Nitinol Steerable Arm for Endoscopic Biopsy Channels
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Solution Overview
Problem
Conventional endoscopic surgical instruments are too thick for common biopsy channels, requiring complex designs and manipulations, limiting dexterity and control during procedures.
Innovation Solution
A steerable arm with a tubular member made of resilient material, featuring a single wire for bending and a continuum structure, allowing curvature change when pulled and reverting to its original shape when released, which is easier to use and saves space for other components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If discrete joint-based mechanisms are used to allow articulation, then the surgical instrument can be steered, but the diameter increases to 4 mm which does not fit into common biopsy channels
Solution Approach 1:
The patent uses a flexible backbone made from a single body of flexible material (nitinol tube) instead of discrete rigid joints. This flexible shell approach allows the instrument to articulate and steer while maintaining a thin profile that fits within common biopsy channels (2.8-3.7 mm diameter), resolving the contradiction between steerability and diameter.
2Volume of moving object
If nested concentric nitinol tubes are used to reduce diameter, then the instrument fits biopsy channels, but the lifting force is too weak for some procedures
Solution Approach 1:
The patent employs composite construction by combining a flexible nitinol tube backbone with discrete articulation joints and wire mechanisms. This composite approach allows the thin nitinol tube to provide flexibility and fit within biopsy channels, while the added structural elements (joints and wires) provide the necessary lifting force and mechanical strength, resolving the contradiction between diameter and force.
3Ease of operation
If multiple wires are used to control bending in opposite directions, then the steerable arm can bend accurately, but the manipulation becomes complex
Solution Approach 1:
The patent inverts the conventional two-wire antagonistic mechanism by using a single wire attached to only one side of the tubular member. When the wire is pulled, it creates bending in one direction; when released, the resilient material's bias returns the arm to its original shape. This inversion simplifies the control mechanism from complex multi-wire manipulation to simple single-wire operation, resolving the contradiction between bending control and device complexity.
4Shape
If the endoscope is placed far from the target site to allow tube extension, then sufficient curvature is achieved, but the camera is too far from the distal end to provide good visualization
Solution Approach 1:
The patent creates a dynamic steerable arm where the tubular member can be actively bent by pulling the wire, rather than relying on passive tube extension. This dynamic bending capability allows the instrument to achieve sufficient curvature even when positioned closer to the target site, maintaining both good visualization distance and adequate curvature for tissue manipulation, resolving the contradiction between curvature and camera distance.
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 dexterous tissue manipulation with improved control and reduced mechanical complexity, allowing the camera to maintain better visualization and accommodating various bending directions within a single plane, while being compatible with standard endoscope biopsy channels.
Implementation Method 1
the resilience of the material providing the tubular member with a bias such that the curvature change reverses when the pull on the distal end is released
Data Source
AI summary
A steerable arm for use in endoscopic surgical procedures. The steerable arm cut from a tube of nitinol to provide flexibility and resilience by the structure into which the tube is cut. Typically, the cut tube comprises a spiralling coil, the loops of which are in contact on one lateral side of the tube and the tube is bent to open apart the loops on the other lateral side. The material which the tube is made of is capable of retaining memory of the bend. This provides a bias for restoring the tube to the bend whenever a force causing the tube to flex is removed.