Structured Glass Recess Walls With Low-Roughness Microfeatures
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Solution Overview
Problem
Current methods for structuring glass substrates, such as ultrasonic machining and laser processing, are limited in creating microstructures with smooth surfaces and precise features, leading to stress, microcracks, and inefficiencies in industrial manufacturing, particularly for applications like microfluidics and electro-optical components that require precise surface adjustments.
Innovation Solution
A panel-shaped glass element with a recessed structure featuring a multiplicity of adjacent rounded dome-shaped depressions on its recess wall, providing a smooth surface with a mean roughness value of less than 5 µm, which is achieved through the use of an ultrashort-pulse laser to create filamentary channels and subsequent etching, allowing for precise control over the recess wall's structure and roughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If ultrasonic machining or sandblasting is used to structure glass substrates, then holes and cavities can be created, but the structure size is limited to about 400 μm or at least 100 μm and mechanical erosion causes stresses and flaking in the edge region
Solution Approach 1:
The patent replaces mechanical machining methods (ultrasonic machining, sandblasting) with laser-based processing. The laser beam creates structures through photothermal ablation rather than mechanical erosion, enabling precise microstructuring down to a few micrometers without generating mechanical stresses or flaking in the edge region of holes and cavities.
Solution Approach 2:
The patent utilizes the low thermal conductivity of glass and controlled laser parameters to achieve precise microstructuring. By adjusting laser power, pulse duration, and scanning speed, the process creates clean edges and smooth surfaces with minimal thermal damage, overcoming the size limitations and stress issues of mechanical methods.
2Manufacturing precision
If conventional laser processing is used to create fine structures, then smaller structures can be introduced, but high thermal loading causes critical stresses, microcracks and deformations in the edge region
Solution Approach 1:
The patent employs ultrashort pulse laser processing where energy is delivered in extremely short pulses (femtosecond to picosecond range). This periodic pulsed action allows the glass material to cool between pulses, preventing cumulative thermal loading and avoiding the formation of microcracks and deformations while still achieving precise microstructuring.
Solution Approach 2:
The ultrashort pulse duration allows the laser energy to be deposited and removed so quickly that heat diffusion to surrounding areas is minimized. This 'rushing through' the material before heat can spread prevents thermal stress accumulation and maintains structural integrity in the edge regions of created features.
3Manufacturing precision
If a fine laser beam is used to generate microstructures, then precise features can be created, but larger-area structures require very great outlay and the process is only partially suitable for industrial manufacture
Solution Approach 1:
The patent combines multiple laser processing techniques (direct laser writing, two-photon polymerization with subsequent etching) into a unified approach that can handle both small microstructures and larger-area structures. This merged methodology maintains precision while improving throughput through parallel processing capabilities and optimized parameter sets for different scale requirements.
Solution Approach 2:
The patent uses preliminary structuring with the laser to create patterns that are then enhanced or completed through secondary processes such as chemical etching. This preliminary action allows efficient coverage of large areas with the high-precision laser, while the secondary process completes the structuring with minimal additional outlay, making the overall process suitable for industrial manufacture.
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 production of glass elements with enhanced surface smoothness and reduced crack formation, suitable for microfluidics and optical applications, while allowing for efficient industrial manufacturing of components with precise features and improved optical properties.
Implementation Method 1
the laser beam of an ultrashort-pulse laser is directed onto one of the surfaces of the glass element and is concentrated by focusing optics in order to form an elongate focus in the glass element, a multiplicity of filamentary channels being generated in the volume of the glass element by the incident energy of the laser beam
Implementation Method 2
the glass element is exposed to an etchant which erodes glass of the glass element with an erosion rate, the channels being widened by the etchant
Data Source
AI summary
A panel-shaped glass element is provided that includes vitreous material having a thermal expansion coefficient of less than 10×10-6 K-1 as well as two opposing surfaces. The glass element furthermore has at least one recess which runs through the glass of the glass element and has a recess wall which runs around the recess and adjoins the two opposing surfaces. The recess wall has a structure with a multiplicity of mutually adjacent rounded dome-shaped depressions. A roughness of the recess wall is formed by these depressions as well as the ridges enclosing the depressions. The recess wall has a mean roughness value (Ra) which is less than 5 µm.