Planar Waveguide Biosensor Diffractive Detection
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Solution Overview
Problem
Current biosensor techniques for detecting binding affinities, such as those using fluorescent labels, face issues like costly labeling, steric hindrance, photo-bleaching, and quenching effects, as well as constructional limitations due to precise detector positioning requirements.
Innovation Solution
A device comprising a leakproof planar waveguide with a grating and decoupler structure, where receptor molecules are arranged along straight parallel lines, allowing for the detection of diffracted coherent light at a greater distance, reducing the dependency on detector positioning accuracy and enabling easier construction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fluorescent labels are used to detect binding affinities, then the binding events can be detected, but the detected signal is produced by the labels rather than the binding partners themselves, requiring additional preparation steps and incurring higher costs
Solution Approach 1:
The patent extracts and removes the fluorescent labeling step from the detection process. Instead of using labeled target samples, the invention detects the binding event through the refractive index change caused by the binding partners themselves, eliminating the need for labeling preparation while maintaining detection capability
Solution Approach 2:
The patent introduces an intermediary mechanism - the evanescent field and refractive index change - to detect binding events. The evanescent field interacts with the bound molecules to produce a detectable signal without requiring direct labeling of the target samples, thus avoiding the complexity of labeling while preserving detection accuracy
2Measurement precision
If fluorescent labels are attached to target samples, then binding can be detected, but steric hindrance occurs which interferes with the binding of target samples to capture molecules
Solution Approach 1:
The patent removes the fluorescent label from the target sample structure. Detection is achieved by measuring the refractive index change of the target sample itself when bound to the capture molecule, eliminating steric hindrance and ensuring that binding accuracy is not compromised by the presence of labels
3Measurement precision
If fluorescent labels are used for detection, then binding events can be visualized, but photo-bleaching and quenching effects occur which falsify the results
Solution Approach 1:
The patent replaces the fragile fluorescent label (which undergoes photo-bleaching and quenching) with a robust, label-free detection approach. The target sample itself serves as the signal source through its refractive index, providing a stable and reliable signal that does not degrade over time or under illumination
Solution Approach 2:
The evanescent field acts as an intermediary that converts the physical presence of bound molecules into a detectable optical signal without requiring fluorescent labels. This intermediary mechanism produces a stable signal based on refractive index changes, eliminating photo-bleaching and quenching effects while maintaining detection sensitivity
4Measurement precision
If a planar waveguide with grating is used to couple coherent light, then binding affinities can be detected, but the detector must be positioned at a very close distance with high precision (around 1 micrometer)
Solution Approach 1:
The patent transitions from a two-dimensional microarray detection approach to a three-dimensional detection geometry using the evanescent field. The evanescent field extends perpendicular to the waveguide surface, allowing detection in the depth dimension and enabling the use of curved line arrangements that focus diffracted light to a point, thereby reducing the stringent lateral positioning requirements
5Measurement precision
If curved lines are used to arrange capture molecules, then diffracted coherent light can be focused to a point for detection, but the detector positioning still requires very high accuracy
Solution Approach 1:
The patent employs curved lines arranged in the depth dimension (perpendicular to the waveguide surface) rather than only in the lateral plane. This three-dimensional arrangement of capture molecules along curved paths in the evanescent field enables focusing of diffracted light to a detection point, reducing the lateral positioning tolerance to around 1 micrometer while maintaining effective signal 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
This approach allows for more flexible and cost-effective detection of binding affinities with improved signal reliability and reduced interference, enabling the simultaneous detection of multiple binding events at a distance from the waveguide.
Implementation Method 1
The 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
The depth of penetration of the evanescent field into the medium of lower refractive index at the outer surface of the planar waveguide is in the order of magnitude of a fraction of the wavelength of the coherent light propagating through the planar waveguide
Implementation Method 3
light of the evanescent field is diffracted by target samples bound to the binding sites. The binding sites are arranged along a plurality of straight parallel lines which are spaced from each other such that a portion of the light of the evanescent field is diffracted by target samples bound to the binding sites and forms a collimated beam of diffracted coherent light propagating away from the planar waveguide
Data Source
AI summary
A device for use in the detection of binding affinities comprises a substrate, a planar waveguide arranged thereon and having an outer surface. The device further comprises a grating for coupling coherent light of a predetermined wavelength into the planar waveguide such that the coherent light coupled into the planar waveguide propagates through the planar waveguide in a predetermined propagation direction. An evanescent field of the coherent light propagates along the outer surface of the planar waveguide. The outer surface of the planar waveguide has receptor molecules arranged thereon capable of binding target samples to the receptor molecules such that light of the evanescent field is diffracted by the target samples bound to the receptor molecules. The receptor molecules are arranged along a plurality of straight parallel lines such that a portion of the light of the evanescent field is diffracted by the target samples bound to the receptor molecules.