Reliability of a MEMS Actuator Improved by Spring Corner Designs and Reshaped Driving Waveforms

Area of Science:

• Micro-Electro-Mechanical Systems (MEMS)
• Mechanical Engineering
• Materials Science

Background:

• Micro-Electro-Mechanical System (MEMS) actuators face reliability issues due to spring cracking caused by high stress concentration during long displacements.
• Preventing stiction in MEMS actuators often involves designs that lack stoppers or damping, leading to potential over-momentum and increased spring stress.
• Existing MEMS actuator designs are susceptible to failure from stress concentration in springs, limiting their operational lifespan and performance.

Purpose of the Study:

• To develop novel spring corner designs and driving waveforms for MEMS actuators to enhance reliability and prevent mechanical failure.
• To mitigate stress concentration in MEMS actuator springs, thereby improving their durability and preventing cracking.
• To optimize the driving waveform to minimize spring displacement and stress, ensuring longevity and preventing overshooting.

Main Methods:

• Simulated stress distribution across various spring designs to identify optimal configurations.
• Selected a serpentine spring with circular and wide corners for its superior stress concentration characteristics.
• Analyzed discrete Fourier transfer functions to identify and remove resonant frequencies from the driving waveform.

Main Results:

• The chosen serpentine spring design with circular, wide corners exhibited reduced stress concentration, particularly with increasing displacement.
• Resonant frequencies were successfully removed from the driving waveform, leading to shorter switching times and controlled spring displacement.
• The optimized MEMS actuator design maintained maximum stress below 200 MPa, preventing spring overshooting and failure.

Conclusions:

• The developed spring corner designs and driving waveforms significantly improve MEMS actuator reliability, preventing stiction and spring cracking.
• The optimized MEMS actuator demonstrated exceptional resilience, surviving 500 g shock tests and exceeding 150 million switching cycles without failure.
• This research provides a viable strategy for designing highly reliable and durable MEMS actuators for demanding applications.