All-Silicon Electrode Capacitive Transducer on Glass
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Solution Overview
Problem
Capacitive transducers face precision issues due to contact potential differences (CPD) between electrodes made of different materials, leading to erroneous sensor signals and actuator forces, which can degrade performance over time due to variations in temperature, chemical reactions, and surface contaminants.
Innovation Solution
Replacing metal electrodes with stationary silicon electrodes that have a matched electronic work function to the movable silicon electrodes, thereby reducing or eliminating CPD, and using overhanging structures to shield the movable microstructure from stray charges and electric fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal electrodes are used in capacitive transducers, then the transducer can function as a sensor or actuator, but contact potential differences between different materials lead to erroneous sensor signals and actuator forces
Solution Approach 1:
The patent applies homogeneity by making both the stationary electrode and movable electrode entirely silicon-based, eliminating material heterogeneity at the electrode interface. This ensures uniform electronic work function across both electrodes, thereby eliminating contact potential difference and the associated erroneous signals and forces.
2Ease of manufacture
If different materials are used for stationary and movable electrodes, then manufacturing flexibility is improved, but performance degrades over time due to temperature variations, chemical reactions, and surface contaminants
Solution Approach 1:
The invention uses identical silicon material for both stationary and movable electrodes, eliminating material heterogeneity. This homogeneous material selection ensures consistent electronic properties under varying temperature, chemical, and surface conditions, thereby maintaining performance stability over time.
Solution Approach 2:
The patent modifies the material parameter by transitioning from heterogeneous materials (metal and silicon) to homogeneous silicon material. This parameter change ensures that the electronic work function remains constant across different environmental conditions, preventing performance degradation.
3Object-affected harmful factors
If overhanging structures are added to shield the movable microstructure, then protection from stray charges is improved, but device complexity increases
Solution Approach 1:
The patent employs an overhanging stationary electrode structure that extends into the capacitive gap region, using the third dimension (vertical extension) to provide electrostatic shielding. This dimensional approach blocks stray electric field lines from reaching the movable microstructure without adding lateral complexity.
Solution Approach 2:
The overhanging stationary electrode acts as an intermediary structure between the external environment and the movable microstructure. It intercepts and shields stray charges and electric fields before they can affect the sensitive movable components, thereby protecting the device with minimal added complexity.
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 solution enhances the precision and reliability of capacitive transducers by minimizing CPD-induced errors, providing stable and accurate sensing and actuation capabilities.
Implementation Method 1
When a voltage difference is applied between the two electrodes, a change in position of the electrodes induces a change in the electrical charge on the electrodes, which is detected by external electronics
Implementation Method 2
A capacitive transducer can also act as an actuator for a movable microstructure, by producing electrostatic forces on the electrodes when a voltage difference is applied between the electrodes
Data Source
Figure 1
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Figure 2B
AI summary
An all-silicon electrode capacitive transducer comprising: a movable silicon microstructure coupled to a glass substrate, the movable silicon microstructure having a movable silicon electrode, the glass substrate having a top surface and at least one recess, the movable silicon electrode having a first flat surface parallel to a plane of the top surface of the glass substrate, the movable silicon electrode having a first electronic work function; and a stationary silicon electrode coupled to a glass substrate, the stationary silicon electrode located adjacent to the movable silicon electrode, the stationary silicon electrode configured to sense or actuate displacement of the movable silicon microstructure, wherein the stationary silicon electrode has a second flat surface parallel to the first flat surface, the stationary silicon electrode having a second electronic work function equal to the first electronic work function.