Auxetic Elastomeric Membrane Structure to Prevent Mesh Pore Collapse
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Solution Overview
Problem
Current urogynecologic meshes experience pore collapse under tensile loads, leading to inflammation, fibrosis, and poor tissue integration, with material stiffness issues causing tissue damage and mesh exposure.
Innovation Solution
An elastomeric auxetic membrane with pores designed to expand transversely when stretched longitudinally, manufactured via molding or 3D printing, using polymers like polycarbonate urethane to maintain pore size and complement tissue stiffness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional surgical mesh is used to provide structural support, then tensile strength is improved, but pore collapse occurs under tensile loads leading to inflammation and fibrosis
Solution Approach 1:
The patent inverts the conventional behavior of mesh pores by using auxetic geometry that expands laterally when stretched longitudinally. This negative Poisson's ratio behavior prevents pore collapse under tensile loads, directly resolving the contradiction between maintaining tensile strength and preventing pore collapse. The auxetic pattern causes pores to open up rather than close when the mesh is subjected to physiological tension.
Solution Approach 2:
The patent changes the geometric parameters of the pore structure by implementing specific auxetic patterns (such as re-entrant honeycomb, zigzag, or rotated square patterns) that fundamentally alter how the material responds to mechanical loading. This geometric parameter change enables the mesh to maintain or increase pore size under tension, eliminating the pore collapse problem while preserving structural support.
2Strength
If polypropylene mesh is used to ensure material strength, then structural integrity is improved, but material stiffness becomes orders of magnitude stiffer than vaginal tissue causing tissue damage
Solution Approach 1:
The patent employs composite construction by combining polypropylene fibers with an elastomeric matrix material. This composite structure allows the mesh to achieve structural integrity from the fiber architecture while the elastomeric matrix provides tissue-compatible stiffness and flexibility. The composite nature enables the mesh to withstand physiological loads without being excessively stiff.
Solution Approach 2:
The patent incorporates an elastomeric coating or matrix that forms a flexible shell around the polypropylene fiber structure. This elastomeric layer provides a compliant interface with vaginal tissue, reducing stiffness-related tissue damage while the underlying fiber structure maintains structural integrity. The elastomeric material allows the mesh to deform more naturally with tissue movement.
3Stability of the object's composition
If mesh pores are made small to prevent migration, then positional stability is improved, but tissue integration decreases and inflammation increases
Solution Approach 1:
The patent introduces dynamic behavior to the pore structure through auxetic geometry that adapts its size in response to mechanical loading. Pores dynamically expand under tension to facilitate tissue integration and cell infiltration, then return to their original configuration when loaded. This dynamic pore size adjustment allows the mesh to maintain positional stability while providing adequate space for tissue integration during physiological movements.
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 auxetic membrane maintains pore size and porosity under tension, reducing inflammation and fibrosis, enhancing tissue integration, and minimizing permanent deformation.
Implementation Method 1
each pore is defined by the plurality of fibers and has an auxetic shape such that a size of the pores expands in a direction transverse to a longitudinal axis when the membrane is subject to a tensile load along the longitudinal axis
Implementation Method 2
the plurality of fibers have an original length and are configured to return to a second length after tensile loading or unloading at 15 N, wherein the second length is less than or equal to 40% longer than the original length
Data Source
AI summary
Embodiments relate to the use of auxetic geometries to construct the pores of membranes. Auxetic geometries expand in the transverse direction when stretched along the longitudinal direction. This behavior is counterintuitive as most materials contract in the transverse direction when stretched longitudinally. A mesh with pores that are auxetic has the potential to overcome the primary limitation of most prolapse meshes—pore collapse with tensile loading.