FET Sensing Cell Noise Cancellation via Reference Device
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Solution Overview
Problem
Current FET sensing cells face challenges in achieving high sensitivity and specificity for detecting ions, biomolecules, and bio-entities, particularly in distinguishing between subtle changes in bio-entities and noise signals.
Innovation Solution
The development of FET sensing cells, such as ISFETs and BioFETs, which incorporate a bio-compatible layer with immobilized probe molecules as receptors, and a method involving the use of CMOS processes to form a fluidic gate region and sensing film, allowing for conductance modulation upon target binding, with electrodes positioned close to the sensing film to enhance signal-to-noise ratio and sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If FET sensing cells are used for detecting ions and biomolecules, then detection capability is provided, but sensitivity and specificity are insufficient for distinguishing subtle changes from noise signals
Solution Approach 1:
The patent introduces a reference FET device as an intermediary element that experiences the same noise signals as the sensing FET but does not interact with target analytes. By measuring the reference device's output and subtracting it from the sensing device's output, noise signals are canceled out, thereby improving detection sensitivity and specificity without compromising the sensing capability.
2Measurement precision
If conventional FET sensing structures are used, then device simplicity is maintained, but detection precision is limited
Solution Approach 1:
The patent divides the sensing system into two separate but identical FET devices: a sensing FET for detecting target analytes and a reference FET for capturing noise signals. This segmentation allows each device to be optimized for its specific function while maintaining overall system simplicity through identical structural design, thereby improving detection precision without significantly increasing device complexity.
3Measurement precision
If signal detection is performed without noise reduction, then measurement speed is maintained, but measurement precision deteriorates
Solution Approach 1:
The patent implements preliminary noise characterization by continuously monitoring the reference FET device's output signal. This pre-measured noise profile is then subtracted from the sensing FET's output in real-time, enabling noise reduction without adding significant processing time. The preliminary action of establishing a noise baseline allows for rapid, accurate signal interpretation.
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 enables improved detection sensitivity and specificity by modulating drain current in response to target binding, allowing for precise identification of ions, biomolecules, and bio-entities, even at low concentrations, through enhanced signal timing and noise reduction.
Implementation Method 1
a sensing film over the channel region... modulating drain current in response to target binding
Implementation Method 2
FET sensing cells operate on the basis of at least one of electronic, electrochemical, optical, or mechanical detection principles
Data Source
AI summary
The present disclosure provides a device, such as a FET sensing cell, which includes a first dielectric layer over a substrate, an active layer over the first dielectric layer, a source region in the active layer, a drain region in the active layer, a channel region in the active layer situated between the source region and the drain region, a sensing film over the channel region, a second dielectric layer over the active layer, wherein an opening is formed in the second dielectric layer and the sensing film is located within the opening, a first electrode located within the second dielectric layer and a fluidic gate region located over the second dielectric layer and extending into the opening. The present disclosure also provides a method for improving the sensitivity of a device by adjusting a sensing value.