Particle Suspensions for Low-Contrast Liquid Inspection
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Solution Overview
Problem
Current calibration and validation methods using polystyrene beads are inadequate for optical instruments analyzing biological particles due to refractive index and shape differences, leading to misclassification and erroneous analysis results, especially for low-contrast and irregularly shaped particles.
Innovation Solution
A standard particle suspension with refractive indices between 1.34 and 1.42, formed from materials like PTFE, ETFE, and PDMS, and designed to mimic biological particles in size, shape, and refractive index, is used to calibrate and validate optical analysis instruments, ensuring accurate detection and counting of biological particles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If polystyrene beads are used for calibration, then calibration is simple and beads are readily available, but the refractive index mismatch causes misclassification of biological particles
Solution Approach 1:
The patent changes the refractive index parameter of calibration particles by using materials like PTFE (n=1.35), ETFE (n=1.40), or PDMS (n=1.41) instead of polystyrene (n=1.59). This parameter change ensures the calibration particles have refractive indices (1.34-1.42) that match biological particles, thereby resolving the measurement precision issue while maintaining calibration simplicity.
2Stability of the object's composition
If polystyrene beads are used for calibration, then uniform spherical shape provides consistent calibration, but irregular shapes of biological particles are not represented
Solution Approach 1:
The patent applies asymmetry by providing calibration particles with irregular shapes (ellipsoidal, threadlike, amorphous, crystalline) that match biological particles, rather than using uniform spheres. This allows the calibration standard to represent the diverse shapes of actual biological particles while maintaining composition stability through controlled synthesis methods.
3Illumination intensity
If polystyrene beads with higher refractive index are used, then optical signal is stronger for calibration, but low-contrast biological particles generate weaker signals and may be eliminated from analysis
Solution Approach 1:
The patent changes the refractive index parameter of calibration particles to match biological particles (n=1.34-1.42), which reduces the optical signal strength compared to polystyrene beads. However, this parameter change ensures that the detection threshold and analysis parameters are calibrated accurately for low-contrast particles, improving reliability by preventing elimination of valid biological particle events.
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 standard particle suspension improves the accuracy of instrument calibration and validation, reducing errors in particle detection and allowing for consistent comparison across instruments and laboratories, by closely matching the properties of biological particles and providing a stable, reproducible reference for adjusting instrument parameters.
Implementation Method 1
Instruments used to inspect (detect) micron sized particles typically involve imaging, or light scattering, or light obscuration of the particles as they flow through a clear flow cell
Implementation Method 2
Instruments used to inspect (detect) micron sized particles typically involve imaging, or light scattering, or light obscuration of the particles as they flow through a clear flow cell
Data Source
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AI summary
In certain embodiments, a method for validating the human visual inspection process or an optical analysis instrument for use with biological particles may include inspecting a standard particle solution using the optical analysis instrument. The standard particle solution may include a known concentration of standard particles suspended in solution with the standard particles having a defined size and shape distribution. The standard particles may have a refractive index that is substantially similar to a refractive index of the biological particles. The method may include assessing a concentration of standard particles in the standard particle solution from the inspection. The method may include assessing a difference between the assessed concentration of standard particles and the known concentration of standard particles. The method may include modifying one or more parameters of the optical analysis instrument based on the assessed difference between the concentrations. The method may include assessing a detection efficiency of the optical analysis instrument.