Self-Mixing Interferometry for Sensitive Lateral Flow Absorption Detection

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Solution Overview

Problem

Existing methods for detecting analytes in lateral flow testing are limited by inefficiencies in sensitivity, cost, speed, reproducibility, and automation, particularly in determining absorption and color changes.

Innovation Solution

Applying self-mixing interferometry (SMI) to detect absorption and color changes by illuminating a substance with light from a resonant-cavity light source, coupling back the interacting light into the source, and monitoring measurement signals such as intensity, amplitude, and phase to determine absorption and color intensity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If visual detection methods are used for analyte detection in lateral flow testing, then the device complexity is low, but the measurement precision and sensitivity are insufficient

Engineering Contradiction:

Improvedetection sensitivityVSAvoiddetection system complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces visual detection methods with self-mixing interferometry, an optical measurement technique. The system uses a light source to illuminate the test area and detects absorption changes through interferometric measurement of reflected light, substituting subjective visual assessment with objective optical measurement to improve precision and sensitivity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces an optical measurement system as an intermediary between the analyte-marker complex and the detector. The self-mixing interferometry setup acts as a mediator that converts absorption changes into measurable optical signal variations, enabling precise quantification without direct visual observation.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If automated detection systems are implemented, then the productivity and reproducibility improve, but the device complexity and cost increase

Engineering Contradiction:

Improvedetection speedVSAvoidsystem complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent employs self-mixing interferometry where the detected light is fed back into the light source cavity, creating a self-regulating measurement system. The system automatically measures absorption changes without requiring manual intervention for calibration or reading, enabling automated high-throughput detection while maintaining relatively simple device architecture.

Inventive Principle:

Principle #25Self-service

3Productivity

If multiple analytes are detected simultaneously in small spots, then the productivity increases, but the measurement precision may deteriorate due to signal weakness

Engineering Contradiction:

Improvemulti-analyte detection capabilityVSAvoidsignal detection accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent divides the detection process into separate measurement channels, each dedicated to detecting a specific analyte in a defined test area. The self-mixing interferometry system can be configured with multiple light sources or detection zones to independently measure absorption changes at different locations on the lateral flow strip, enabling simultaneous multi-analyte detection while maintaining precision through dedicated measurement paths.

Inventive Principle:

Principle #1Segmentation

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

Enables high-sensitivity, cost-effective, fast, and reproducible detection of substances in an automated fashion, allowing simultaneous detection of multiple analytes in small spots with energy efficiency.

Implementation Method 1

The reflected light interacts and in particular interferes with the light inside the light source, more particularly inside the cavity

Methodology Applied

Scientific EffectSelf-mixing interferometry: Interference

Implementation Method 2

illuminating a substance with light emitted from a light source, letting the light interact with the substance

Methodology Applied

Scientific EffectLight absorption: Absorption (EM radiation)

Data Source

PatentUS12584914B2Self-mixing interferometry for absorption or color detection and application in lateral flow testing

Publication Date: 2026.03.24 AUSTRIAMICROSYSTEMS AG

AI summary

It is proposed to use self-mixing interferometry for determining an absorption. The monitoring device for use in lateral flow testing for detecting presence or amount of an analyte in a liquid includes a housing, the housing including a carrier holder for holding a carrier for transport of the liquid; at least a first light source which is a resonant-cavity light source having a cavity; and an evaluation unit, operationally connected to at least the first light source for detecting a measurement signal. The first light source is structured and arranged to illuminate with light a test range in a test area of a carrier held in the carrier holder; and to couple back into the cavity of the first light source a portion of the light coming back from the test range.