GaN Biosensor with Spaced Reactive Electrode for Serum Analysis
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Solution Overview
Problem
Conventional MOSFET biosensors face contamination issues due to ion interaction with the oxide layer and struggle to detect analytes in high ionic strength samples like serum, leading to adverse electrical effects and charge-screening problems.
Innovation Solution
A biosensor design featuring a transistor with a reactive electrode spaced apart from the gate surface, where a receptor immobilized on the electrode specifically binds with analytes, and a voltage pulse is applied to monitor response currents correlated with analyte concentration, using a high electron mobility transistor with a chemically inert GaN layer and a silicon nitride dielectric layer to minimize sensing errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional MOSFET biosensor uses an oxide layer for sensing, then the sensor can detect analytes in low ionic strength samples, but the oxide layer becomes contaminated by ions in liquid samples causing adverse electrical effects
Solution Approach 1:
The patent extracts the reactive layer from direct contact with the liquid sample by introducing a gate dielectric layer between the gate electrode (which has the reactive layer) and the sample. This separation prevents ion contamination of the sensitive oxide/gate dielectric layer while maintaining sensing capability through capacitive coupling.
Solution Approach 2:
The gate dielectric layer acts as an intermediary between the reactive layer and the liquid sample. It allows the sensing function to be transmitted through capacitive coupling while preventing direct interaction between ions and the sensitive electrical components, thus eliminating contamination issues.
2Device complexity
If conventional FET sensors are used to detect analytes in high ionic strength liquid samples, then the sensor structure remains simple, but charge-screening effects severely reduce detection capability
Solution Approach 1:
The gate dielectric layer serves as a mediator that shields the sensitive electrical components from the high ionic strength environment while still allowing detection of analyte binding events. This intermediary structure enables reliable detection in complex samples like serum without requiring complex sample preparation or dilution.
Solution Approach 2:
The patent transitions from direct electrical contact sensing to capacitive coupling sensing, effectively moving the sensing mechanism to a different dimensional approach. The electric field penetrates the gate dielectric to detect analyte binding without requiring direct ionic contact, thereby overcoming charge-screening effects.
3Ease of manufacture
If the gate electrode is directly contact with the liquid sample in conventional biosensors, then fabrication is simpler, but the oxide layer suffers from ion contamination and electrical property degradation
Solution Approach 1:
The gate dielectric layer is deposited on the gate electrode before the reactive layer is formed, creating a protective barrier in advance. This preliminary protective action prevents ion contamination during subsequent sample exposure while maintaining ease of fabrication through standard semiconductor processing techniques.
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 design facilitates easy fabrication and enhances the ability to detect analytes in high salt concentration samples by minimizing charge-screening effects and amplifying response currents, allowing for accurate analyte concentration analysis without the need for sample dilution.
Implementation Method 1
the reactive electrode has a receptor immobilized thereon for specific binding with an analyte in the liquid sample
Implementation Method 2
The reactive electrode is spaced apart from the gate surface of the transistor... applying a voltage pulse between the reactive electrode and the source of the transistor... monitoring a response current
Data Source
AI summary
A biosensor includes a transistor and a reactive electrode. The transistor has a source, a drain and a gate surface disposed therebetween. The reactive electrode is spaced apart from the gate surface of the transistor, has a receptor immobilized thereon for specific binding with an analyte in a liquid sample, and is configured to contact the liquid sample together with the gate surface of the transistor.