Search

The force‐induced light‐emitting phenomenon in polymer composites plays an important role in the soft electronic field due to its display function. Here, a magnetic‐force‐induced‐luminescence (MFIL) effect is reported in ZnS:Cu particle‐doped polydimethylsiloxane incorporated with a NdFeB magnetic tip mass for real‐time incident magnetic field strength light‐emitting display. Investigations show that the luminescence intensity increases nearly linear in response to the applied AC magnetic field, HAC; meanwhile, the minimum HAC for inducing MFIL is as low as 0.1 mT (1 Oe) at the resonance. The MFIL effect is 1000 times better and more energy‐efficient than the best result published previously. The findings, thus, indicate that the MFIL effect could serve as an effective method for light‐emitting display triggered by HAC; MFIL essentially originates from the donor–acceptor recombination between shallow donor level and the t2 level of Cu2 in ZnS:Cu semiconductor particles. The present results could, thus, provide a viable pathway toward multifunctional flexible electronic designs and applications, especially toward those for the real‐time visualization of remote magnetic field sensing. [ABSTRACT FROM AUTHOR]

It is desired to obtain a piezoceramic with a high piezoelectric coefficient and low dielectric loss simultaneously for energy harvester application. Herein, it is reported that the 0.025Pb(Mn1/3Nb2/3)O3‐0.525Pb(Ni1/3Nb2/3)O3‐0.135PbZrO3‐0.315PbTiO3 (PMNN‐PZT) ceramic exhibits superior piezoelectric charge parameter e33 of 37.74 pC m−2 and low dielectric loss tanδ of 0.45%. Furthermore, a PMNN‐PZT ceramic‐based magneto‐mechano‐electric coupled energy harvester (MMEC‐EH) with a varying‐stiffness cantilever is designed and fabricated, which shows the strong self‐resonance effect in response to a random, transient impulse vibration or magnetic field stimulus. The investigations show that under a 0.6 s pulse vibration stimulus, the MMEC‐EH can tune itself into self‐resonance damping oscillation lasting for six seconds at its resonance frequency of 16 Hz, and the produced maximum power is 1.96 mWRMS. Under both weak magnetic field and force‐field dual‐stimulus (Hac = 0.5 Oe and a = 0.05 g), the generated power density is about 60 mWRMS Oe−2g−2cm−3, which is one to two orders of magnitude higher than those previously reported MMEC‐EHs. Finally, the MMEC‐EH is successfully demonstrated to power temperature/humidity sensors, indicating its potential for harvesting both weak vibration and magnetic field energy from environments for self‐powered sensor application. [ABSTRACT FROM AUTHOR]

A magneto‐mechano‐electric (MME) generator that can harvest ambient magnetic noise plays a significant role in powering Internet of Things (IoT) sensor networks. However, it is still a challenge to capture sufficient energy and continuously drive IoT nodes from extremely low‐intensity magnetic noise below 1 Oe. To circumvent the close dependence of the resonant frequency on the magnetic proof mass in conventional MME generators, a new clamped‐clamped (C‐C) MME generator is proposed, that allows a much heavier magnetic mass to be attached at the beam center. Under weak magnetic fields of 0.48 and 0.96 Oe at 50 Hz, optimized output powers of 370 and 970 μWRMS, respectively are achieved, which shows an enhancement of ≈120% over that of cantilevered MME generators. The underlying mechanics are theoretically revealed by comparing the lumped parameters with a cantilevered MME generator and by calculating their deflection gain. Finally, it is demonstrated that the harvested energy from the proposed C‐C MME generator from a 0.48 Oe magnetic field at 50 Hz is sufficient to continuously drive an IoT sensor without any additional intervals for recharging. It is believed that this work will open new possibilities for designing MME generators suitable for weak field energy harvesting. [ABSTRACT FROM AUTHOR]

Multiferroic magnetoelectric (ME) composites have been continually attracting researchers' attention because of the significant potential for building functional devices. Unlike conventional ME devices under quasi-static or low-power excitation, e.g., sensors, energy harvesters, and random memories, high-power ME devices like recently proposed ME antennas will perform complex dynamic behavior. The voltage-driven nonlinearity in 1–1-typed ME resonators was reported from the perspective of frequency-response curve in our last work. Here, we described both theoretically and experimentally a previously unobserved jumping and hysteresis effect in its magnetic bias characteristic. A direct link between the bias-response and the frequency-response characteristics was also experimentally provided to analyze the origin of the nonlinear behavior in the bias-response curve. In addition, the cubic spring constant k3 was theoretically calculated and compared to qualitatively explain the difference of our obtained threshold voltage that generated the first and second jumping resonances in the dual-peak bias-response curve. In contrast to our previous research, this work reveals the loading direction of the applied magnetic bias field, which plays a significant role when we consider the selection of an optimized bias field for high-power ME devices. Moreover, the sharp jumping in the bias-response curve is also a potential for opening dimensions for ME community. [ABSTRACT FROM AUTHOR]

In this work, we theoretically and experimentally report a NdFeB magnet/piezoelectric composite cantilever with varying stiffness for enhancing magneto-mechano-electric (MME) coupling under weak AC magnetic field Hac excitation. Measurement results show that the MME composite cantilever can produce a relatively high peak-peak output power of 12.8 mW and a peak-peak current of 0.735 mApp under Hac = 7 Oe at a resonance frequency of 36 Hz. Even when Hac is as low as 0.2 Oe, equivalent to the level of the earth magnetic field, it can still drive 4 LED lighting. The obtained results are obviously superior to previous reports, confirming the MME cantilever harvester has potential to harvest the stray magnetic field energy from electrical power cables for continuously powering wireless sensor networks. [ABSTRACT FROM AUTHOR]

In previous theoretical analyses, magnetoelectric (ME) coupling coefficient αME of piezoelectric/piezomagnetic laminates for static and dynamic modes is usually regarded as one that is not related to laminates' sizes (length and width). In micrometer or sub-millimeter ME laminates, the decrease in ME coupling was normally attributed to the substrate's clamping effect. Here, we report an effective ME coefficient αME,eff including sizes' effect based on magnetic circuit method including the size induced demagnetization effect, which predicted that as sizes of ME laminates decrease from 100 mm to 10-3 mm, αME,eff will dramatically decreases from ∼5 V/cm-Oe to 0.08 V/cm-Oe. Size decrease in ME laminates will result in a decrease in effective magnetic induction Bμ inside piezomagnetic phase in an applied magnetic field H. Our analyses further disclose a degenerate mode occurred between the longitudinal and transverse resonance modes, which may cause a weakened ME coupling. Finally, our analyses indicate that a thin and long ME laminate will exhibit a stronger ME coupling, which was then confirmed by our experimental results. [ABSTRACT FROM AUTHOR]

A magnetoelectric composite consisting of a multilayer Pb(Zr,Ti)O3 piezoelectric (d33) stack and a magnetostrictive (Galfenol and/or Terfenol-D) rod assembled in a prestressed frame in a longitudinal-longitudinal configuration has been found to have a high magnetoelectric (ME) charge coupling to an applied magnetic field. Values of the ME charge coefficient as high as 16.4 nC/Oe (or 3.6×10-6 C/m2 Oe) were found at quasistatic frequencies and 123 nC/Oe (or 2.8×10-5 C/m2 Oe) under resonance drive, which are 100–1000 times higher than that previously reported for other ME laminates. [ABSTRACT FROM AUTHOR]

Three-phase magnetoelectric (ME) laminate composites made of high-permeability (μ) MnZnFe2O4, magnetostrictive Tb1-xDyxFe2-y, and piezoelectric Pb(Zr,Ti)O3 layers and operated in longitudinal magnetization and transverse polarization (L-T) bending modes have been studied. High-μ MnZnFe2O4 layers act as flux concentrators. This results in increased apparent piezomagnetic coefficients in the magnetostrictive Tb1-xDyxFe2-y layer and consequently larger induced voltages across the piezoelectric Pb(Zr,Ti)O3 layers. We find the enhanced ME field coefficients of up to 8 times for longitudinal magnetization mode, and up to 28 times for transverse magnetization mode, under small dc magnetic field bias. [ABSTRACT FROM AUTHOR]

Tremendous progress has been made in boosting the realization of magnetoelectric (ME) magnetometers based on the direct ME effect (DME) for bulk ME laminates. In this work, we studied the potential of an electrically driven bulk magnetic field sensor based on the converse ME effect (CME). Starting from a discussion about the dependence of the induced voltage from the pickup coil on coil parameters and the CME coupling process, we then experimentally measured the optimized bias field in the off resonance region and observed the double-peak phenomenon that occurred within the resonance window. More importantly, the optimization with respect to the sample's dimension, excitation voltage, and frequency was conducted to improve the sensing capability for low-frequency magnetic fields. It was experimentally found that a limit of detection (LoD) of ∼115 pT for a magnetic field of 10 Hz and ∼300 pT for a magnetic field of 1 Hz was achieved when exciting the ME laminate at 1 V without any bias field. In this case, the power consumption for the ME laminate is only 0.56 mW, which is much lower compared to tens of milliwatts (10–100 mW) for optically pumped or flux gate sensors (excluding the power consumption from the electronics) and also shows advantages over conventional ME magnetic field sensors based on DME with a current pump. [ABSTRACT FROM AUTHOR]

This study reports the improvement in the magnetoelectric (ME) coupling effect in a locally heat-treated FeBSi (Metglas)/Pb(Mg1/3Nb2/3)O3-PbZrO3-PbTiO3 single crystal laminated composite under zero magnetic bias. The high-temperature pulse laser treatment could induce local crystallization along the laser scanning line, but adjacent domains remained still amorphous, which resulted in the thermal and lattice mismatch. Therefore, it could produce a residual stress between the crystalline and amorphous phases, which generated an internal bias field in the Metglas foil. The experimental results showed that the ME coefficient for the laser-treated laminate was enhanced to 1220 V/cm Oe at the resonance frequency of 23.32 kHz without a magnetic bias, which was two times higher than that of the untreated ME laminates. The induced ME voltage also showed a linear response to the applied AC magnetic field with an amplitude as low as 10−10 T at the resonance. The excellent ME performance could, therefore, serve as a promising and practicable application for highly sensitive magnetic field sensors under the zero bias field. [ABSTRACT FROM AUTHOR]

It is an important scientific and engineering challenge to sense a weak magnetic field HAC at extremely low-frequency (LF) below 1 Hz due to the large LF noise. In this work, we presented an amplitude modulation method (AMM) for quasi-static magnetic field detection based on a magnetoelectric (ME) sensor and a lock-in amplifier. Different from previously reported frequency conversion technology, the weak LF magnetic signal is demodulated directly from the output response of a ME sensor driven at its resonance frequency. Experimental results demonstrated that the absolute resolution with respect to a 100 mHz HAC is as low as 100 pT, indicating an enhancement by a factor of 50% in comparison with previous reports. This proposed AMM should pave another route for LF weak HAC detection. [ABSTRACT FROM AUTHOR]

In this work, a multi-terminal hexagonal-framed magnetoelectric composite (HFMEC) made of amorphous FeBSi alloy (Metglas) ribbons and three sandwiched [011]-oriented PMN-PT single-crystal fibers (Pb(Mg1/3Nb2/3)O3-PbTiO3) arranged with a 120° interval is presented, and the directional magnetoelectric (ME) effect of the HFMEC operating in the L-T mode under a constant-amplitude AC magnetic field is investigated. It is found that the HFMEC exhibits threefold symmetric directional ME coupling in response to an applied in-plane DC magnetic field HDC, while each ME terminal shows a twofold symmetry due to the magnetization and demagnetization effect of HDC. Moreover, a valid formula for calculating the angular direction of the magnetic field is also presented. It is further revealed that the HFMEC exhibits a “V” shaped ME voltage output as a response to HDC due to the geomagnetic field (HGeo) effect, and the knee point of the curve literally reveals the magnitude of local HGeo, while the direction of HDC indicates a reverse direction of HGeo. The proposed HFMEC provides a great potential for a vector magnetometer as well as geomagnetic sensor application. [ABSTRACT FROM AUTHOR]

The current paper reports a digital piezoelectric bimorph actuator having segmented electrodes and producing 2 to the nth power digital bending actuation in on/off switch mode and under a fix applied voltage. Correspondingly, a simple model for predicting digital actuation under applied coding voltage is also presented. Experimental results have confirmed that the proposed actuator can produce a linear digital displacement without a hysteresis loop. The proposed method is significant for open-loop high precise actuation. [ABSTRACT FROM AUTHOR]

Magnetoelectric equivalent circuit analytical method is presented for laminate composites of magnetostrictive Terfenol-D (TbxDy1-xFe2) and piezoelectric Pb(Zr1-xTix)O3 (PZT) operated in longitudinal magnetized and transverse polarized (or L-T), and transverse magnetized and transverse polarized (or T-T) modes. Magnetoelectric (ME) couplings both at low-frequency and resonance-frequency have been studied, and our analysis predicts that (i) the ME voltage coefficients of both L-T and T-T modes increase with increasing the thickness of the piezoelectric phase whereas magnetostrictive phase thickness keeps constant, and then tend to saturation when the thickness ratio of piezoelectric phase to magnetic phases is >3; (ii) there are the optimum thickness ratios that maximize magnetoelectric (ME) voltage coefficients for the two modes, which are dependent on elastic compliances ratio of piezoelectric phase and magnetostrictive phase; and (iii) the ME voltage coefficients are dramatically increased by a factor of ~Qm, when operated at resonance frequency. A series of Terfenol-D/PZT laminates were fabricated, and the results were compared with the theoretical ones. Experiments confirmed that equivalent circuit method is a useful tool for optimum designs of ME laminates. [ABSTRACT FROM AUTHOR]

Here, the authors report a new type of geomagnetic field sensor based on the giant magnetoelectric effect in Metglas/piezoelectric-fiber laminates that are wrapped with a coil. These sensors can measure quite precisely the value of both the Earth’s magnetic field and its inclination. The geomagnetic field sensor does not require a dc magnetic bias and is driven by a 10 mA ac. Highly sensitive dc magnetic field variations of less than 10-9 T and angular inclinations of ≤10-5 deg can be detected, potentially offering opportunities for a small global positioning device [ABSTRACT FROM AUTHOR]

A promising generation of extremely low frequency magnetic field sensors, based on multilayer composites (MLCs) of magnetostrictive Terfenol-D (Tb1-xDyxFe2-y) and piezoelectric Pb(Mg1/3Nb2/3)O3–PbTiO3, has been developed. Our MLC magnetoelectric sensor presently shows a limit in (i) working frequency of ∼5×10-3 Hz; and (ii) magnetic field sensitivity of 10-7, 10-9, and 10-11 T for frequencies of f=10-2, 1, and 102 Hz, respectively. The results open up possibilities for sensitive low frequency passive magnetic anomaly detection. [ABSTRACT FROM AUTHOR]

Magneto‐mechano‐electric (MME) energy harvesters (EHs) have emerged as a promising solution for powering Internet of Things (IoT) sensor networks by capturing ambient stray magnetic fields in urban circumstance. Despite significant advancements, achieving milliwatt‐level power generation from extremely weak (<1 Oe) and randomly oriented magnetic fields remains challenging. Drawing inspiration from the configuration of cross‐shaped spider legs, this study introduces an innovative X‐shaped MME‐EH featuring fourfold symmetric architecture with symmetrically distributed magnets at each end, enabling near‐isotropic in‐plane omnidirectional energy harvesting. Under extremely weak magnetic fields 0.75 and 0.3 Oe at 60 Hz, the device achieves a record‐high output power of 7.31 and 1.67 mWRMS, respectively, representing a 362% improvement in normalized power over the state‐of‐the‐art results. The theoretical model attributes these gains to the synergistic enhancement effect of the second bending mode and the dual‐mode structure, collectively improving both magnetomechanical and electromechanical coupling by augmenting the magnetic moments and suppressing the clamp loss. The device further demonstrates robust real‐world applications, efficiently powering a wireless IoT sensor system by harvesting multidirectional magnetic field energy from household appliances. This work opens new avenues for developing efficient multimodal MME‐EHs capable of harnessing omnidirectional, weak magnetic fields for widespread IoT applications. [ABSTRACT FROM AUTHOR]

As the rapid development of the Internet of Things (IoT), the demand for the self-powered sensors and devices has become urgent. In this work, we present a self-powered magnetic field sensor based on a biomimetic dragonfly-wings like magnetoelectric (DWL-ME) laminated cantilever. The two pairs of wings in DWL-ME cantilever operating in anti-phase vibration modal has shown a strong magnetoelectric coupling for converting magnetic field energy into electric energy with an energy harvesting density of as high as 100 µWOe−2cm−3. It also shows a linear response to an alternating magnetic field (H AC) with a high detectability of 2.7 nT at 60 Hz. Compared to traditional cantilever beam ME sensors, its vibration noise is also effectively decreased by more than 30 dB due to the anti-phase vibration modal of two pairs of wings. The proposed biomimetic design strategy has inspirational significance for future sustainable, self-powered intelligent sensor networks. [Display omitted] • A self-powered biomimetic dragonfly-wings like magnetic field sensor has been developed. • The vibration noise was decreased by 30 dB compared to traditional cantilever beam ME sensors. • The energy harvesting density of 100 µW Oe-2 cm-3 and a detectability of 2.7 nT for AC magnetic field was obtained. [ABSTRACT FROM AUTHOR]