ISFET Biosensor Strip for Quantitative Low-Concentration Detection
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Solution Overview
Problem
Lateral flow immunoassays (LFAs) suffer from low sensitivity, subjective interpretation, and require expensive equipment for quantitative results, especially when testing low concentrations of virus proteins or antigens, limiting their use in home or point-of-care settings.
Innovation Solution
An ISFET biosensor device with a porous membrane and ion-sensitive field effect transistors (ISFETs) integrated into a capillary paper-based strip, allowing for quantitative detection of target molecules through electrochemical markers without the need for external pumps, providing accurate and portable results.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If lateral flow immunoassay (LFA) is used for testing, then the device is low cost, fast, and portable, but the sensitivity is low and it cannot detect low concentrations of analytes
Solution Approach 1:
The patent combines LFA with ISFET sensor technology, merging the simplicity and portability of LFA with the high sensitivity of electrochemical sensing. The ISFET sensor is integrated into the LFA strip to detect pH changes caused by analyte-antibody reactions, enabling quantitative detection while maintaining device simplicity
Solution Approach 2:
The patent introduces pH as an intermediary parameter to detect analyte concentration. Instead of directly detecting the analyte, the system uses pH changes in the test region as a mediator signal that correlates with analyte concentration, enabling sensitive detection through the ISFET sensor
2Measurement precision
If LFA is used for self-testing, then the device is simple to use, but the results are subjective and lack reproducibility due to visual interpretation
Solution Approach 1:
The patent replaces the visual/optical interpretation system with an electronic sensing system. Instead of relying on human eyes to interpret color changes, the ISFET sensor electronically measures pH changes and the controller processes this data to generate objective, quantifiable results that eliminate subjective interpretation
Solution Approach 2:
The patent implements a feedback system where the ISFET sensor continuously monitors pH changes in real-time as the sample flows through the strip. The controller processes this feedback signal to determine analyte concentration, providing objective and reproducible results that can be displayed to the user
3Measurement precision
If quantitative results are required, then measurement precision improves, but expensive readout equipment is needed at point of care
Solution Approach 1:
The patent extracts the readout function from external expensive equipment and integrates it directly into the biosensor device. The controller and interface module are built into the strip, eliminating the need for separate expensive readout devices at point-of-care settings
Solution Approach 2:
The patent makes the device self-sufficient by integrating all necessary components including the ISFET sensor, controller, and interface module into a single portable unit. The device performs self-diagnosis and self-readout, eliminating dependence on external expensive equipment while maintaining quantitative measurement capabilities
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
The ISFET biosensor enables quantitative detection of low-concentration analytes with high sensitivity and reproducibility, offering fast and reliable results suitable for home or point-of-care use, eliminating the need for expensive equipment.
Implementation Method 1
A sensor die has an ion sensing field effect transistor (ISFET) with an ion-sensitive gate element located in an active sensor surface of the sensor die
Implementation Method 2
A porous membrane with a test region that contains a test analyte
Data Source
AI summary
In described examples, a biosensor device has a porous membrane with a test region that contains a test analyte. A sensor die has an ion sensing field effect transistor (ISFET) with an ion sensitive gate element located in an active sensor surface of the sensor die. The active sensor surface is in contact with the porous membrane test region. A controller is coupled to the ISFET and an interface module is coupled to the controller to provide a human readable test result.