Flushable Catheter Bi-layer Structure for Hydrophilic Lubricity
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Solution Overview
Problem
Existing flushable urinary catheters with oil-based coatings do not achieve high enough lubricity values, and water-based coatings are not feasible as they dissolve or degrade water-soluble catheters, limiting the options for customers seeking hydrophilic lubricity.
Innovation Solution
Development of flushable catheters with a bi-layer tube structure, featuring a biodegradable outer layer made from polylactic acid that supports a hydrophilic coating and acts as a temporary water barrier, preventing premature degradation of a water-disintegrable inner layer, such as polyvinyl alcohol, allowing for hydration and lubricity without substrate instability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a water-based hydrophilic coating is applied to a water-soluble catheter, then lubricity is improved, but the coating dissolves or degrades the catheter substrate
Solution Approach 1:
The patent introduces an intermediary substance (oil-based coating or hydrophobic polymer layer) between the water-based hydrophilic coating and the water-soluble catheter substrate. This intermediary layer acts as a barrier that prevents water from penetrating through the hydrophilic coating to dissolve the PVOH substrate, while still allowing the hydrophilic coating to provide its lubricity function. The intermediary layer is temporarily present during use and degrades or is removed after use, enabling the catheter to be flushed away.
Solution Approach 2:
The patent creates a composite structure consisting of multiple layers: a water-soluble inner layer (PVOH), an intermediary oil-based coating or hydrophobic polymer layer, and a water-based hydrophilic coating on the outer surface. Each layer serves a specific function, and their combination resolves the contradiction by preventing direct contact between water and the water-soluble substrate while maintaining hydrophilic lubricity.
2Reliability
If an oil-based coating is applied to a flushable catheter, then coating stability is improved, but lubricity values are insufficient compared to hydrophilic coatings
Solution Approach 1:
The patent merges the advantages of both oil-based and water-based coatings by applying a water-based hydrophilic coating over an oil-based intermediary layer. The outer hydrophilic coating provides high lubricity values comparable to traditional hydrophilic catheters, while the underlying oil-based layer provides coating stability and prevents water penetration. This layered combination achieves both desired properties simultaneously.
3Ease of manufacture
If a water-soluble catheter is made fully water-disintegrable, then flushability is improved, but the catheter degrades prematurely before use
Solution Approach 1:
The patent applies an oil-based coating or hydrophobic polymer layer to the water-soluble catheter substrate before use. This preliminary action creates a protective barrier that prevents water from contacting and dissolving the PVOH substrate during storage and use. The barrier is designed to degrade or be removed after use, allowing the catheter to disintegrate properly during flushing. This preliminary protective action resolves the contradiction by preventing premature degradation while maintaining flushability.
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 bi-layer structure enables hydrophilic coatings to achieve lubricity values comparable to traditional hydrophilic catheters while ensuring the catheter remains functional and stable during use, with the outer layer breaking down quickly enough for flushability standards, preventing the coating from falling off and allowing for easy disposal.
Implementation Method 1
The outer layer acts as a temporary water barrier. This water barrier allows the hydrophilic coating to be hydrated but prevents water molecules attacking the PVOH substrate
Implementation Method 2
The hydrophilic coating is active or wetted with a non-aqueous activation agent or a mixture of an activation agent and water
Implementation Method 3
a hydrophilic coating that reduces friction to allow for easier and less traumatic insertion
Implementation Method 4
The outer layer breaks down at a slower rate than the inner layer and bonds well to the PVOH inner layer. The outer layer acts as a stable primer layer for hydrophilic style coatings.
Implementation Method 5
The water disintegratable and enzymatically hydrolysable materials are preferably flushable materials which are suitable for disposal in a toilet or sanitary system and, even more preferably, biodegradable flushable materials
Data Source
Figure 1
AI summary
This is a water disintegrable, flushable catheter that will dissolve or biodegrade in water. It is coated with a hydrophilic coating and will achieve lubricity values typical of a hydrophilic catheter. The catheter may be formed of a bi-layer tube that has a biodegradable outer layer such as polylactic acid and a purely water disintegrable inner layer, e.g., polyvinyl alcohol (PVOH). The outer layer will support the hydrophilic coating even when it's wetted and thus acts as a stable primer layer for hydrophilic style coatings. The outer layer bonds well to the water disintegrable inner layer but also allows a hydrophilic coating to be applied on top. The outer layer acts as a temporary water barrier. This water barrier allows the hydrophilic coating to be hydrated prior to use but prevents water molecules from attacking the PVOH inner layer. Alternatively, a hydrophilic coating that bonds to either the tubing directly or a via a primer layer but unlike typical hydrophilic coatings the coating is pre- activated by organic activation agents other than water and thus the catheter does not break down in the packaging or sterilization