Sawtooth Prism Substrate for TIR Analyte Detection
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Solution Overview
Problem
Existing methods for determining analytes in samples using arrays of capture elements on substrates face challenges in minimizing diffraction effects and maintaining beam polarization, especially when using total internal reflection (TIR) for imaging binding events.
Innovation Solution
A substrate with a sawtooth-shaped bottom surface, featuring prisms with non-parallel outer planes, is used to direct light and minimize diffraction effects, ensuring that the light enters and exits the prism film without significant polarization changes, allowing for effective imaging of binding events between ligands and analytes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a diffraction grating is used to direct light, then light can be split into several beams based on wavelength, but diffraction effects cause significant beam divergence and polarization changes
Solution Approach 1:
The substrate bottom surface is segmented into multiple discrete prisms arranged in an array, where each prism independently directs light at a specific angle. This segmentation allows precise control of light direction without the diffraction effects that occur in continuous grating structures.
Solution Approach 2:
The prisms are designed with asymmetric sawtooth cross-sectional shapes, where the inclined surfaces are at specific non-symmetric angles to the substrate surface. This asymmetric geometry enables the prisms to redirect light at precise angles while maintaining beam integrity and minimizing polarization changes.
2Length of moving object
If the substrate is made thin to reduce overall device size, then device compactness is improved, but beam divergence increases and polarization effects are enhanced
Solution Approach 1:
The prism dimensions are optimized with specific parameter ranges: prism height between 1-10 micrometers, base width between 5-50 micrometers, and inclined surface angles between 30-60 degrees. These parameter changes enable effective light direction control in thin substrates while minimizing beam divergence and polarization effects.
3Illumination intensity
If the incident beam is directed at a steep angle to achieve total internal reflection, then evanescent field generation is improved, but beam divergence increases
Solution Approach 1:
The prisms act as intermediary optical elements between the incident beam and the substrate top surface. They transform the incident beam angle into the optimal angle for total internal reflection and evanescent field generation, while the prism geometry itself controls and limits beam divergence throughout the process.
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 precise imaging of binding events with reduced diffraction and minimal polarization effects, enhancing the sensitivity and accuracy of analyte detection by up to five orders of magnitude, while maintaining the polarization state of the light beam.
Implementation Method 1
The beam is directed at an angle to obtain total internal reflection (TIR) and to generate an evanescent field in the plane of the array
Implementation Method 2
The beam is directed at an angle to obtain total internal reflection (TIR) and to generate an evanescent field in the plane of the array
Implementation Method 3
The beam is directed at an angle to obtain total internal reflection (TIR) and to generate an evanescent field in the plane of the array
Data Source
AI summary
In one embodiment, an apparatus is provided for testing for the presence of analytes in a sample. The apparatus comprises a source of light directed at the bottom surface of a substrate to achieve total internal reflection and to generate an evanescent field. An array of capture elements is immobilized on the top surface of the substrate. The bottom surface of the substrate is configured as a sawtooth (in cross section), the “teeth” aligned with the rows or the columns in the array. The outer faces of the sawtooth “prisms” are non-parallel to the substrate top surface, and specific requirements are imposed on the prism light-entrance face, and the substrate thickness and refractive index.