Staged MEMS Stopper Contacts with Flexible Beams for Shock Absorption
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Solution Overview
Problem
MEMS devices face issues with movable masses contacting fixed structures due to electrostatic attraction and excessive shock, leading to device failure, component breakage, and stiction, which can render sensors inoperative.
Innovation Solution
The implementation of a controlled contact system with staged, flexible beams that absorb impact forces, reducing wear and stiction by providing a gradual, progressive reaction to shocks, using multiple contact stages with varying flexibilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fixed rigid stoppers are used to prevent contact during shock events, then the movable mass is protected from contacting other components, but the stoppers wear out and cause stiction or electrostatic capture failures due to continuous shock contact
Solution Approach 1:
The patent transitions from fixed rigid stoppers to movable compliant structures (beams or springs) that dynamically adjust their position and stiffness in response to impact forces. These compliant structures can deform during shock events to absorb energy, then return to their original position, preventing permanent wear and stiction while maintaining protection functionality.
Solution Approach 2:
The invention changes the mechanical parameters of the stopper structures by making them compliant rather than rigid. The compliant structures have controlled elasticity that allows them to deform under impact loads, absorbing shock energy through elastic deformation rather than rigid contact, thereby extending their operational life and preventing wear-related failures.
2Reliability
If fixed rigid stoppers are used to prevent contact during shock events, then the movable mass is protected from contacting other components, but excessive shock generates large impact forces that break MEMS structures or dislocate particles
Solution Approach 1:
The patent implements compliant structures (beams or springs) positioned between the movable mass and fixed structures that act as shock-absorbing cushions before impact occurs. These structures are designed to deform elastically during shock events, absorbing impact energy and reducing the peak forces transmitted to critical MEMS components, thereby preventing breakage and particle dislocation.
Solution Approach 2:
The compliant structures serve as intermediary elements between the movable mass and fixed structures. During shock events, these intermediaries deform to absorb impact energy, acting as a buffer that protects the fragile MEMS components from direct transmission of excessive forces while maintaining the protective function of the stopper system.
3Duration of action of stationary object
If continuous shock keeps the mass contacting the stopper, then the stoppers wear out and cause stiction, but using compliant structures increases device complexity
Solution Approach 1:
The patent employs flexible beams or spring structures that can be integrated into the existing MEMS device architecture. These flexible elements are designed to be compatible with standard MEMS fabrication processes, allowing them to be formed as thin structural components that provide compliance without requiring complex external mechanisms or additional subsystems.
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 solution effectively mitigates shock, reduces component wear, and minimizes stiction, ensuring the sensor's functionality and longevity by absorbing impact forces through a staged, progressive reaction mechanism.
Implementation Method 1
a first beam flexing upon impact when a first stage contact surface of the first beam contacts a first opposing surface within the gap
Implementation Method 2
the fingers may stick due to electrostatic attraction, causing the device to fail
Data Source
Figure 1A~1B
Figure 2
Figure 3~4
AI summary
Devices and associated method are shown that include a mass movably coupled over a substrate. In selected configurations, a controlled contact system is coupled between the mass and the at least one stopper. Examples are also shown where the controlled contact system includes a first stage contact coupled to a flexible beam and a second stage contact.