Needle Activation Force Limiter for TBNA
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Solution Overview
Problem
Needle aspiration devices, such as transbronchial needle aspiration (TBNA) devices, face issues where the distal end deflects or buckles if the activation force exceeds the needle's translational strength, reducing their effectiveness in tissue sampling.
Innovation Solution
A medical device with a handle and a needle actuator featuring a flexible engagement member with a protrusion that maintains engagement with a groove until a predefined threshold force is reached, disengaging to prevent excessive force from being applied to the needle, thereby preventing buckling and maintaining effective sampling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the activation force applied to the needle is increased to improve penetration capability, then the needle can penetrate tougher tissue, but the needle deflects or buckles when the force exceeds its translational strength
Solution Approach 1:
The patent changes the mechanical parameter of the engagement member by making it flexible rather than rigid. This flexibility allows the engagement member to deform elastically under normal operating forces, maintaining reliable engagement, but to deform plastically or disengage when excessive forces are applied, thereby protecting the needle from buckling while allowing high penetration forces to be applied.
Solution Approach 2:
The flexible engagement member acts as a cushioning mechanism that absorbs excess force before it can reach the needle. When the operator applies force greater than the needle's translational strength, the engagement member deforms or disengages, absorbing the excess energy and preventing the needle from buckling.
2Reliability
If the needle is made more rigid to prevent buckling, then needle stability improves, but the needle cannot withstand high activation forces for penetrating tough tissue
Solution Approach 1:
The flexible engagement member serves as an intermediary between the operator's applied force and the needle. It mediates the force transmission by allowing controlled deformation and disengagement under excessive loads, thereby protecting the rigid needle from buckling while still enabling high activation forces to be applied during normal operation.
3Force
If a rigid engagement member is used to maintain strong connection with the groove, then force transmission is efficient, but excessive force causes needle buckling
Solution Approach 1:
The engagement member's mechanical parameters are changed from rigid to flexible. This allows the engagement member to maintain strong force transmission during normal operation through elastic deformation, but to fail safely (disengage or deform permanently) when excessive forces cause needle buckling, thereby eliminating the harmful effect while maintaining efficient force transmission.
Solution Approach 2:
The patent converts the potentially harmful effect of excessive force into a beneficial protective mechanism. The flexible engagement member is designed to fail safely under excessive loads, transforming the harmful force that would cause needle buckling into a signal that triggers engagement member disengagement or deformation, thereby protecting the needle.
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 device ensures that the needle applies a controlled force below the threshold value for effective tissue sampling, preventing buckling and allowing for repeat activations, thus enhancing the device's effectiveness and safety.
Implementation Method 1
the flexible engagement member is configured to be flexible thus allowing the protrusion to move in a direction perpendicular to a longitudinal axis of the handle
Implementation Method 2
when the distal force is greater than the predefined threshold value, the protrusion disengages from the groove by overcoming a frictional force between the protrusion and the groove
Data Source
AI summary
A medical instrument having an aspiration needle, handle device and an actuation force limiter. The actuation force limiter provides an active or passive force release mechanism that keeps the force from overpowering operation of the needle.