Laser-Patterned Transparent Substrates for Durable Anti-Fogging
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Solution Overview
Problem
Existing methods for imparting anti-fogging properties to substrates, such as glass and polymers, are susceptible to mechanical stress, require complex optical adjustments, limited in minimum structure dimensions, and can impair transparency with diffraction effects, and are not universally applicable.
Innovation Solution
A patterned substrate with a first periodic dot structure in the micro- or submicrometer range, formed by inverse cones, which has a controlled water contact angle and avoids self-organization processes, ensuring robustness and transparency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coating is applied to the substrate surface to improve hydrophilicity and anti-fogging properties, then the substrate gains anti-fogging properties, but the coating is susceptible to mechanical stress and shows rapid degradation
Solution Approach 1:
The invention extracts the anti-fogging function from a separate coating layer and integrates it directly into the substrate surface through laser-induced periodic surface structures (LIPSS). By creating hierarchical microstructures (combining DLIP dot patterns with self-organized LIPSS ripples) on the substrate surface, the hydrophilic properties are inherent to the substrate itself rather than dependent on an external coating, thereby eliminating coating degradation issues while maintaining anti-fogging functionality.
2Reliability
If direct laser interference patterning is used to generate structures on glass, then the substrate gains hydrophilic properties, but complex conversion and realignment of optical elements is required
Solution Approach 1:
The invention uses preliminary action by first creating a periodic dot pattern through direct laser interference patterning (DLIP), which then serves as a template for the self-organization process. The initial DLIP structure pre-defines the locations where LIPSS will form, eliminating the need for complex real-time optical adjustments. The self-organization process automatically generates the hierarchical LIPSS structures on top of the pre-formed dot pattern, simplifying the overall process control.
3Reliability
If laser-induced periodic surface structures are generated by exciting glass at high radiation intensity points, then hierarchical structures with anti-fogging properties are created, but the minimum structure dimensions are limited to the micrometer range causing diffraction effects
Solution Approach 1:
The invention applies local quality by creating hierarchical structures with two distinct size scales: the DLIP dot pattern provides a larger periodicity (micrometer range) for robust anti-fogging properties, while the self-organized LIPSS provide finer sub-structures (sub-micrometer to nanometer range) that reduce diffraction effects. This multi-scale hierarchical approach allows different regions of the structure to fulfill different functions - the coarser structure ensures anti-fogging reliability while the finer structures maintain optical transparency.
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 substrate maintains anti-fogging properties without degradation, is environmentally friendly, and can be applied to a wide range of materials without affecting transparency, with precise control over hydrophilicity and optical properties.
Implementation Method 1
A laser beam is emitted from a laser radiation source. The laser beam is divided by a beam splitter element into at least three sub-beams, in particular into four sub-beams. The at least three sub-beams hit a focusing element, in particular a focusing mirror, so that the at least three sub-beams interfere on the surface or inside the substrate
Implementation Method 2
The at least three sub-beams are focused into a small focal spot on the surface or inside the substrate. By means of the focusing, a periodic interference pattern with alternating radiation intensity maxima and minima is generated on the substrate surface or inside the substrate. Due to the high energy input of the incident laser beam at these points, the heated substrate is reshaped
Implementation Method 3
the heated substrate is reshaped in such a way that a quasi-periodic line pattern is created in which the substrate subsequently solidifies
Data Source
AI summary
The present invention relates to the field of patterning substrates with periodic dot structures in the micro- and/or sub-micrometer range, in particular a patterned substrate and a method for patterning surfaces of a transparent substrate by means of laser interference patterning. The patterning produced in this way with periodic dot structures in the micro- and/or sub-micrometer range is characterized by pronounced anti-fogging properties.