ISFET pH Sensor with Dual Dielectric Thicknesses
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Ion-sensitive field-effect transistors (ISFETs) face irreversible deterioration due to ion adsorption, leading to drift in source-drain current and requiring frequent recalibrations for accurate pH measurements.
Innovation Solution
A pH sensor system comprising two ISFETs with different dielectric layer thicknesses, where both ISFETs share the same chamber and measurement circuit, allowing for simultaneous resistance measurements to account for dielectric layer degradation and eliminate unknown parameters, thereby reducing the need for repetitive calibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ISFETs are used for pH measurement, then measurement precision is improved, but reliability deteriorates due to dielectric layer deterioration and drift
Solution Approach 1:
The patent changes the dielectric layer thickness parameter to create ISFETs with different sensitivities to dielectric deterioration. By having ISFETs with varying thicknesses (e.g., 5nm, 10nm, 15nm), the system can monitor drift effects and compensate for them mathematically, maintaining both measurement precision and reliability over time
Solution Approach 2:
The patent implements a feedback mechanism where the responses of multiple ISFETs are continuously monitored and compared. The system detects drift in the dielectric layer through the differential responses of ISFETs with different thicknesses and automatically compensates by adjusting measurement parameters or applying correction algorithms, thus maintaining reliable pH measurements
2Adaptability or versatility
If ISFETs operate in electrolyte solution, then pH measurement function is achieved, but dielectric layer deteriorates due to ion adsorption
Solution Approach 1:
The patent varies the dielectric layer thickness parameter across multiple ISFETs to create a gradient of resistance to ion adsorption. Thinner layers provide higher initial sensitivity while thicker layers offer better protection, allowing the system to compensate for degradation effects and maintain long-term sensing capability
Solution Approach 2:
The patent employs a composite structure of multiple ISFETs with different dielectric layer configurations, effectively creating a diversified sensor array that combines the advantages of different thickness profiles. This composite approach allows the system to withstand ion adsorption damage while maintaining pH sensing functionality
3Reliability
If dielectric layer thickness is increased, then resistance to ion adsorption is improved, but pH sensitivity decreases
Solution Approach 1:
The patent systematically varies the dielectric layer thickness parameter across multiple ISFETs, creating a spectrum of sensitivity and durability characteristics. By analyzing the differential responses of ISFETs with different thicknesses, the system can mathematically separate the effects of pH changes from dielectric deterioration, maintaining both sensitivity and reliability
4Reliability
If multiple ISFETs with different dielectric thicknesses are used, then drift compensation is achieved, but device complexity increases
Solution Approach 1:
The patent divides the sensing function across multiple ISFETs with different dielectric layer thicknesses, segmenting the measurement task to capture different aspects of the pH environment. This segmentation allows the system to differentiate between actual pH changes and dielectric drift effects, achieving compensation while maintaining manageable device complexity through modular architecture
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 stabilizes pH measurements by accounting for dielectric layer degradation and surface contamination, enhancing the accuracy and reliability of ISFETs without the need for continuous recalibration.
Implementation Method 1
ISFETs transduce the acidity by the capacitance effect measuring hydrogen ions adsorbed on a sensitive dielectric layer able to trap the protons from the electrolyte solution depending on its bulk concentration
Implementation Method 2
measuring hydrogen ions adsorbed on a sensitive dielectric layer able to trap the protons from the electrolyte solution
Implementation Method 3
A reference electrode in contact with the analyte solution is used to determine the potential of the analyte solution
Data Source
AI summary
A pH sensor comprises: a chamber for receiving an electrolyte solution; a first and a second ion-sensitive field effect transistor (ISFETs), each of the first and second ISFETs having a source terminal, a drain terminal and a transistor channel extending between the source terminal and the drain terminal, a dielectric layer with a sensing surface arranged in the chamber so as to be contactable by the electrolyte solution, the dielectric layer separating the sensing surface from the transistor channel; a first measurement circuit configured to measure a first source-drain resistance across the transistor channel of the first ISFET; and a second measurement circuit configured to measure a second source-drain resistance across the transistor channel of the second ISFET. The first and second measurement circuits include a common reference electrode, the reference electrode arranged contactable by the electrolyte solution in the chamber. The dielectric layer of first ISFET has a first thickness and the dielectric layer of the second ISFET has a second thickness different from the first thickness.