Microfluidic Channel Fabrication with Temporary Aperture Sealing
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Solution Overview
Problem
Current microfabrication methods using femtosecond laser pulses face limitations in creating long, narrow channels due to etchant depletion and irregularities, especially in transparent materials like fused silica, where the aspect ratio of channels is restricted, and the etching process can lead to discontinuities and variations in channel sections.
Innovation Solution
The method involves creating a temporary opening with a sealing feature that protrudes above the surface, allowing for etching to proceed and then sealing it by selectively melting the feature, using localized heat sources like infrared lasers or miniaturized flames to form a tight, integral plug within the substrate, which can be used to close the aperture without additional sealants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If wet etching is used to create long channels in transparent materials, then channel length can be increased, but etchant depletion causes irregularities and variations in channel section
Solution Approach 1:
The patent applies preliminary action by creating temporary openings at strategic locations before performing wet etching on long channels. These temporary openings allow fresh etchant to be introduced into the channel interior during the etching process, preventing etchant depletion and maintaining uniform channel section throughout the length of the channel.
Solution Approach 2:
The patent uses temporary openings as intermediary structures that facilitate the etching process. These openings serve as conduits for etchant delivery and enable control over the etching progression, allowing the etchant to reach deep into long channels without depleting before completing the etch, thus maintaining section uniformity.
2Device complexity
If femtosecond laser is used to write complex three-dimensional structures, then structural complexity can be increased, but temporary openings require additional sealing steps
Solution Approach 1:
The patent merges the sealing function with the substrate material itself by melting and solidifying the substrate to form integral seals. This eliminates the need for separate sealant materials and reduces the number of discrete sealing steps, simplifying the manufacturing process while maintaining the ability to create complex three-dimensional structures with temporary openings.
Solution Approach 2:
The patent utilizes phase transitions (melting and solidification) of the substrate material to create seals. By locally melting the substrate at temporary opening locations and then allowing it to solidify, the openings are sealed integrally with the substrate, avoiding the need for additional sealant materials and simplifying the manufacturing process.
3Ease of manufacture
If temporary openings are created for etching long channels, then etching access is improved, but additional sealing steps are required
Solution Approach 1:
The patent merges the sealing operation with the substrate material by using localized melting and solidification. This approach integrates the sealing function into the substrate itself, eliminating the need for separate sealant application steps and reducing overall process complexity while maintaining improved etching access through temporary openings.
Solution Approach 2:
The substrate material serves itself by being melted and solidified to form seals at temporary opening locations. This self-service approach eliminates the need for external sealant materials and additional sealing steps, as the substrate itself performs the sealing function through controlled phase transitions.
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 approach enables the fabrication of channels with consistent cross-sections and lengths beyond previous limits, maintaining the substrate's surface integrity and allowing for precise control over channel dimensions and sealing, applicable to various microfabrication processes beyond femtosecond laser techniques.
Implementation Method 1
When femtosecond light pulses are focused inside the bulk of a transparent substrate, the local instant power may be brought above the threshold of nonlinear absorption. The bulk of the material can thus be modified and functionalized without affecting its surface properties.
Implementation Method 2
it can be closed by selectively melting the sealing feature. The method of the invention leads to the creation of tight seams that are integral with the substrate without discontinuities.
Data Source
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AI summary
A method for micro-fabricating a device on a substrate (20), comprising the steps of providing a cavity (31) having a temporary aperture (35) communicating with the outside; providing a sealing structure (45) adjacent to a perimeter of the temporary aperture (35); applying heat to the sealing structure (45), whereby the sealing structure melts and seals the temporary aperture (35).