Capacitive Sensor Recessed Layout for Drift Compensation
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Solution Overview
Problem
Capacitive environmental sensors face challenges in maintaining sensitivity to target substances due to factors like substrate permittivity changes and interface layer buildup, which existing solutions fail to address effectively, leading to sensor drift and reduced accuracy.
Innovation Solution
Introducing a recessed substrate layout with alternating recessed and non-recessed spaces between electrodes, allowing for differential capacitive measurements that reduce sensitivity to factors other than the target substance while retaining sensitivity to the target, using multiple electrical configurations and scaling factors to compensate for interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If differential measurements are made using multiple electrode layers or complex electrical configurations, then sensitivity to non-target factors is reduced, but device complexity and manufacturing cost increase
Solution Approach 1:
The electrode array is segmented into multiple groups that can be independently configured. Each group can be switched to different electrical configurations (e.g., adjacent electrode groups vs. separated electrode groups), enabling differential measurements without requiring multiple physical electrode layers. This segmentation allows the same physical structure to serve multiple measurement functions.
Solution Approach 2:
The electrical configuration of the electrode groups is made dynamic through switching mechanisms. The sensor can switch between different measurement modes (e.g., configuration where adjacent electrodes are connected vs. configuration where separated electrodes are connected) to perform differential measurements. This dynamic reconfiguration enables the sensor to adapt its measurement strategy without physical restructuring.
2Ease of manufacture
If a single level of electrodes is used to simplify manufacturing, then ease of manufacture improves, but sensitivity to target substance decreases
Solution Approach 1:
The patent introduces asymmetric spacing between different groups of electrodes. Some electrode groups are arranged with adjacent spacing while others have separated spacing. This asymmetric configuration creates different field line distributions that are differentially sensitive to the target substance, enabling sensitivity enhancement while maintaining a single-level electrode structure that is easy to manufacture.
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 enhances the sensor's accuracy in detecting target substances like moisture or gases by mitigating interference from substrate changes and interface layers, improving the reliability of capacitive measurements.
Implementation Method 1
measuring the capacitance of the electrodes can determine the presence of the target substance, since the capacitance of the electrodes is governed at least in part by the permittivity of the sensor layer
Implementation Method 2
The sensor layer has a permittivity ∈ that is sensitive to the presence of a target substance such as moisture or a gas
Data Source
AI summary
A capacitive environmental sensor and a method for determining the presence of a target substance (e.g. water) using differential capacitive measurements. The sensor includes a semiconductor substrate having a surface. The sensor also includes a plurality of sensor electrodes located on the surface. The electrodes are laterally separated on the surface by intervening spaces. The sensor further includes a sensor layer covering the electrodes. The sensor layer has a permittivity that is sensitive to the presence of the target substance. The surface of the substrate, in a space separating at least one pair of electrodes, includes a recess. The surface of the substrate, in a space separating at least one pair of electrodes, does not include a recess. The sensor may be provided in a Radio Frequency Identification (RFID) tag. The sensor may be provided in a smart building.