Resolution limit of mode-localised sensors
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. RESEARCH PAPER .
April 2021, Vol. 64 142401:1–142401:10 https://doi.org/10.1007/s11432-020-2974-9
Resolution limit of mode-localised sensors Zhao ZHANG & Honglong CHANG* Ministry of Education Key Laboratory of Micro/Nano Systems for Aerospace, School of Mechanical Engineering, Northwestern Polytechnical University, Xi’an 710072, China Received 22 February 2020/Revised 7 May 2020/Accepted 2 July 2020/Published online 25 November 2020
Abstract In recent years, the mode localisation phenomenon of weakly coupled resonators has been successfully utilised to improve the sensitivity of microelectromechanical system (MEMS) sensors. However, controversy remians about the resolution limits of mode-localised sensors. This paper asks two questions of the community: what are the resolution limits of the mode-localised sensors, and can the resolution improvement be obtained using mode-localised sensing? To answer these questions, we report a series of resolution models of mode-localised sensors. We conclude that mode-localised sensing can realise a higher measuring resolution by orders of magnitude when more than three resonators are weakly coupled, and this will lay the theoretical foundation for a breakthrough for the MEMS sensors industry. Keywords
MEMS, mode-localised sensors, resolution limit, 2-degree-of-freedom, higher degree-of-freedom
Citation Zhang Z, Chang H L. Resolution limit of mode-localised sensors. Sci China Inf Sci, 2021, 64(4): 142401, https://doi.org/10.1007/s11432-020-2974-9
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Introduction
Microelectromechanical system (MEMS) sensors have given birth to a large industry and there are billions of MEMS units sold every year [1]. Microelectromechanical system sensors have been well developed and widely used in consumer electronics, as well as automobile and healthcare fields. Although the MEMS industry is booming, it appears that several kinds of MEMS sensors have reached their fundamental accuracy limit [2, 3]. It is difficult to improve the practical resolution limit further as the fabrication process and signal conditioning capabilities have reached a bottleneck state. For example, the etching aspect ratio has been improved to 40:1 under the current deep reactive ion etching process to improve the capacitance [4]. The vacuum packaging level has been increased to a few pascals to increase the quality factor to the millions [5]. These process technologies already operate at a high level, and further improvement is difficult to achieve. Nevertheless, to make such improvements to performance, a variety of novel methods have been proposed, such as using two-dimensional (2D) materials [6] and new principles [7]. However, often, these attempts are not fully compatible with current MEMS foundry, which has already existed as a large industry for some time. Among these attempts, mode-localised sensors in which two or more resonators are weakly coupled to improve the sensitivity of MEMS sensors [8–11] are fully compatible with current MEMS foundry. Under the mode-localised sensing paradigm, the frequently use
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