Dual-Shell Capsules for Low-Permeability, Controlled Release
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Solution Overview
Problem
Existing microencapsulation technologies face challenges in achieving complete retention of encapsulated active agents throughout the supply chain while ensuring safe, environmentally friendly, and controlled release, particularly for small molecules, with limited success in balancing low shell permeability, mechanical properties, and rupture profile.
Innovation Solution
A method involving the use of a dual-shell structure comprising a first shell component made from a condensation product of specific inorganic precursors and a second shell component, such as SiO2, to create a dense and robust capsule with low permeability and mechanical integrity, using a 'brick and mortar' mechanism for shell formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If monomers such as tetramethoxysilane (TMOS) and tetraethoxysilane (TEOS) are used for capsule shell formation, then the reaction speed increases due to higher water solubility and lower molecular weight, but the shell permeability increases and mechanical integrity decreases
Solution Approach 1:
The patent uses composite materials by combining silane monomers with prepolymers made from similar monomers but with different molecular weights and solubilities. This composite approach allows the system to benefit from both the fast reaction of monomers and the low permeability/mechanical strength of prepolymers, resolving the contradiction between reaction speed and shell integrity.
Solution Approach 2:
The patent changes the parameters of the shell material by using a mixture of monomers and prepolymers with varying molecular weights, solubilities, and reaction kinetics. This parameter variation allows optimization of both reaction speed and shell properties, achieving low permeability and good mechanical integrity while maintaining acceptable reaction rates.
2Reliability
If cationic surfactants such as CTAC or CTAB are used to drive hydrolyzed intermediates to the oil/water interface, then the shell formation is enhanced, but environmental safety and human health safety deteriorate
Solution Approach 1:
The patent extracts and removes the harmful cationic surfactants from the capsule formation process. By eliminating these toxic substances while maintaining alternative mechanisms for shell formation (using silane monomers and prepolymers that can self-assemble at the interface), the patent achieves both low toxicity and effective encapsulation.
Solution Approach 2:
The patent replaces persistent harmful surfactants with biodegradable, environmentally friendly alternatives that perform the necessary function temporarily during capsule formation but do not persist in the environment, thus resolving the contradiction between effectiveness and environmental safety.
3Ease of manufacture
If a single-shell structure is used, then the manufacturing process is simpler, but the ability to provide both low permeability and controlled rupture is insufficient
Solution Approach 1:
The patent segments the capsule shell into multiple functional layers with different properties. The inner layer provides low permeability for controlled release, while the outer layer provides mechanical strength and controlled rupture characteristics. This segmentation allows each layer to be optimized for its specific function while maintaining overall manufacturing feasibility.
Solution Approach 2:
The patent employs a nested shell structure where an inner shell layer is surrounded by an outer shell layer. This nested configuration allows the inner layer to control permeability and the outer layer to control mechanical properties and rupture behavior, achieving multiple functions that a single shell cannot provide.
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 dual-shell capsules provide enhanced stability and controlled release of benefit agents, maintaining integrity in harsh environments and reducing shell permeability, especially in surfactant-based matrices, while ensuring mechanical robustness and targeted rupture.
Implementation Method 1
The silane precursor undergoes hydrolysis in the presence of water to form silanol groups
Implementation Method 2
which then condense to form a dense inorganic shell network
Data Source
Figure 1A
Figure 2A~3B
Figure 4A~5
AI summary
A population of capsules, the capsules can include a core including a benefit agent and a shell surrounding the core, wherein the shell can include a first shell component.