Light Guiding Measuring Cell for Flow Cytometry
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Solution Overview
Problem
Current analytical techniques for characterizing small particles or molecules in fluids face limitations such as low signal-to-noise ratio, temporal resolution constraints, and the need for sample preparation due to limited measurable sample volumes and background interference, especially when detecting small particles using methods like flow cytometry and nanoparticle tracking analysis.
Innovation Solution
A measuring cell configured as an optical waveguide with a core and cladding, featuring a hollow channel with a small cross-sectional area to restrict particle movement and enhance light intensity penetration, allowing for efficient illumination and detection of small particles without spatial fixation, using a core with a refractive index difference from the cladding to guide light effectively through total reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a laser beam is focused onto the liquid stream in flow cytometry, then high measurement numbers per time unit can be achieved, but the exactly measurable sample volume is limited to a small spatial region
Solution Approach 1:
The measuring cell is divided into a light-guiding region with core and cladding for illumination, and a separate detection region, allowing independent optimization of illumination volume and detection sensitivity
Solution Approach 2:
An optical waveguide (core-cladding structure) is introduced as an intermediary to deliver light to the sample, enabling extended illumination volume while maintaining focused detection capability through the waveguide's light-confining properties
2Device complexity
If scattered light is used for particle detection, then the measurement method is simple, but the signal-to-noise ratio is low due to light scattering on cell walls and background interference
Solution Approach 1:
The light-guiding function is extracted from the bulk medium and concentrated into a defined core-cladding waveguide structure, confining light to specific paths that minimize interaction with cell walls and reduce background scattering
Solution Approach 2:
Different regions of the measuring cell have different optical properties: the core provides high light intensity for scattering detection, while the cladding region with smaller refractive index minimizes background interference, creating optimal local conditions for signal detection
3Measurement precision
If the excitation laser is focused on a finite area for nanoparticle tracking analysis, then the spot size is on the order of magnitude of the wavelength, but measurements are time-limited as particles pass through the excitation region
Solution Approach 1:
The waveguide provides continuous light delivery along its length, allowing particles to be tracked over an extended path rather than passing through a limited focal spot, thereby extending the detection period while maintaining spatial resolution
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
This configuration enables the detection of small particles with improved signal-to-noise ratios, prolonged detection periods, and the ability to track particles in real-time, reducing the need for complex equipment and sample preparation, while maintaining high radiation energy penetration for effective analysis.
Implementation Method 1
The core has a refractive index difference from the cladding to guide light effectively through total reflection
Data Source
AI summary
A measuring cell includes a cavity for receiving a test sample to be used in a particle detection apparatus. The measuring cell is configured as an optical waveguide for guiding a light beam. The waveguide has a core which has a refractive index nK, extends along a longitudinal axis of the waveguide, has a cross-sectional area AK of less than 80 μm2 in a cross section perpendicular to the longitudinal axis, and which is surrounded by a cladding having a smaller refractive index than nK. The cavity forms a channel. The channel extends along the longitudinal axis, is formed inside of or in contact with the core, and has at least one open end with an opening area AH of less than 0.2 μm2.