Optical Chopper for Nanoparticle Size Resolution
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Solution Overview
Problem
Conventional methods for measuring nanoparticle properties in polydisperse samples are inaccurate due to difficulties in resolving nanoparticles of different sizes, as the intensity of scattered light varies vastly with particle size, leading to errors in concentration and size distribution analysis.
Innovation Solution
A system using an optical chopper with rotating filters to rapidly adjust light intensity synchronized with the sensor's frame rate, allowing for the detection and tracking of particles of varying sizes by alternating between different filter settings, thereby overcoming the challenges of wildly varying scattered light intensities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional methods measure light scattered from all nanoparticles simultaneously, then the measurement can be performed on an ensemble of particles, but the nanoparticles cannot be resolved into their constituent sizes due to varying scattering intensities
Solution Approach 1:
The patent segments the measurement process by dividing the light scattering signal into discrete size bins using a series of optical filters. Each filter transmits light scattered by particles of a specific size range, allowing individual size classes to be measured separately while maintaining ensemble measurement capability. This resolves the contradiction by enabling both quantitative measurement of total particle number and precise size resolution through sequential filtering.
Solution Approach 2:
The patent applies local quality by using different optical filters with distinct transmission characteristics for different particle size ranges. Each filter is optimized to transmit light from specific size classes while blocking others, creating localized measurement conditions for each size bin. This allows simultaneous measurement of multiple size populations without mutual interference, resolving the resolution accuracy problem.
2Measurement precision
If the intensity of scattered light is increased to detect small nanoparticles, then small particles can be detected, but the high scattering signals from larger nanoparticles obscure the signals from smaller nanoparticles
Solution Approach 1:
The patent segments the light scattering signal by using a series of optical filters that divide the size range into discrete bins. Each filter is designed to transmit light from specific size classes while blocking light from other sizes. This segmentation allows the system to detect small particles without signal obscuration from large particles, as each filter isolates the signal from its target size range.
Solution Approach 2:
The patent extracts the scattering signal from specific size classes using optical filters that selectively transmit light from desired particle sizes while blocking light from other sizes. By taking out the signal from larger particles using filters that block their scattering, the system can detect small nanoparticles without obscuration, resolving the signal interference problem.
3Measurement precision
If multiple lasers with different colors and intensities are used to visualize particles of different sizes, then particles can be visualized, but the system complexity increases and thermal convection is generated
Solution Approach 1:
The patent makes a single laser source multi-functional by using a series of optical filters to enable visualization of particles of different sizes. Instead of requiring multiple lasers with different colors and intensities, the system uses one laser combined with multiple filters that can be sequentially applied. This reduces device complexity while maintaining the ability to visualize particles across different size ranges.
Solution Approach 2:
The patent changes the optical parameters of the system by using a single laser source and varying the filter transmission characteristics instead of changing laser properties. By modifying the filter parameters (transmission wavelength, cutoff frequencies) rather than laser parameters (color, intensity), the system achieves particle size differentiation with reduced complexity and minimal thermal convection.
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 accurate determination of particle sizes and concentrations by synchronizing light intensity changes with the sensor's frame rate, effectively tracking and measuring nanoparticles of different sizes within a single image frame, improving the precision of nanoparticle analysis.
Implementation Method 1
The chopper includes a rotation structure with a first filter and a second filter. The first filter permits a different amount or a different type of electromagnetic radiation to pass there through than the second filter.
Implementation Method 2
a specimen chamber constructed to allow a portion of the beam to scatter when illuminating particles within the chamber
Implementation Method 3
A sensor is positioned to detect the scatter of the beam
Data Source
AI summary
The disclosure provides for a novel optical chopper that can rapidly change the intensity of light incident on a colloid under investigation. This helps record images of various sizes of nanoparticles that scatter light with very different efficiencies (effective cross-sections), typically orders of magnitude different.