Vacuum Membrane Thermoforming of P4HB Porous Meshes
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Solution Overview
Problem
Current methods lack the ability to effectively thermoform porous poly-4-hydroxybutyrate and copolymer meshes without compromising their porosity, mechanical properties, or exposing them to water, which is essential for producing medical implants with desirable characteristics.
Innovation Solution
Vacuum membrane thermoforming process where a porous substrate of poly-4-hydroxybutyrate or copolymer is heated under tension, using a membrane to apply vacuum and prevent shrinkage, allowing for the formation of implants with enhanced mechanical properties and controlled degradation profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If conventional vacuum thermoforming is used on porous poly-4-hydroxybutyrate meshes, then the mesh can be shaped, but the porosity and mechanical properties are compromised
Solution Approach 1:
The patent applies parameter changes by precisely controlling the heating temperature (below the melting point of P4HB), vacuum pressure, and heating duration to achieve shaping without compromising the porous structure. The mesh is heated to a temperature sufficient for forming but below the melting point, maintaining porosity while achieving the desired shape.
Solution Approach 2:
The patent employs preliminary action by pre-heating the mesh to the appropriate temperature before applying vacuum pressure. This sequence ensures the mesh is pliable enough for shaping while preventing premature collapse of the porous structure that would occur if vacuum were applied to a cold mesh.
2Stability of the object's composition
If the mesh is heated to high temperature for thermoforming, then the mesh becomes pliable for shaping, but the mesh shrinks and porosity is lost
Solution Approach 1:
The patent changes the temperature parameter to be below the melting point of P4HB (typically 180°C), using a lower temperature range (e.g., 100-170°C) that provides sufficient pliability for shaping while preventing the thermal shrinkage and pore collapse that occurs at higher temperatures.
Solution Approach 2:
The patent applies preliminary anti-action by using a support structure or mandrel during the heating and vacuum process that physically prevents the mesh from shrinking. The mesh is formed over a support that maintains the desired shape and prevents thermal contraction, counteracting the natural tendency of the mesh to shrink when heated.
3Shape
If water is used in the thermoforming process, then the mesh can be shaped effectively, but the mesh is exposed to water which is undesirable for medical implants
Solution Approach 1:
The patent introduces an intermediary substance (such as oil, silicone, or another non-aqueous fluid) that replaces water as the shaping medium. This intermediary allows effective thermoforming by transmitting heat and pressure while avoiding water exposure, which is critical for maintaining the biocompatibility and degradation characteristics of the P4HB mesh.
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 method enables the production of porous thermoforms with minimal shrinkage and maintained porosity, suitable for medical implants like hernia meshes and breast reconstruction devices, offering improved mechanical strength and biocompatibility.
Implementation Method 1
heating the shaped substrate while it is under tension to a temperature equal to or greater than the softening point of poly-4-hydroxybutyrate
Implementation Method 2
applying a vacuum to the membrane so that the membrane and substrate are drawn down on the mold and tension is applied to the substrate
Data Source
Figure 1
AI summary
Methods to produce thermoformed implants comprising poly-4-hydroxybutyrate homopolymer, copolymer, or blend thereof, including surgical meshes, have been developed. These thermoforms are preferably produced from porous substrates of poly-4-hydroxybutyrate homopolymer or copolymer thereof, such as surgical meshes, by vacuum membrane thermoforming. The porous thermoformed implant is formed by placing a porous substrate of poly-4-hydroxybutyrate homopolymer or copolymer thereof over a mold, covering the substrate and mold with a membrane, applying a vacuum to the membrane so that the membrane and substrate are drawn down on the mold and tension is applied to the substrate, and heating the substrate while it is under tension to form the thermoform. The method is particularly useful in forming medical implants of poly-4-hydroxybutyrate and copolymers thereof, including hernia meshes, mastopexy devices, breast reconstruction devices, and implants for plastic surgery, without exposing the resorbable implants to water and without shrinking the porous substrate during molding.