Introduction: The current COVID-19 pandemic has caused large shortages in personal protective equipment, leading to hospitals buying their supplies from alternative suppliers or even reusing single-use items. Equipment from these alternative sources first needs to be tested to ensure that they properly protect the clinicians that depend on them. This work demonstrates a test suite for protective face masks that can be realized rapidly and cost effectively, using mainly off-the-shelf as well as 3D printing components. Materials and Methods: The proposed test suite was designed and evaluated in order to assess its safety and proper functioning according to the criteria that are stated in the European standard norm EN149:2001+A1 7. These include a breathing resistance test, a CO2 build-up test, and a penetration test. Measurements were performed for a variety of commercially available protective face masks for validation. Results: The results obtained with the rapidly deployable test suite agree with conventional test methods, demonstrating that this setup can be used to assess the filtering properties of protective masks when conventional equipment is not available. Discussion: The presented test suite can serve as a starting point for the rapid deployment of more testing facilities for respiratory protective equipment. This could greatly increase the testing capacity and ultimately improve the safety of healthcare workers battling the COVID-19 pandemic.
Although motion energy harvesting at the small scales has been a research topic for over 20 years, the implementation of such generators remains limited in practice. One of the most important contributing factors here is the poor performance of these devices under low-frequency excitation. In this research, a new metric is proposed to evaluate the performance and bandwidth of generators at low frequencies. For that, a classification based on the dynamics was made. It was found that the highest efficiencies were found in single-degree-of-freedom resonators where a large motion amplification was achieved. Smaller generators can be designed by limiting the motion through end-stops at the cost of a reduced efficiency. Moreover, it was argued that upon miniaturization, resonators could be outperformed by generators using a frequency up-conversion principle.
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