Search

Abstract Biological molecule-semiconductor interfacing has triggered numerous opportunities in applied physics such as bio-assisted data storage and computation, brain-computer interface, and advanced distributed bio-sensing. The introduction of electronics into biological embodiment is being quickly developed as it has great potential in providing adaptivity and improving functionality. Reciprocally, introducing biomaterials into semiconductors to manifest bio-mimetic functionality is impactful in triggering new enhanced mechanisms. In this study, we utilize the vulnerable perovskite semiconductors as a platform to understand if certain types of biomolecules can regulate the lattice and endow a unique mechanism for stabilizing the metastable perovskite lattice. Three tiers of biomolecules have been systematically tested and the results reveal a fundamental mechanism for the formation of a “reverse-micelle” structure. Systematic exploration of a large set of biomolecules led to the discovery of guiding principle for down-selection of biomolecules which extends the classic emulsion theory to this hybrid systems. Results demonstrate that by introducing biomaterials into semiconductors, natural phenomena typically observed in biological systems can also be incorporated into semiconducting crystals, providing a new perspective to engineer existing synthetic materials.

Abstract To achieve optimal thermoelectric performance, it is crucial to manipulate the scattering processes within materials to decouple the transport of phonons and electrons. In half-Heusler (hH) compounds, selective defect reduction can significantly improve performance due to the weak electron-acoustic phonon interaction. This study utilized Sb-pressure controlled annealing process to modulate the microstructure and point defects of Nb0.55Ta0.40Ti0.05FeSb compound, resulting in a 100% increase in carrier mobility and a maximum power factor of 78 µW cm−1 K−2, approaching the theoretical prediction for NbFeSb single crystal. This approach yielded the highest average zT of ~0.86 among hH in the temperature range of 300-873 K. The use of this material led to a 210% enhancement in cooling power density compared to Bi2Te3-based devices and a conversion efficiency of 12%. These results demonstrate a promising strategy for optimizing hH materials for near-room-temperature thermoelectric applications.

Conventional wet chemistry method represents an inefficient way for bulk crystal synthesis. Here, the authors report a universal approach using electrical and mechanical field-assisted sintering technique to generate halide perovskites from solid precursors into large bulk crystal within minutes.

ABSTRACT: Quantifying digestive and fermentative processes within the rumen environment has been the subject of decades of research; however, our existing research methodologies preclude time-sensitive and spatially explicit investigation of this system. To better understand the temporal and spatial dynamics of the rumen environment, real-time and in situ monitoring of various chemical and physical parameters in the rumen through implantable microsensor technologies is a practical solution. Moreover, such sensors could contribute to the next generation of precision livestock farming, provided sufficient wireless data networking and computing systems are incorporated. In this review, various microsensor technologies applicable to real-time metabolic monitoring for ruminants are introduced, including the detection of parameters for rumen metabolism, such as pH, temperature, histamine concentrations, and volatile fatty acid concentrations. The working mechanisms and requirements of the sensors are summarized with respect to the selected target parameters. Lastly, future challenges and perspectives of this research field are discussed.

Light control of living systems is an emerging field in bioelectronics, in regenerative medicine and cell‐based therapy. Herein, the design of a semitransparent bio–photoelectrolytic platform for control of a neuroblastoma cell line via light pulses is laid out. The platform is based on conjugated polymer films interfaced with a biological electrolyte solution confined in a compact chamber. Human SH‐SY5Y neuroblastoma cells are cultured for 3 days on the organic semiconductor and subjected to a pulsed light protocol. At the end of the culture time, proliferative activity of cells on the polymer film subjected to light pulses is reduced by 50% compared to the cultures kept in dark. An increase in intracellular Ca2+ level is observed, indicating a significant perturbation of the equilibrium potential of the cells. It is shown that the platform, in a sandwich‐type closed architecture with two transparent electrodes, can provide a tool for the initial recording of bioelectrical photovoltage signals (mV) that can complement analysis with more sophisticated electrophysiological tools. Obtained results can pave the way to new noninvasive photomanipulation techniques to stimulate/control living cells and their proliferation through both optical and electrical stimulation and probes, for application in the fields of biosensing and biomedicine.

“k” is the electromechanical coupling factor, and determines the efficiency of conversion between electrical and mechanical energy or vice-versa in piezoelectric materials. Here, Yan et al. present an optimization strategy for “k” via texturing and covalency tuning that results in “k” values comparable to that of single crystals.

Maximizing the health, productivity, and sustainability of ruminant animals is an essential societal goal for a variety of reasons including food security, impact on the environment, and global nutrition; however, monitoring the metabolism of ruminant animals is currently a time-consuming and imprecise process. An indwelling robot residing within the ruminant gut would likely revolutionize metabolic monitoring in ruminants by providing a new level of detail into the complex and stratified chemistry of fermentation that goes on hour by hour. Indwelling robots could become an essential tool for ruminant health monitoring because many of the health, productivity, and sustainability challenges experienced by ruminants can be indicated and potentially influenced by changes in biomarkers within the rumen. We believe next-generation ruminant health monitoring will evolve from continuous biomarker measurement, reliable data transmission, and precise locomotion, all of which can be enabled by advances in indwelling ruminal robot design. Within this review, we summarize the requirements of and progress toward engineering advancements necessary to develop field-deployable robots for ruminant metabolic monitoring. The vital elements of an autonomous indwelling medical robot include locomotion, localization, wireless data transmission, and wireless power transfer. The state-of-the-art technologies associated with each element are articulated in this review. The comprehensive techniques of locomotion, the approaches for precise localization, as well as technologies for wireless power and data transmission that will make the indwelling robot entirely autonomous are enunciated, with a special focus on ruminants. The evaluated indices are potentially useful not only to assess the health of the ruminant but also to refine and standardize the assessment protocols. The overview presented in this article on the advances, imperative requirements, and challenges enables the deployment of the ruminal robot for health monitoring in ruminants.

The Scintillating Bubble Chamber (SBC) collaboration is developing liquid-noble bubble chambers for the detection of sub-keV nuclear recoils. These detectors benefit from the electron recoil rejection inherent in moderately-superheated bubble chambers with the addition of energy reconstruction provided from the scintillation signal. The ability to measure low-energy nuclear recoils allows the search for GeV-scale dark matter and the measurement of coherent elastic neutrino-nucleus scattering on argon from MeV-scale reactor antineutrinos. The first physics-scale detector, SBC-LAr10, is in the commissioning phase at Fermilab, where extensive engineering and calibration studies will be performed. In parallel, a functionally identical low-background version, SBC-SNOLAB, is being built for a dark matter search underground at SNOLAB. SBC-SNOLAB, with a 10 kg-yr exposure, will have sensitivity to a dark matter–nucleon cross section of 2×10−42 cm2 at 1 GeV/c2 dark matter mass, and future detectors could reach the boundary of the argon neutrino fog with a tonne-yr exposure. In addition, the deployment of an SBC detector at a nuclear reactor could enable neutrino physics investigations including measurements of the weak mixing angle and searches for sterile neutrinos, the neutrino magnetic moment, and the light Z’ gauge boson.

Medical implants with functionalities such as sensing, health monitoring, stimulation, diagnosis, and physiological treatment are rapidly growing. With the increasing functional sophistication and addition of modules such as data transmission, on-chip processing, and data storage, energy demand of the implantable system is also growing. Using implantable energy harvester either to recharge or ultimately replace hazardous battery is essential to provide a long-term sustainable solution. Energy harvesting techniques using piezoelectric, thermoelectric, radio frequency power transmission, biofuel, and photoelectronic (or sometimes termed as “photovoltaic” in terms of solar light harvesting, i.e., PV) conversion, have been attempted for the implantable, but these methods are currently limited by insufficient power output, large footprint, and low efficiency. Nevertheless, the planar PV with potential of lighter weight, higher energy density, and higher efficiency, provides promising power solution for in-body medical implants. In this short review, we will discuss the potential opportunities and challenges associated with PV's for medical implants, covering materials, to devices, and to system level requirements.

Abstract Piezoelectric materials enable the conversion of mechanical energy into electrical energy and vice‐versa. Ultrahigh piezoelectricity has been only observed in single crystals. Realization of piezoelectric ceramics with longitudinal piezoelectric constant (d33) close to 2000 pC N–1, which combines single crystal‐like high properties and ceramic‐like cost effectiveness, large‐scale manufacturing, and machinability will be a milestone in advancement of piezoelectric ceramic materials. Here, guided by phenomenological models and phase‐field simulations that provide conditions for flattening the energy landscape of polarization, a synergistic design strategy is demonstrated that exploits compositionally driven local structural heterogeneity and microstructural grain orientation/texturing to provide record piezoelectricity in ceramics. This strategy is demonstrated on [001]PC‐textured and Eu3+‐doped Pb(Mg1/3Nb2/3)O3‐PbTiO3 (PMN‐PT) ceramics that exhibit the highest piezoelectric coefficient (small‐signal d33 of up to 1950 pC N–1 and large‐signal d33* of ≈2100 pm V–1) among all the reported piezoelectric ceramics. Extensive characterization conducted using high‐resolution microscopy and diffraction techniques in conjunction with the computational models reveals the underlying mechanisms governing the piezoelectric performance. Further, the impact of losses on the electromechanical coupling is identified, which plays major role in suppressing the percentage of piezoelectricity enhancement, and the fundamental understanding of loss in this study sheds light on further enhancement of piezoelectricity. These results on cost‐effective and record performance piezoelectric ceramics will launch a new generation of piezoelectric applications.

Designing efficient sensors for smart tires for autonomous vehicles remains a challenge. Here, the authors present a tire-integrated system that combines direct mask-less 3D printed strain gauges, flexible piezoelectric energy harvester for powering the sensors and secure wireless data transfer electronics, and machine learning for predictive data analysis.

Traditional organic–inorganic halide perovskites (OIHPs), in which perovskites layers are separated by an organic spacer material, have been mainly explored for photovoltaics devices, but they also offer promises for nonlinear optics and quantum light applications. These attributes include (a) high quantum efficiency, (b) large binding energy of excitons in low-dimensional structures, (c) polarons of long coherence times at room temperature, and (d) a large spin–orbit coupling. OIHP systems can be engineered to have photoluminescence (PL) emissions from UV to IR regions, in addition to power conversion efficiencies, in excess of 24%. This class of materials offers broad tunability of its properties, through controlling the number of atomic layers in the quantum well, tuning the organic spacer thickness, or even engineering the composition with exotic dopants. In this work, we present PL and time-resolved PL measurements of quasi-2D BA2PbI4 and provide new insights on the temperature dependence of their excitonic dynamics and fine structures of their PL emissions. We observed long lifetimes, which can result from the formation of large polarons, screening the Coulomb interactions of the charge carriers and reducing the scattering of the carriers with charge defects.

In order to ensure the health and welfare of livestock, there has been an emphasis on precision farming of ruminant animals. Monitoring the life index of ruminant animals is of importance for intelligent farming. Here, a wearable sensor for monitoring ultraviolet (UV) radiation is demonstrated to understand the effect of primary and secondary photosensitization on dairy animals. Thin films of wide bandgap semiconductor zinc oxide (ZnO) comprising multilevel of nanostructures from microparticles (MP) to nanoparticles (NP), and tetrapod (T–ZnO), were prepared as the UV sensing active materials. The sensitivity was evaluated by exposing the films to various radiation sources, i.e., 365 nm (UV A), 302 nm (UV B), and 254 nm (UV C), and measuring the electrical resistance change. T–ZnO is found to exhibit higher sensitivity and stable response (on/off) upon exposure to UV A and UV B radiation, which is attributed to their higher surface area, aspect ratio, porosity, and interconnective networks inducing a high density of chemical interaction sites and consequently improved photocurrent generation. A wearable sensor using T–ZnO is packaged and attached to a collar for dynamic monitoring of UV response on ruminant animals (e.g., sheep in this study). The excellent performance of T–ZnO wearable sensors for ruminant animals also holds the potential for a wider range of applications such as residential buildings and public spaces.

Abstract Even though ZnO is commonly used as the ETL in the perovskite solar cell (PSC), the reactivity of perovskite deposited thereupon limits its performance. Herein, an ethylene diamine tetraacetic acid‐complexed ZnO (E‐ZnO) is successfully developed as a significantly improved electron selective layer (ESLs) in perovskite device. It is found that E‐ZnO exhibits higher electron mobility and better matched energy level with perovskite compared to ZnO. In addition, in order to eliminate the proton transfer reaction at the ZnO/perovskite interface, a high quality perovskite film fabrication process that requires neither annealing nor antisolvent is developed. By taking advantages of both E‐ZnO and the new process, the highest efficiency of 20.39% is obtained for PSCs based on E‐ZnO. Moreover, the efficiency of unencapsulated PSCs with E‐ZnO retains 95% of its initial value exposed in an ambient atmosphere after 3604 h. This work provides a feasible path toward high performance of PSCs, and it is believed that the present work will facilitate transition of perovskite photovoltaics in flexible and tandem devices since the annealing‐ and antisolvent‐free technology.

Wearable thermoelectric coolers (TECs), whose performance depends on optimal module design and environmental thermal resistance, are an attractive next-generation technology for on-body applications. Here, the authors report an optimized wearable TEC with 170% higher cooling than commercial devices.

Voltage tunable inductors (VTIs) with high working frequency and tunability are desired for new design of energy efficient electronics. Here the authors demonstrate magnetoelectric VTIs operating up to 10 MHz with tunability over 750% via strain mediated magnetoelectric effect and magnetocrystalline anisotropy cancellation strategy.

Abstract Simultaneously achieving high efficiency and high durability in perovskite solar cells is a critical step toward the commercialization of this technology. Inverted perovskite photovoltaic (IP‐PV) cells incorporating robust and low levelized‐cost‐of‐energy (LCOE) buffer layers are supposed to be a promising solution to this target. However, insufficient inventory of materials for back‐electrode buffers substantially limits the development of IP‐PV. Herein, a composite consisting of 1D cation‐doped TiO2 brookite nanorod (NR) embedded by 0D fullerene is investigated as a top modification buffer for IP‐PV. The cathode buffer is constructed by introducing fullerene to fill the interstitial space of the TiO2 NR matrix. Meanwhile, cations of transition metal Co or Fe are doped into the TiO2 NR to further tune the electronic property. Such a top buffer exhibits multifold advantages, including improved film uniformity, enhanced electron extraction and transfer ability, better energy level matching with perovskite, and stronger moisture resistance. Correspondingly, the resultant IP‐PV displays an efficiency exceeding 22% with a 22‐fold prolonged working lifetime. The strategy not only provides an essential addition to the material inventory for top electron buffers by introducing the 0D:1D composite concept, but also opens a new avenue to optimize perovskite PVs with desirable properties.

Perovskite nanocrystals have attracted worldwide attention due to their outstanding optical versatility, high photoluminescence quantum yields, and facile synthesis. In this review, we firstly revisit the synthetic methods for perovskite nanocrystals (PNCs), including hot injection, anion exchange, solvothermal reaction, etc. In the meantime, we discuss effects of the different synthetic methods on the properties of PNCs, including the crystal size, emission spectral feature, quantum yield, etc., followed by several optimizing strategies. Finally, lasing and display applications of these PNCs in combination with liquid crystal materials are discussed thoroughly. Outlooks on the challenges and opportunities of these nanocrystalline materials in terms of adjunct applications with liquid crystals have been presented at the end, which are highly promising for next-generation light emission applications.

Summary: Thermoelectric generators (TEGs) offer cost-effective and sustainable solid-state energy conversion mechanism from wasted heat into useful electrical power. Thermoelectric (TE) materials based upon bismuth telluride (BiTe) systems are widely utilized in applications ranging from energy generation to sensing to cooling. There is demand for BiTe materials with high figure of merit (zT) and TEG modules with high conversion efficiency over intermediate temperatures (25°C–250°C). Here we provide fundamental breakthrough in design of BiTe-based TE materials and utilize them to demonstrate modules with outstanding conversion efficiency of 8%, which is 40% higher compared with state-of-the-art commercial modules. The average zT of 1.08 for p-type and 0.84 for n-type bismuth telluride alloys is obtained between 25 and 250°C. The significant enhancement in zT is achieved through compositional and defect engineering in both p- and n-type materials. The high conversion efficiency accelerates the transition of TEGs for waste heat recovery.

The development of high efficiency planar-type perovskite solar cell has been lagging behind the mesoporous-type counterpart. Here Yang et al. modify the oxide based electron transporting layer with organic acid and obtain planar-type cells with high certified efficiency of 21.5% and decent stability.

This paper is concerned with the development of a piezoelectric d15 shear-induced torsion actuator made of a lead-free piezoceramic material exhibiting giant piezoelectric shear stress coefficient (e15) and piezoelectric transverse shear actuation force comparable to that of lead-based shear-mode piezoceramics. The Mn-modified 0.93(Na0.5Bi0.5TiO3)-0.07BaTiO3 (NBT-BT-Mn) composition exhibited excellent properties as a torsional transducer with piezoelectric shear stress coefficient on the order of 11.6 C m–2. The torsional transducer, consisting of two oppositely polarized NBT-BT-Mn d15 mode piezoceramic shear patches, provided a rate of twist of 0.08 mm m–1 V–1 under quasi-static 150 V drive. The high value of piezoelectric shear d15 coefficient in NBT-BT-Mn sample further demonstrated its potential in practical applications. These results confirm that the lead-free piezoceramics can be as effective as their lead-based counterparts.

Solid-state emissions from coal burning remain an environmental concern. Here, the authors have found that TiO2 minerals present in coal are converted into titanium suboxides during burning, and initial biotoxicity screening suggests that further testing is needed to look into human lung consequences.

High piezoelectric voltage coefficients drive the sensitivity of piezoelectric sensors. Here, the authors synthesized textured Sm- and Mn-doped PbTiO3ceramics and demonstrate significant enhancement in voltage coefficient.

We synthesized epitaxial BTO-BFO heterostructure with decreased leakage and simultaneously improved the multiferroic properties. This study provides new direction for ferromagnetic resonance studies, in high quality BTO-BFO films grown on LSMO. We observed small Gilbert damping (α=0.004) and the absence of large inhomogeneous broadening, in a film with 80 nm thickness of BTO-BFO on LSMO (110). This fact offers opportunities for employing this material system for spin transfer in multifunctional materials where controlling magnetization by a flow of spin angular momentum, or spin current, is crucial toward developing nanoscale spin-based memory and devices. Magnetic insulators, such as BTO-BFO on LSMO, are potentially excellent candidates for pure spin current without the existence of charge current.

Thermoelectric skutterudite materials have been widely investigated for their potential application in mid-temperature waste heat recovery that has not been efficiently utilized A large amount of research has focused on developing materials with a high thermoelectric figure of merit (zT). However, the translation of material properties to device performance has limited success. Here, we demonstrate single-filling n-type Yb0.25Fe0.25Co3.75Sb12 and multi-filling La0.7Ti0.1Ga0.1Fe2.7Co1.3Sb12 skutterudites with a maximum zT of ~1.3 at 740 K and ~0.97 at 760 K. The peak zT of skutterudites usually occurs above 800 K, but, as shown here, the shift in peak zT to lower temperatures is beneficial for enhancing conversion efficiency at a lower hot-side temperature. In this work, we have demonstrated that the Fe-substitution significantly reduces the thermal conductivity of n-type skutterudite, closer to p-type skutterudite thermal conductivity, resulting in a module that is more compatible to operate at elevated temperatures. A uni-couple skutterudite module was fabricated using a molybdenum electrode and Ga−Sn liquid metal as the thermal interface material. A conversion efficiency of 7.27% at a low temperature gradient of 366 K was achieved, which is among the highest efficiencies reported in the literature at this temperature gradient. These results highlight that peak zT shift and optimized module design can improve conversion efficiency of thermoelectric modules at a low temperature gradient.

We report synthesis of cetyltrimethyl ammonium bromide (CTAB) stabilized Zn1+xSnO3+x (0 ≤ x ≤1) nano-crystallites by facile cost-effective wet chemistry route. The X-ray diffraction patterns of as-synthesized powders at the Zn/Sn ratio of 1 exhibited formation of ZnSn(OH)6. Increasing the Zn/Sn ratio further resulted in the precipitation of an additional phase corresponding to Zn(OH)2. The decomposition of these powders at 650°C for 3h led to the formation of the orthorhombic phase of ZnSnO3 and tetragonal SnO2-type phase of Zn2SnO4 at the Zn/Sn ratio of 1 and 2, respectively, with the formation of their mixed phases at intermediate compositions, i.e., at Zn/Sn ratio of 1.25, 1.50 and 1.75, respectively. The lattice parameters of orthorhombic and tetragonal phases were a ~ 3.6203 Å, b ~ 4.2646 Å and c ~ 12.8291Å (for ZnSnO3) and a = b ~ 5.0136 Å and c ~ 3.3055Å (for Zn2SnO4). The transmission electron micrographs revealed the formation of nano-crystallites with aspect ratio ~ 2; the length and thickness being 24, 13 nm (for ZnSnO3) and 47, 22 nm (for Zn2SnO4), respectively. The estimated direct bandgap values for the ZnSnO3 and Zn2SnO4 were found to be 4.21 eV and 4.12 eV, respectively. The ac conductivity values at room temperature (at 10 kHz) for the ZnSnO3 and Zn2SnO4 samples were 8.02 × 10-8 Ω-1 cm-1 and 6.77 × 10-8 Ω-1 cm-1, respectively. The relative permittivity was found to increase with increase in temperature, the room temperature values being 14.24 and 25.22 for the samples ZnSnO3 and Zn2SnO4, respectively. Both the samples, i.e., ZnSnO3 and Zn2SnO4, exhibited low values of loss tangent up to 300 K, the room temperature values being 0.89 and 0.72, respectively. A dye-sensitized solar cell has been fabricated using the optimized sample of zinc stannate photo-anode, i.e., Zn2SnO4. The cyclic voltammetry revealed oxidation and reduction around 0.40 V (current density ~ 11.1 mA/cm2) and 0.57 V (current density- 11.7 mA/cm2) for Zn2SnO4 photo-anode in presence of light.

Bicycles are known to be rich source of kinetic energy, some of which is available for harvesting during speedy and balanced maneuvers by the user. A conventional dynamo attached to the rim can generate a large amount of output power at an expense of extra energy input from the user. However, when applying energy conversion technology to human powered equipments, it is important to minimize the increase in extra muscular activity and to maximize the efficiency of human movements. This study proposes a novel energy harvesting methodology that utilizes lateral oscillation of bicycle frame (weaving) caused by user weight shifting movements in order to increase the pedaling force in uphill riding or during quick speed-up. Based on the 3D motion analysis, we designed and implemented the prototype of an electro-dynamic energy harvester that can be mounted on the bicycle’s handlebar to collect energy from the side-to-side movement. The harvester was found to generate substantial electric output power of 6.6 mW from normal road riding. It was able to generate power even during uphill riding which has never been shown with other approaches. Moreover, harvesting of energy from weaving motion seems to increase the economy of cycling by helping efficient usage of human power.

Magnetoelectric (ME) composites that simultaneously exhibit ferroelectricity and ferromagnetism have recently gained significant attention as evident by the increasing number of publications. These research activities are direct results of the fact that multiferroic magnetoelectrics offer significant technological promise for multiple devices. Appropriate choice of phases with co-firing capability, magnetostriction and piezoelectric coefficient, such as Ni-PZT and NZFO-PZT, has resulted in fabrication of prototype components that promise transition. In this manuscript, we report the properties of Ni-PZT and NZFO-PZT composites in terms of ME voltage coefficients as a function of frequency and magnetic DC bias. In order to overcome the problem of toxicity of lead, we have conducted experiments with Pb-free piezoelectric compositions. Results are presented on the magnetoelectric performance of Ni-NKN, Ni-NBTBT and NZFO-NKN, NZFO-NBTBT systems illustrating their importance as an environmentally friendly alternative.

Combined rejected and naturally available heat constitute an enormous energy resource that remains mostly untapped. Thermal energy harvesting can provide a cost-effective and reliable way to convert available heat into mechanical motion or electricity. This extensive review analyzes the literature covering broad topical areas under solid-state low temperature thermal energy harvesting. These topics include thermoelectricity, pyroelectricity, thermomagneticity, and thermoelasticity. For each topical area, a detailed discussion is provided comprising of basic physics, working principle, performance characteristics, state-of-the-art materials, and current generation devices. Technical advancements reported in the literature are utilized to analyze the performance, identify the challenges, and provide guidance for material and mechanism selection. The review provides a detailed analysis of advantages and disadvantages of each energy harvesting mechanism, which will provide guidance towards designing a hybrid thermal energy harvester that can overcome various limitations of the individual mechanism.

Thermoelectric generators (TEGs) are rapidly becoming the mainstream technology for converting thermal energy into electrical energy. The rise in the continuous deployment of TEGs is related to advancements in materials, figure of merit, and methods for module manufacturing. However, rapid optimization techniques for TEGs have not kept pace with these advancements, which presents a challenge regarding tailoring the device architecture for varying operating conditions. Here, we address this challenge by providing artificial neural network (ANN) models that can predict TEG performance on demand. Out of the several ANN models considered for TEGs, the most efficient one consists of two hidden layers with six neurons in each layer. The model predicted TEG power with an accuracy of ±0.1 W, and TEG efficiency with an accuracy of ±0.2%. The trained ANN model required only 26.4 ms per data point for predicting TEG performance against the 6.0 minutes needed for the traditional numerical simulations.

In this manuscript, we review the progress made in the synthesis of thick film-based piezoelectric and magnetoelectric structures for harvesting energy from mechanical vibrations and magnetic field. Piezoelectric compositions in the system Pb(Zr,Ti)O3–Pb(Zn1/3Nb2/3)O3 (PZNT) have shown promise for providing enhanced efficiency due to higher energy density and thus form the base of transducers designed for capturing the mechanical energy. Laminate structures of PZNT with magnetostrictive ferrite materials provide large magnitudes of magnetoelectric coupling and are being targeted to capture the stray magnetic field energy. We analyze the models used to predict the performance of the energy harvesters and present a full system description.

We report the physical behavior of self-biased multi-functional magneto-mechano-electric (MME) laminates simultaneously excited by magnetic and/or mechanical vibrations. The MME laminates composed of Ni and single crystal fiber composite exhibited strong ME coupling under Hdc = 0 Oe at both low frequency and at resonance frequency. Depending on the magnetic field direction with respect to the crystal orientation, the energy harvester showed strong in-plane anisotropy in the output voltage and was found to generate open circuit output voltage of 20 Vpp and power density of 59.78 mW/Oe2 g2 cm3 under weak magnetic field of 1 Oe and mechanical vibration of 30 mg, at frequency of 21 Hz across 1 MΩ resistance.

The development of a rowing jellyfish biomimetic robot termed as "Robojelly", has led to the discovery of a passive flexible flap located between the flexion point and bell margin on the Aurelia aurita. A comparative analysis of biomimetic robots showed that the presence of a passive flexible flap results in a significant increase in the swimming performance. In this work we further investigate this concept by developing varying flap geometries and comparing their kinematics with A. aurita. It was shown that the animal flap kinematics can be replicated with high fidelity using a passive structure and a flap with curved and tapered geometry gave the most biomimetic performance. A method for identifying the flap location was established by utilizing the bell curvature and the variation of curvature as a function of time. Flaps of constant cross-section and varying lengths were incorporated on the Robojelly to conduct a systematic study of the starting vortex circulation. Circulation was quantified using velocity field measurements obtained from planar Time Resolved Digital Particle Image Velocimetry (TRDPIV). The starting vortex circulation was scaled using a varying orifice model and a pitching panel model. The varying orifice model which has been traditionally considered as the better representation of jellyfish propulsion did not appear to capture the scaling of the starting vortex. In contrast, the pitching panel representation appeared to better scale the governing flow physics and revealed a strong dependence on the flap kinematics and geometry. The results suggest that an alternative description should be considered for rowing jellyfish propulsion, using a pitching panel method instead of the traditional varying orifice model. Finally, the results show the importance of incorporating the entire bell geometry as a function of time in modeling rowing jellyfish propulsion.

Obtaining accurate kinematic data of animals is essential for many biological studies and bio-inspired engineering. Many animals, however, are either too large or too delicate to transport to controlled environments where accurate kinematic data can be easily obtained. Often, in situ recordings are the only means available but are often subject to multi-axis motion and relative magnification changes with time leading to large discrepancies in the animal kinematics. Techniques to compensate for these artifacts were applied to a large jellyfish, Cyanea capillata, freely swimming in ocean waters. The bell kinematics were captured by digitizing exumbrella profiles for two full swimming cycles. Magnification was accounted for by tracking a reference point on the ocean floor and by observing the C. capillata exumbrella arclength in order to have a constant scale through the swimming cycles. A linear fit of the top bell section was used to find the body angle with respect to the camera coordinate system. Bell margin trajectories over two swimming cycles confirmed the accuracy of the correction techniques. The corrected profiles were filtered and interpolated to provide a set of time-dependent points along the bell. Discrete models of the exumbrella were used to analyze the bell kinematics. Exumbrella discretization was conducted using three different methods. Fourier series were fitted to the discretized models and subsequently used to analyze the bell kinematics of the C. capillata. The analysis showed that the bell did not deform uniformly over time with different segments lagging behind each other. Looping of the bell trajectory between contraction and relaxation was also present through most of the exumbrella. The bell margin had the largest looping with an outer path during contraction and inner path during relaxation. The subumbrella volume was approximated based on the exumbrella kinematics and was found to increase during contraction.

Multiferroic magnetoelectric (ME) composites are attractive materials for various electrically and magnetically cross-coupled devices. Many studies have been conducted on fundamental understanding, fabrication processes, and applications of ME composite material systems in the last four decades which has brought the technology closer to realization in practical devices. In this article, we present a review of ME composite materials and some notable potential applications based upon their properties. A brief summary is presented on the parameters that influence the performance of ME composites, their coupling structures, fabrications processes, characterization techniques, and perspectives on direct (magnetic to electric) and converse (electric to magnetic) ME devices. Overall, the research on ME composite systems has brought us closer to their deployment.

The primary aims of this review article are (a) to develop the fundamental understanding of ME behavior in perovskite piezoelectric-spinel magnetostrictive composite systems, (b) to identify the role of composition, microstructural variables, phase transformations, composite geometry, and postsintering heat treatment on ME coefficient, and (c) to synthesize, characterize, and utilize the high ME coefficient composite. The desired range of ME coefficient in the sintered composite is 0.5–1 V/cm⋅Oe. The studies showed that the soft piezoelectric phase quantified by smaller elastic modulus, large grain size of piezoelectric phase (~1 μm), and layered structures yields higher magnitude of ME coefficient. It is also found that postsintering thermal treatment such as annealing and aging alters the magnitude of magnetization providing an increase in the magnitude of ME coefficient. A trilayer composite was synthesized using pressure-assisted sintering with soft phase [0.9 PZT–0.1 PZN] having grain size larger than 1 μm and soft ferromagnetic phase of composition Ni0.8Cu0.2Zn0.2Fe2O4 [NCZF]. The composite showed a high ME coefficient of 412 and 494 mV/cm⋅Oe after sintering and annealing, respectively. Optimized ferrite to PZT thickness ratio was found to be 5.33, providing ME coefficient of 525 mV/cm⋅Oe. The ME coefficient exhibited orientation dependence with respect to applied magnetic field. Multilayering the PZT layer increased the magnitude of ME coefficient to 782 mV/cm⋅Oe. Piezoelectric grain texturing and nanoparticulate assembly techniques were incorporated with the layered geometry. It was found that with moderate texturing, d33 and ME coefficient reached up to 325 pC/N and 878 mV/cm⋅Oe, respectively. Nanoparticulate core shell assembly shows the promise for achieving large ME coefficient in the sintered composites. A systematic relationship between composition, microstructure, geometry, and properties is presented which will lead to development of high-performance magnetoelectric materials.

Flexible bell margins are characteristic components of rowing medusan morphologies and are expected to contribute towards their high propulsive efficiency. However, the mechanistic basis of thrust augmentation by flexible propulsors remained unresolved, so the impact of bell margin flexibility on medusan swimming has also remained unresolved. We used biomimetic robotic jellyfish vehicles to elucidate that propulsive thrust enhancement by flexible medusan bell margins relies upon fluid dynamic interactions between entrained flows at the inflexion point of the exumbrella and flows expelled from under the bell. Coalescence of flows from these two regions resulted in enhanced fluid circulation and, therefore, thrust augmentation for flexible margins of both medusan vehicles and living medusae. Using particle image velocimetry (PIV) data we estimated pressure fields to demonstrate a mechanistic basis of enhanced flows associated with the flexible bell margin. Performance of vehicles with flexible margins was further enhanced by vortex interactions that occur during bell expansion. Hydrodynamic and performance similarities between robotic vehicles and live animals demonstrated that the propulsive advantages of flexible margins found in nature can be emulated by human-engineered propulsors. Although medusae are simple animal models for description of this process, these results may contribute towards understanding the performance of flexible margins among other animal lineages.

A broadband/wideband magnetoelectric (ME) composite offers new opportunities for sensing wide ranges of both DC and AC magnetic fields. The broadband/wideband behavior is characterized by flat ME response over a given AC frequency range and DC magnetic bias. The structure proposed in this study operates in the longitudinal-transversal (L-T) mode. In this paper, we provide information on (i) how to design broadband/wideband ME sensors and (ii) how to control the magnitude of ME response over a desired frequency and DC bias regime. A systematic study was conducted to identify the factors affecting the broadband/wideband behavior by developing experimental models and validating them against the predictions made through finite element modeling. A working prototype of the sensor with flat bands for both DC and AC magnetic field conditions was successfully obtained. These results are quite promising for practical applications such as current probe, low-frequency magnetic field sensing, and ME energy harvester.