MEMS Actuator Asymmetrical Spring Structure Stiction
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Solution Overview
Problem
In MEMS devices using piezoelectric actuators, symmetric spring structures on both sides of the electrode lead to weak restoring forces, increasing the risk of stiction failure, and the addition of a fixed electrode complicates the process and increases costs.
Innovation Solution
An asymmetrical spring structure is implemented between the electrode and the fixed ends, with different spring constants for the actuators and spring members, allowing for effective stress relaxation and enhanced restoring forces without the need for a second cavity or thick electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a symmetric spring structure is given on both sides of the electrode, then the structure is simple to manufacture, but the restoring force becomes weak and stiction failure occurs
Solution Approach 1:
The patent applies asymmetry by giving different spring constants to the first and second spring structures. Specifically, the first spring structure (between the first fixed end and first electrode) has a different spring constant than the second spring structure (between the second fixed end and first electrode). This asymmetric configuration optimizes the restoring force to prevent stiction while maintaining manufacturing simplicity.
2Reliability
If a fixed electrode is further provided above the electrode to secure restoring force, then the restoring force is sufficiently secured, but the process becomes complicated and cost increases
Solution Approach 1:
Instead of adding a fixed electrode (structural addition), the patent changes the parameters of the existing spring structures by giving them different spring constants. This parameter modification achieves the desired restoring force without complicating the manufacturing process or increasing device complexity.
3Reliability
If the spring structure is given asymmetrically, then the restoring force is enhanced and stiction is reduced, but the manufacturing process becomes more complex
Solution Approach 1:
The patent applies local quality by making the spring structures different only where necessary - the first spring structure has a different spring constant than the second, while other aspects of the device remain symmetric. This localized differentiation achieves enhanced restoring force with minimal impact on overall manufacturing complexity.
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 asymmetrical spring structure enhances the restoring force and displacement of the electrode, reducing the risk of stiction and process complexity while maintaining effective stress relaxation, resulting in improved performance and cost-effectiveness.
Implementation Method 1
MEMS device using a piezoelectric type actuator
Implementation Method 2
a spring structure member arranged at one of (i) a position between the first fixed end and the first electrode and (ii) a position between the second fixed end and the first electrode
Data Source
AI summary
A micro-electro-mechanical system (MEMS) includes a first electrode interposed between a first fixed end and a second fixed end, the first electrode being movable by an actuator element. The MEMS also includes a substrate on which the first and second fixed ends are located. The MEMS further includes a second electrode formed on the substrate to face the first electrode. A shape from the first electrode to the first fixed end and a shape from the first electrode to the second fixed end are asymmetrical, the first electrode to be lowered to the second electrode.