Concentric Tube Robots with Torsional Spring Force Control
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Solution Overview
Problem
Existing minimally invasive cardiac surgery catheters struggle to maintain a consistent, optimal contact force on beating heart tissue due to the rapid motion of the heart, leading to reduced procedure efficacy and increased surgical risks such as blood heating and tissue perforation, while existing haptic feedback systems and force sensors introduce complications like sterilization issues and mechanical alterations.
Innovation Solution
A passively controlled robotic catheter using concentric tubes with a torsional spring mechanism to counter-rotate and maintain a pseudo-constant contact force, eliminating the need for active control systems and force sensors, ensuring MRI compatibility and miniaturization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If haptic feedback systems and force sensors are incorporated for contact force control, then surgical precision is improved, but device complexity and sterilization difficulty increase
Solution Approach 1:
The catheter tip naturally maintains constant contact force with the beating heart tissue through its passive mechanical design, without requiring active sensors or control systems. The compliant mechanism self-regulates the force application, eliminating the need for external force monitoring and control infrastructure.
Solution Approach 2:
The invention removes force sensors and active control systems from the catheter design, extracting the complex measurement and control infrastructure while retaining the essential force control function through passive mechanical compliance alone.
2Measurement precision
If real-time imaging systems are used for surgical guidance, then localization accuracy is improved, but response time deteriorates due to processing delays
Solution Approach 1:
The catheter passively adapts to heart tissue motion through its compliant mechanical structure, automatically tracking tissue movement without requiring active imaging guidance or computational processing. The system self-regulates contact force despite chaotic heart displacement, eliminating time delays associated with image acquisition and processing.
3Measurement precision
If active control systems with force sensors are implemented, then contact force precision is improved, but MRI compatibility and miniaturization are compromised
Solution Approach 1:
The invention removes all force sensors and active control electronics from the catheter, extracting the components that prevent MRI compatibility. The passive compliant mechanism provides force control without any magnetic or electronic interference, enabling full MRI compatibility and potential miniaturization.
4Force
If manual manipulation is used to maintain contact force, then force control is achieved, but surgical time increases and stability decreases
Solution Approach 1:
The catheter tip automatically maintains constant contact force with beating heart tissue through its passive compliant mechanism, eliminating the need for repetitive manual manipulation. The system self-regulates force despite tissue motion, significantly reducing surgical time and improving procedural efficiency.
Solution Approach 2:
Instead of requiring continuous active manual adjustment to maintain contact force, the passive compliant catheter provides sufficient force control through its mechanical design alone, reducing the frequency and intensity of manual intervention needed during surgery.
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 robotic catheter achieves consistent contact force with beating heart tissue, reducing surgical injuries and time requirements by natural force control, while being MRI-compatible and ergonomically suitable.
Implementation Method 1
a torsional spring mechanism connected to the proximal end of the concentric tubes via a geared mechanism
Implementation Method 2
The concentric tubes can snap between two stable equilibrium positions when they are counter-rotated and the torsional spring mechanism can compensate for the energy released by the concentric tubes snapping
Data Source
AI summary
A robotic catheter can include bi-stable concentric tubes and a torsional spring mechanism that can provide torque at the proximal extremity of one or more tubes. The robotic catheter can compensate for the energy that may be released by the tubes snapping from on stable-equilibrium position to another by using the energy stored in the torsional spring mechanism. The energy released by the tubes upon snapping from one stable-equilibrium position to the other can be compensated by the energy stored in the torsional spring at the base, thereby resulting in the first, energy-free, zero stiffness catheter system that (1) synchronizes with the motion of the heart and (2) naturally results in optimal, pseudo-constant contact force with the tissue.