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Recent Advances in Smart Materials for Sensor and Actuator Applications

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A special issue of Sensors (ISSN 1424-8220). This special issue belongs to the section "Nanosensors".

Deadline for manuscript submissions: closed (20 April 2022) | Viewed by 31892

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Special Issue Editors

Prof. Dr. Jung Woo Sohn

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Guest Editor

Department of Mechanical Design Engineering, Kumoh National Institute of Technology, Daehak-ro 61, Gumi 39177, Gyeongbuk, Republic of Korea
Interests: smart material sensor and actuator; smart system and structure; active and semi-active control; vibration control; artificial intelligence; piezoelectric material; shape memory alloy; magnetorheological fluid
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Heung Soo Kim

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Guest Editor

Department of Mechanical, Robotics and Energy Engineering, Dongguk University, 30 Pil-dong 1 Gil, Jung-gu, Seoul 04620, Korea
Interests: Prognostics and Health Management (PHM), Artificial Intelligence, Biomimetic Actuator, Adaptive Structures, Structural Analysis, Structural Optimization, Numerical Analysis, Composite Structures
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Smart materials are intelligent materials that can change their material properties in response to external stimuli such as electric, magnetic, and strain. Smart materials are widely used as sensors and actuators for various engineering applications due to their advantages such as fast response time, high energy efficiency, and easy implementation in control systems. The aim of this Special Issue is to disseminate the latest, new, original, and collective knowledge gathered from esteemed professionals like yourself on the use of Smart Materials for Sensors and Actuator Applications.

You are cordially invited to submit your original research articles and review papers that address the subject of the current Special Issue. The list of potential research topics includes, but is not limited to:

Vibration/noise control and isolation;
Prognostics and health management;
Modeling of smart structures and systems;
Structural health monitoring;
Soft robotics and artificial muscle;
Flexible and wearable sensors;
Energy harvesting;
Haptic systems.

Prof. Dr. Jung Woo Sohn
Prof. Dr. Heung Soo Kim
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. Sensors is an international peer-reviewed open access semimonthly 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 2600 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

Smart/intelligent structures/systems
Piezoelectric materials
Electro/magneto-rheological materials
Magnetostrictive materials
Electroactive polymers (EAPs)
Shape memory alloys/polymers
Sensors and actuators

Published Papers (12 papers)

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Research

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13 pages, 4487 KiB

Open AccessArticle

Monitoring the Early Strength Development of Cement Mortar with Piezoelectric Transducers Based on Eigenfrequency Analysis Method

by Guocheng Wang, Wenying Qiu, Dongkai Wang, Huimin Chen, Xiaohao Wang and Min Zhang

Sensors 2022, 22(11), 4248; https://doi.org/10.3390/s22114248 - 2 Jun 2022

Cited by 4 | Viewed by 1890

Abstract

Monitoring the early strength formation process of cement is of great importance for structural construction management and safety. In this study, we investigated the relationship between the eigenfrequency and the early strength development of cement mortar. Embedded piezoceramic-based smart aggregates recorded the early strength of cement mortar. An eigenfrequency analysis model demonstrated the relationship between strength and frequency. Experiments were performed by using piezoelectric transducers to monitor the early strength formation process during the testing period. Three types of specimens with different strength grades were tested, and the early strength formation processes were recorded. The experimental results demonstrate that cement mortar strength has a good linear relationship with the resonance frequency, and the average square of the correlation coefficient is greater than 0.98. The results show that structural health monitoring technology is a feasible method of assessing structural safety conditions and has a broad market in the structural construction industry. Full article

(This article belongs to the Special Issue Recent Advances in Smart Materials for Sensor and Actuator Applications)

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33 pages, 6693 KiB

Open AccessArticle

Trajectory Control for Vibrating Screen with Magnetorheological Dampers

by Szymon Ogonowski and Piotr Krauze

Sensors 2022, 22(11), 4225; https://doi.org/10.3390/s22114225 - 1 Jun 2022

Cited by 6 | Viewed by 2463

Abstract

The article presents a method of vibrating screen trajectory control based on MR (magnetorheological) dampers applied in a screen suspension. A mathematical description of the dynamic screen model was derived, and parameters of this model were estimated based on experimental data from a semi-industrial vibrating screen. The investigated screen included a single mechanical exciter with unbalanced masses, generating a circular vibration trajectory and operating with over-resonant frequency close to 19 Hz. It was experimentally tested in several phases of operation: start-up, nominal operation at a target vibration frequency and shutdown. The implemented screen model was further extended and included several MR dampers oriented horizontally and vertically in the form of Bouc–Wen models. The Bouc–Wen model was identified based on experiments carried out for an MR damper subjected to harmonic excitations generated by the MTS (material testing system). Dominant frequencies of excitation varied by up to 20 Hz during experiments. The main novelty of the reported solution is that according to the proposed control algorithm, the desired forces generated by MR dampers emulate an additional virtual mechanical exciter of the vibrating screen. In turn, it interacts with the available exciter, resulting in conversion of the trajectory from circular to linear, which was validated in the presented study. For the purpose of simulation accuracy, the desired control force was additionally limited within the simulator by MR damper dissipative domain, which maps the constraints of a semi-active damper. The presented approach allows one to obtain a close to linear trajectory with only one exciter and with semi-active control of suspension stiffness. The results were successfully repeated with different configurations of desired trajectory, indicating that the effectiveness of the desired linear trajectory generation depends on its orientation. The reported findings may lead to the design of new vibrating screen constructions, taking advantage of the semi-active control of a suspension in the attenuation of disturbance resulting from varying processed material parameters. Full article

(This article belongs to the Special Issue Recent Advances in Smart Materials for Sensor and Actuator Applications)

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17 pages, 2352 KiB

Open AccessArticle

Multiferroic Cantilevers Containing a Magnetoactive Elastomer: Magnetoelectric Response to Low-Frequency Magnetic Fields of Triangular and Sinusoidal Waveform

by Gašper Glavan, Inna A. Belyaeva and Mikhail Shamonin

Sensors 2022, 22(10), 3791; https://doi.org/10.3390/s22103791 - 17 May 2022

Cited by 8 | Viewed by 1920

Abstract

In this work, multiferroic cantilevers comprise a layer of a magnetoactive elastomer (MAE) and a commercially available piezoelectric polymer-based vibration sensor. The structures are fixed at one end in the horizontal plane and the magnetic field is applied vertically. First, the magnetoelectric (ME) response to uniform, triangle-wave magnetic fields with five different slew rates is investigated experimentally. Time and field dependences of the generated voltage, electric charge, and observed mechanical deflection are obtained and compared for four different thicknesses of the MAE layer. The ME responses to triangular and sinusoidal wave excitations are examined in contrast. Second, the ME response at low frequencies (≤3 Hz) is studied by the standard method of harmonic magnetic field modulation. The highest ME coupling coefficient is observed in the bias magnetic field strength of ≈73 kA/m and it is estimated to be about 3.3 ns/m (ME voltage coefficient ≈ 25 V/A) at theoretically vanishing modulation frequency (

f \to 0

Hz). Presented results demonstrate that the investigated heterostructures are promising for applications as magnetic-field sensors and energy harvesting devices. Full article

(This article belongs to the Special Issue Recent Advances in Smart Materials for Sensor and Actuator Applications)

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19 pages, 3500 KiB

Open AccessArticle

Design and Analysis of a Hybrid Annular Radial Magnetorheological Damper for Semi-Active In-Wheel Motor Suspension

by Olivier Munyaneza, Pacifique Turabimana, Jong-Seok Oh, Seung-Bok Choi and Jung Woo Sohn

Sensors 2022, 22(10), 3689; https://doi.org/10.3390/s22103689 - 12 May 2022

Cited by 8 | Viewed by 1676

Abstract

In this study, a novel hybrid annular radial magnetorheological damper (HARMRD) is proposed to improve the ride comfort of an electric vehicle (EV) powered by an in-wheel motor (IWM). The model primarily comprises annular-radial ducts in series with permanent magnets. Mathematical models representing the governing motions are formulated, followed by finite element analysis of the HARMRD to investigate the distribution of the magnetic field density and intensity of the magnetorheological (MR) fluid in both the annular and radial ducts. The optimized model generates a damping force of 87.3–445.7 N at the off-state (zero input current) with the excitation velocity ranging between 0 and 0.25 m/s. By contrast, the generated damping force varies from 3386.4 N to 3753.9 N at an input current of 1.5 A with the same velocity range as the off state. The damping forces obtained using the proposed model are 31.4% and 19.2% higher for the off-field and on-field states, respectively, compared with those of the conventional annular radial MR damper. The efficiency of the proposed model is evaluated by adopting two different vehicles: a conventional vehicle powered by an engine and an EV powered by an IWM. The simulation results demonstrate that the proposed HARMRD along with the skyhook controller significantly improves both the ride comfort and road-holding capability for both types of vehicles. Full article

(This article belongs to the Special Issue Recent Advances in Smart Materials for Sensor and Actuator Applications)

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15 pages, 19129 KiB

Open AccessArticle

Design, Fabrication and Analysis of Magnetorheological Soft Gripper

by Jakub Bernat, Piotr Gajewski, Rafał Kapela, Agnieszka Marcinkowska and Paulina Superczyńska

Sensors 2022, 22(7), 2757; https://doi.org/10.3390/s22072757 - 2 Apr 2022

Cited by 14 | Viewed by 2787

Abstract

The magnetorheological elastomer is promising material for applications in soft robotics. Its properties like reactive to external magnetic field and softness allow to construct an attractive devices. This work presents a construction of soft gripper assembled with magnetorheological elastomers. The work describes the detailed molding process of magnetorheological elastomers. Further, the electromechanical properties of magnetorheological elastomers are shown using a simple beam. Finally, the soft gripper is constructed and analyzed with the series of experiments. Full article

(This article belongs to the Special Issue Recent Advances in Smart Materials for Sensor and Actuator Applications)

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10 pages, 4584 KiB

Open AccessCommunication

Dilute Polymerization of Aniline on PDMS Substrate via Surface Modification Using (3-Aminopropyl)Triethoxysilane for Stretchable Strain Sensor

by Chang-Joo Yim, Ji-Yeon Choy, Hae-Kyung Youi, Jung-Hoon Hwang, Eun-Bee Jo, Jun-Ho Lee and Hyun-Seok Kim

Sensors 2022, 22(7), 2741; https://doi.org/10.3390/s22072741 - 2 Apr 2022

Cited by 2 | Viewed by 4126

Abstract

Stretchable strain sensors are capable of acquiring data when in contact with human skin or equipment and are widely used in wearable applications. Most strain sensors have tensile properties of less than 20% and have limitations regarding body motion linkage, complex sensor structure, and motion nonreliability. To address these problems, we developed a high tension and high sensitivity sensor with a gauge factor over 40 and tensile stress about 50%. Polydimethylsiloxane (PDMS) was selected as the flexible substrate to ensure tensile strength, and polyaniline (PANI) was used to measure the resistance changes in the sensor. In particular, problems regarding poor uniformity of PANI on PDMS were resolved by surface treatment of the PDMS, wherein PANI polymerization was performed sequentially after forming a self-assembled monolayer (SAM) on the PDMS substrate. O₂ plasma and (3-aminopropyl)triethoxysilane were used to form the SAM. It is expected that this sensor can obtain stable characteristics even under high tensile stress through the evenly formed PANI films on the surface-treated PDMS substrate and may be used in various flexible sensor applications. Full article

(This article belongs to the Special Issue Recent Advances in Smart Materials for Sensor and Actuator Applications)

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22 pages, 7947 KiB

Open AccessArticle

Design and Control of Multi-Plate MR Clutch Featuring Friction and Magnetic Field Control Modes

by Jin-Young Park, Jong-Seok Oh and Young-Choon Kim

Sensors 2022, 22(5), 1757; https://doi.org/10.3390/s22051757 - 23 Feb 2022

Cited by 3 | Viewed by 2575

Abstract

A magnetorheological (MR) multi-plate clutch was proposed with both mechanical friction mode and magnetic field control modes. The magnetic field control mode was based on an MR fluid coupler that changed its viscous properties according to the density of an applied magnetic field. This mode was used in the early stage of clutch operation to reduce the impact of friction between the disc and plate, and eliminate to the extent possible the difference in their relative speeds when contacting each other in later stages. Once the rotational speed difference between the disc and plate was reduced, the clutch was operated in mechanical friction mode by compressing the friction surfaces together. A torque modeling equation was then derived for each mode based on the Bingham model of the MR fluid, and the transmission torque of the proposed multi-plate clutch was derived using these equations as well as magnetic field analysis results obtained using ANSYS Maxwell. A multi-plate MR clutch was then fabricated, and its torque transmission characteristics were evaluated in the magnetic field control and mechanical friction modes. The results confirmed that the model-based torque calculations were consistent with the observed transmission torque. Finally, control algorithms for mechanical friction only and mixed mechanical friction/magnetic field control torque tracking of the proposed MR multi-plate clutch were designed, and their performances were evaluated when applying unit step command, half-sine-wave command, and rotational speed changes. The results indicated that the torque tracking control was performed smoothly, demonstrating the advantages of the proposed clutch. Full article

(This article belongs to the Special Issue Recent Advances in Smart Materials for Sensor and Actuator Applications)

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17 pages, 9481 KiB

Open AccessArticle

Improvement in Strain Sensor Stability by Adapting the Metal Contact Layer

by Ji-Yeon Choy, Eun-Bee Jo, Chang-Joo Yim, Hae-Kyung Youi, Jung-Hoon Hwang, Jun-Ho Lee and Hyun-Seok Kim

Sensors 2022, 22(2), 630; https://doi.org/10.3390/s22020630 - 14 Jan 2022

Cited by 4 | Viewed by 2023

Abstract

Research on stretchable strain sensors is actively conducted due to increasing interest in wearable devices. However, typical studies have focused on improving the elasticity of the electrode. Therefore, methods of directly connecting wire or attaching conductive tape to materials to detect deformation have been used to evaluate the performance of strain sensors. Polyaniline (PANI), a p-type semiconductive polymer, has been widely used for stretchable electrodes. However, conventional procedures have limitations in determining an appropriate metal for ohmic contact with PANI. Materials that are generally used for connection with PANI form an undesirable metal-semiconductor junction and have significant contact resistance. Hence, they degrade sensor performance. This study secured ohmic contact by adapting Au thin film as the metal contact layer (the MCL), with lower contact resistance and a larger work function than PANI. Additionally, we presented a buffer layer using hard polydimethylsiloxane (PDMS) and structured it into a dumbbell shape to protect the metal from deformation. As a result, we enhanced steadiness and repeatability up to 50% strain by comparing the gauge factors and the relative resistance changes. Consequently, adapting structural methods (the MCL and the dumbbell shape) to a device can result in strain sensors with promising stability, as well as high stretchability. Full article

(This article belongs to the Special Issue Recent Advances in Smart Materials for Sensor and Actuator Applications)

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20 pages, 14557 KiB

Open AccessArticle

Classification of Chaotic Squeak and Rattle Vibrations by CNN Using Recurrence Pattern

by Jaehyeon Nam and Jaeyoung Kang

Sensors 2021, 21(23), 8054; https://doi.org/10.3390/s21238054 - 2 Dec 2021

Cited by 7 | Viewed by 1753

Abstract

The chaotic squeak and rattle (S&R) vibrations in mechanical systems were classified by deep learning. The rattle, single-mode, and multi-mode squeak models were constructed to generate chaotic S&R signals. The repetition of nonlinear signals generated by them was visualized using an unthresholded recurrence plot and learned using a convolutional neural network (CNN). The results showed that even if the signal of the S&R model is chaos, it could be classified. The accuracy of the classification was verified by calculating the Lyapunov exponent of the vibration signal. The numerical experiment confirmed that the CNN classification using nonlinear vibration images as the proposed procedure has more than 90% accuracy. The chaotic status and each model can be classified into six classes. Full article

(This article belongs to the Special Issue Recent Advances in Smart Materials for Sensor and Actuator Applications)

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15 pages, 3904 KiB

Open AccessArticle

Dual Properties of Polyvinyl Alcohol-Based Magnetorheological Plastomer with Different Ratio of DMSO/Water

by Norhiwani Mohd Hapipi, Saiful Amri Mazlan, Ubaidillah Ubaidillah, Siti Aishah Abdul Aziz, Seung-Bok Choi, Nur Azmah Nordin, Nurhazimah Nazmi, Zhengbin Pang and Shahir Mohd Yusuf

Sensors 2021, 21(22), 7758; https://doi.org/10.3390/s21227758 - 22 Nov 2021

Cited by 1 | Viewed by 2069

Abstract

Polyvinyl alcohol (PVA)-based magnetorheological plastomer (MRP) possesses excellent magnetically dependent mechanical properties such as the magnetorheological effect (MR effect) when exposed to an external magnetic field. PVA-based MRP also shows a shear stiffening (ST) effect, which is very beneficial in fabricating pressure sensor. Thus, it can automatically respond to external stimuli such as shear force without the magnetic field. The dual properties of PVA-based MRP mainly on the ST and MR effect are rarely reported. Therefore, this work empirically investigates the dual properties of this smart material under the influence of different solvent compositions (20:80, 40:60, 60:40, and 80:20) by varying the ratios of binary solvent mixture (dimethyl sulfoxide (DMSO) to water). Upon applying a shear stress with excitation frequencies from 0.01 to 10 Hz, the storage modulus (G′) for PVA-based MRP with DMSO to water ratio of 20:40 increases from 6.62 × 10⁻⁵ to 0.035 MPa. This result demonstrates an excellent ST effect with the relative shear stiffening effect (RSTE) up to 52,827%. In addition, both the ST and MR effect show a downward trend with increasing DMSO content to water. Notably, the physical state of hydrogel MRP could be changed with different solvent ratios either in the liquid-like or solid-like state. On the other hand, a transient stepwise experiment showed that the solvent’s composition had a positive effect on the arrangement of CIPs within the matrix as a function of the external magnetic field. Therefore, the solvent ratio (DMSO/water) can influence both ST and MR effects of hydrogel MRP, which need to be emphasized in the fabrication of hydrogel MRP for appropriate applications primarily with soft sensors and actuators for dynamic motion control. Full article

(This article belongs to the Special Issue Recent Advances in Smart Materials for Sensor and Actuator Applications)

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19 pages, 4119 KiB

Open AccessArticle

Autonomous Assessment of Delamination Using Scarce Raw Structural Vibration and Transfer Learning

by Asif Khan, Salman Khalid, Izaz Raouf, Jung-Woo Sohn and Heung-Soo Kim

Sensors 2021, 21(18), 6239; https://doi.org/10.3390/s21186239 - 17 Sep 2021

Cited by 19 | Viewed by 2300

Abstract

Deep learning has helped achieve breakthroughs in a variety of applications; however, the lack of data from faulty states hinders the development of effective and robust diagnostic strategies using deep learning models. This work introduces a transfer learning framework for the autonomous detection, isolation, and quantification of delamination in laminated composites based on scarce low-frequency structural vibration data. Limited response data from an electromechanically coupled simulation model and from experimental testing of laminated composite coupons were encoded into high-resolution time-frequency images using SynchroExtracting Transforms (SETs). The simulated and experimental data were processed through different layers of pretrained deep learning models based on AlexNet, GoogleNet, SqueezeNet, ResNet-18, and VGG-16 to extract low- and high-level autonomous features. The support vector machine (SVM) machine learning algorithm was employed to assess how the identified autonomous features were able to assist in the detection, isolation, and quantification of delamination in laminated composites. The results obtained using these autonomous features were also compared with those obtained using handcrafted statistical features. The obtained results are encouraging and provide a new direction that will allow us to progress in the autonomous damage assessment of laminated composites despite being limited to using raw scarce structural vibration data. Full article

(This article belongs to the Special Issue Recent Advances in Smart Materials for Sensor and Actuator Applications)

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Review

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26 pages, 2910 KiB

Open AccessReview

Functionality Analysis of Electric Actuators in Renewable Energy Systems—A Review

by Abhijeet Redekar, Dipankar Deb and Stepan Ozana

Sensors 2022, 22(11), 4273; https://doi.org/10.3390/s22114273 - 3 Jun 2022

Cited by 6 | Viewed by 4418

Abstract

Various mechanical, hydraulic, pneumatic, electrical, and hybrid actuators can alter motion per the requirements of particular applications. However, except for electrical ones, all actuators are restricted due to their size, complex auxiliary equipment, frequent need for maintenance, and sluggish environment in renewable applications. This brief review paper highlights some unique and significant research works on applying electrical actuators to renewable applications. Four renewable energy resources, i.e., solar, wind, bio-energy, and geothermal energy, are considered to review electric actuators applicable to renewable energy systems. This review analyses the types of actuators associated with the mentioned renewable application, their functioning, their motion type, present use, advantages, disadvantages, and operational problems. The information gathered in this paper may open up new ways of optimization opportunities and control challenges in electrical actuators, thereby making more efficient systems. Furthermore, some energy-efficient and cost-effective replacements of convectional actuators with new innovative ones are suggested. This work aims to benefit scientists and new entrants working on actuators in renewable energy systems. Full article

(This article belongs to the Special Issue Recent Advances in Smart Materials for Sensor and Actuator Applications)

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