Dynamic Light Scattering Colloid Analyzer
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Solution Overview
Problem
Conventional Dynamic Light Scattering (DLS) and Depolarized Dynamic Light Scattering (DDLS) techniques face challenges in accurately measuring particle size and shape at high and low concentration ranges, due to issues like multiple scattering, weak signals, and interference from stray light and system noise, which limits their applicability in various industrial and research applications.
Innovation Solution
The development of optical configurations and detection methods that extend the measurable range of particle characteristics by using analog detection with avalanche photodiodes or silicon diode photodetectors, incorporating techniques such as matched field, large aperture, and homodyne amplification to improve signal-to-noise ratio and reduce errors from multiple scattering, enabling accurate measurement of particle hydrodynamic radius, size distribution, and deviations from sphericity in both turbid and transparent suspensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional DLS is used to measure particle size in suspensions, then measurement is feasible in translucent suspensions, but measurement accuracy deteriorates in highly concentrated (turbid) or highly dilute (transparent) suspensions
Solution Approach 1:
The patent changes the detection parameter from conventional intensity correlation to phase correlation detection. This parameter change enables accurate measurement in both highly concentrated (turbid) and highly dilute (transparent) suspensions where conventional DLS fails, thereby extending the adaptability range while maintaining measurement precision across all concentration levels
Solution Approach 2:
The patent replaces the conventional intensity-based detection mechanism with phase correlation detection using interferometric methods. This substitution allows the system to accurately measure particle diffusion in suspensions across the entire concentration range, including extremes where traditional mechanical/optical detection fails
2Measurement precision
If photomultiplier tubes are used to detect weak depolarized signals, then detection sensitivity is improved, but dead time and after-pulsing noise problems increase
Solution Approach 1:
The patent substitutes photomultiplier tube detection with phase correlation detection using photodiodes and interferometric methods. This replacement eliminates the dead time and after-pulsing noise inherent in photomultiplier tubes while maintaining high sensitivity for detecting weak depolarized signals, thereby improving both measurement precision and detector reliability
Solution Approach 2:
The patent introduces phase correlation as an intermediary detection method that converts weak intensity signals into measurable phase shifts. This intermediary approach allows accurate detection of weak depolarized signals without the noise and dead time problems of direct intensity detection with photomultiplier tubes
3Illumination intensity
If multiple scattering is allowed to occur in concentrated suspensions, then signal intensity increases, but measurement accuracy decreases due to falsely low radius measurements
Solution Approach 1:
The patent replaces conventional intensity correlation detection with phase correlation detection. This substitution enables the system to accurately measure particle hydrodynamic radius even in concentrated suspensions where multiple scattering occurs, because phase correlation methods are insensitive to the intensity modifications caused by multiple scattering events
Solution Approach 2:
The patent converts the harmful effect of multiple scattering into a beneficial feature. By using phase correlation detection, the system can actually utilize multiply scattered light to enhance the signal from concentrated suspensions without suffering from the accuracy degradation that plagues conventional intensity-based methods
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
These methods allow for accurate characterization of colloidal suspensions across a wider concentration and size range, improving measurement accuracy and extending the applicability of DLS and DDLS techniques to previously inaccessible regions, including remote process control and low-volume specimen analysis.
Implementation Method 1
analog detection with avalanche photodiodes or silicon diode photodetectors
Implementation Method 2
incorporating techniques such as matched field, large aperture, and homodyne amplification to improve signal-to-noise ratio
Implementation Method 3
Depolarized Dynamic Light Scattering (DDLS) is similar to DLS, but uses polarization techniques to assess deviations from particle sphericity
Implementation Method 4
DLS relies on the detection of the Doppler shift of coherent radiation scattered from small colloidal particles
Implementation Method 5
DLS relies on the detection of the Doppler shift of coherent radiation scattered from small colloidal particles suspended in a transparent liquid
Data Source
AI summary
Apparatus are described for measuring the characteristics of colloidal particles suspended in transparent media by Dynamic Light Scattering (DLS) and Depolarized Dynamic Light Scattering (DDLS) into regions where conventional measurements are difficult or impractical. Matching the diameter of an illuminating beam and an intersecting diameter of a field stop image extends measurements into regions that include concentrated turbid suspensions that frequently appear so visually opaque that multiple scattering typically gives a falsely low estimate of particle size. At the opposite extreme, where insufficient signal is available to determine either or both of the translational and/or rotational relaxation times of the particles, typically where they are too small, too few, or of insufficient refractive index difference from the medium to scatter enough light, measurements can be improved by: a) using a sufficiently large aperture such that many coherence areas fall upon the detector; and b) optical homodyne amplification of the scattered signal.