Glass Spring Structure for Linear Force-Deflection in Pressure Sensors

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Solution Overview

Problem

Conventional capacitive pressure sensors with flat, disc-shaped membranes face challenges in achieving linear force-deflection characteristics due to non-linear membrane behavior, sensitivity loss, and mechanical stress sensitivity, which complicates calibration and reduces accuracy.

Innovation Solution

A method for manufacturing a capacitive pressure sensor using a glass spring structure with a toroidal, omega-shaped membrane geometry, where the glass material is tempered and bulged to form a continuous glass bulge acting as a spring element, providing adjustable elasticity and reduced mechanical stress sensitivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a flat disc-shaped membrane is used, then the manufacturing process is simple, but the force-deflection characteristic becomes non-linear and sensitivity is lost

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidforce-deflection linearity

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent applies curvature by forming the glass membrane into a toroidal or omega-shaped geometry instead of a flat disc. This curved configuration fundamentally changes the mechanical behavior of the membrane, enabling it to exhibit linear force-deflection characteristics while maintaining manufacturing feasibility through glass tempering and bulging processes.

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Measurement precision

If the membrane deflection is increased to improve sensitivity, then the measurement range expands, but non-linearity appears significantly

Engineering Contradiction:

ImprovesensitivityVSAvoidcharacteristic curve linearity

Core Design Contradiction:

Measurement precisionVSShape

Solution Approach 1:

The curved toroidal or omega-shaped geometry of the glass membrane inherently provides linear elastic behavior over a broad pressure range. The curvature distributes stresses uniformly, allowing the membrane to deflect significantly while maintaining a linear relationship between applied force and deflection, thus improving sensitivity without sacrificing linearity.

Inventive Principle:

Principle #14Spheroidality (Curvature)

3Reliability

If planar glass membranes are used, then chemical durability is maintained, but mechanical stress sensitivity increases

Engineering Contradiction:

Improvechemical durabilityVSAvoidmechanical stress sensitivity

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The curved toroidal or omega-shaped configuration of the glass membrane reduces sensitivity to mechanical stresses during assembly and operation. The geometry distributes and relaxes internal stresses, making the sensor less susceptible to characteristic curve changes caused by external mechanical loads while preserving the chemical durability of glass material.

Inventive Principle:

Principle #14Spheroidality (Curvature)

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 glass spring structure achieves a linear force-deflection characteristic over a broad pressure range, enhances sensitivity, and minimizes the impact of mechanical stresses, while maintaining uniformity and chemical durability, allowing for precise control of elasticity and improved sensor performance.

Implementation Method 1

tempering the cover substrate and the mold substrate to decrease the viscosity of the glass material of the cover substrate

Methodology Applied

Scientific EffectViscosity decrease through tempering: Heat Treatment

Implementation Method 2

providing an overpressure in the closed surrounding cavity with respect to the ambient atmosphere, to cause, based on the decreased viscosity of the glass material of the cover substrate and the overpressure in the closed surrounding cavity with respect to the ambient atmosphere, bulging of the glass material of the cover substrate

Methodology Applied

Scientific EffectPressure-induced deformation: Pressure Increase

Implementation Method 3

the surrounding glass bulge is effective as a spring element between the outer area and the inner area

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentUS20250012652A1Spring structure and method for manufacturing a spring structure, capacitive pressure sensor and method for manufacturing a capacitive pressure sensor

Publication Date: 2025.01.09 FRAUNHOFER GESELLSCHAFT ZUR FORDERUNG DER ANGEWANDTEN FORSCHUNG EV

AI summary

According to an embodiment, a method for manufacturing a spring structure (glass spring structure) comprises: —providing a mold substrate and a cover substrate comprising a glass material, said mold substrate and said cover substrate being connected, wherein a surface area of the mold substrate and/or of the cover substrate is structured to form a closed (or enclosed or sealed) surrounding cavity between the cover substrate and the mold substrate, —tempering the cover substrate and the mold substrate to decrease the viscosity of the glass material of the cover substrate, and providing an overpressure in the closed surrounding cavity with respect to the ambient atmosphere, to cause, based on the decreased viscosity of the glass material of the cover substrate and the overpressure in the closed surrounding cavity with respect to the ambient atmosphere, bulging of the glass material of the cover substrate starting from the closed surrounding cavity to obtain a cover substrate provided with a surrounding glass bulge, and—(subsequently) removing the mold substrate from the cover substrate to obtain the spring structure with the surrounding glass bulge.