Silver-Containing Polyurethane Foam for Sustained Ion Release
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Solution Overview
Problem
Existing wound dressings with antimicrobial silver do not provide a sufficient initial release and prolonged maintenance of silver ions, which is desirable for infected wounds that require high and sustained antimicrobial activity.
Innovation Solution
A method for producing an antibacterial and hydrophilic polyurethane foam structure that includes silver salts like silver sulphate, silver citrate, silver acetate, silver carbonate, or silver phosphate, dispersed in the water phase during foam manufacturing, allowing for controlled release of silver ions over time, and coated with a cross-linked silicone gel for enhanced skin adhesion and antimicrobial efficacy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If silver salts are included in the water phase during foam manufacturing, then silver ion release is improved and prolonged, but the manufacturing process complexity increases
Solution Approach 1:
The patent combines the silver salt incorporation step with the existing foam manufacturing process by adding silver salts directly to the water phase before foam formation. This merging of functions allows silver ion release capability to be built into the standard production line without requiring separate processing stages, thereby achieving prolonged silver release while minimizing manufacturing complexity increases
Solution Approach 2:
The water phase serves multiple functions: it acts as the foaming agent base, the dispersing medium for silver salts, and the precursor for silver ion release. By making the water phase multi-functional, the patent achieves prolonged silver ion release without adding separate dedicated components or processes, thus resolving the contradiction between improved duration and manufacturing complexity
2Productivity
If silver salts are dispersed in the water phase, then initial silver release rate is improved, but control over release rate becomes more difficult
Solution Approach 1:
The patent controls the release rate by adjusting parameters of the silver salt dispersion in the water phase, including concentration, particle size distribution, and dispersion uniformity. By optimizing these parameters, the invention achieves high initial release rates while maintaining controllable and sustained release profiles, resolving the contradiction between productivity and ease of operation
Solution Approach 2:
The patent creates local variations in silver salt distribution and concentration within the foam structure, with different regions providing different release characteristics. This local quality approach allows the foam to deliver high initial release rates from certain regions while maintaining overall release rate control through the heterogeneous structure
3Stability of the object's composition
If foam moisture content is reduced to at most 10%, then foam stability is improved, but silver ion release is reduced
Solution Approach 1:
The patent introduces the water phase with dispersed silver salts as an intermediary component that mediates between foam stability requirements and silver ion release needs. This intermediary water phase provides the necessary moisture for silver release while the foam structure itself maintains stability, resolving the contradiction by decoupling the stability function from the release function
Solution Approach 2:
The patent creates a composite structure combining the foam matrix with dispersed silver salt particles in the water phase. This composite material allows the foam to maintain its stable structure at low moisture content while the embedded silver salt-water phase composite provides sustained ion release, thus resolving the contradiction between stability and release quantity
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 foam structure achieves a sustained release of silver ions, effectively reducing bacterial counts of Pseudomonas aeruginosa and Staphylococcus aureus, with significant antimicrobial activity lasting up to 120 hours, outperforming commercial silver foam products in terms of silver release and bacterial reduction.
Implementation Method 1
antimicrobial silver ions are released from the foam in a favourable manner during a prolonged period of time
Implementation Method 2
providing a water phase containing a surfactant
Implementation Method 3
isocyanate-terminated polyether having functionality of more than 2
Data Source
AI summary
A method of producing a hydrophilic polyurethane foam structure containing a silver salt, chosen from the group of silver sulphate, silver citrate, silver acetate, silver carbonate, silver lactate and silver phosphate, or a mixture of these salts includes the steps of (a) providing a water phase containing a surfactant, and at least one silver salt, wherein the at least one silver salt is dispersed in the water phase; (b) providing a isocyanate-terminated polyether having functionality of more than (2); (c) mixing the water phase and the isocyanate-terminated polyether, immediately transferring the resulting mixture to a mould whereby a foam structure is obtained; and (d) drying the foam structure until it has a moisture content of at most 10% (wt). The hydrophilic polyurethane foam structure produced by the method and a wound dressing containing the foam structure are also described.