Hyper-elastic Surgical Needle Shaping and Oxide Removal
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Solution Overview
Problem
Existing manufacturing processes for surgical needles made from hyper-elastic alloys, such as those described in patents EP 0529675 and EP 1251785, face challenges in maintaining the needle's elongated shape for cannula passage and curved shape for surgical use while ensuring resistance to bending during tissue perforation.
Innovation Solution
A manufacturing method involving cold shaping of a curved profile, heat treatment at 470°C for 15 minutes followed by iced water cooling, chemical cleaning to remove oxide layers, and optional thermomechanical treatment to enhance bending resistance, with a non-circular section design to stabilize bending in the intended plane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the needle is made from hyper-elastic alloy with curved profile to enable passage through cannula, then the needle can transition from elongated to curved shape, but the resistance to bending during tissue perforation is reduced
Solution Approach 1:
The needle is designed with a non-circular cross-section (oval or flattened circular) specifically at the shaft portion that undergoes bending during tissue perforation. This local geometric modification increases the area moment of inertia in the bending plane, thereby enhancing bending resistance precisely where needed during surgical operation, while maintaining the overall hyper-elastic curved profile for cannula passage.
Solution Approach 2:
The needle employs an asymmetric non-circular cross-section rather than a symmetric circular one. This asymmetric geometry creates different moment of inertia values along different axes, with the larger moment of inertia oriented to resist bending in the primary surgical plane, thus improving strength without compromising the ability to navigate through the cannula in its intended configuration.
2Stability of the object's composition
If heat treatment is applied to memorize curved profile geometry, then the needle maintains super-elastic properties, but oxide layer deposits on the needle surface
Solution Approach 1:
The patent applies a chemical cleaning solution containing hydrofluoric acid (HF), nitric acid (HNO3), and hydrogen peroxide (H2O2) in specific proportions (1:3:6) to remove the oxide layer formed during heat treatment. This converts the harmful oxide deposition into a manageable intermediate state that can be efficiently eliminated, restoring the needle surface to its original condition without compromising the heat treatment benefits.
Solution Approach 2:
The cleaning process uses a specifically formulated chemical solution with controlled concentrations of multiple acids and peroxide, applied for a precise duration (1-3 minutes). This controlled parameter change effectively removes oxides through chemical dissolution and reduction reactions, transforming the surface condition from oxidized to clean while preserving the underlying metallurgical structure.
3Strength
If thermomechanical treatment is applied to increase bending resistance, then the difference between austenite-martensite transformation temperature and use temperature increases, but the manufacturing process complexity increases
Solution Approach 1:
The patent combines the thermomechanical treatment step with the existing heat treatment process used for memorizing the curved profile. By integrating the bending resistance enhancement treatment into the already-necessary heat treatment sequence, the patent achieves dual benefits (shape memorization + bending resistance) without adding a separate, independent manufacturing step, thus minimizing process complexity.
Solution Approach 2:
The thermomechanical treatment is performed as a preliminary or concurrent action during the heat treatment process, preparing the material's phase transformation characteristics before final cooling and shape fixation. This preliminary adjustment of the austenite-martensite transformation temperature difference ensures enhanced bending resistance is built into the material structure during the essential heat treatment, rather than requiring additional post-processing steps.
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 method effectively maintains the needle's super-elastic properties, ensuring it can transition from an elongated to a curved shape without irreversible deformation, while increasing bending resistance and maintaining stability during tissue perforation.
Implementation Method 1
a surgical needle made from a shape memory alloy which has a first state called 'low-temperature', and a second state called 'high-temperature'
Implementation Method 2
the needle in its support is subjected to annealing whose heating temperature is 470°C for 15 minutes followed by cooling with iced water in order to memorize the imposed curved profile geometry
Implementation Method 3
followed by cooling with iced water in order to memorize the imposed curved profile geometry
Implementation Method 4
the chemical cleaning solution consists of HF+HNO 3 +H 2 O 2 in the respective proportions of 1:3:6
Implementation Method 5
cleaning the needle by means of chemical stripping of the electrochemical or electrolytic polishing type or of a chemical solution to remove the oxide layer deposited on the latter during its heat treatment
Implementation Method 6
a thermomechanical treatment making it possible to increase its resistance to bending by increasing the difference between the temperature of end austenite - martensite transformation and the temperature of use
Implementation Method 7
the needle undergoes, prior to cold shaping, a thermomechanical treatment making it possible to increase its resistance to bending
Data Source
Figure 1
AI summary
The process for manufacturing a surgical needle produced from a wire of hyper-elastic or super-elastic alloy comprising an Ni-Ti alloy base, consist: • in carrying out a shaping of the curved profile of the needle at low temperature or at ambient temperature in an appropriate support; • in subjecting the needle in its support to a heat treatment in order to memorize the imposed curved profile geometry; • in cleaning the needle by means of a chemical pickling of electrochemical or electrolytic polishing type or a chemical solution for removing the oxide layer deposited on the needle during the heat treatment thereof.