Liquid-Core Waveguide Detection for Wall-Near Biomolecules
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Solution Overview
Problem
Existing optical detection methods for biological samples using solid waveguides and fluid-filled microchannels are inefficient and fail to detect particles near channel walls, particularly those labeled with single or few fluorescent dyes, due to leaky-mode waveguiding principles and refractive index mismatches.
Innovation Solution
Employing a liquid-core waveguide with a higher refractive index than the cladding, allowing a non-zero field strength at the interface, enabling efficient excitation and detection of particles near the channel walls using total internal reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If ARROW or Bragg waveguides are used to confine light in low-index materials, then light propagation loss is reduced, but detection sensitivity for particles near channel walls deteriorates because the field is zero at the interfaces
Solution Approach 1:
The patent inverts the conventional waveguide design by using a high-index liquid core instead of a low-index solid core. This reversal changes the refractive index profile from n_core < n_cladding to n_core > n_cladding, enabling the optical mode to have non-zero field strength at the liquid-core/cladding interfaces, thereby allowing efficient detection of particles near the channel walls while maintaining low propagation loss through total internal reflection
2Ease of operation
If surface-based excitation/detection using evanescent fields is used, then target binding to surface is enabled, but detection efficiency deteriorates and dynamic range is limited
Solution Approach 1:
The patent employs a liquid-core waveguide design where the sample flows through a liquid-filled microchannel surrounded by optical cladding. This hydraulic approach allows targets to remain in solution phase rather than requiring surface binding, enabling excitation and detection of fluorescently labeled targets throughout the entire liquid volume, thereby dramatically increasing detection efficiency and dynamic range while maintaining ease of operation for sample introduction
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
Enhances detection efficiency by ensuring particles near the channel walls are detectable, improving signal-to-noise ratio and reducing loss, thus overcoming limitations of previous methods.
Implementation Method 1
allowing a non-zero field strength at the interface, enabling efficient excitation and detection of particles near the channel walls using total internal reflection
Implementation Method 2
a liquid-core waveguide with a higher refractive index than the cladding, allowing a non-zero field strength at the interface
Data Source
Figure 1A~2B
Figure 3A
Figure 3B
AI summary
Disclosed herein are systems, methods, and techniques for optical detection of analytes (e.g., biomarkers or other objects) using a liquid-core waveguide in which the analytes are suspended in a high-index liquid inside a liquid channel of the waveguide. The term "high-index" may indicate a refractive core index of the carrier liquid that is higher than or equal to that of one or more surrounding cladding layer(s) (e.g., ethylene glycol liquid inside a glass channel). In some embodiments, a method includes illuminating, by a light-source, one or more particles in a liquid-core waveguide, wherein the liquid-core waveguide comprises a first cladding layer having a first index of a refraction, and a hollow core comprising a liquid inside the hollow core, wherein the liquid has a second index of refraction higher than the first index of refraction; and detecting, by a detector, light emitted from the one or more particles.