Multi-Layer Electrospun Graft Kink Resistance
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Solution Overview
Problem
Conventional tubular vascular grafts made from biocompatible plastics and polymers often cause irritation and biologic responses, and lack sufficient kink resistance, especially when produced by electrospinning on small mandrels, which results in non-uniform thickness and inadequate mechanical properties.
Innovation Solution
A tubular electrospun graft with multiple layers of polymer sheets rolled around a longitudinal axis, where each layer can move independently, providing superior kink resistance and eliminating the need for additional support elements, while ensuring uniform thickness and bioabsorbability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional electrospinning is used on a small diameter mandrel to produce tubular grafts, then the graft can be manufactured with biocompatible materials, but the graft lacks sufficient kink resistance and has non-uniform thickness distribution
Solution Approach 1:
The graft wall is segmented into multiple independent layers (at least two layers) that can move relative to each other during bending. This segmentation allows each layer to independently accommodate bending stresses, preventing kink formation while maintaining uniform thickness distribution through the wall.
Solution Approach 2:
The layers are designed to be dynamically movable relative to each other during bending operations. This dynamic capability allows the layers to shift positions to accommodate bending stresses, providing kink resistance without requiring rigid structural support that would compromise thickness uniformity.
2Strength
If additional support structures (such as filaments or stents) are added to improve kink resistance, then the graft gains mechanical strength, but the device complexity increases and uniform degradation behavior is compromised
Solution Approach 1:
Instead of adding discrete support elements, the graft wall itself is segmented into multiple layers that provide structural support through their collective arrangement. This eliminates the need for additional filaments or stents, maintaining device simplicity and uniform degradation behavior while achieving kink resistance.
Solution Approach 2:
The graft utilizes a composite structure of multiple polymer layers, where each layer contributes to the overall mechanical properties. This composite approach provides enhanced kink resistance through the layered architecture itself, without requiring heterogeneous support elements that would complicate the device structure.
3Strength
If the graft wall is made thicker to improve mechanical properties and kink resistance, then the burst pressure increases, but the bending stiffness increases and kink resistance may be compromised
Solution Approach 1:
The thick graft wall is segmented into multiple thin layers that can move independently. This segmentation maintains the overall thickness for burst pressure resistance while allowing each thin layer to flex independently, reducing bending stiffness and preventing kink formation.
Solution Approach 2:
The layered structure introduces dynamic movement capability between layers, allowing the graft to adapt its mechanical properties during bending. The layers can shift relative to each other to reduce bending stiffness during flexion while maintaining the thickness necessary for burst pressure resistance in the unloaded state.
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 multi-layered graft exhibits significantly higher burst pressure and improved kink resistance, with crushing zones between layers allowing for better bending flexibility and reduced bending stiffness, while maintaining uniform thickness and bioabsorbability, thus overcoming the limitations of conventional electrospun grafts.
Implementation Method 1
A tubular electrospun graft implant is provided distinguishing an electrospun tubular layer which has a longitudinal axis and an outer surface
Data Source
AI summary
A tubular electrospun graft implant is provided distinguishing an electrospun tubular layer which has a longitudinal axis and an outer surface. Polymer layers of an electrospun sheet have been rolled over the outer surface of the electrospun tubular layer and around the longitudinal axis of the electrospun tubular layer. A polymer layer electrospun is further distinguished over the rolled polymer layers of the electrospun sheet. Also provided is a tubular graft implant having layers of an electrospun polymer sheet rolled around a longitudinal axis defining the inner diameter of the tubular graft implant. These layers of the electrospun polymer sheet are moving independent from each other when the tubular graft implant is bending. Compared to regular spun graft, higher burst pressure is achieved, and crushing zones have been created between the layers to reduce the bending stiffness and facilitate bending with superior kink resistance.