Mechanical Resonator With Bending Beams for Low-Frequency Sensing

Solution Overview

Problem

Existing mechanical resonators for acceleration and position sensors face challenges in achieving a compact design with low natural frequency and high quality factor, limiting their sensitivity to low-frequency mechanical disturbances.

Innovation Solution

A method for producing a mechanical resonator using materials like glass, glass ceramic, sapphire, or silicon carbide, with a monolithic design and very long, thin bending beams, achieved through wafer bonding and precise polishing, to maintain a compact size while ensuring low natural frequency and high quality factor.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If a compact resonator geometry is used, then the device size is reduced, but the quality factor decreases and natural frequency increases

Engineering Contradiction:

Improveresonator sizeVSAvoidquality factor

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The resonator is segmented into a test specimen and a frame connected by three separate bending beams. This segmentation allows the test specimen to be small and compact while the bending beams provide the necessary mechanical compliance to achieve low natural frequency and high quality factor, resolving the contradiction between compact size and performance.

Inventive Principle:

Principle #1Segmentation

2Volume of moving object

If a compact resonator geometry is used, then the device size is reduced, but the natural frequency increases

Engineering Contradiction:

Improveresonator sizeVSAvoidnatural frequency

Core Design Contradiction:

Volume of moving objectVSSpeed

Solution Approach 1:

The resonator is segmented into a test specimen and a frame connected by three separate bending beams. This segmentation allows the test specimen to be small and compact while the bending beams provide the necessary mechanical compliance to achieve low natural frequency and high quality factor, resolving the contradiction between compact size and performance.

Inventive Principle:

Principle #1Segmentation

3Device complexity

If monolithic glass resonators are used, then the structure is simplified, but the natural frequency is high and quality factor is low

Engineering Contradiction:

Improveresonator structureVSAvoidquality factor

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The resonator is segmented into a test specimen and a frame connected by three separate bending beams. This segmentation allows the test specimen to be small and compact while the bending beams provide the necessary mechanical compliance to achieve low natural frequency and high quality factor, resolving the contradiction between compact size and performance.

Inventive Principle:

Principle #1Segmentation

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 resulting resonator achieves a low natural frequency of up to 20 Hz and a high quality factor of 10,000 to 1,000,000, enhancing sensitivity to low-frequency disturbances.

Implementation Method 1

Polishing the substrate and the cover substrates by means of chemical-mechanical polishing (CMP), pitch polishing, or ion beam polishing

Methodology Applied

Scientific EffectChemical-mechanical polishing:

Implementation Method 2

Coating at least some areas of the test specimen with a reflective coating by means of physical vapor deposition (PVD)

Methodology Applied

Scientific EffectPhysical vapor deposition: Physical Vapour Deposition

Implementation Method 3

Creating a cantilever geometry on the cover substrates by means of laser ablation and/or chemical etching

Methodology Applied

Scientific EffectLaser ablation: Laser Ablation

Implementation Method 4

connecting the frame and the test specimen to the bending beams of the cover substrates by wafer bonding to create a monolithic resonator

Methodology Applied

Scientific EffectWafer bonding:

Implementation Method 5

filling the holes in the substrates with a chemically soluble putty and then curing the putty, removing the putty by dissolving it with an acid, an alkali or a solvent

Methodology Applied

Scientific EffectDissolution: Solvation

Data Source

PatentEP4628903A1Mechanical resonator, method for the production thereof and use thereof

Publication Date: 2025.10.08 FRAUNHOFER GESELLSCHAFT ZUR FORDERUNG DER ANGEWANDTEN FORSCHUNG EV

Figure 1~2
Figure 3~4

AI summary

The present invention relates to a mechanical resonator for acceleration and position sensors that has a compact design and simultaneously exhibits a low natural frequency with a high quality factor. The invention also relates to a method for manufacturing this mechanical resonator. The mechanical resonator is used, for example, in gravitational wave detectors, atom interferometers, and EUV lithography systems. The position of the test specimen of the mechanical resonator can then be read out later interferometrically using an optical system.