Dual-Gate ISFET Biosensor Eliminates Reference Electrode
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing biosensors, such as ion-sensitive field-effect transistors (ISFETs), face challenges with stability and miniaturization, requiring frequent recalibration and maintenance due to variations in reference electrode potential caused by oxidation-reduction reactions, especially in smaller sizes.
Innovation Solution
A dual-gate ion-sensitive field-effect transistor (ISFET) design with physically independent front and back gates, where the front gate is in contact with the solution, allowing for electrostatic coupling to sense analytes without an external reference electrode, enabling stable and miniaturized operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a reference electrode is used in ISFETs to maintain stable potential, then measurement accuracy is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent extracts and removes the reference electrode from the ISFET structure, replacing it with a solid-state reference layer integrated into the gate stack. This eliminates the need for separate reference electrodes while maintaining stable potential through the use of a reference metal layer (such as silver or gold) that provides a stable electrochemical potential without requiring bulky external reference electrode components.
Solution Approach 2:
The patent merges the reference electrode function with the gate structure by integrating a reference metal layer directly into the gate stack. This combination allows the gate to serve dual purposes: as the control electrode for the transistor channel and as the stable potential reference, thereby reducing device complexity while maintaining measurement accuracy.
2Measurement precision
If a reference electrode is used in ISFETs to maintain stable potential, then measurement accuracy is improved, but manufacturing cost increases
Solution Approach 1:
The patent removes the expensive and complex reference electrode component from the device, replacing it with a simple solid-state reference layer that can be deposited directly during the gate fabrication process. This eliminates the need for separate reference electrode assembly, significantly reducing manufacturing cost while maintaining stable potential for accurate measurements.
Solution Approach 2:
The patent uses inexpensive reference metal layers (such as silver or gold) that can be deposited directly on the gate dielectric during standard semiconductor fabrication processes. These thin metal layers provide stable reference potential at very low cost compared to bulky reference electrodes, making the sensor economically viable for mass production.
3Stability of the object's composition
If reference electrode potential is stabilized through redox reactions, then measurement stability is improved, but device size increases
Solution Approach 1:
The patent extracts the bulky reference electrode assembly and replaces it with a thin solid-state reference layer integrated into the gate stack. This eliminates the need for large-volume reference electrode structures while maintaining stable potential through the use of reference metals that provide stable electrochemical potential in a compact form factor.
Solution Approach 2:
The patent uses thin film reference metal layers (such as silver or gold) deposited directly on the gate dielectric to provide stable reference potential in a space-efficient manner. These thin films maintain measurement stability without requiring the bulky structures needed for traditional reference electrodes, enabling miniaturization of the overall device.
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 provides a stable, low-cost biosensor that does not require frequent calibration, allowing for accurate concentration measurements of charged molecules without the need for a separate reference electrode, facilitating miniaturization and cost-effective mass production.
Implementation Method 1
the front gate is in contact with the solution, allowing for electrostatic coupling to sense analyte concentrations
Implementation Method 2
Ions or charged molecules or analytes in the solution generate a surface potential at the solution—gate dielectric interface
Implementation Method 3
adsorbed charged molecules produce a surface potential φ0 on the gate oxide resulting in a threshold voltage Vth change of the ISFET
Implementation Method 4
it can modify the gate potential and contribute to the electrostatic control of the transistor channel thus affecting the source to drain current to be sensed
Data Source
AI summary
A biosensor includes a source element; a drain element; a semiconductor channel element between the source element and the drain element for forming an electrically conductive channel with adjustable conductivity between the source and drain elements; a first gate element configured to be electrically biased to set a given operational regime of the sensor with given electrical conductivity of the channel; and a second gate element, physically separate from the first gate element, configured to contact a solution comprising analytes allowed to interact with a gate contact surface of the second gate element to generate a surface potential change dependent on the concentration of the analytes in the solution. The channel element is substantially fully depleted allowing the first and second gate elements to be electrostatically coupled such that the surface potential change at the second gate element is configured to modify the electrical conductivity of the channel.