Thin Wall Cannula Length-to-Diameter Ratio Optimization
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Solution Overview
Problem
Cannulas for medical devices face a challenge in minimizing patient discomfort and injury while ensuring adequate fluid flow, as existing designs struggle to balance a small outer diameter with a sufficient inner diameter to accommodate various viscosities of medicaments or fluids.
Innovation Solution
A medical injection cannula with a specific length-to-diameter ratio, defined by the hydrodynamic theoretical needle length and inner diameter, is designed to optimize flow rates, featuring a beveled tip and a constant outer diameter, which corresponds to industry standards for 27G, 29G, or 30G cannulas, and is integrated with a syringe assembly to enhance fluid delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the outer diameter of the cannula is minimized to reduce patient discomfort and injury risk, then the outer diameter decreases, but the inner diameter becomes insufficient to allow adequate fluid flow through the cannula
Solution Approach 1:
The patent applies parameter changes by optimizing the length-to-diameter ratio (L/D) of the cannula to a specific range (8.5×10^11 to 4.5×10^12). This parameter optimization allows the cannula to maintain a small outer diameter for patient comfort while ensuring sufficient inner diameter and hydrodynamic characteristics for adequate fluid flow, even for viscous medicaments. The beveled tip geometry further modifies flow parameters to enhance delivery efficiency.
2Quantity of substance
If the inner diameter of the cannula is increased to allow adequate fluid flow, then the fluid flow rate improves, but the outer diameter increases causing greater patient discomfort and injury risk
Solution Approach 1:
The patent resolves this contradiction by establishing an optimized length-to-diameter ratio range (8.5×10^11 to 4.5×10^12) that decouples the relationship between outer diameter and fluid flow capability. Within this ratio range, the cannula achieves maximum flow efficiency for a given outer diameter, allowing minimal outer diameter while maintaining adequate inner diameter for fluid flow. The beveled tip further optimizes flow characteristics without increasing outer dimensions.
3Length of moving object
If the cannula length is increased to achieve proper insertion depth, then the insertion depth increases, but the hydrodynamic resistance increases reducing fluid flow rate
Solution Approach 1:
The patent addresses this contradiction by optimizing the length-to-diameter ratio within a specific range (8.5×10^11 to 4.5×10^12) rather than simply increasing length. This ratio optimization ensures that as cannula length increases for proper insertion depth, the inner diameter is proportionally adjusted to maintain adequate hydrodynamic characteristics and fluid flow rate. The beveled tip further reduces hydrodynamic resistance at the distal end.
Data Source
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AI summary
A medical injection cannula configured for use with a syringe includes a sidewall defining a lumen and having a proximal end and a distal end, and a beveled tip defining an opening to the lumen. A length-to-diameter ratio of the cannula is defined by a ratio LhydrodynamictheoreticalneedleDneedle_inner4, wherein Lhydrodynamic theoretical needle is a theoretical hydrodynamic length of the cannula, and Dneedle_inner is an inner diameter of the sidewall of the cannula. The length-to-diameter ratio is between 8.5×1011 and 8.5×1012 m-3.