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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. 

Abstract Progress in gravitational-wave (GW) astronomy depends upon having sensitive detectors with good data quality. Since the end of the Laser Interferometer Gravitational-Wave Observatory-Virgo-KAGRA third Observing run in March 2020, detector-characterization efforts have lead to increased sensitivity of the detectors, swifter validation of GW candidates and improved tools used for data-quality products. In this article, we discuss these efforts in detail and their impact on our ability to detect and study GWs. These include the multiple instrumental investigations that led to reduction in transient noise, along with the work to improve software tools used to examine the detectors data-quality. We end with a brief discussion on the role and requirements of detector characterization as the sensitivity of our detectors further improves in the future Observing runs.