OPTIR Microplastic Analysis Using Polarized Imaging and Photothermal IR
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Solution Overview
Problem
Existing techniques for analyzing microplastic particles smaller than 20 μm are inefficient, inaccurate, and prone to photodamage, particularly for colored or dark samples, leading to difficulties in chemical identification and characterization.
Innovation Solution
An automated optical photothermal infrared (OPTIR) system with polarization optical imaging and image analysis is used to identify and characterize micron-scale microplastic particles, employing crossed polarized microscopy and photothermal infrared spectroscopy for high-speed, reliable chemical composition analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional infrared spectroscopy or Raman techniques are used to analyze microplastic particles smaller than 20 μm, then chemical identification can be achieved, but the analysis is inefficient, inaccurate, and prone to photodamage particularly for colored or dark samples
Solution Approach 1:
The patent introduces an optical photothermal infrared spectroscopy technique that uses an optical intermediary (probe beam) to detect infrared absorption. The infrared radiation heats the microplastic particles, and this thermal effect is detected through changes in the optical properties of a probe beam, enabling sensitive detection of chemical composition without direct infrared detection limitations
Solution Approach 2:
The patent changes the detection parameter from direct infrared signal measurement to optical photothermal signal measurement. By measuring changes in optical properties (refractive index, absorption) of a probe beam caused by infrared-induced heating, the system achieves higher sensitivity and accuracy for sub-20 μm particles while reducing photodamage
2Measurement precision
If higher sensitivity is achieved for detecting micron-scale microplastic particles, then chemical composition analysis improves, but the system complexity increases
Solution Approach 1:
The patent replaces complex mechanical detection systems with an optical photothermal detection system. Instead of using complex infrared detectors or Raman spectroscopy equipment, the system uses simple optical beam measurement to detect thermal effects, achieving high sensitivity with reduced mechanical and electronic complexity
Solution Approach 2:
The optical photothermal infrared spectroscopy system performs multiple functions: it detects chemical composition, identifies particle type, and provides spectral information all through a single unified measurement approach, reducing the need for multiple specialized instruments and simplifying the overall system
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 system achieves high chemical identification success rates and improved sensitivity for micron-scale microplastic particles, overcoming limitations of conventional methods by providing accurate and rapid analysis of a wide variety of chemical compositions.
Implementation Method 1
IR absorbing regions of the sample convert absorbed IR radiation into heat, causing a local temperature rise in the sample
Implementation Method 2
IR absorbing regions of the sample convert absorbed IR radiation into heat
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
Implementation Method 5
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 6
One or more of these changes can change the intensity, angle, and or optical phase of probe light after interacting with 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.