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Microsystem and Nanosystem Researches for Sensors, Actuators and Energy Conversion Devices

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A special issue of Micro (ISSN 2673-8023). This special issue belongs to the section "Microscale Engineering".

Deadline for manuscript submissions: 30 June 2024 | Viewed by 15595

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Special Issue Editors

Prof. Dr. Vittorio Ferrari

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Department of Information Engineering (DII), University of Brescia, Via Branze 38, 25123 Brescia, Italy
Interests: piezoelectric sensors and transducers; resonant and acoustic-wave sensors; energy harvesting for sensors; sensor interface electronics; MEMS and microsensors for physical quantities
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Prof. Dr. Elisabetta Comini

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Sensor Lab, Department of Information Engineering, University of Brescia and CNR INO, Via Valotti 9, 25133 Brescia, Italy
Interests: metal oxides; nanowires; chemical sensors; gas sensors; heterostructures; functional materials; material synthesis
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Dr. Marco Baù

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Guest Editor

Department of Information Engineering (DII), University of Brescia, Via Branze 38, 25123 Brescia, Italy
Interests: interface electronic circuits for sensors; contactless interrogation techniques for resonant and capacitive sensors; MEMS sensors; energy harvesting for autonomous sensors and microsystems; acoustic-wave sensors; electro-mechanical modeling and FEM simulations; low-noise circuits for sensors and detectors
Special Issues, Collections and Topics in MDPI journals

Dr. Dario Zappa

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Guest Editor

Sensor Lab, Department of Information Engineering (DII), University of Brescia, Via Valotti 9, 25133 Brescia, Italy
Interests: metal oxides; nanowires; chemical sensors; heterostructures; artificial olfaction; material characterization; material synthesis
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The world of micro- and nanosystems is continuously evolving and the number of available applications is exponentially growing. Progresses in nanostructured innovative materials and fabrication techniques, combined with the miniaturization processes of microdevices, have led to new micro-electromechanical systems (MEMS) and nano-electromechanical systems (NEMS). The advanced development, and often the combination, of nano- and microsystems is resulting in new devices, such as physical, chemical, biological or optical sensors; miniaturized actuators; and micro-instruments. Additionally, applications in energy-related and conversion devices (e.g., batteries, fuel cells, solar cells, energy harvesters) based on thermo-/piezo-/pyro-/triboelectric materials, are emerging. New challenges and opportunities for applications are now at the outset in both traditional and more recent research fields, such as physics, electronics, chemistry biology, biomedical sciences, and microfluidics, to name a few. This rapidly evolving scenario is in turn pushing advances in the field of electronic circuits, techniques and systems for signal conditioning/processing and power management, and in the development of analytical and simulation models.

In this context, we invite researchers and scientists to submit contributions on scientific and technical aspects of micro- and nanosystems for sensors, actuators and energy-conversion devices. Both review articles and original research articles are welcome.

The covered topics include, but are not limited to, the following:

Fabrication techniques and processes;
Sensors, actuators, and transducers at the micro- and nanoscale;
Electronic circuits and techniques for micro- and nanosystems;
Energy conversion devices and energy harvesters;
Micro- and nanoinstruments and metrology;
Novel material trends for micro- and nanosystems;
Analytical and simulation modeling techniques;
Innovative applications.

Prof. Dr. Vittorio Ferrari
Prof. Dr. Elisabetta Comini
Dr. Marco Baù
Dr. Dario Zappa
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Micro is an international peer-reviewed open access quarterly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

physical, chemical, biological, optical sensors
miniaturized actuators and micro-instruments
energy-conversion devices
energy harvesting
mems nems
fabrication techniques
simulation techniques
modeling techniques
electronic circuits and techniques

Published Papers (10 papers)

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Research

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15 pages, 10680 KiB

Open AccessArticle

Characterization of Thin AlN/Ag/AlN-Reflector Stacks on Glass Substrates for MEMS Applications

by Christian Behl, Regine Behlert, Jan Seiler, Christian Helke, Alexey Shaporin and Karla Hiller

Micro 2024, 4(1), 142-156; https://doi.org/10.3390/micro4010010 - 29 Feb 2024

Viewed by 341

Abstract

Thin metal layers such as silver (Ag) are being utilized for various optical and plasmonic applications as well as for electrical purposes, e.g., as transparent electrodes in display devices or solar cells. This paper focuses on optical MEMS applications such as the Fabry–Pérot interferometer (FPI). Within such filters, reflector materials such as distributed Bragg reflectors (DBRs) or subwavelength gratings (SWGs) have been widely used so far, whereas metallic thin films (MTFs) were limited in application due to their comparatively higher absorption. In this paper, thin sputtered Ag layers with thicknesses of 20, 40 and 60 nm on glass substrates have been investigated, and it is shown that the absorption is very low in the visible spectral range (VIS) and increases only in near-infrared (NIR) with increasing wavelength. Thus, we consider Ag-thin layers to be an interesting reflector material at least for the VIS range, which can be easily fabricated and integrated. However, Ag is not inert and stable when exposed to the atmosphere. Hence, it needs a passivation material. For this purpose, AlN has been chosen in this contribution, which can be deposited by sputtering as well. In this contribution, we have chosen thin AlN layers for this purpose, which can also be deposited by sputtering. Thus, various AlN/Ag/AlN-reflector stacks were created and patterned by lift-off technology preferably. The fabricated reflectors were characterized with respect to adhesion, stress, cohesion, homogeneity, and most importantly, their optical properties. It was found that the thickness of the AlN can be used to adjust the reflectance–transmittance ratio in the VIS range, and influences the adsorption in the NIR range as well. Based on the measured values of the reflectors with 40 nm Ag, an exemplary transmission filter characteristics has been predicted for a wavelength range from 400 to 800 nm. Both the maximum transmittance and the full width at half maximum (FWHM) can be tuned by variation of the AlN thickness from 20 to 60 nm. Full article

(This article belongs to the Special Issue Microsystem and Nanosystem Researches for Sensors, Actuators and Energy Conversion Devices)

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12 pages, 3216 KiB

Open AccessArticle

Toward Remote Detection of Chemical Warfare Simulants Using a Miniature Potentiostat

by Amer Dawoud, Rashid Mia, Jesy Alka Motchaalangaram, Wujian Miao and Karl Wallace

Micro 2024, 4(1), 49-60; https://doi.org/10.3390/micro4010004 - 22 Jan 2024

Cited by 1 | Viewed by 934

Abstract

A miniaturized electrochemical sensor was developed for the remote detection of chemical warfare agent (CWA) simulants. To facilitate drone-based remote sensing, this present study focuses on advancing the miniaturized and compact electrochemical sensor for monitoring two CWA simulants, diisopropyl fluorophosphate (DFP) and O,S-diethylmethylphosphonothioate (O,S-DEMPT). The differential pulse voltammetry (DPV) signal was processed, and the DPV signature features were extracted on the basis of the redox properties associated with the absence and the presence of DFP and O,S-DEMPT. Upon the addition of 0.10 equivalence of DFP or O,S-DEMPT, a shift in potential (E) of ~0.13 V was recorded. The limit of detection (LOD) was calculated to be 0.25 µM (0.046 ppm) and 0.10 µM (0.017 ppm) for DFP and O,S-DEMPT, respectively. These results were validated using a portable Palmsens Emstat HR potentiostat, which corroborated the results obtained using a lab benchtop potentiostat. Additionally, Boolean logic (“AND” operation) was implemented for future drone technology deployment. This advancement enables the fabrication of a networked device capable of autonomously executing tasks without constant oversight. Full article

(This article belongs to the Special Issue Microsystem and Nanosystem Researches for Sensors, Actuators and Energy Conversion Devices)

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13 pages, 3230 KiB

Open AccessArticle

Design Guideline for a Cantilever-Type MEMS Switch with High Contact Force

by Ilia V. Uvarov and Igor A. Belozerov

Micro 2024, 4(1), 1-13; https://doi.org/10.3390/micro4010001 - 20 Dec 2023

Viewed by 746

Abstract

Micromechanical switches are of significant interest for advanced radio frequency and microwave systems, but their practical implementation is limited by low reliability. Electrodes of a microscopic size develop weak contact force that leads to high and unstable contact resistance. The force is typically increased by using a sophisticated switch design with extended lateral dimensions, although a simple and compact cantilever is more preferable. The paper describes for the first time a comprehensive approach to enhance the force of an electrostatically actuated switch. The strategy is applied to a miniature device based on a 50 µm long cantilever. The contact force is increased from 10 to 112 µN, making the switch strong enough to achieve low and stable contact resistance. The restoring force is also enhanced in order to ensure reliable de-actuation. The growth of forces is accompanied by a reduction in the pull-in voltage. Connecting several cantilevers in parallel and manipulating the number and position of contact bumps additionally improves the force and mechanical stability of the switch. An optimal design contains a triple cantilever with two bumps. It provides 50% higher force per contact compared to the single-cantilever switch at the same pull-in voltage and keeps the advantages of a miniature device. The proposed design strategy may be used for building reliable MEMS switches. Full article

(This article belongs to the Special Issue Microsystem and Nanosystem Researches for Sensors, Actuators and Energy Conversion Devices)

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11 pages, 3667 KiB

Open AccessCommunication

Enhancing Linearity in Parallel-Plate MEMS Varactors through Repulsive Actuation

by Roufaida Bensalem, Mohannad Y. Elsayed, Hani H. Tawfik, Frederic Nabki and Mourad N. El-Gamal

Micro 2023, 3(4), 811-821; https://doi.org/10.3390/micro3040057 - 26 Oct 2023

Viewed by 754

Abstract

This paper presents a new MEMS varactor that uses repulsive actuation to achieve an ultra-linear capacitance-to-voltage response. The approach proposed involves actuating the moveable electrode away from the fixed electrode, instead of the conventional closing-the-gap direction. This increasing-gap movement reduces the capacitance as the actuation voltage increases. The MEMS variable capacitor is fabricated using PolyMUMPs technology and exhibits an excellent linearity factor of 99.7% in capacitance-to-voltage response, and a capacitance tuning ratio of 11× was achieved. The proposed strategy will enable the development of high-performance MEMS-based tunable devices for various applications. Full article

(This article belongs to the Special Issue Microsystem and Nanosystem Researches for Sensors, Actuators and Energy Conversion Devices)

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15 pages, 2417 KiB

Open AccessArticle

Advanced Technologies in the Fabrication of a Micro-Optical Light Splitter

by Giovanna Stella, Lorena Saitta, Alfredo Edoardo Ongaro, Gianluca Cicala, Maïwenn Kersaudy-Kerhoas and Maide Bucolo

Micro 2023, 3(1), 338-352; https://doi.org/10.3390/micro3010023 - 10 Mar 2023

Cited by 3 | Viewed by 1333

Abstract

In microfluidics, it is important to confine and transport light as close as possible to the sample by guiding it into a small volume of the microfluidic channel, acquiring the emitted/transmitted radiation. A challenge in this context is the miniaturization of the optical components and their integration into the microfluidic device. Among all of the optical components, a particular role is played by the beam splitter, an important optical device capable of splitting light into several paths. In this paper, a micro-splitter is designed and realized by exploiting low-cost technologies. The micro-splitter consists of a micro-mirror in-between two micro-waveguides. This component was fabricated in different materials: poly-dimethyl-siloxane (PDMS), poly(methyl methacrylate) (PMMA), and VeroClear RGD810. A 3D printing master–slave fabrication protocol was used with PDMS, a direct 3D printing approach with VeroClear, and a laser cutting procedure with PMMA. The experimental results obtained show the high potential of the proposed fabrication protocols, based on low-cost technologies, for the realization of micro-optical components, which could also be easily integrated with microfluidics systems. Full article

(This article belongs to the Special Issue Microsystem and Nanosystem Researches for Sensors, Actuators and Energy Conversion Devices)

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16 pages, 4053 KiB

Open AccessArticle

Capacitive-Type Pressure Sensor for Classification of the Activities of Daily Living

by Ji Su Park, Sang-Mo Koo and Choong Hyun Kim

Micro 2023, 3(1), 35-50; https://doi.org/10.3390/micro3010004 - 09 Jan 2023

Viewed by 1345

Abstract

In order to operate a gait rehabilitation device, it is necessary to accurately classify the states appearing in activities of daily living (ADLs). In the case of force sensing resistors (FSRs), which are often used as pressure sensors in gait analysis, it is desirable to replace them with other sensors because of their low durability. In the present study, capacitive-type pressure sensors, as an alternative to FSRs, were developed, and their performance was evaluated. In addition, the timed up and go test was performed to measure the ground reaction force in healthy individuals, and a machine learning technique was applied to the calculated biosignal parameters for the classification of five types of ADLs. The performance evaluation results showed that a sensor with thermoplastic polyurethane (substrate and dielectric layer material) and multiwall carbon nanotubes (conductive layer) has sufficient sensitivity and durability for use as a gait analysis pressure sensor. Moreover, when an overlapping filter was applied to the four-layer long short-term memory (LSTM) or the five-layer LSTM model developed for motion classification, the precision was greater or equal to 95%, and unstable errors did not occur. Therefore, when the pressure sensor and ADLs classification algorithm developed in this study are applied, it is expected that motion classification can be completed within a time range that does not affect the control of the gait rehabilitation device. Full article

(This article belongs to the Special Issue Microsystem and Nanosystem Researches for Sensors, Actuators and Energy Conversion Devices)

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11 pages, 3281 KiB

Open AccessArticle

Identification of MEMS Geometric Uncertainties through Homogenization

by David Faraci, Valentina Zega, Alessandro Nastro and Claudia Comi

Micro 2022, 2(4), 564-574; https://doi.org/10.3390/micro2040037 - 23 Sep 2022

Cited by 1 | Viewed by 1645

Abstract

Fabrication imperfections strongly influence the functioning of Micro-Electro-Mechanical Systems (MEMS) if not taken into account during the design process. They must be indeed identified or precisely predicted to guarantee a proper compensation during the calibration phase or directly in operation. In this work, we propose an efficient approach for the identification of geometric uncertainties of MEMS, exploiting the asymptotic homogenization technique. In particular, the proposed strategy is experimentally validated on a MEMS filter, a device constituted by a complex periodic geometry, which would require high computational costs if simulated through full-order models. The complex periodic structure is replaced by an equivalent homogeneous medium, allowing a fast optimization procedure to identify imperfections by comparing a simplified analytical model with the experimental data available for the MEMS filter. The actual over-etch, obtained after the release phase, and the electrode offset of a fabricated MEMS filter are effectively identified through the proposed strategy. Full article

(This article belongs to the Special Issue Microsystem and Nanosystem Researches for Sensors, Actuators and Energy Conversion Devices)

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11 pages, 3236 KiB

Open AccessArticle

Experimental Characterization of Water Condensation Processes on Self-Assembled Monolayers Using a Quartz Crystal Microbalance with Energy Dissipation Monitoring

by Subin Song, Glenn Villena Latag, Evan Angelo Quimada Mondarte, Ryongsok Chang and Tomohiro Hayashi

Micro 2022, 2(3), 513-523; https://doi.org/10.3390/micro2030033 - 29 Aug 2022

Cited by 2 | Viewed by 1878

Abstract

Water condensation on solid surfaces is a universal phenomenon that plays an essential role in many interfacial phenomena, such as friction, corrosion, adsorption, etc. Thus far, the initial states of water condensation on surfaces with varying chemical properties have yet to be fully explained at the nanoscale. In this study, we performed a real-time characterization of water condensation on self-assembled monolayers (SAMs) with different functional groups using quartz crystal microbalance with energy dissipation monitoring (QCM-D). We found that the kinetics of water condensatison is critically dependent on the head group chemistries. We discovered that the condensed water’s viscoelasticity cannot be predicted from macroscopic water contact angles, but they were shown to be consistent with the predictions of molecular simulations instead. In addition, we also found a highly viscous interfacial water layer on hydrophilic protein-resistant SAMs. In contrast, the interfacial water layer/droplet on either hydrophilic protein-adsorbing or hydrophobic SAMs exhibited lower viscosity. Combining our and previous findings, we discuss the influence of interfacial hydration on the viscoelasticity of condensed water. Full article

(This article belongs to the Special Issue Microsystem and Nanosystem Researches for Sensors, Actuators and Energy Conversion Devices)

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21 pages, 1063 KiB

Open AccessArticle

Efficient and Accurate Modeling of the Surface Deflection of Thin Layers on Composite Substrates with Applications to Piezoelectric Parameter Measurements

by Thomas Voglhuber-Brunnmaier, Roman Beigelbeck, Ulrich Schmid, Thilo Sauter, Tiangui You, Xin Ou and Bernhard Jakoby

Micro 2022, 2(3), 369-389; https://doi.org/10.3390/micro2030025 - 29 Jun 2022

Viewed by 1605

Abstract

The electrical and mechanical response of multilayered structures involving a piezoelectric layer and bull’s eye shaped electrodes is investigated. A boundary element method is employed based on spectral domain Green’s functions. With this method, the electric field distribution is determined first, and the local mechanical displacement in a second step. As will be shown, this allows us to exploit cylindrical symmetry for the electric surface charge distribution, but not for the vertical surface displacements. The effect of substrate bending due to in plane-stress, introduced by the piezoelectric constant

d_{31}

, and the benefits of using bull’s eye electrode geometries with thick metallic backplates intended to reduce this effect are studied. A rigorous analysis and a largely simplified, but accurate approximation are compared. The application of this technique is demonstrated on a practical example for highly efficient and accurate determination of selected piezoelectric coefficients from surface topography measurements on such structures. Full article

(This article belongs to the Special Issue Microsystem and Nanosystem Researches for Sensors, Actuators and Energy Conversion Devices)

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Review

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20 pages, 3915 KiB

Open AccessReview

Resurgence of Electron Quantum Tunneling Sensors

by Aishwaryadev Banerjee and Carlos H. Mastrangelo

Micro 2022, 2(4), 679-698; https://doi.org/10.3390/micro2040046 - 13 Dec 2022

Cited by 1 | Viewed by 3671

Abstract

Quantum tunneling sensors are typically ultra-sensitive devices that have been specifically designed to convert a stimulus into an electronic signal using the wondrous principles of quantum mechanical tunneling. In the early 1990s, William Kaiser developed one of the first micromachined quantum tunneling sensors as part of his work with the NASA Jet Propulsion Laboratory. Since then, there have been scattered attempts at utilizing this phenomenon for the development of a variety of physical and chemical sensors. Although these devices demonstrate unique characteristics, such as high sensitivity, the principle of quantum tunneling often acts as a double-edged sword and is responsible for certain drawbacks of this sensor family. In this review, we briefly explain the underlying working principles of quantum tunneling and how they are used to design miniaturized quantum tunneling sensors. We then proceed to describe an overview of the various attempts at developing such sensors. Next, we discuss their current necessity and recent resurgence. Finally, we describe various advantages and shortcomings of these sensors and end this review with an insight into the potential of this technology and prospects. Full article

(This article belongs to the Special Issue Microsystem and Nanosystem Researches for Sensors, Actuators and Energy Conversion Devices)

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