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Creating self-sustaining wireless sensor networks to power the Internet of Things requires universal energy harvesting systems. MEMS energy harvesters are in particular demand as they can be batch fabricated to meet the large supply demands. However, currently silicon MEMS kinetic energy harvesters are fabricated with a narrow bandwidth of 1–2 Hz, so each application requires a custom designed device which limits the advantages of batch fabrication. This paper investigates the development of a passive tuning MEMS vibration energy harvesting method that is based on distributing the load to various locations along the proof mass using a liquid load. A 3D printed proof mass with an array of cavities was developed, where each cavity could be filled with liquid to alter the resonant frequency as desired. Cavities were filled with silicone oil to validate the concept. The results illustrate tuning of the frequency with a resolution of < 1 Hz and a range of approximately 50 Hz. This method represents a passive tuning method as no power is required and the tuning can be accomplished during manufacturing so that one single universal energy harvester could be made and then tuned to meet the end user’s frequency specification.
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This content will become publicly available on November 17, 2025
Parylene Capping Layer for Embedded Liquid Mass for MEMS Packaging
Microelectromechanical Systems (MEMS) packaging is over 80% of the cost of a typical MEMS device because there are no standard packaging methods, and each device requires unique packaging. Recently several MEMS devices have illustrated the desire to have a liquid filled cavity within the MEMS device for applications such as biomedical sensors, tunable energy harvesters, or liquid cooling microelectronics. However, embedded liquids in silicon pose a challenge when it comes to packaging. This paper illustrates a novel concept of using a conformal parylene coating to cap or encapsulate the liquid. The concept is validated using various liquids such as various viscosity silicone oils as well as Galinstan a Ga-based liquid metal. The study investigates the packaging reliability through a series of systematic accelerated life-time testing, elevated temperature testing, accelerated soak testing, and mechanical testing (shock and resonant frequency testing). Mass changes were monitored and compared to control (no capping), glass epoxy bonded packaging, and silicone spray coating encapsulation. The results demonstrate the superior mean-time-to-failure of the parylene capping method compared to the other methods. The results confirm that parylene can be used to package embedded liquids in silicon or 3D printed structures.
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- Award ID(s):
- 2237086
- PAR ID:
- 10586737
- Publisher / Repository:
- American Society of Mechanical Engineers
- Date Published:
- ISBN:
- 978-0-7918-8868-1
- Subject(s) / Keyword(s):
- Microelectronics, MEMS, Packaging, Parylene, Embedded Liquid
- Format(s):
- Medium: X
- Location:
- Portland, Oregon, USA
- Sponsoring Org:
- National Science Foundation
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