Dual Gate ISFET Dynamic Biasing for Sensitivity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing ion sensitive field effect transistors (ISFETs) suffer from limited sensitivity, which hampers their commercialization and ability to detect small amounts of biomolecules, requiring extended sensing times or failing to make detections.
Innovation Solution
A dual gate ISFET configuration with dynamically controlled back and control gate voltages, where the control gate voltage is inversely polarized and proportional in magnitude to the back gate voltage, enhancing sensitivity through dynamic biasing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional ISFET configuration is used, then device simplicity is maintained, but sensitivity is limited
Solution Approach 1:
The gate function is segmented into two independent gates: a control gate for applying external voltage and a sensing gate for detecting ion concentrations. This segmentation allows each gate to perform its specific function optimally, with the control gate enabling dynamic biasing to enhance sensitivity and the sensing gate maintaining contact with the test liquid for accurate measurement.
Solution Approach 2:
The invention transitions from a single-gate two-dimensional structure to a dual-gate three-dimensional structure. The addition of the back gate (sensing gate) dimension allows for independent control of the channel, enabling dynamic adjustment of the electric field to amplify sensitivity while maintaining device functionality.
2Measurement precision
If single gate configuration is used, then manufacturing is simpler, but detection precision for small charge levels is insufficient
Solution Approach 1:
The gate is divided into two separate gates with distinct functions: the front gate for sensing and the back gate for control. This segmentation enables independent optimization of each gate's role, allowing the back gate to provide dynamic biasing that enhances detection precision while the front gate maintains simplicity in contact with the test liquid.
Solution Approach 2:
The dual-gate structure provides multi-functionality where the front gate serves as the sensing interface and the back gate serves as the control mechanism. This multi-functionality allows a single device to achieve both high detection precision and simplified operation by separating sensing and control functions into different gates.
3Measurement precision
If static biasing is applied, then device operation is simpler, but sensitivity enhancement is limited
Solution Approach 1:
The back gate is configured to receive a dynamically varying voltage rather than a static bias. This dynamic biasing allows the electric field in the channel to be modulated in real-time, enhancing the sensitivity of the ISFET to ion concentration changes in the test liquid while maintaining ease of operation through automated voltage control.
Solution Approach 2:
The invention changes the voltage parameter at the back gate from a fixed static value to a dynamically varying parameter. This parameter change enables the device to adapt its sensitivity dynamically, optimizing detection capability for different ion concentration levels while the control system manages the complexity of dynamic operation.
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 dual gate configuration achieves a fivefold increase in sensitivity, enabling detection of smaller charge levels and improving the device's ability to function in applications requiring high sensitivity, such as protein sensing and DNA hybridization.
Implementation Method 1
ion sensitive field effect transistor (ISFET) having higher sensitivity in response to dynamic biasing
Implementation Method 2
the drain current of the ISFET is modulated by the ion content of the test liquid
Data Source
AI summary
A dual gate ion sensitive field effect transistor (ISFET) includes a first bias voltage node coupled to a back gate of the ISFET and a second bias voltage node coupled to a control gate of the ISFET. A bias voltage generator circuit is configured to generate a back gate voltage having a first magnitude and a first polarity for application to the first bias voltage node. The bias voltage generator circuit is further configured to generate a control gate voltage having a second magnitude and a second polarity for application to the second bias voltage node. The second polarity is opposite the first polarity.