Capacitive Sensor Protrusion Geometry to Prevent Collision Sticking
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Solution Overview
Problem
Capacitive sensors are prone to damage due to collisions between the movable body and protrusions when significantly displaced, leading to operational defects such as sticking and reliability issues.
Innovation Solution
A capacitive sensor design featuring movable portions with protrusions having curved surfaces and slopes, which disperse impact and reduce the risk of damage during collisions, combined with a manufacturing method involving thermal oxidation and mask patterning to form these protrusions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the movable body is significantly displaced due to impact, then the sensor may detect the impact, but the sensor is damaged by collision between the movable body and the protrusion
Solution Approach 1:
The protrusion is designed with a rounded contact surface instead of a sharp edge, which disperses the impact force over a larger area during collision. This curvature modification prevents stress concentration and reduces damage to both the movable body and the protrusion when significant displacement occurs due to impact.
Solution Approach 2:
The rounded contact surface of the protrusion acts as a pre-designed cushioning feature that mitigates collision damage before it occurs. By anticipating potential impact events, the design incorporates a geometry that naturally distributes impact forces, protecting the sensor components from damage during unexpected significant displacements.
2Reliability
If a protrusion is provided on the movable body, then sticking is reduced, but damage occurs due to collision between the movable body and the protrusion when significantly displaced
Solution Approach 1:
The protrusion features a rounded contact surface that maintains the sticking-prevention function while adding impact resistance. The curved geometry allows the protrusion to withstand collision forces without breaking or causing damage, thus preserving both operational stability and impact resistance.
Solution Approach 2:
The shape parameter of the protrusion is changed from a sharp or flat top to a rounded top with a specific curvature radius. This parameter modification enables the protrusion to fulfill dual functions: preventing sticking during normal operation and withstanding impact forces when significant displacement occurs.
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 design enhances the sensor's reliability by preventing sticking and reducing damage, thereby maintaining performance and preventing dust generation, thus improving overall operational stability.
Implementation Method 1
thermally oxidizing the base through openings in the first mask to form thermally oxidized regions
Implementation Method 2
thermally oxidizing the base through openings in the first mask to form thermally oxidized regions
Data Source
AI summary
A capacitive sensor that includes: a first substrate layer; and a device layer having a movable portion. The movable portion has a first main surface facing the first substrate layer and at least one first protrusion on the first main surface. The first protrusion has a first top portion having a curved surface in a central area of the first protrusion in a plan view of the device layer, and a first slope around the first top portion. The capacitive sensor is configured to detect a change in electrostatic capacity based on a distance between the first substrate layer and the movable portion.