Martensitic Stylet Segmentation for Reduced Removal Force
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Solution Overview
Problem
During endoscopic ultrasound procedures, the removal of stylets from needles requires significant force due to binding friction along tortuous paths, leading to increased procedure time and potential misalignment of the needle and scope.
Innovation Solution
A single-wire stylet made from a memory-metal alloy with a martensitic phase at body temperature, combined with a polymeric distal tip, provides enhanced flexibility and reduced friction, allowing for easier removal by maintaining a martensitic phase at operating temperatures and incorporating a flexible polymeric tip to minimize retraction force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a standard bevel-tipped stylet is used through the entire length of the needle lumen, then columnar strength is provided during needle direction, but significant removal force is required due to binding friction along tortuous paths
Solution Approach 1:
The stylet is divided into two distinct segments: a proximal rigid portion that provides columnar strength during needle direction, and a distal flexible portion that reduces binding friction during removal. This segmentation allows each portion to perform its specific function optimally without compromising the other.
Solution Approach 2:
Different portions of the stylet are given different mechanical properties - the proximal portion maintains rigidity for structural support, while the distal portion is made flexible to navigate tortuous paths with reduced friction. This local differentiation of material properties resolves the contradiction between needing strength and needing easy removal.
2Adaptability or versatility
If the needle is directed through tortuous paths in the endoscope working channel, then access to target sites is achieved, but binding friction increases requiring higher removal force
Solution Approach 1:
The stylet transitions from a static, uniformly rigid structure to a dynamic structure with varying flexibility along its length. The distal flexible portion can dynamically adapt to the tortuous geometry of the working channel during insertion, while the proximal rigid portion maintains stability. During removal, the flexible portion reduces frictional binding, enabling easier extraction without compromising access capability.
3Force
If a flexible stylet is used to reduce removal force, then easier removal is achieved, but columnar strength during needle direction is compromised
Solution Approach 1:
The stylet is segmented into proximal and distal portions with different mechanical properties. The proximal portion retains rigidity to provide necessary columnar strength for directing the needle, while the distal portion is made flexible to reduce removal force. This segmentation resolves the contradiction by assigning different functional requirements to different segments.
Solution Approach 2:
The stylet exhibits local quality differentiation where the proximal portion has high rigidity for structural support and the distal portion has low rigidity for easy removal. This spatial variation in material properties allows the single stylet to simultaneously satisfy both contradictory requirements of strength and ease of removal.
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 stylet design significantly reduces the removal force required, enhancing workflow efficiency and minimizing the risk of needle misalignment during procedures by accommodating tortuous paths with increased flexibility and reduced friction.
Implementation Method 1
At least a lengthwise portion of the single-wire body is at least partially in martensitic phase at operating temperatures at and below about 37°C
Implementation Method 2
a single-wire stylet including a proximal end terminus and a distal end terminus, constructed as an elongate single-wire, memory-metal alloy body
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A single-wire stylet may be constructed as an elongate single-wire, memory-metal alloy body with a generally cylindrical body profile, extending distally from a proximal end terminus, where embodiments include a polymeric distal tip member fixedly attached directly at a distal end of the single-wire body. At least one lengthwise portion of the single- wire body is at least partially in martensitic phase at operating temperatures at and below about 37°C. Where present, the polymeric distal tip member has a generally cylindrical body profile circumferentially bounded by an outer circumference substantially equal to or greater than that of the metal body. The polymeric distal tip member may be overmolded upon a distal-end tip length of an elongate single-wire, memory-metal alloy stylet body, where the distal end and/or discrete intermediate distal-portion length(s) that include martensitic-phase alloy and any polymeric member have greater flexibility than a proximal-most length of the alloy stylet body.