BioFET Isolated Gate Electrode Debye Screening Reduction
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Solution Overview
Problem
Existing lab-on-chip bioFETs face challenges due to the inherent concentration of ions at the interface between the solution and the sensing layer, leading to Debye screening, high electric fields, and pH corruption, which hinder accurate measurements.
Innovation Solution
The introduction of an isolated electrode that applies an electric field along the interface between the sensing layer and the fluid, reducing or eliminating excess ion concentration and creating a more physiological environment for sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If bioFET sensing is performed in high ionic strength solutions, then the sensor can detect biomolecules in physiological conditions, but Debye screening reduces the sensing range and detection sensitivity
Solution Approach 1:
The patent applies different electric field strengths at different locations: a strong electric field is applied locally at the sensing interface to compress the Debye layer and eliminate screening effects, while the bulk solution maintains physiological ionic strength. This local field application resolves the contradiction by creating a favorable sensing environment only where needed, preserving physiological compatibility in the bulk while achieving high sensitivity at the interface.
Solution Approach 2:
The patent dynamically changes the electric field parameter at the sensing interface by applying a controlled voltage to the gate electrode. This parameter change compresses the Debye layer thickness and modifies the ion distribution, allowing the system to transition between physiological compatibility and high-sensitivity detection modes, thereby resolving the contradiction between these two requirements.
2Device complexity
If the sensing layer interface is exposed to bulk solution, then the sensor structure is simple, but excess ion concentration at the interface corrupts pH and creates non-physiological conditions
Solution Approach 1:
The patent introduces a gate electrode as an intermediary element between the sensing layer and the solution. This intermediary applies a controlled electric field that modulates the ion concentration at the interface, acting as a mediator that prevents excess ions from corrupting the pH and creating non-physiological conditions, while maintaining the simple overall sensor structure.
3Ease of operation
If the Debye layer is allowed to form naturally at the interface, then the sensor operates passively, but the compressed Debye layer prohibits effective readout from the solution
Solution Approach 1:
The patent applies a preliminary electric field to the gate electrode before the actual sensing measurement is performed. This preliminary action compresses the Debye layer and creates a favorable electrostatic environment that enables effective readout, while the sensor itself remains relatively simple in operation. The preliminary field application prepares the interface for accurate measurement without complicating the overall device 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
This approach effectively increases the Debye screening length, reduces surface ion density and electric fields, and ensures pH homogeneity across the interface, thereby enhancing the accuracy and reliability of bioFET measurements.
Implementation Method 1
at least one isolated electrode which is isolated from the fluid, the isolated electrode is configured to apply an electric field along at least an interface between the sensing layer and the fluid that in turn reduces or eliminates excess ion concentration along the interface during sensing
Implementation Method 2
a sensing layer for producing an indicative signal... The sensing layer typically includes 'capturing molecules' that are selected to 'capture' specific molecules from the solution. The interaction with the solution modifies the electrostatics at the interface between the sensing layer and the solution
Implementation Method 3
a readout module that receives, amplifies, and outputs the indicative signal
Data Source
AI summary
In one aspect, the invention relates to an integrated circuit lab-on-chip bio-sensor, comprising: (a) a fluid compartment configured to receive a fluid; (b) a sensing layer at the bottom of the fluid compartment, the sensing layer has a top surface comprising molecules that are sensitive to target molecules of the fluid; (c) a readout structure in communication with the sensing layer, the readout circuit is configured to output a signal which is proportional to a sensing of target molecules by the sensing layer; and (d) at least one isolated electrode which is isolated from the fluid, the isolated electrode is configured to apply an electric field along at least an interface between the sensing layer and the fluid that in turn reduces or eliminates excess ion concentration along the interface during sensing.