Off-Stoichiometric Thiol-Ene Bonding for Microfluidics
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Solution Overview
Problem
Existing methods for bonding multilayer polymer or hybrid articles at low temperature and solvent-free conditions are inefficient, particularly when incorporating patterns, as liquids tend to wick into cavities, altering geometries, and traditional surface activation methods damage biofunctionalization. Additionally, microfluidic devices face challenges with surface functionalization and assembly due to poor mechanical properties of off-stoichiometric thiol-ene polymers.
Innovation Solution
A method involving off-stoichiometric thiol-ene (OSTE) polymers with a specific ratio of thiol groups to carbon-carbon double bonds, allowing for unreacted groups to form covalent bonds with chemical moieties on other articles, enabling direct and solvent-free bonding without plasma treatment, and allowing for temperature-tuned mechanical properties and controlled surface modification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional plasma treatment or surface activation methods are used to functionalize microfluidic channels, then surface functionalization is achieved, but the biofunctionalization is destroyed
Solution Approach 1:
The patent changes the chemical parameters of the polymer system by using off-stoichiometric thiol-ene polymers with excess reactive groups. This allows surface functionalization to occur through controlled chemical reactions during polymerization rather than through aggressive plasma treatment, thereby achieving the desired surface modification without damaging biofunctionalization layers
Solution Approach 2:
The patent performs preliminary surface functionalization during the polymerization process itself, before any subsequent bonding or assembly steps. The excess thiol or ene groups are already present on the channel surfaces after curing, ready for controlled reaction with biofunctional molecules, eliminating the need for post-processing plasma activation that would damage sensitive biochemical layers
2Strength
If heat, solvents or oxygen plasma treatment is used to activate surfaces prior to bonding, then bonding capability is improved, but the biofunctionalization is destroyed
Solution Approach 1:
The polymer material provides its own bonding capability through the excess reactive groups incorporated during polymerization. The unreacted thiol or ene groups on the polymer surface can directly react with complementary groups on substrates or other layers, enabling the material to bond itself and other components without requiring external activation treatments like plasma or chemical solvents that would damage biofunctionalization
Solution Approach 2:
The patent creates a composite system where the thiol-ene polymer with excess reactive groups acts as both the structural material and the bonding agent. The polymer combines mechanical structural functions with chemical reactivity for bonding, eliminating the need for separate surface activation steps and compatible adhesives that would compromise biofunctionalized surfaces
3Strength
If two stiff substrates are used to form microfluidic devices, then structural integrity is maintained, but perfect sealing cannot be achieved without perfect molecular smoothness
Solution Approach 1:
The patent employs the off-stoichiometric thiol-ene polymer as a compliant bonding layer that can deform elastically during the bonding process. This flexible polymer layer conforms to surface irregularities and creates perfect contact between rigid substrates, enabling reliable sealing while maintaining the structural integrity provided by the stiff substrate components
4Adaptability or versatility
If off-stoichiometric formulations are used to enable surface modification, then surface reactivity is improved, but mechanical properties deteriorate due to non-optimized polymeric network
Solution Approach 1:
The patent optimizes the off-stoichiometry ratio parameters to achieve a balance between surface reactivity and bulk mechanical properties. By carefully controlling the excess thiol or ene group concentration (typically 5-20% excess), the polymer maintains sufficient crosslinking density for good mechanical strength while providing enough unreacted groups on the surface for effective bonding and functionalization
Solution Approach 2:
The patent creates a composite network structure where the polymer matrix provides mechanical integrity through extensive crosslinking, while the controlled excess of reactive groups provides surface functionality. The bulk material achieves optimal mechanical properties through near-stoichiometric crosslinking, while the surface retains reactive capability for bonding applications
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 OSTE polymers provide robust, durable microfluidic devices with improved bonding to biofunctionalized surfaces, controlled surface modification, and enhanced mechanical properties, enabling perfect interlocking and sealing, thus overcoming the limitations of traditional methods.
Implementation Method 1
reacting a compound comprising at least two thiol groups and a compound comprising at least two carbon-carbon double bonds... to obtain a first intermediate article, wherein said first intermediate article comprises at least one unreacted group selected from an unreacted thiol group and an unreacted carbon-carbon double bond
Implementation Method 2
reacting at least a part of said unreacted groups on said first intermediate article with chemical groups on said second article to obtain covalent bonds and forming a final article
Data Source
AI summary
A method for the manufacture of articles of thiol-ene polymers comprises the steps: a) reacting a compound comprising at least two thiol groups and a compound comprising at least two carbon-carbon double bonds, in off stochiometry ratios to obtain a first intermediate article, wherein said first intermediate article comprises at least one unreacted group selected from an unreacted thiol group and an unreacted carbon-carbon double bond, and b) contacting said first intermediate article with a second article, wherein the surface of said second article at least partially comprises reactive groups and reacting at least a part of said unreacted groups on said first intermediate article with chemical groups on said second article to obtain covalent bonds and forming a final article.