In-Plane Actuated MEMS Resonator with Decoupled Piezoelectric Suspension
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Solution Overview
Problem
Existing MEMS and NEMS resonant devices face challenges in achieving in-plane movement due to limitations in actuation methods, particularly with piezoelectric and thermoelastic actuations, which result in small deformations and difficulties in manufacturing nanometric-sized resonators with sufficient air gaps for effective signal-to-noise ratio and large amplitude vibrations.
Innovation Solution
The device decouples actuation means from the resonator beam, allowing it to be anchored independently near its displacement points, using either piezoelectric or thermoelastic actuation, with suspended elements capable of moving under control voltage to achieve in-plane displacement, and incorporates detection means like piezoresistive or capacitive sensors for displacement measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If piezoelectric or thermoelastic actuation is used to achieve in-plane movement, then high stress levels can be reached, but the deformation amplitude remains very small (a few tenths of a percent)
Solution Approach 1:
A suspended element acts as an intermediary between the actuation means and the resonator beam. The suspended element amplifies the small deformation from piezoelectric or thermoelastic actuation into larger beam displacement, while the actuation means itself remains small and can be positioned near the beam anchor point
Solution Approach 2:
The actuation means is positioned in a different spatial location (near the beam anchor point rather than along the beam length), utilizing the vertical dimension and lateral positioning to achieve mechanical advantage through the suspended element's motion
2Length of moving object
If electrostatic actuation is used to achieve in-plane movement, then large amplitude vibrations can be obtained, but an air gap must be maintained which increases device complexity
Solution Approach 1:
The patent replaces electrostatic actuation with piezoelectric or thermoelastic actuation, substituting a mechanical/thermal system for an electrical field-based system, thereby eliminating the need for air gaps while maintaining actuation functionality
Solution Approach 2:
The air gap requirement is extracted and removed from the system by using contact-based or near-contact actuation methods (piezoelectric or thermoelastic) that do not require separation between actuator and resonator
3Measurement precision
If the resonator size is reduced to nanometric dimensions, then sensitivity is improved, but manufacturing precision becomes more difficult to achieve
Solution Approach 1:
The device is segmented into functionally independent components: the resonator beam, the suspended element, and the actuation means. This allows each component to be optimized independently, with the actuation means positioned near the anchor point where manufacturing constraints are less stringent
Solution Approach 2:
Different regions of the device have different functional requirements and design priorities. The actuation means is positioned locally near the anchor point where space is available, while the beam itself maintains nanometric dimensions for sensitivity, with each region optimized for its specific function
4Stress or pressure
If piezoelectric actuation is used, then three layers are required (piezoelectric layer between two conducting layers), but this increases device complexity
Solution Approach 1:
Instead of stacking piezoelectric layers vertically (increasing vertical complexity), the actuation means is positioned laterally near the beam anchor point, utilizing horizontal space and reducing the need for multiple vertical layers
Solution Approach 2:
The piezoelectric actuation layer is extracted from the main resonator structure and positioned separately as an independent actuation means, reducing the layer complexity of the resonator itself while maintaining actuation functionality
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
This approach enables high stress levels and controlled in-plane movement in resonators of various sizes, overcoming the limitations of traditional actuation methods by allowing for larger amplitude vibrations and flexible manufacturing techniques, while maintaining the advantages of piezoelectric and thermoelastic actuations.
Implementation Method 1
the actuation means are of the piezoelectric type and the suspended element comprises a piezoelectric stack
Implementation Method 2
the actuation means are of the thermoelastic type and the suspended element comprises an electrically conducting layer
Implementation Method 3
a suspended strain gauge 10 made of a piezoresistive material
Data Source
AI summary
An in-plane actuated resonant device, and method of manufacturing the device. The device includes a support; a suspended beam, moving parallel to the plane of the surface of the support and anchored to the support through at least one of its ends; and a mechanism actuating the beam to enable its displacement parallel to the support. The actuation mechanism includes at least one suspended element, anchored to the support and to one lateral face of the beam. The element moves when a control voltage is applied to the element and thus causes displacement of the beam. The device may be manufactured using surface technology and is applicable particularly for resonant mass sensors.