MEMS Electric Field Detector Using Capacitive Proof Mass
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Solution Overview
Problem
Existing technologies face challenges in accurately measuring faint electromagnetic fields generated by the human body, such as those from brain activity, due to high noise levels and cost constraints, limiting their practical application in diagnostic tools.
Innovation Solution
A compact, low-noise electric field detector using microelectromechanical systems (MEMS) that measures torsional motion of a suspended proof mass to detect electric fields, incorporating capacitive sense electrodes and a control circuit to determine field characteristics, with features like flux concentrators and counterbalances for improved stability and noise performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If highly sensitive magnetometers are employed to detect magnetic fields, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces complex magnetometer-based magnetic field detection with a simpler capacitive sensing system that measures electric field-induced mechanical displacement of a proof mass. This substitution achieves comparable measurement precision for bioelectrical signals while dramatically reducing device complexity and cost.
Solution Approach 2:
The invention extracts and measures only the electric field component of electromagnetic signals generated by the body, rather than attempting to measure the full electromagnetic spectrum or magnetic field components. This extraction approach simplifies the detection system while maintaining diagnostic utility.
2Measurement precision
If numerous electrodes are arranged to measure voltages at the scalp, then measurement precision is improved, but device complexity and ease of operation worsen
Solution Approach 1:
The patent extracts the electric field measurement function from complex multi-electrode EEG systems, using a single capacitive sensor to detect electric field-induced displacement. This reduces the measurement system from numerous electrodes to a single sensor element, dramatically improving ease of operation.
Solution Approach 2:
The capacitive proof mass sensor serves multiple functions: it acts as both the sensing element and the signal source, eliminating the need for separate electrodes, amplifiers, and signal conditioning circuits required by traditional EEG systems.
3Volume of moving object
If compact size is reduced, then ease of operation is improved, but measurement precision worsens due to increased noise
Solution Approach 1:
The patent introduces a counterbalance mass coupled to the proof mass to compensate for gravitational effects and mechanical asymmetries. This counterbalancing technique reduces noise from environmental disturbances, enabling compact detector design without sacrificing measurement precision.
Solution Approach 2:
The invention optimizes the physical parameters of the proof mass and suspension system, including mass distribution, suspension stiffness, and gap dimensions, to maximize sensitivity while minimizing noise. These parameter optimizations enable the detector to achieve high precision in a compact form factor.
4Ease of manufacture
If production cost is reduced, then ease of manufacture is improved, but measurement precision worsens
Solution Approach 1:
The patent employs inexpensive, readily available materials such as silicon for the proof mass, standard capacitor dielectrics, and conventional suspension structures. These cost-effective materials and manufacturing approaches enable low production cost while achieving sufficient measurement precision for diagnostic applications.
Solution Approach 2:
The invention replaces expensive, complex magnetometer systems with a simple capacitive sensing mechanism that can be manufactured using standard MEMS or PCB fabrication techniques. This mechanical substitution dramatically reduces production cost while maintaining adequate noise performance for detecting bioelectrical signals.
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 direct measurement of bio-electrical signals with enhanced signal-to-noise ratio and reduced volume, facilitating more comfortable and cost-effective diagnostic applications, such as electric field encephalography (EFEG), while maintaining robustness and low production costs.
Implementation Method 1
a source of concentrated charge coupled to the proof mass
Implementation Method 2
a first sense electrode positioned proximate the proof mass and configured to measure a change in capacitance relative to the proof mass from movement of the proof mass
Data Source
AI summary
Aspects are generally directed to a compact and low-noise electric field detector, methods of operation, and methods of production thereof. In one example, an electric field detector includes a proof mass, a source of concentrated charge coupled to the proof mass, and a substrate having a substrate offset space defined therein, the proof mass being suspended above the substrate offset space. The electric field detector further includes a sense electrode disposed on the substrate within the substrate offset space and proximate the proof mass, the sense electrode being configured to measure a change in capacitance relative to the proof mass from movement of the proof mass in response to a received electric field at the source of concentrated charge. The electric field detector includes a control circuit coupled to the sense electrode and configured to determine a characteristic of the electric field based on the measured change in capacitance.