Ferromagnetic Thermal Cutting Wire for Curie-Controlled Tissue Separation

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Solution Overview

Problem

Existing electrosurgical instruments face challenges in efficiently and accurately cutting treated tissue after coagulation or sealing, as they often require mechanical knives or energy-based methods that may not provide precise control over the cutting process.

Innovation Solution

The integration of a ferromagnetic thermal cutting wire with self-regulating properties, which heats to a specific Curie temperature for precise cutting, eliminating the need for additional sensors or feedback mechanisms, and ensures consistent temperature control by automatically adjusting based on tissue contact.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a mechanical knife is used to cut tissue, then cutting function is achieved, but device complexity and risk of mechanical damage increase

Engineering Contradiction:
Improvecutting functionVSAvoiddevice complexity
Core Design Contradiction:
Ease of operationVSDevice complexity

Solution Approach 1:

The patent replaces the mechanical knife system with a thermal cutting wire that uses electromagnetic induction and ferromagnetic heating to cut tissue. The cutting wire incorporates a ferromagnetic coating that converts electromagnetic energy into thermal energy, eliminating the need for mechanical moving parts while achieving the same cutting function through thermal energy.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the cutting mechanism from mechanical force to thermal energy by controlling the temperature of the cutting wire. The ferromagnetic coating is designed to heat to a specific Curie temperature, providing precise thermal control for cutting without requiring complex mechanical adjustment mechanisms.

Inventive Principle:
Principle #35Parameter changes

2Manufacturing precision

If energy-based cutting is used, then cutting precision is improved, but temperature control difficulty increases

Engineering Contradiction:
Improvecutting precisionVSAvoidtemperature control
Core Design Contradiction:
Manufacturing precisionVSDevice complexity

Solution Approach 1:

The ferromagnetic coating on the cutting wire exhibits self-regulating temperature control through its Curie temperature property. When the coating reaches its Curie temperature, it loses its ferromagnetic properties, which automatically reduces the heating efficiency and prevents overheating. This self-regulating mechanism eliminates the need for external temperature sensors or feedback control systems.

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The patent utilizes the phase transition of the ferromagnetic material at its Curie temperature to achieve automatic temperature regulation. The transition from ferromagnetic to non-ferromagnetic state at a specific temperature provides an inherent safety mechanism that prevents thermal runaway and ensures consistent cutting temperature without complex control electronics.

Inventive Principle:
Principle #36Phase transitions

3Manufacturing precision

If ferromagnetic coating is applied to cutting wire, then temperature control is improved, but manufacturing complexity increases

Engineering Contradiction:
Improvetemperature controlVSAvoidmanufacturing complexity
Core Design Contradiction:
Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The cutting wire is constructed as a composite structure with a conductive core and a ferromagnetic coating layer. This composite design allows the wire to simultaneously conduct electricity for heating while the ferromagnetic coating provides temperature regulation through its Curie temperature property. The coating can be applied through standard industrial processes such as plating or coating techniques.

Inventive Principle:
Principle #40Composite materials

4Manufacturing precision

If thermal cutting is used instead of mechanical knife, then tissue separation quality is improved, but risk of overheating increases

Engineering Contradiction:
Improvetissue separation qualityVSAvoidoverheating risk
Core Design Contradiction:
Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The ferromagnetic coating on the cutting wire exhibits self-regulating temperature control through its Curie temperature property. When the coating reaches its Curie temperature, it loses its ferromagnetic properties, which automatically reduces the heating efficiency and prevents overheating. This self-regulating mechanism eliminates the need for external temperature sensors or feedback control systems.

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The patent converts the potential harmful effect of uncontrolled heating into a beneficial self-regulating mechanism. The Curie temperature transition, which could be seen as a limitation of the ferromagnetic material, is actually utilized as a safety feature that automatically prevents overheating and tissue damage.

Inventive Principle:
Principle #22Blessing in disguise (Convert harm into benefit)

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 ferromagnetic thermal cutting wire provides precise and controlled tissue cutting, preventing overheating and ensuring effective separation of treated tissue without mechanical damage, enhancing surgical precision and safety.

Implementation Method 1

the first portion defines a first Curie temperature and the second portion defines a second Curie temperature different from the first Curie temperature

Methodology Applied
Scientific EffectCurie temperature: Curie Point (ferromagnetic)

Implementation Method 2

a ferromagnetic thermal cutting wire with self-regulating properties, which heats to a specific Curie temperature for precise cutting

Methodology Applied
Scientific EffectFerromagnetic heating: Ferromagnetism

Implementation Method 3

an energy-based tissue cutting element may be provided to cut the treated tissue using energy, e.g., thermal, electrosurgical

Methodology Applied
Scientific EffectJoule heating: Joule Heating

Data Source

PatentEP3861950B1Electrosurgical instruments and systems including thermal cutting elements
Publication Date: 2025.08.20 COVIDIEN LP
  • EP3861950B1 patent drawingFigure 1
  • EP3861950B1 patent drawingFigure 2
  • EP3861950B1 patent drawingFigure 3

AI summary

An electrosurgical instrument includes an end effector assembly including first and second jaw members at least one of which is movable relative to the other from a spaced-apart position to an approximated position to grasp tissue between first and second opposed surfaces of the first and second jaw members, respectively. The first jaw member includes a thermal cutting wire including a first portion extending distally along at least a portion of a length of the first opposed surface and a second portion extending about a distal tip of the first jaw member. The first and second portions of the thermal cutting wire each include a ferromagnetic coating such that the first and second portions are ferromagnetically heated and provide automatic Curie temperature control upon supply of an AC signal thereto.