Graphene Capacitive Liquid Level Sensor for Stratified Fuel Tanks
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Solution Overview
Problem
Existing capacitive sensors for measuring liquid levels in fuel tanks face challenges in accurately determining the level of stratified liquids and require electrodes that are thin and closely spaced to minimize stack length, while also being resistant to corrosion and contamination.
Innovation Solution
A capacitive sensor using a stack of capacitors with graphene measurement and reference electrodes, alternately arranged to maintain a narrow stack length, and formed through reductive etching of graphene oxide to ensure close electrode spacing and high capacitance measurements, allowing for accurate liquid level detection in both single and stratified liquids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If conventional electrodes are used in capacitive sensors, then the sensor can measure liquid levels, but the electrodes become thick and widely spaced resulting in excessive stack length
Solution Approach 1:
The patent changes the material parameter of the electrodes from conventional metals to graphene, which has superior electrical conductivity. This allows the electrodes to be made extremely thin (on the order of nanometers) while maintaining high capacitance values, thereby reducing the stack length without compromising measurement precision
Solution Approach 2:
The patent replaces the mechanical/physical constraint of thick electrode structures with a chemical/material solution using graphene's intrinsic properties. The exceptional electrical conductivity of graphene substitutes for the need for thick conventional electrodes, enabling thin-film electrode design that achieves both compact dimensions and accurate measurements
2Length of moving object
If electrodes are made thin and closely spaced to reduce stack length, then the sensor becomes compact, but the electrodes become susceptible to corrosion and contamination
Solution Approach 1:
The patent employs graphene, a composite carbon material with unique properties, to create electrodes that are both thin and highly resistant to corrosion and contamination. The graphene structure forms a protective barrier that prevents degradation while maintaining electrical functionality, thus achieving reliability in compact thin-film electrode designs
Solution Approach 2:
By changing the material composition to graphene, the patent alters the chemical stability parameter of the electrodes. Graphene's inert nature and resistance to chemical reactions provide superior corrosion and contamination resistance compared to conventional metals, enabling thin electrode designs to maintain high reliability in harsh environments
3Device complexity
If conventional electrode arrangements are used, then the sensor structure is simple, but the stack length becomes too great for practical applications
Solution Approach 1:
The patent changes the dimensional parameter of the electrodes by using graphene's thin-film properties. This allows the implementation of interleaved electrode arrangements where multiple electrode pairs can be stacked closely together without increasing the overall stack length significantly, thus enabling more complex spatial arrangements while maintaining compact dimensions
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
Enables precise measurement of liquid levels, including stratified layers, with high resolution and resistance to corrosion, while maintaining a compact sensor design suitable for fuel tanks, and the ability to measure electrical resistance of the fuel.
Implementation Method 1
formed in one or more layers of graphene oxide—for instance by thermochemical nanolithography, by applying a reducing agent such as hydrazine monohydrate, or by any other reductive etching method
Implementation Method 2
A measurement system is arranged to measure a capacitance value of each capacitor between its measurement electrode(s) and one or more reference electrodes
Implementation Method 3
This ensures that the dielectric distance through the liquid is very small and enables a measureable capacitance
Data Source
AI summary
A sensor for measuring a level of a liquid such as fuel and/or water in a tank such as a fuel tank. The sensor includes a stack of capacitors, each capacitor with one or more graphene measurement electrodes and one or more graphene reference electrodes. A measurement system is arranged to measure a capacitance of each capacitor between its measurement electrode(s) and its reference electrode(s) and thereby infer the liquid level. The graphene measurement and reference electrodes are formed in a single layer of graphene oxide by reductive etching.