Microfluidic Device Bonding with UV-Crosslinked Hydrophilic Coatings
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Solution Overview
Problem
The challenge in microfluidic device manufacturing lies in the combination of surface modification and bonding processes, which are often time-consuming, laborious, and not scalable, particularly when dealing with thermoplastic polymers that are hydrophobic and prone to biofouling, and require separate steps for surface modification and bonding.
Innovation Solution
A process that simultaneously bonds and modifies the inner surface of microfluidic devices using a coating composition comprising mono- and multifunctional monomers, applied to transparent substrates, which are then crosslinked with UV light to form a hydrophilic, anti-biofouling coating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate steps for surface modification and bonding are used, then surface properties can be modified, but the process becomes time-consuming and not scalable
Solution Approach 1:
The patent combines surface modification and bonding into a single simultaneous process. The coating composition is applied to the substrate, then UV irradiation crosslinks the coating to modify the surface while also bonding the substrate to other components. This eliminates the need for separate sequential steps, thereby improving manufacturing productivity while maintaining reliable surface property modification.
Solution Approach 2:
The coating composition is applied to the substrate before bonding occurs. This preliminary coating step ensures that surface modification is prepared in advance, and the subsequent UV irradiation simultaneously activates both the crosslinking of the coating and the bonding process, resolving the contradiction between modifying surface properties and maintaining manufacturing speed.
2Ease of manufacture
If thermoplastic polymers are used, then devices can be manufactured at low cost, but they are hydrophobic and prone to biofouling
Solution Approach 1:
The patent creates a composite structure by coating the thermoplastic polymer substrate with a crosslinkable coating composition that provides hydrophilic and anti-biofouling properties. The coating layer combines with the substrate to form a composite material that retains the low-cost manufacturing advantage of thermoplastics while adding protective surface properties that resist biofouling.
Solution Approach 2:
The patent changes the surface parameters of the thermoplastic polymer by applying a coating that alters surface energy and wettability. The crosslinked coating transforms the hydrophobic surface into a hydrophilic one, thereby changing the surface properties to resist biofouling while maintaining the bulk material's cost-effective thermoplastic characteristics.
3Strength
If thermal bonding is used, then polymer substrates can be bonded, but temperatures above 100°C may damage pre-deposited coating and biological reagents
Solution Approach 1:
The patent replaces thermal bonding with photochemical bonding using UV irradiation. Instead of using heat (thermal energy) to activate bonding, the process uses light energy to initiate crosslinking of the coating composition, which simultaneously bonds the substrate. This substitution eliminates the harmful high temperatures that would damage sensitive coatings and biological reagents while still achieving strong bond strength.
Solution Approach 2:
The patent utilizes the phase transition of the photoinitiator in the coating composition from inactive to active state upon UV irradiation. This photochemical phase transition triggers crosslinking and bonding at ambient temperatures, avoiding the need for thermal activation and protecting temperature-sensitive materials from damage.
4Strength
If adhesive bonding is used, then substrates can be bonded, but uniformity and patterning may be compromised
Solution Approach 1:
The patent extracts and eliminates the intermediate adhesive layer from the bonding process. Instead of using a separate adhesive material between substrates, the coating composition itself serves as both the surface modification layer and the bonding agent. This removal of the intermediate adhesive layer eliminates the uniformity and patterning issues associated with adhesive application while maintaining strong bond strength through direct crosslinked bonding.
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 method achieves strong, transparent, and hydrophilic bonding of polymer substrates with minimal deformation, reducing biofouling and enabling passive flow of aqueous liquids, suitable for large-scale production of microfluidic devices.
Implementation Method 1
irradiating the assembly with light having a wavelength between 200 and 800 nm to crosslink the liquid coating to bond the first flat part and the second flat part
Data Source
AI summary
A process for manufacturing a microfluidic device including:1. providing two substrates which, when assembled, define a microfluidic structure;2. coating at least one of the surfaces defining the microfluidic structure with a coating composition including:a. a monomer A including one moiety represented by CH2═CR1R2 wherein R1 represents H or CH3 and R2 represents —COO— or —CONH—, and a non-ionic hydrophilic moiety;b. a monomer B including two or more moieties represented by CH2═CR1R2 wherein R1 represents H or CH3 and R2 represents —COO— or —CONH—, and a non-ionic hydrophilic moiety;3. assembling the substrates to obtain a microfluidic structure between the first and the second substrate; and4. at least partially irradiating the assembly with light to crosslink the liquid coating to bond the substrates and to obtain a crosslinked coating inside the microfluidic structure.