Antireflective Filter Wafer for Direct Microparticle Spectral Analysis
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Solution Overview
Problem
Current methods for filtering and analyzing microplastic particles in aqueous systems lack harmonized, efficient, and representative sampling techniques, particularly for sizes less than 500 μm, due to issues with sample transfer and interference from naturally occurring particles, which impairs optical spectral analysis.
Innovation Solution
A filter substrate comprising a wafer with a thickness of at least 100 μm and an antireflection layer for broadband transparency, combined with filter holes of 1 μm to 5 mm diameter, allowing for both effective filtration and high-quality optical characterization of microparticles directly on the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional filter materials (plastic, metal, inorganic fibres) are used for filtering microparticles, then filtering function is achieved, but optical transparency and measurement quality are impaired due to interfering background signals
Solution Approach 1:
The patent employs a porous wafer structure with controlled pore sizes (1 μm to 500 μm) that allows microparticles to be retained on the filter surface while maintaining high optical transparency. The porous architecture enables both effective filtration and broadband optical transmission (200 nm to 10,000 nm) without the interfering background signals characteristic of conventional solid filter materials.
Solution Approach 2:
The filter substrate combines a wafer material (glass, plastic, or metal) with a porous structure and optional antireflection coating to create a composite system that simultaneously achieves mechanical strength, filtration capability, and optical transparency. This composite approach resolves the contradiction by integrating multiple functions into a single substrate that does not interfere with optical measurements.
2Ease of operation
If sample transfer from filter to optical sample holder is performed, then optical analysis is enabled, but sample contamination and measurement errors increase
Solution Approach 1:
The wafer-based filter substrate serves dual functions: it acts as both the filtration medium and the optical sample holder. The flat, stable wafer structure with defined optical properties allows direct placement on optical measurement devices without requiring transfer to separate sample holders, thereby eliminating contamination risks associated with sample handling and transfer operations.
3Measurement precision
If physical-chemical processing steps (density separation, oxidative treatment) are applied to remove interfering particles, then measurement quality improves, but filter functionality is impaired
Solution Approach 1:
The porous wafer structure performs preliminary size-selective filtration, capturing microparticles on the filter surface before any processing steps. This preliminary action allows subsequent gentle cleaning procedures (such as rinsing with distilled water or mild oxidative treatment) that remove interfering organic matter without applying harsh conditions that would damage the delicate porous structure or alter captured microparticles.
4Adaptability or versatility
If broadband transparency (200 nm to 10,000 nm) is achieved for optical methods, then spectral analysis capability is improved, but substrate reflection interferes with measurement
Solution Approach 1:
The patent applies antireflection coating selectively on specific regions or surfaces of the wafer to reduce reflection interference in wavelength ranges where optical measurements are performed. This local modification maintains broadband transparency while minimizing reflection effects at the measurement interface, allowing versatile spectral analysis without substrate interference.
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
Enables high-quality filtering and optical characterization of microparticles, minimizing sample contamination and interference, and facilitating direct analysis without the need for transfer, thereby improving measurement quality and efficiency in environmental analysis.
Implementation Method 1
the surface of the front-side and/or the surface of the rear-side of the wafer is provided, completely or in regions, with an antireflection layer which prevents optical reflection of radiation in the wavelength range of 200 nm to 10,000 nm
Implementation Method 2
the wafer has, at least in regions, filter holes with a diameter of 1 μm to 5 mm
Data Source
AI summary
The present invention relates to a filter substrate for filtering and optically characterizing microparticles. The filter substrate comprises a wafer having a thickness of at least 100 pm and a transmittance of at least 10% for radiation in the wavelength range of 2500 nm to 15000 nm. Furthermore, the surface of the front side and/or the surface of the rear side of the wafer is completely or partially provided with an antireflective layer, which prevents the optical reflection of radiation in the wavelength range of 200 nm to 10000 nm. Moreover, the wafer has, at least in some regions, filter holes having a diameter of 1 pm to 5 mm. With the filter substrate according to the invention, microparticles can be filtered and the microparticles on the filter substrate can be subsequently optically characterized with very high measurement quality. The present invention further relates to a method for producing the filter substrate according to the invention and to the use of the filter substrate according to the invention.