Automated OPTIR Analysis for Sub-20 μm Microplastics
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Solution Overview
Problem
Existing techniques are inadequate for the automated, high-speed, and reliable identification of sub-20 μm microplastic particles due to limitations in resolution, sensitivity, and chemical identification accuracy, particularly for dyed or colored plastics, leading to inefficiencies and inaccuracies in microplastic analysis.
Innovation Solution
A method and apparatus using optical photothermal infrared (OPTIR) spectroscopy with automated particle identification and spectroscopic analysis, involving polarization optical imaging and photothermal infrared spectroscopy to characterize micron-scale microplastic particles, including crossed polarized microscopy and automated positioning of particles under a probe beam for infrared wavelength illumination and detection of infrared absorption changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional infrared spectroscopy is used to analyze microplastic particles, then chemical composition information can be obtained, but the spatial resolution is insufficient for sub-20 μm particles
Solution Approach 1:
The patent introduces a mediator substance that enhances the infrared signal from microplastic particles. This mediator absorbs infrared radiation and transfers energy to the probe beam, amplifying the detectable signal from sub-20 μm particles without requiring higher spatial resolution in the direct detection path.
Solution Approach 2:
The patent replaces direct mechanical/optical detection of weak infrared signals from small particles with a photothermal detection system. Instead of directly measuring the faint infrared emission from sub-20 μm particles, the system uses infrared irradiation to heat the particles and detects the resulting photothermal changes in a probe beam, substituting direct optical measurement with a thermal-mechanical detection approach that provides higher sensitivity.
2Productivity
If automated particle identification is implemented, then analysis speed increases, but system complexity increases
Solution Approach 1:
The patent implements preliminary automated particle identification using optical microscopy and image processing before infrared spectroscopic analysis. This preliminary sorting and identification of particles automates the selection process, increasing analysis speed by pre-filtering candidate particles and guiding the subsequent infrared measurement to only those particles of interest.
Solution Approach 2:
The system incorporates automated feedback mechanisms where the detection system itself identifies and locates particles, then automatically positions and measures them without human intervention. The system serves itself by using its own detection capabilities to guide its measurement process, reducing the need for external manual operation while maintaining high productivity.
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-speed, high-accuracy chemical composition analysis of micron-scale microplastic particles with improved signal-to-noise ratio and reduced background interference, facilitating reliable identification across various chemical compositions.
Implementation Method 1
illuminating the microplastic particle with a plurality of infrared wavelengths... measuring a change in the collected probe light from the microplastic particle corresponding to infrared absorption of the microplastic particle
Implementation Method 2
IR absorbing regions of the sample convert absorbed IR radiation into heat, causing a local temperature rise in the sample
Implementation Method 3
This temperature rise can change the shape, size, surface position, and/or index of refraction of the IR absorbing regions of the sample
Implementation Method 4
This temperature rise can change the shape, size, surface position, and/or index of refraction of the IR absorbing regions of the sample. One or more of these changes can change the intensity, angle, and or optical phase of probe light after interacting with the sample
Implementation Method 5
Light that is reflected from, scattered from and/or transmitted through the sample can be collected and analyzed
Implementation Method 6
This temperature rise can change the shape, size, surface position, and/or index of refraction of the IR absorbing regions of the sample
Data Source
AI summary
Detection of microplastics is accomplished using a combination of techniques. A position-detection technique such as crossed-polarization detection, autofluorescence detection, or photothermal infrared imaging is used to determine the locations of microplastics in a sample. Infrared absorption can be detected at those locations to characterize the microplastics. In this way the microplastic content can be located and characterized more quickly and accurately than using conventional techniques.