Semi-flexible proof-mass for MEMS shock protection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
MEMS devices face challenges with stiction and breakage due to unique failure mechanisms, such as adhesion and impact-induced cracking or fracture, which existing solutions like secondary structures and elastic bumps do not adequately address.
Innovation Solution
A semi-flexible proof-mass structure is introduced, divided into primary and secondary parts connected by stiff springs, allowing for reduced impact forces and preventing sticking by utilizing restoring forces to dislodge the proof-mass from stopper structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If secondary structures are used to prevent stiction, then stiction is relieved, but the movable mass may be damaged due to impact caused by shock
Solution Approach 1:
The proof mass is divided into a primary part and a secondary part that can move independently relative to each other. The secondary part is suspended by stiff springs and can disengage from the primary part during shock events, allowing it to prevent stiction through independent motion while the primary part absorbs the main impact force.
Solution Approach 2:
Stiff springs are pre-installed between the primary and secondary parts to provide cushioning during shock events. These springs allow the secondary part to move independently and prevent stiction while limiting the impact force transmitted to the movable mass, effectively cushioning the system before damage can occur.
2Strength
If elastic bumps are used to reduce impact force, then structure breakage risk is reduced, but stiction prevention capability is insufficient
Solution Approach 1:
The proof mass is segmented into primary and secondary parts with independent motion capabilities. The secondary part can move relative to the primary part to prevent stiction, while the overall segmented structure distributes impact forces more effectively than a single rigid mass.
Solution Approach 2:
The secondary part is designed with dynamic motion capability through stiff spring suspension, allowing it to move independently during shock events to prevent stiction. This dynamic behavior enables the system to adapt to both impact reduction and stiction prevention requirements simultaneously.
3Stability of the object's composition
If the proof-mass is made rigid for normal operation, then operational stability is maintained, but impact forces during shock are increased
Solution Approach 1:
The rigid proof mass is segmented into primary and secondary parts connected by stiff springs. During normal operation, the springs maintain fixed spacing and the structure behaves as a rigid body for stability. During shock events, the segmentation allows parts to move independently, reducing peak impact forces.
Solution Approach 2:
The effective rigidity of the proof mass changes based on operating conditions. During normal operation, the stiff springs maintain fixed geometry providing rigidity. During shock events, the springs allow relative motion between parts, effectively reducing the rigidity and impact force transmission.
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 semi-flexible proof-mass effectively reduces the risk of structure cracking and sticking, enhancing the reliability of MEMS devices by distributing impact forces and utilizing restoring motions to maintain normal operation.
Implementation Method 1
The proof-mass is divided into at least two parts, which are mutually connected by stiff springs
Implementation Method 2
When subject to a shock beyond normal operating conditions, this suspension between the primary and secondary parts acts as a spring
Implementation Method 3
Primary part(s) of the proof-mass may hit stopper structure(s) due to a shock, while secondary part(s) of the proof-mass is (are) suspended by the stiff springs
Implementation Method 4
this suspension between the primary and secondary parts acts as a spring, allowing the at least two parts of the semi-flexible proof-mass to move with respect to each other
Implementation Method 5
This restoring force causes a significant part of the semi-flexible proof-mass, i.e. at least the secondary part of the semi-flexible proof-mass, to bounce back and gain momentum
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
The present invention relates to a microelectromechanical device including a semi-flexible proof-mass comprising at least one primary part, at least one secondary part and at least one stiff spring suspending the at least one primary part and the at least one secondary part of the semi-flexible proof-mass. The stiff spring substantially causes the at least one primary part and the at least one secondary part to move as a single, rigid entity when the device is in its normal operation range. The device further includes at least one first stopper structure configured to stop the at least one primary part. The semi-flexible proof-mass is configured to deform through deflection of the at least one stiff spring, when the device is subjected to a shock that impacts the device with a force that is beyond the normal operation range of the device. While the shock causes a motion of the semi-flexible proof-mass at least in one direction along an axis of movement, the at least one stiff spring is further configured to cause a restoring force causing at least the at least one secondary part of the semi-flexible proof-mass to be driven into a restoring motion in a direction opposite to the motion along the axis of movement caused by the shock, wherein momentum of the at least one secondary part in the restoring motion further causes the at least one primary part to dislodge from the first stopper structure.