Actuators

431 KiB

Open AccessArticle

Ultrasonic Transducer Fabricated Using Lead-Free BFO-BTO+Mn Piezoelectric 1-3 Composite

by Yan Chen, Kai Mei, Chi-Man Wong, Dunmin Lin, Helen Lai Wa Chan and Jiyan Dai

Actuators 2015, 4(2), 127-134; https://doi.org/10.3390/act4020127 - 29 May 2015

Cited by 13 | Viewed by 9751

Mn-doped 0.7BiFeO₃-0.3BaTiO₃ (BFO-0.3BTO+Mn 1% mol) lead-free piezoelectric ceramic were fabricated by traditional solid state reaction. The phase structure, microstructure, and ferroelectric properties were investigated. Additionally, lead-free 1–3 composites with 60% volume fraction of BFO-BTO+Mn ceramic were fabricated for ultrasonic transducer applications by a conventional dice-and-fill method. The BFO-BTO+Mn 1-3 composite has a higher electromechanical coupling coefficient (k_t = 46.4%) and lower acoustic impedance (Z_a ~ 18 MRayls) compared with that of the ceramic. Based on this, lead-free piezoelectric ceramic composite, single element ultrasonic transducer with a center frequency of 2.54 MHz has been fabricated and characterized. The single element transducer exhibits good performance with a broad bandwidth of 53%. The insertion loss of the transducer was about 33.5 dB. Full article

(This article belongs to the Special Issue Feature Papers)

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708 KiB

Open AccessArticle

A Compact Ionic Polymer Metal Composite (IPMC) System with Inductive Sensor for Closed Loop Feedback

by Jiaqi Wang, Andrew McDaid, Rajnish Sharma and Kean C. Aw

Actuators 2015, 4(2), 114-126; https://doi.org/10.3390/act4020114 - 19 May 2015

Cited by 15 | Viewed by 8373

Abstract

Ionic polymer metal composite (IPMC), of which a low actuating voltage (<5 V), high power efficiency and biocompatibility makes it a proven candidate for low power devices. However, due to its inherent nonlinear behaviour and time-variance, feedback control, as well as reliable sensing means, are required for accurate operations. This paper presents an IPMC actuator implemented with an inductive sensor to enhance the reliability and compactness of the overall device. A practical, low cost and importantly, compact inductive sensor fabricated on a printed circuit board (PCB) is proposed here. Target material selections and coil design considerations are discussed. It is experimentally determined that the inductive sensor has comparable performance to a laser sensor. Based on a proportional-integral-derivative (PID) control results the inductive sensor has demonstrated to be an alternative to a laser sensor allowing devices using IPMC actuators to be compact. Full article

(This article belongs to the Special Issue Feature Papers)

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699 KiB

Open AccessArticle

Ferroelectric KNNT Fibers by Thermoplastic Extrusion Process: Microstructure and Electromechanical Characterization

by Tony Lusiola, Ali Hussain, Myong Ho Kim, Thomas Graule and Frank Clemens

Actuators 2015, 4(2), 99-113; https://doi.org/10.3390/act4020099 - 8 May 2015

Cited by 12 | Viewed by 9351

Abstract

B-site substitution in KNN with tantalum results in a higher d₃₃ and dielectric constant. This higher value makes KNNT interesting for lead-free actuator applications. KNNT fibers with diameters of 300 and 500 μm have been extruded and sintered at 1200 °C in a KNNT-enriched atmosphere. Subsequently, the influence of fiber diameter on the microstructure (porosity and grain size) was investigated. The measurements revealed that with decreasing fiber diameter, the porosity increases, whereas the grain size decreases. The influence of these microstructural differences on the piezoelectric properties was evaluated using a novel characterization procedure for single fibers. The larger diameter fibers show an increase in the electromechanical properties measured, i.e., d₃₃, tanδ, P_r, E_c and the free longitudinal fiber displacement, when compared to smaller diameter fibers. The lower alkali losses result in a larger grain size, a higher density during sintering and lead to higher electromechanical properties. Full article

(This article belongs to the Special Issue Feature Papers)

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853 KiB

Open AccessReview

Survey of Active Structural Control and Repair Using Piezoelectric Patches

by Ahmed Abuzaid, Meftah Hrairi and M.S.I. Shaik Dawood

Actuators 2015, 4(2), 77-98; https://doi.org/10.3390/act4020077 - 5 May 2015

Cited by 29 | Viewed by 7623

Abstract

The piezoelectric actuator has gained popularity over the last few years. Attention has been directed towards the study of their electromechanical response in active repair and the control of damaged structures. This has been made possible through the development of various numerical and analytical techniques for such studies. The shift of focus towards the piezoelectric based approaches has been due to their advantages, which include strategic cost benefits in maintenance, as well as an increase in the life cycle of the repaired structures. Furthermore, adhesively bonded joints are widely used in the manufacturing and repairing of structures in many industries, especially automotive and aerospace engineering. This is due to the requirement for lightweight materials as well as the potential adhesive used to join materials with different characteristics. The piezoelectric actuator has also shown the capacity in controlling and lowering the shear stress concentration and joint edge peel in adhesively bonded joint systems. The structure’s control of stress and repair can generally be viewed as a reinforcement that influences the structure’s damage tolerance. Therefore, the interest of this review is on the applications of the piezoelectric actuators in both structural damage and the bonded adhesive joint system. The specific goal is to recognize the contemporary scientific challenges, including future opportunities. Full article

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2549 KiB

Open AccessArticle

Fourth-Order Contour Mode ZnO-on-SOI Disk Resonators for Mass Sensing Applications

by Ivan Rivera, Adrian Avila and Jing Wang

Actuators 2015, 4(2), 60-76; https://doi.org/10.3390/act4020060 - 21 Apr 2015

Cited by 9 | Viewed by 8598

Abstract

In this work, we have investigated the design, fabrication and testing of ZnO-on-SOI fourth-order contour mode disk resonators for mass sensing applications. This study aims to unveil the possibility for real-time practical mass sensing applications by using high-Q ZnO-on-SOI contour-mode resonators while taking into account their unique modal characteristics. Through focused ion beam (FIB) direct-write metal deposition techniques, the effects of localized mass loading on the surface of three extensional mode devices have been investigated. Ten microfabricated 40 mm-radius disk resonators, which all have a 20 mm-thick silicon device layer and 1 mm-thick ZnO transducer layer but varied anchor widths and numbers, have exhibited resonant frequencies ranging from 84.9 MHz to 86.7 MHz with Q factors exceeding 6000 (in air) and 10,000 (in vacuum), respectively. It has been found that the added mass at the nodal locations leads to noticeable Q-factor degradation along with lower induced frequency drift, thereby resulting in reduced mass sensitivity. All three measured devices have shown a mass sensitivity of ~1.17 Hz·fg⁻¹ at the maximum displacement points with less than 33.3 ppm of deviation in term of fractional frequency change. This mass sensitivity is significantly higher than 0.334 Hz·fg⁻¹at the nodal points. Moreover, the limit of detection (LOD) for this resonant mass sensor was determined to be 367 ag and 1290 ag (1 ag = 10⁻¹⁸ g) for loaded mass at the maximum and minimum displacement points, accordingly. Full article

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Actuators, Volume 4, Issue 2 (June 2015) – 5 articles , Pages 60-134

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