Planar Waveguide Biosensor Using Evanescent Field Diffraction
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Solution Overview
Problem
Existing biosensors for detecting binding affinities face challenges such as reliance on fluorescent labels, which are costly, cause steric hindrance, and result in photobleaching and quenching effects, leading to inaccurate results and increased complexity.
Innovation Solution
A device with a planar waveguide and optical couplers that uses an evanescent field to diffract light from target samples bound to binding sites, allowing label-free detection and improved sensitivity through constructive interference, enabling the analysis of binding characteristics without the need for labels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fluorescent labels are used for detecting binding affinities, then the detection signal can be generated, but the labels cause steric hindrance, photobleaching, and quenching effects that falsify results
Solution Approach 1:
The invention extracts and eliminates the fluorescent label component from the detection system. Instead of using labeled target samples, the patent employs label-free detection where the target molecules themselves serve as the detection对象. The evanescent field directly interacts with the bound target molecules to generate diffraction signals, removing the harmful effects of labels while maintaining detection capability.
Solution Approach 2:
The invention replaces the optical fluorescence detection mechanism with a diffraction-based detection mechanism. Instead of detecting fluorescent emission, the system detects changes in the diffraction pattern of the evanescent field caused by bound target molecules. This substitution eliminates photobleaching and quenching effects while providing stable, long-term detection capability.
2Measurement precision
If fluorescent labels are used to detect binding affinities, then binding events can be detected, but the labels increase cost and require additional working steps
Solution Approach 1:
The invention removes the labeling step entirely from the workflow. Target molecules are detected in their native state without requiring attachment of fluorescent tags. This simplification reduces both the complexity of sample preparation and the overall cost of the assay while maintaining the ability to detect binding events.
Solution Approach 2:
The target molecules themselves serve as the detection element without requiring external labels. The bound target molecules directly modulate the evanescent field to produce detectable diffraction signals, making the system self-sufficient and eliminating the need for additional labeling reagents and steps.
3Measurement precision
If fluorescent labels are attached to target samples, then binding can be detected, but the labels reduce sensitivity due to background noise and signal loss
Solution Approach 1:
The invention replaces fluorescence emission detection with diffraction pattern detection. The evanescent field diffracts off bound target molecules, creating interference patterns that are detected and analyzed. This mechanism provides superior signal stability without photobleaching and reduces background noise, thereby improving both sensitivity and reliability of binding detection.
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 approach enables sensitive, label-free detection of binding affinities with reduced background noise and increased accuracy, allowing for the analysis of various types of molecules and proteins, including those with dynamic binding processes, without the limitations of traditional fluorescent labeling techniques.
Implementation Method 1
coherent light propagates through the planar waveguide under total reflection with an evanescent field of the coherent light propagating along the outer surface of the planar waveguide
Implementation Method 2
light of the evanescent field is diffracted by target samples bound to the binding sites
Implementation Method 3
an optical coupler for coupling coherent light of a predetermined wavelength into the planar waveguide
Implementation Method 4
such as to interfere at a predetermined detection location with a difference in optical path length which is an integer multiple of the predetermined wavelength
Data Source
AI summary
A device for use in the detection of binding affinities, the device comprising a planar waveguide (2) arranged on a substrate (3), and further comprising an optical coupler (41) having a predetermined length for coupling coherent light (1) of a predetermined wavelength into the planar waveguide (2) such that a parallel beam of coherent light propagates through the planar waveguide (2) with an evanescent field (11) of the coherent light propagating along an outer surface (21) of the planar waveguide (2). The outer surface (21) of the planar waveguide (2) comprises binding sites thereon capable of binding target samples to the binding sites such that light of the evanescent field (11) is diffracted by target samples bound to the binding sites. The binding sites are arranged along a plurality of predetermined straight lines (7) running parallel to one another with a constant distance between adjacent straight lines.