Dual-Gate Electrochemical Sensor for Drift Reduction
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Solution Overview
Problem
Field effect transistor (FET) based sensors, such as EGFETs, face challenges with low analyte concentrations leading to insufficient potential difference across the measurement and reference electrodes, causing sensor drift and corrosion due to bias voltage application, which affects predictability and accuracy.
Innovation Solution
An electrochemical sensor with a dual-gate stack structure, where the sensing gate is capacitively coupled to a bias gate and the substrate, providing galvanic isolation and independent biasing, along with reset transistors for dynamic sensitivity tuning and reduced charge leakage, allowing for accurate measurement without unwanted chemical reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a bias voltage is applied to lower the threshold voltage of the FET, then the sensor can detect low concentrations of chemical compounds, but unwanted electrical current flows through the analyte causing chemical reactions that result in sensor drift and electrode corrosion
Solution Approach 1:
The gate electrode is segmented into a sensing gate (conductively coupled to the measurement electrode) and a bias gate (capacitively coupled to the sensing gate), allowing independent control of detection and biasing functions
Solution Approach 2:
A dielectric layer is introduced as an intermediary between the bias gate and the sensing gate, enabling capacitive coupling that transfers voltage signals while blocking direct current flow that would cause harmful chemical reactions
2Reliability
If the gate electrode is separated from the analyte to prevent chemical reactions, then the FET is protected from damage, but the potential difference caused by the analyte may not exceed the threshold voltage
Solution Approach 1:
The gate structure is divided into sensing and bias gates with different coupling methods to the analyte, enabling simultaneous protection and detection
Solution Approach 2:
The threshold voltage of the FET is dynamically adjusted by applying bias voltage to the bias gate, allowing the sensor to detect low concentration analytes that would otherwise produce insufficient potential difference
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 solution enhances the sensitivity and accuracy of the sensor by maintaining a net zero potential difference, reducing sensor drift, and preventing chemical reactions, while maintaining a compact integrated circuit design.
Implementation Method 1
the sensing gate is capacitively coupled to a bias gate
Implementation Method 2
By capacitive coupling the invention provides galvanic isolation of the sensing electrode from the bias gate
Data Source
AI summary
The invention relates to an electrochemical sensor integrated on a substrate, the electrochemical sensor including: a field effect transistor integrated on the substrate and having a source, gate and drain connections, said gate of the field effect transistor including: a sensing gate conductively coupled to a sensing electrode; and a bias gate, wherein the sensing gate is capacitively coupled to the bias gate and the bias gate is capacitively coupled to the substrate.