Capacitive Pressure Sensor Diaphragm Structure for Wide-Range Sensitivity
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Solution Overview
Problem
Existing pressure sensor devices struggle to maintain sensitivity for detecting capacitance changes across a wide range of pressures, from low to high, due to limitations in gap configurations that affect sensitivity and contact likelihood between electrodes.
Innovation Solution
A pressure sensor device with a base, intermediate layer, and electrode configuration featuring through-holes and recesses, along with protrusions that allow the diaphragm portion to warp and maintain capacitance detection sensitivity by varying film stiffness based on pressure levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the gap between the first electrode and the second electrode is widened, then the sensitivity of detecting capacitance change corresponding to low pressure is improved, but the likelihood of the second electrode coming into contact with the first electrode when high pressure is applied increases
Solution Approach 1:
The second electrode is divided into multiple regions with different stiffness characteristics. The outer peripheral portion has lower stiffness to maintain contact with the first electrode at high pressures, while the inner portion has higher stiffness to prevent contact and maintain capacitance detection sensitivity. This segmentation allows different regions to serve different functions simultaneously.
Solution Approach 2:
Different portions of the second electrode are given different local properties: the outer peripheral portion is designed with lower stiffness (higher flexibility) while the inner portion is designed with higher stiffness. This local differentiation enables the electrode to exhibit appropriate mechanical behavior in different regions under pressure, resolving the contradiction between sensitivity and contact prevention.
2Reliability
If the gap between the first electrode and the second electrode is narrowed, then the likelihood of the second electrode coming into contact with the first electrode when high pressure is applied is reduced, but the sensitivity of detecting capacitance change corresponding to low pressure is lowered
Solution Approach 1:
The second electrode is segmented into regions with different stiffness to allow the use of a smaller overall gap distance. The inner high-stiffness region maintains adequate capacitance detection sensitivity even with reduced gap, while the outer low-stiffness region ensures reliable contact at high pressures.
Solution Approach 2:
By applying different local stiffness properties to different regions of the second electrode, the design enables a smaller overall gap distance without compromising either sensitivity or contact reliability. The inner region's higher stiffness compensates for the reduced gap distance.
3Device complexity
If the outer portion and inner portion of the leg in the second electrode warp as a single film, then the structure is simpler, but the stiffness is insufficient for detecting capacitance changes corresponding to high pressures
Solution Approach 1:
The leg structure is segmented into outer and inner portions with different stiffness characteristics. The inner portion has higher stiffness to provide the necessary structural support for detecting high pressure capacitance changes, while the outer portion has lower stiffness to maintain contact capability.
Solution Approach 2:
Different local stiffness properties are assigned to different portions of the leg structure. The inner portion is designed with higher stiffness to detect high pressure, while the outer portion maintains lower stiffness for contact functionality, resolving the contradiction between structural simplicity and sufficient stiffness.
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 device achieves high sensitivity for both low and high pressure measurements by ensuring the diaphragm portion warps as a single or multiple films, maintaining accurate capacitance detection across a wide pressure range.
Implementation Method 1
Based on a change of the distance between the first electrode and the second electrode that occurs during warpage, a change of capacitance between the first electrode and the second electrode is detected. Based on the detected capacitance change, the pressure applied to the second electrode is measured.
Implementation Method 2
The second electrode warps with an application of pressure.
Data Source
AI summary
A pressure sensor device that includes: a base having electroconductivity; an intermediate layer on the base and defining an opening; and an electrode on the intermediate layer and including a diaphragm portion that faces the opening. The opening includes a through-hole that extends through the intermediate layer in the lamination direction, and a pair of recesses on an upper surface of the intermediate layer such that the through-hole is therebetween. The intermediate layer includes a base-side electroconductive layer that is a bottom surface of the pair of recesses. The pressure sensor device further includes a pair of opposing portions that oppose each other and that protrude from at least one of the base-side electroconductive layer or the diaphragm portion and protrude toward the pair of recesses. The pair of opposing portions overlap edge portions of the pair of recesses closer to the through-hole.