Lyophilized Sponge Molding Process for Reservoir Defect Reduction
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Solution Overview
Problem
The existing manufacturing processes for medical articles with reservoirs, such as bone void fillers, often result in air bubbles and imperfections at the mold/slurry interface, leading to scrapped parts and increased post-processing time, especially when forming sponges with complex shapes like those with reservoirs.
Innovation Solution
A method involving a mold with a tube and obstruction, where the slurry is forced through to fill the mold and then lyophilized, forming a sponge with a reservoir defined by a sidewall and recessed surface, including cutouts to retain rehydrating fluid without spilling, is used to reduce defects and improve manufacturing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If sponges are formed by lyophilizing slurry in a mold with reservoir shapes, then the sponges can hold rehydrating fluid in a reservoir, but air bubbles and imperfections occur at the mold/slurry interface
Solution Approach 1:
Instead of filling the mold from the bottom and hoping air bubbles escape, the patent inverts the approach by filling the mold from the top using a syringe. The slurry is injected through a needle into the mold cavity, allowing air bubbles to escape during injection while ensuring complete filling of complex reservoir geometries. This inversion of the filling direction resolves the contradiction between creating reservoir shapes and avoiding interface defects.
Solution Approach 2:
The patent introduces a syringe and needle as intermediary tools between the slurry source and the mold cavity. This intermediary system allows precise control of slurry injection, enabling the formation of complex reservoir shapes while minimizing air entrapment. The syringe-needle assembly acts as a mediator that delivers the slurry in a controlled manner, filling the mold from top to bottom and preventing the formation of air bubbles at the mold/slurry interface.
2Adaptability or versatility
If complex shapes with reservoirs are formed, then fluid retention capability is improved, but manufacturing complexity and post-processing time increase
Solution Approach 1:
The patent inverts the conventional molding approach by filling the mold from the top rather than from the bottom. This allows complex reservoir shapes to be formed directly during the lyophilization process without requiring additional post-processing steps. The slurry is injected through a needle into the mold cavity, and the freeze-drying process preserves the complex geometries, eliminating the need for subsequent machining or shaping operations.
Solution Approach 2:
The patent utilizes the phase change properties of water during freeze-drying to form complex shapes. By controlling the freezing and sublimation parameters, the slurry transforms into a solid sponge structure that retains the reservoir geometry. This parameter-based approach allows complex shapes to be formed through physical transformation rather than mechanical machining, reducing manufacturing complexity and post-processing requirements.
3Manufacturing precision
If vacuum degassing is applied to remove air bubbles, then defect reduction is achieved, but part distortion and unintended pores are created
Solution Approach 1:
The patent applies preliminary action by removing air bubbles during the slurry injection process itself, before the lyophilization begins. The syringe-needle injection method allows air to escape as the slurry fills the mold cavity from top to bottom. By addressing the air bubble issue in advance, during the filling stage rather than after molding, the need for vacuum degassing is eliminated, preventing both defect formation and part distortion.
Solution Approach 2:
The patent converts the potentially harmful effect of air bubbles into a beneficial process feature. During the top-to-bottom injection process, air bubbles are naturally expelled as the slurry displaces them toward the mold cavity opening. This transforms the air bubble problem from a defect source into an automatic self-cleaning mechanism, eliminating the need for vacuum degassing and preventing the associated part distortion and unintended pore formation.
4Ease of operation
If manual manipulation is used to rehydrate the sponge, then ease of use is improved, but consistency and uniformity of rehydration are reduced
Solution Approach 1:
The patent inverts the conventional approach by pre-forming the reservoir structure during manufacturing rather than relying on manual manipulation during use. The reservoir is created as an integral part of the sponge during the lyophilization process, with cutouts designed to facilitate fluid distribution. This inversion transfers the complexity from the use phase to the manufacturing phase, where it can be precisely controlled, ensuring uniform rehydration while maintaining ease of use.
Solution Approach 2:
The patent enables the sponge to self-rehydrate through its built-in reservoir structure. The reservoir, formed during manufacturing, automatically distributes the rehydrating fluid throughout the sponge matrix as the fluid is added. This self-service mechanism eliminates the need for manual manipulation to achieve uniform rehydration, while the simple act of adding fluid to the reservoir maintains ease of operation. The cutouts in the sidewall facilitate fluid penetration and distribution throughout the sponge structure.
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 approach reduces part defects, lowers scrap rates, increases manufacturing throughput, and enhances the mechanical properties and consistency of the medical articles, while allowing for new geometries and reduced fluid leakage.
Implementation Method 1
The slurry is dispensed into a mold. The mold and slurry together are then placed in a freeze-dryer and the slurry lyophilized, resulting in a sponge.
Data Source
AI summary
Disclosed are medical articles and processes for forming the medical articles. The medical articles may take the form of a sponge having a three-dimensional shape comprising a reservoir. In an embodiment, the sponge is formed by placing a collagen slurry, optionally further comprising a mineral, in a mold and lyophilizing the slurry. In an embodiment, an improved molding process for such medical articles comprises forcing a slurry through a mold comprising the shape of a tube having an obstruction connected to the sidewall of the tube via an arm extending from the sidewall to the obstruction.