditional protection approach. This parameter change ensures that during relative motion, the sheath wears instead of the critical drive shaft, preserving shaft integrity during insertion and operation while still providing necessary external protection
4Strength
If the drive shaft is made too stiff to maintain structural integrity, then the shaft can transmit torque effectively, but the catheter cannot be led along the desired path through the body
Solution Approach 1:
The composite wire bundle construction provides an optimal balance between torsional stiffness for effective torque transmission and flexibility for navigating vascular paths. The multiple fine wires twisted together create a structure that resists torsional deformation while remaining flexible enough to follow the desired catheter path through the body
Solution Approach 2:
Segmenting the shaft into multiple flexible wire segments allows each segment to bend and conform to the catheter path while the collective bundle maintains sufficient torsional stiffness to transmit rotational force from the drive motor to the functional element at the distal end
Data Source
AI summary
A flexible catheter with a drive shaft, and associated devices and systems. In some examples, the disclosure describes a flexible catheter with a drive shaft, with a sleeve surrounding the drive shaft and with a sheath surrounding the drive shaft and the sleeve, wherein the drive shaft, the sleeve and the sheath are pliable, wherein the drive shaft at a proximal end of the drive shaft comprises a coupling element for connecting the drive shaft to a drive motor, wherein the drive shaft at least regionally consist of a alloy which contains at least 10% by weight of chromium, nickel and cobalt in each case.