Nanostructure Field Effect Sensors with Modified Trap Density
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Solution Overview
Problem
Field effect transistors (FETs) used as single-molecule charge sensors face limitations in sensing zone due to Debye screening length, which reduces signal levels to the limit of detectability, especially at biologically relevant salt conditions, and buffer exchange is not feasible for real-time sensing.
Innovation Solution
Modifying the nanostructure channel of FETs by increasing trap state density through ion implantation, energetic beam irradiation, or plasma exposure, and linking enzymes or aptamers to the nanostructure to enhance the sensing zone's sensitivity, allowing for improved signal detection at biologically relevant salt conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If FETs are operated at biologically relevant salt conditions, then the sensing can be performed in physiological environments, but the Debye screening length limits the sensing zone to a few nanometers and reduces signal levels to the limit of detectability
Solution Approach 1:
The patent applies local quality by creating a modified portion of the nanostructure with increased trap state density specifically at the sensing zone where the active moiety is linked. This localized modification enhances the signal output at the critical sensing interface without affecting the entire nanostructure, thereby improving measurement precision while maintaining adaptability to biological environments.
Solution Approach 2:
The patent changes the physical parameter of trap state density in the nanostructure by modifying a portion of it through ion implantation, energetic beam irradiation, or plasma exposure. This parameter change increases the signal output and improves the limit of detection, allowing effective biological sensing at physiological salt conditions without buffer exchange.
2Measurement precision
If buffer exchange is performed to overcome Debye screening, then signal levels can be improved, but buffer exchange is not possible for single-molecule sensors where real-time sensing is required
Solution Approach 1:
The patent applies preliminary action by pre-modifying the nanostructure to create a portion with increased trap state density before the actual sensing operation. This preliminary modification enhances the sensing capability and signal level permanently, eliminating the need for buffer exchange during operation and simplifying the operational process for real-time single-molecule sensing.
3Measurement precision
If the nanostructure is modified to increase trap state density, then the signal output is enhanced and limit of detection is improved, but the manufacturing process becomes more complex
Solution Approach 1:
The modification processes (ion implantation, energetic beam irradiation, plasma exposure) are applied locally to only a portion of the nanostructure rather than the entire structure. This localized approach minimizes the impact on manufacturing complexity while achieving the desired enhancement in signal output and limit of detection.
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 increased trap state density enhances the signal output and improves the limit of detection for FETs, enabling more effective biological sensing without the need for buffer exchange, thus overcoming the limitations of Debye screening.
Implementation Method 1
The sensor is a field effect sensor having a sensitive element in the form of a field effect transistor whose specific electrical field-sensitive properties are utilized for sensor operation
Data Source
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AI summary
Apparatus and methods are disclosed for single molecule field effect sensors having conductive channels functionalized with a single active moiety. A region of a nanostructure (e.g., such as a silicon nanowire or a carbon nanotube) provide the conductive channel. Trapped state density of the nanostructure is modified for a portion of the nanostructure in proximity with a location where the active moiety is linked to the nanostructure. In one example, the semiconductor device includes a source, a drain, a channel including a nanostructure having a modified portion with an increased trap state density, the modified portion being further functionalized with an active moiety. A gate terminal is in electrical communication with the nanostructure. As a varying electrical signal is applied to an ionic solution in contact with the nanostructure channel, changes in current observed from the semiconductor device can be used to identify composition of the analyte.