Resonating MEMS Structure Openings for Lower Thermoelastic Damping
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Solution Overview
Problem
Thermoelastic damping is prominent at the desired operating frequency of microelectromechanical (MEMS) devices, leading to reduced quality factor of oscillators due to heat dissipation in resonating structures.
Innovation Solution
Incorporating internal thermal resistance by introducing openings and bridge elements in the oscillating structure to reduce heat flow, maintaining mechanical integrity and resonance as a single body.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the oscillating structure is made solid and continuous, then mechanical integrity is maintained, but heat flow between oscillating sides increases causing thermoelastic damping
Solution Approach 1:
The oscillating structure is segmented by introducing openings that divide the central region into first and second side regions. This segmentation reduces heat flow paths between oscillating sides while maintaining mechanical integrity through bridge elements that connect the side regions.
Solution Approach 2:
Different regions of the oscillating structure are given different thermal properties. The central region contains openings to reduce thermal conduction, while the side regions maintain structural strength. This local differentiation allows the structure to have low thermal conductivity where needed while preserving mechanical integrity elsewhere.
2Temperature
If openings are introduced to reduce heat flow, then thermal resistance increases reducing thermoelastic damping, but structural strength may be compromised
Solution Approach 1:
Bridge elements are introduced as intermediary structures that connect the first and second side regions across the openings. These bridge elements provide mechanical support and maintain structural strength while their small cross-section limits heat flow, thus preserving high thermal resistance.
Solution Approach 2:
The oscillating structure employs a composite design combining solid side regions for mechanical strength and opening regions for thermal isolation. The bridge elements act as composite features that simultaneously provide structural support and thermal barrier functions.
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
Reduces thermoelastic damping, enhancing the quality factor of MEMS devices by minimizing heat transfer between oscillating sides, thereby improving resonance performance.
Implementation Method 1
Thermoelastic damping can occur in any oscillating structure which undergoes structural deformation, such as bending. Compression of the material on a first side (the 'inside' of the bending motion) raises the local temperature in the material on that side, while stretching of the material on a second side (the outside) reduces the local temperature on that side.
Implementation Method 2
At some oscillation frequencies this alternating temperature gradient, and the consequent back-and-forth heat flow inside the oscillating structure, dissipates a part of the mechanical oscillation energy.
Data Source
Figure 1a~1c
Figure 2a~2c
Figure 2d~3b
AI summary
A MEMS device which comprises a structure which is configured to undergo bending oscillation in a plane. The structure comprises a first end, a second end, a first side region, a second side region and a central region which extends from the first end to the second end between the first side region and the second side region. The central region comprises one or more openings which extend through the structure.