MEMS Capacitive Electric Field Detector for Bio-Signal Sensing
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Solution Overview
Problem
Current technologies face challenges in accurately measuring faint and attenuating electromagnetic fields generated by the human body, such as those from the heart and muscles, due to their low signal strength and interference, which limits the effectiveness of diagnostic applications.
Innovation Solution
A sensor system comprising a substrate, an electric field detector with a proof mass and electrodes, and a control circuit that measures changes in capacitance to determine the characteristics of electric fields in multiple dimensions, allowing for non-invasive detection of bio-physical signals without direct contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If numerous electrodes are arranged to measure scalar potential differences across the patient's chest with ECG, then the electromagnetic activity of the heart can be determined, but the device complexity increases and the measurement precision is limited for faint signals
Solution Approach 1:
The patent replaces the traditional ECG electrode system with a MEMS-based capacitive sensor that directly measures electric field variations. The proof mass with embedded electrodes forms a capacitive structure that detects electric field-induced displacement, eliminating the need for multiple surface electrodes and complex potential difference measurements while improving sensitivity to faint bioelectric signals.
Solution Approach 2:
The invention transitions from measuring scalar potential differences (0D/1D) to detecting vector electric field characteristics through capacitive coupling (3D spatial resolution). The capacitive sensor measures displacement in multiple dimensions, providing enhanced spatial resolution and signal detection capability compared to traditional ECG's limited measurement geometry.
2Length of stationary object
If the distance from the human body is increased, then the measurement range is expanded, but the signal strength attenuates and becomes harder to detect
Solution Approach 1:
The patent employs a MEMS capacitive sensor with high-impedance readout circuitry that can detect extremely small capacitance changes induced by distant electric fields. The proof mass structure amplifies the coupling effect between the sensor and the body, enabling detection of faint signals at increased distances while maintaining measurement precision through optimized capacitive coupling geometry and low-noise electronics.
3Reliability
If traditional electrode-based methods are used to detect bio-electrical signals, then direct measurement is achieved, but user comfort is reduced and signal-to-noise ratio is limited
Solution Approach 1:
The patent replaces direct skin-contact electrodes with a non-contact or minimal-contact capacitive sensor that measures electric fields through air or tissue. This eliminates skin-electrode interface artifacts, motion artifacts, and discomfort associated with traditional electrodes while improving signal-to-noise ratio by removing the primary sources of interference at the measurement interface.
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 system enhances the signal-to-noise ratio and improves user comfort by enabling direct measurement of bio-electrical signals, such as brain or muscle activity, with improved performance metrics compared to existing technologies.
Implementation Method 1
the control circuit being configured to determine a respective change in capacitance between the proof mass and each respective electrode of the one or more electrodes responsive to torsional movement of the proof mass in response to the electric field
Implementation Method 2
an electric field detector to detect an electric field generated by the user
Implementation Method 3
the proof mass is configured to rotate about a first torque axis orthogonal to the polarization axis responsive to the electric field having a first vector component aligned with a first electric field axis
Data Source
AI summary
According to various aspects, a sensor system is provided comprising a first substrate configured to be coupled to a user, an electric field detector to detect a user electric field and comprising a second substrate, a proof mass positioned above the second substrate, one or more electrodes coupled to the second substrate, and a control circuit coupled to the one or more electrodes, the control circuit being configured to determine a change in capacitance between the proof mass and each electrode responsive to torsional movement of the proof mass responsive to the electric field, and a controller coupled to the first substrate and being configured to receive, from the detector, information indicative of each change in capacitance between the proof mass and each electrode, and determine, based on the information, characteristics of the electric field in at least two dimensions.