Rectangular Cuvette Geometry for Low-Volume Turbidity Measurement
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Solution Overview
Problem
Current laboratory methods for determining bacterial concentration in small fluid volumes are inaccurate and prone to variability due to the use of non-disposable round tubes and instruments designed for larger sample volumes, leading to inconsistent turbidity measurements and potential cross-contamination.
Innovation Solution
An automated nephelometer system with specialized cuvettes of varying sizes and rectangular configuration, equipped with electronic sensors and a light source, that allows for precise turbidity measurement and sample dilution within the vessel, minimizing diffraction and refraction effects and accommodating volumes as low as 200 μL to 500 μL.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If small fluid volumes (200-500 μL) are used for bacterial suspension, then sample purity is maintained and automated colony picking efficiency is improved, but accurate determination of bacterial concentration becomes difficult
Solution Approach 1:
The patent changes the geometric parameters of the cuvette from conventional round tubes to rectangular prisms with specific dimensions (e.g., 16mm width, 12mm height, 40mm length). This parameter change optimizes the light path through the small volume sample, enabling accurate turbidity measurements in 200-500 μL volumes while maintaining the benefits of small volume handling.
Solution Approach 2:
The patent creates a standardized optical path model by using rectangular cuvettes with precisely defined dimensions. This standardized geometry serves as a reproducible template that ensures consistent light scattering measurements across different samples and instruments, enabling accurate bacterial concentration determination in small volumes.
2Reliability
If round tubes are used for nephelometry measurements, then existing instruments can be used, but light path consistency and measurement reliability are compromised
Solution Approach 1:
The patent transitions from symmetric round tubes to asymmetric rectangular prism cuvettes. This asymmetric geometry provides flat, parallel surfaces that create consistent light paths and minimize optical artifacts. The rectangular shape with specific aspect ratios ensures reproducible light scattering patterns, significantly improving measurement reliability and reducing variability between samples.
3Quantity of substance
If multiple passes are made over the media plate to harvest sufficient bacterial colonies, then adequate bacterial concentration is achieved, but sample purity is reduced
Solution Approach 1:
The patent optimizes the vertical dimension (height) of the cuvette to 12mm, creating an optimized light path length that maximizes light scattering signal from small volume samples. This dimensional optimization allows accurate measurement of bacterial concentration in just 200-500 μL volumes, enabling single-pass or minimal-pass colony harvesting that maintains sample purity while achieving adequate bacterial concentration.
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 provides accurate and consistent turbidity measurements for small bacterial suspensions, enabling precise determination of McFarland values and reducing the need for multiple passes over the media plate, thus maintaining sample purity and efficiency in automated colony picking systems.
Implementation Method 1
The instruments base their measurements on physical principles of light scattering which result from the interaction of light with particle(s) in a suspension. Turbidity of the samples effects the transmission and scattering of the light, and allows for a measure of intensity of light transmitted through a sample.
Implementation Method 2
Apparatuses and methods are needed that are designed to minimize variability of measurements among the vessels as well as minimize the effect of diffraction and refraction on the light as it passes through and between different mediums.
Implementation Method 3
Apparatuses and methods are needed that are designed to minimize variability of measurements among the vessels as well as minimize the effect of diffraction and refraction on the light as it passes through and between different mediums.
Data Source
AI summary
A nephelometer that measures turbidity of low volume suspensions using measurements of light transmitted through and/or scattered by the sample. The sample suspension is placed in a tiered cuvette adapted to facilitate measuring the turbidity of low volume samples. The lower portion of the cuvette has smaller dimensions, in horizontal cross section, than the top portion. Both lower and upper portions have angled surfaces. The lower, smaller portion of the cuvette is interrogated by the nephelometer.