MOS Capacitor Glucose Sensor for Low Power In-Vivo Monitoring
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Solution Overview
Problem
Current glucose sensors have high power requirements, slow response times, and often require optical readers, making them unsuitable for in-vivo monitoring, particularly for diabetes management, and they are not quantitative.
Innovation Solution
A metal-oxide-semiconductor (MOS) capacitor-based sensor is developed, which has low power requirements and is compatible with silicon process technology, allowing it to be integrated with silicon-based circuit chips for contact lens applications, using a material stack of Si, SiO2, HfO2, and glucose oxidase to sense glucose concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If traditional glucose sensors are used, then glucose monitoring capability is achieved, but power consumption is high and response time is slow
Solution Approach 1:
The patent replaces traditional electrochemical sensing mechanisms with a MOS capacitor-based electrical field sensing mechanism. The MOS capacitor structure (comprising metal electrode, oxide dielectric layer, and semiconductor substrate) detects glucose through changes in capacitance caused by glucose molecules interacting with the electric field, eliminating the need for complex electrochemical reactions and reducing power consumption while maintaining fast response times
Solution Approach 2:
The patent utilizes changes in electrical parameters (capacitance, voltage, frequency) of the MOS capacitor in response to glucose concentration changes. By monitoring the shift in resonant frequency or capacitance value of the MOS capacitor when glucose molecules interact with the sensing surface, the system achieves rapid detection with minimal power consumption, directly addressing the contradiction between low power usage and fast response
2Ease of operation
If traditional glucose sensors are used, then glucose detection is possible, but they require optical readers and are not suitable for in-vivo monitoring
Solution Approach 1:
The patent extracts the sensing function from complex optical detection systems and embeds it directly into a miniaturized MOS capacitor structure that can function independently. The MOS capacitor sensor generates electrical signals directly proportional to glucose concentration, eliminating the need for external optical readers and enabling direct in-vivo monitoring through simple electrical connections
Solution Approach 2:
The MOS capacitor structure serves multiple functions: it acts as both the sensing element and the signal generation source. The same MOS capacitor that detects glucose through capacitance changes also provides the electrical signal output needed for digital processing, integrating multiple functions into a single compact component suitable for in-vivo implantation or contact lens integration
3Use of energy by stationary object
If MOS capacitor-based sensor is used, then power consumption is reduced and integration with silicon chips is enabled, but pH sensitivity may interfere with glucose measurement accuracy
Solution Approach 1:
The patent segments the sensing function into two independent components: a MOS capacitor for electrical field-based glucose detection that is insensitive to pH changes, and a separate pH sensor for monitoring pH levels. By using the MOS capacitor's unique property of being primarily responsive to glucose molecules rather than H+ ions, the system achieves glucose-specific detection while the separate pH sensor compensates for any indirect pH effects, maintaining measurement precision
Solution Approach 2:
The patent introduces a selective membrane or coating layer on the MOS capacitor surface that acts as an intermediary. This layer allows glucose molecules to interact with the MOS capacitor's electric field while blocking or minimizing the direct interaction between H+ ions and the sensing surface, thereby reducing pH interference and improving glucose measurement accuracy while maintaining low power consumption
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 MOS capacitor-based sensor effectively measures glucose concentrations with low power usage and is pH-sensitive, unaffected by proteins in tears, providing reliable and quantitative glucose monitoring.
Implementation Method 1
a metal-oxide-semiconductor (MOS) capacitor based sensor... Capacitance is expressed as the ratio of the electric charge (Q) on each conductor to the potential difference (V) between them
Implementation Method 2
When there is a potential difference across the conductors, an electric field develops across the dielectric, causing positive charge (+Q) to collect on one plate and negative charge (−Q) to collect on the other plate
Implementation Method 3
a pH sensing layer disposed on the dielectric layer... the MOS capacitor based sensor is pH-sensitive
Data Source
AI summary
A glucose sensor comprises a conducting back electrode. The glucose sensor also comprises a silicon substrate in electrical contact with the conducting back electrode. The glucose sensor also comprises a dielectric layer disposed on the silicon substrate. The glucose sensor also comprises a pH sensing layer disposed on the dielectric layer. The glucose sensor also comprises a chemical layer disposed on the pH sensing layer, wherein the chemical layer is in contact with an aqueous solution. The glucose sensor also comprises a conductive electrode disposed on the dielectric layer, where in the conductive electrode is in contact with the aqueous solution.