Variable Stiffness Catheter with Shape Memory Actuators
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Solution Overview
Problem
Current steerable catheters and endoscopes face limitations due to their large diameter, lack of mobility, and inability to navigate complex or cramped spaces, making it difficult to access critical areas within systems like turbomachines for non-destructive testing, and they require manual control.
Innovation Solution
A steerable structure with an elastically deformable longitudinal body featuring actuators made of shape memory material and Joule effect heating, integrated with variable stiffness sections and extra thickness for adaptable curvature, allowing for precise angular orientation and navigation through narrow passages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the diameter of the distal end is increased to avoid bending under gravity, then the structural stability is improved, but the ability to access critical areas through narrow passages deteriorates
Solution Approach 1:
The catheter incorporates variable stiffness sections that allow it to dynamically adjust its rigidity. The stiff sections maintain structural stability and resist bending under gravity, while the flexible sections enable the catheter to navigate narrow passages and complex geometries. This dynamic adaptation resolves the contradiction between stability and accessibility.
Solution Approach 2:
The catheter is divided into multiple sections with different stiffness characteristics. By segmenting the structure into stiff and flexible zones, the invention allows different parts of the catheter to perform different functions simultaneously - the stiff sections provide structural support while the flexible sections enable navigation through tight spaces.
2Measurement precision
If the length and diameter of actuator wires are modified to obtain desired angular orientation, then the positioning precision is improved, but the device complexity and manufacturing time increase
Solution Approach 1:
The invention places actuators specifically within the flexible section of the catheter, concentrating the actuation functionality where it is most needed for navigation. This local placement simplifies the overall device design compared to distributing actuators throughout the entire catheter length, while still achieving precise angular orientation control.
Solution Approach 2:
The variable stiffness sections modify the mechanical parameters of the catheter structure, allowing actuators to generate more effective bending moments with smaller forces. This parameter change enables precise positioning without requiring complex actuator configurations or extensive modifications to wire dimensions.
3Strength
If the rigidity of the device is kept constant to maintain structural integrity, then the structural strength is improved, but the maneuverability in geometrically complex spaces deteriorates
Solution Approach 1:
The catheter transitions from a static, constant-rigidity structure to a dynamic, variable-rigidity structure. The flexible sections allow the catheter to bend and conform to complex geometries during navigation, while the stiff sections maintain structural integrity. This dynamic adaptation enables both maneuverability and structural strength.
Solution Approach 2:
Different sections of the catheter have different rigidity properties tailored to their specific functions. The flexible section prioritizes maneuverability and conformability, while the stiff section prioritizes structural strength and stability. This local differentiation resolves the contradiction between overall strength and local maneuverability.
4Device complexity
If conventional catheters are used to explore complex three-dimensional cavities, then the structural simplicity is maintained, but the ability to inspect areas requiring various successive changes of orientation deteriorates
Solution Approach 1:
The catheter is segmented into flexible and stiff sections, enabling it to perform successive changes of orientation in flexible zones while maintaining structural control in stiff zones. This segmentation allows the catheter to navigate complex three-dimensional cavities with multiple bends and turns.
Solution Approach 2:
The variable stiffness design allows the catheter to dynamically adapt its flexibility to match the complexity of the passage being navigated. In complex regions requiring multiple orientation changes, the flexible sections enable smooth bending, while the stiff sections provide structural support.
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 access to previously inaccessible areas with improved maneuverability and precision, allowing for automatic control and enhanced non-destructive testing capabilities in complex systems.
Implementation Method 1
means of heating by Joule effect making it possible to contract the actuator longitudinally to cause a flexion of the longitudinal body
Implementation Method 2
these actuators see their length reduced under the effect of an increase in temperature, which induces a modification of the curvature of the catheter or of the endoscope in the zones where the actuators are located
Data Source
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AI summary
A steerable structure (21, 27) of the catheter or endoscope type, comprising an elastically deformable longitudinal body (22, 28) having at least one actuator (16, 38) of shape memory material integrated longitudinally into the body (22, 28) and Joule effect heating means enabling longitudinal contraction of the actuator (16, 38) to cause flexion of the longitudinal body (22, 28), characterized in that the actuator (16, 38) extends over at least one part with variable rigidity of the body (22, 28).