Catheter Shaft Composite Layering for Kink Resistance
Solution Overview
Problem
Current intracorporeal medical devices, such as catheters, lack alternatives in design, materials, and manufacturing methods that provide enhanced strength, flexibility, and resistance to kinking, cutting, and premature polymerization, which are essential for various medical interventions.
Innovation Solution
The development of a catheter shaft with a layered structure comprising an inner polymeric layer, an intermediate layer, and an outer polymeric reinforcement, where the polymeric reinforcement has a lower melting temperature than the inner and outer layers, allowing for a composite structure that is extruded to embed the reinforcement within the outer layer, enhancing strength and resistance while maintaining a thin profile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a catheter shaft is made with traditional single-layer or simple multi-layer structure, then manufacturing is simpler, but tensile strength and resistance to kinking and cutting are insufficient
Solution Approach 1:
The catheter shaft employs a composite layered structure consisting of an inner polymeric layer, an intermediate layer, and an outer polymeric reinforcement layer. This composite construction combines materials with different properties to achieve superior tensile strength, kink resistance, and cut resistance while maintaining manufacturing feasibility through extrusion processes.
Solution Approach 2:
The catheter shaft is divided into distinct functional layers: an inner polymeric layer for flexibility, an intermediate layer for structural support, and an outer polymeric reinforcement layer for enhanced strength. This segmentation allows each layer to contribute specific properties, resolving the contradiction between strength and complexity by making the complexity functional rather than arbitrary.
2Ease of manufacture
If the polymeric reinforcement layer has a higher melting temperature than the inner and outer layers, then thermal stability is improved, but the reinforcement becomes less embeddable during extrusion
Solution Approach 1:
The patent specifies that the outer polymeric reinforcement layer has a lower melting temperature than the inner and outer polymeric layers. This parameter change enables the reinforcement layer to become pliable during extrusion, facilitating embedding into the intermediate layer while maintaining structural integrity after cooling, thus resolving the contradiction between ease of manufacture and thermal stability.
3Strength
If the catheter shaft wall thickness is increased to improve strength, then resistance to kinking and cutting is improved, but the device profile becomes larger and less flexible
Solution Approach 1:
The composite layered structure provides enhanced strength and kink resistance without requiring increased wall thickness. The combination of the inner polymeric layer, intermediate layer, and outer polymeric reinforcement layer creates a thin-walled structure with superior mechanical properties, resolving the contradiction between strength and profile/flexibility.
Solution Approach 2:
The outer polymeric reinforcement layer is specifically designed with reinforcement elements positioned to provide localized strength where needed for kink and cut resistance, while the overall thin-walled construction maintains flexibility and small profile. This local quality approach allows strength enhancement without uniform thickness increase.
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
This design results in catheter shafts with improved tensile strength, resistance to kinking and cutting, and reduced risk of premature polymerization, enabling effective use in procedures like embolization and intravascular interventions with enhanced durability and performance.
Implementation Method 1
Heating the catheter shaft may cause the outer polymeric reinforcing layer to become at least partially embedded within the intermediate layer
Data Source
Figure 1
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AI summary
Medical devices (10) and methods for making and using medical devices are disclosed. An example medical device (10) may include a catheter shaft (12, 112, 212, 312) having an inner surface defining a lumen. A liner (16, 216) may be disposed within the lumen and along the inner surface. At least a portion of the liner may be radially spaced from the inner surface of the catheter shaft so that a space is defined therebetween. The liner may include an inner layer (116, 316), an outer layer (126, 326), and a polymeric reinforcing member (118, 318). At least a portion of the polymeric reinforcing member may be disposed between an outer surface of the inner layer and an outer surface of the outer layer. The polymeric reinforcing member may have a melting temperature lower than the melting temperature of the inner layer, the outer layer, or both.