Inkjet Printed Microfluidic Channels Using Photo-Hydrolyzable Polymers
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Solution Overview
Problem
The current process for creating three-dimensional microfluidic channels is expensive and complex, requiring precise calibration and alignment of femtosecond lasers, making it costly and difficult to execute.
Innovation Solution
Inkjet printing using thermally cross-linkable photo-hydrolyzable polymers, where droplets of a hydrophobic polymer and a cross-linking agent are deposited outside the channel pattern, and a mixture containing poly(tetrahydropyranyl methacrylate) and a photoacid generator are deposited inside, followed by UV exposure to form hydrophilic poly(methacrylic acid) and covalent cross-links, defining the microfluidic channels layer-by-layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the 2-photon writing process is used to create three-dimensional microfluidic channels, then the channels can be fabricated with high precision, but the process becomes extremely complex and expensive requiring precise calibration and alignment of femtosecond lasers
Solution Approach 1:
The patent replaces the complex 2-photon laser writing process with a simpler inkjet printing process. Instead of using femtosecond lasers that require precise calibration and alignment, the invention uses inkjet printed droplets containing photoacid generator and polymer composition that can be cured with standard UV lighting, thereby substituting a complex optical-mechanical system with a simpler printing and curing system while maintaining manufacturing precision
Solution Approach 2:
The patent changes the fundamental parameters of the fabrication process by switching from laser-based 2-photon polymerization to inkjet printing with UV-curable photoacid generator systems. This parameter change includes using different energy sources (UV light vs. femtosecond laser), different material delivery methods (inkjet droplets vs. spin-coated brushes), and different chemical mechanisms (photoacid-catalyzed hydrolysis vs. direct photopolymerization), thereby simplifying the overall process while achieving comparable precision
2Manufacturing precision
If the 2-photon writing process is used to create three-dimensional microfluidic channels, then the channels can be fabricated, but the process becomes costly and difficult to execute
Solution Approach 1:
The patent substitutes expensive and difficult-to-operate femtosecond laser systems with inexpensive and easy-to-use inkjet printers and standard UV lights. This replacement maintains the ability to fabricate three-dimensional microfluidic channels while dramatically improving ease of manufacture by eliminating the need for precise calibration and alignment procedures
Solution Approach 2:
The patent employs disposable inkjet-printed droplets containing the polymer composition and photoacid generator, replacing the need for expensive, reusable laser systems. The printed droplets serve as single-use patterns that are cured in place, eliminating the need for complex, costly equipment while maintaining fabrication capability
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 simplifies the creation of well-defined microfluidic channels by avoiding phase separation and reducing the complexity and cost associated with the 2-photon writing process, enabling efficient fabrication of microfluidic channels.
Implementation Method 1
flood exposure of the entire substrate to UV radiation releases acid from the PAG which hydrolyzes PTHPMA
Implementation Method 2
The photoacid hydrolyzes the PTHPMA during heating, forming hydrophilic poly(methacrylic acid) (PMAA)
Implementation Method 3
The cross-linking agent (e.g., triallyl isocyanurate TAIC) forms covalent cross-links between the polymer matrix and the discrete channels printed to form the microfluidic channels
Implementation Method 4
The substrate is heated so that the cross-linking agent in each of the mixtures copolymerizes with the hydrophobic polymer in each of the mixtures
Data Source
AI summary
Thermally cross-linkable photo-hydrolyzable inkjet printable polymers are used to print microfluidic channels layer-by-layer on a substrate. In one embodiment, for each layer, an inkjet head deposits droplets of a mixture of hydrophobic polymer and cross-linking agent in a pattern lying outside a two-dimensional layout of the channels, and another inkjet head deposits droplets of a mixture of poly(tetrahydropyranyl methacrylate) PTHPMA (or another hydrophobic polymer which hydrolyzes to form a hydrophilic material), cross-linking agent, and a photoacid generator (PAG) in a pattern lying inside the two-dimensional layout of the channels. After all layers are printed, flood exposure of the entire substrate to UV radiation releases acid from the PAG which hydrolyzes PTHPMA to form hydrophilic poly(methacrylic acid) PMAA, thereby rendering the PTHPMA regions hydrophilic. The layers of these now-hydrophilic patterned regions together define the microfluidic channels. The cross-linking agent (e.g., triallyl isocyanurate TAIC) forms covalent cross-links between the two polymer phases.