Search Results (5,498)

In order to solve the problem of continuous and stable energy supply of underwater sensor nodes, a shear mode bidirectional piezoelectric energy harvesting structure based on underwater vortex-induced vibration is proposed. The structure was investigated through fluid–solid and piezoelectric coupling numerical simulations using ANSYS 2020, and the relationship between the vibration mode, thickness, flow velocity, spacing diameter ratio of the bluff body and energy harvester (L/D) was studied. The vibration and piezoelectric characteristics of parallel and tandem energy harvesters were analyzed. The results verify that the piezoelectric material with d₁₅ mode has higher output power than that with d₃₃ and d₃₁ modes, under the same conditions, the output power has increased by 50%. When the flow velocity is 1.1 m/s, the bluff body is a wavy cylinder, the L/D is 2, and the maximum voltage and output power values generated by the energy harvesting structure are 56.97 V and 3.25 mW, respectively. Its power density reaches 1.35 mW/cm³, superior to similar-scale collectors reported in the recent literature. In the case of the double energy harvesting structure, it can capture vortex-induced vibration energy in both flow and lateral directions, thereby expanding the working bandwidth and improving the overall energy capture efficiency; the parallel output voltage is also the largest. When L/D is 1.5 and the flow velocity is 1.1 m/s, the maximum output voltage values of the upper and lower energy harvesting structures are 78.65 V and 83.05 V, respectively, and the corresponding output power is 6.19 mW and 6.90 mW. The above simulation results verify that the shear mode energy harvesting structure and its array can appropriately increase the open-circuit output voltage of the structure, which provides a new reference scheme for the study of underwater vortex-induced vibration piezoelectric energy harvesting structures. Full article

Vibration energy harvesting from ambient mechanical sources offers a sustainable alternative to batteries for powering low-power electronics in remote environments, yet challenges persist in achieving broadband efficiency, low-frequency operation, and concurrent vibration suppression. Here, we introduce a pyramidal piezoelectric sandwich beam (PPSB) with periodic elastic constraints, leveraging homogenized lattice truss cores for enhanced electromechanical coupling. Using Lagrange equations, we derive the coupled dynamics, validated against finite element simulations with resonant frequency errors below 3%. Compared to equivalent-stiffness uniform beams, the PPSB exhibits 3.42-fold higher voltage and 11.68-fold greater power output, attributed to optimized strain distribution and resonance amplification. Parametric analyses reveal trade-offs: increasing core thickness or spring stiffness elevates resonant frequencies but reduces voltage peaks due to stiffness–strain imbalances; conversely, a larger beam length, truss radius or tilt angle will reduce the natural frequency while increasing the output through inertia and shear enhancement. Piezoelectric constants and load resistance minimally affect mechanics but optimize electrical impedance matching. This single-phase, geometrically tunable design bridges gaps in multifunctional metamaterials, enabling self-powered sensors with vibration attenuation for aerospace, civil infrastructure, and biomedical applications, paving the way for energy-autonomous systems. Full article

BU–MIT whistler wave injection experiments, which were conducted at Arecibo Observatory, started with the joint US–USSR Active Space Plasma Program Experiment on 24 December 1989. In this experiment, a satellite-borne VLF transmitter injected radio waves at the frequency and power of 10 kHz and 10 kW. A series of controlled whistler wave experiments with the Arecibo HF heater were subsequently carried out during 1990–1998 until the HF heater was damaged by Hurricane Georges in 1998. In these ionospheric HF heating experiments, 28.5 kHz whistler waves were launched from the nearby naval transmitter (code-named NAU) located at Aguadilla, Puerto Rico. HF heater waves were used to create ionospheric ducts (in the form of parallel-plate waveguides) to facilitate the entry of NAU whistler waves from the neutral atmosphere into the ionosphere. Conjugate whistler wave propagation experiments were conducted between Arecibo, Puerto Rico and Trelew, Argentina in 1997. After 1999, whistler wave experiments in the absence of an HF heater had been conducted. Naturally-occurring large-scale ionospheric irregularities due to spread F or Traveling Ionospheric Disturbances (TIDs) were relied on to guide NAU launched 40.75 kHz whistler waves to propagate from the ionosphere further into the radiation belts, to cause 390 keV charged-particle precipitation. A train of TIDs, resulting from the9.2 Mw earthquake off the west coast of Sumatra, Indonesia, was observed in our 26 December 2004 Arecibo experiments, about a day after the earthquake-launched tsunami waves traveled across the Indian Ocean, then into remote parts of the Atlantic Ocean. The author’s recent research efforts, motivated by Arecibo experiments, focus on Solar Powered Microwave Transmitting Systems, to simulate Solar Energy Harvesting via Solar Power Satellite (SPS) (also known as Space Based Solar Power (SBSP)) These experiments involved a large number of the author’s BU and MIT students working on theses and participating in the Undergraduate Research Opportunities Program (UROP), in collaboration with other colleagues at several universities and national laboratories. Full article

Single-walled carbon nanotube (SWCNT) films are potential materials for thermoelectric generators (TEGs) owing to their flexibility and high thermoelectric performance near 300 K. However, they inherently exhibit low mechanical strength and high thermal conductivity. To address these limitations, SWCNT-based composite films were fabricated by combining SWCNTs with varying amounts of an inorganic-blended acrylic emulsion additive. The resulting SWCNT-based composite films exhibited significantly improved mechanical properties, with breaking strain and tensile strength values approximately thirty and two times higher, respectively, than those of the additive-free SWCNT film. Thermal conductivity decreased from 7.3 W/(m·K) for the additive-free SWCNT film to 2.1 W/(m·K) for the SWCNT-based composite films. Two types of TEGs were fabricated using the composite films: (1) the water-floating TEG, which generated a temperature difference through evaporative cooling; and (2) the standard TEG, which generated a temperature difference when vertically mounted on a heater. The output voltage of the first type of TEGs decreased as the additive amount increased, owing to reduced evaporative cooling. However, the second type of TEGs increased the output voltage by adding the appropriate amount of additive owing to the film’s low thermal conductivity. These findings are significantly helpful in using TEGs with appropriate designs and placements. Full article

Chronic wounds constitute a major global public health challenge, characterized by a high risk of infection, prolonged healing times, and frequent recurrence. Conventional wound assessment methods, which primarily rely on visual clinical inspection and laboratory-based analyses, are limited by inherent subjectivity, delayed feedback, and a lack of capacity for real-time monitoring of the dynamic biochemical changes at the wound site. Significantly, recent advancements in flexible electronics, nanomaterials, and energy harvesting technologies have boosted the rapid development of wearable electrochemical biosensors. These devices have emerged as a transformative platform for the continuous, non-invasive analysis of critical biomarkers within the wound microenvironment, including pH, temperature, inflammatory cytokines, metabolites, and pathogen-derived molecules. This review critically examines the latest progress in wearable electrochemical biosensors for wound monitoring and management. Key discussions include (1) the special requirements for sensor design, targeting the chronic wound’s pathological characteristics; (2) cutting-edge development in self-powered systems, multimodal sensor integration, closed-loop theranostics, and artificial intelligence (AI)-assisted decision-making; and (3) a critical appraisal of challenges in accuracy, stability, biocompatibility, energy management, and clinical translation. Finally, the review explores future trends, such as biodegradable sensors, multi-parameter fusion algorithms, and remote intelligent management systems, with the aim of establishing a foundational framework and providing technical guidance for developing next-generation intelligent wound care solutions. Full article

The increasing accumulation of medical waste, especially discarded pharmaceutical blister packs, poses both environmental risks and missed opportunities for resource recovery. In this work, we demonstrate, for the first time, the direct upcycling of tablet blister waste into a potential frictional layer in triboelectric nanogenerators (TENGs). The polymer structure of blister packs, combined with Silicone rubber as a counter frictional layer, enabled the fabrication of durable TENG devices (TS-TENGs). Systematic electrical testing revealed that the TS-TENG achieved an open-circuit voltage of approximately 300 V, a short-circuit current of about 40 μA, and a peak power density of 3.54 W/m² at an optimal load resistance of 4 MΩ. The devices maintained excellent stability over 10,000 mechanical cycles, confirming their durability. Practical demonstrations included powering 240 LEDs, four LED lamps, and portable electronic devices, such as calculators and hygrometers, through capacitor charging. This study shows that not only can tablet blister waste be used as a triboelectric material but it also presents a sustainable method to reduce pharmaceutical waste while advancing self-powered systems. The approach offers a scalable and low-cost means to integrate medical waste management with renewable energy technologies. Full article

Reverse electrodialysis (RED) is a relatively recent technology for renewable energy harvesting from the interaction of river and seawater. This paper revisits the thermodynamic equilibrium governing the ionic transport processes through ion-exchange membranes (IEMs) under RED conditions and theoretically derives approximate analytical expressions for the ionic concentrations at the inner boundaries of a permeable membrane with well-stirred baths. The equation for the Donnan ion partitioning at the membrane–solution interface, which is based on the equality of the electrochemical potential in the two phases, is analysed for binary salts with symmetric (1:1) and asymmetric (2:1) electrolytes, by considering bathing solutions with the equivalent concentrations 0.02 M in the dilute bath, and 0.5, 1, and 1.5 M in the concentrate one. Simple approximate analytical expressions exhibiting the evolution with the membrane fixed-charge concentration of the counter-ionic concentrations at the inner boundaries of the membrane, the concentration gradients inside the membrane, the total Donnan electric potential, and the ionic partitioning coefficients have been derived. The approximate generalised expressions for a general z₁:z₂ binary electrolyte are also presented for the first time. Full article

This study investigates the use of Si and CdTe-based Timepix3 detectors for photovoltaic energy conversion using solar X-rays and other high-energy electromagnetic radiation in space. As space missions increasingly rely on miniaturized platforms like CubeSats, power generation in compact and radiation-prone environments remains a critical challenge. Conventional solar panels are limited by size and spectral sensitivity, prompting the need for alternative energy harvesting solutions—particularly in the high-energy X-ray domain. A novel CubeSat-compatible payload design incorporates a UV-visible filter to isolate incoming X-rays, which are then absorbed by semiconductor detectors to generate electric current through ionization. Laboratory calibration was performed using Fe-55, Ba-133, and Am-241 sources to compare spectral response and clustering behaviour. CdTe consistently outperformed Si in detection efficiency, spectral resolution, and cluster density due to its higher atomic number and material density. Equalization techniques further improved pixel threshold uniformity, enhancing spectroscopic reliability. In addition to experimental validation, simulations were conducted to quantify the expected energy conversion performance under orbital conditions. Under quiet-Sun conditions at 500 km LEO, CdTe absorbed up to 1.59 µW/cm² compared to 0.69 µW/cm² for Si, with spectral power density peaking between 10 and 20 keV. The photon absorption efficiency curves confirmed CdTe’s superior stopping power across the 1–100 keV range. Under solar flare conditions, absorbed power increased dramatically, up to 159 µW/cm² for X-class and 15.9 µW/cm² for C-class flares with CdTe sensors. A time-based energy model showed that a 10 min X-class flare could yield nearly 1 mJ/cm² of harvested energy. These results validate the concept of a compact photovoltaic payload capable of converting high-energy solar radiation into electrical power, with dual-use potential for both energy harvesting and radiation monitoring aboard small satellite platforms. Full article

In plants, proline acts as a compatible osmolyte with multiple stress-related functions, contributing to cell turgor regulation and the dissipation of excess energy. In this study, the use of a proline-rich yeast derivative (SYD) on pot-grown grapevines cv. Chardonnay was tested as a priming strategy to enhance vine water status and water deficit tolerance. Well-watered control vines were compared to those subjected to reduced irrigation at 80% of daily evapotranspiration for 43 days, with and without foliar SYD applications. Additionally, a group of vines received only 40% of daily evapotranspiration (ET) along with foliar SYD applications. The soil moisture content clearly mirrored the three irrigation levels (full water, 80% ET, and 40% ET). However, considering vines kept at 80%ET, SYD-treated vines had a consistently higher midday leaf water potential than controls (+0.22 MPa on Day of Year—DOY—214). SYD-treated vines kept at 80% ET and control vines at 100% ET exhibited similar stomatal conductance and assimilation rates (0.24 vs. 0.25 mol m⁻² s⁻¹, and 14.9 vs. 15.3 μmol m⁻² s⁻¹ on average from all measurements), while control vines kept at 80% ET lagged behind SYD-treated vines at 80% ET. On July 20th (DOY 201), in SYD-treated vines kept at 80% ET, leaves accumulated nearly twice the proline concentration compared to control vines receiving the same irrigation (17.7 vs. 10.6 µmol/g). Treated vines kept at 40% ET had stomatal conductance and leaf assimilation rates comparable to control vines at 80% ET (0.17 vs. 0.20 mol m⁻² s⁻¹ and 11.7 vs. 11.5 μmol m⁻² s⁻¹ on average). At harvest, the average yield of SYD-treated vines kept at 80% ET was similar to fully watered control vines maintained at 100% ET (1.75 vs. 1.82 kg), but showed higher soluble solids concentrations (20.9° Brix, vs. 19° Brix in fully watered control vines) and lower average titratable acidity (6.62 g/L vs. 7.7 g/L in fully watered control vines), while no differences were observed in the average titratable acidity between control vines kept at 80% ET and SYD-treated vines kept at 40% ET (6.15 g/L). Proline-rich SYD increased endogenous leaf proline levels and vine water status, also interacting with H₂O₂ accumulation, and resulted in long-term better physiological functioning at comparable water availability. The applications improved grapevine productive performance, effectively mitigating the negative impacts of reduced irrigation. Full article

Piezoelectric wind energy harvesters can collect a small amount of energy from wind without the need for rotary equipment. In practice, such harvesters can be excited concurrently by wind-induced and base vibrations. In this study, combined wind and base excitation is investigated, with a focus on random base vibrations and the effect of the bandwidth of band-limited random excitation, thereby filling the research gap between results obtained with wide-band random excitation and those with harmonic excitation. Since flow-induced vibrations can produce several phenomena, in this research, galloping and vortex-induced vibration (VIV) harvesters are considered due to their structural similarity and the ease with which a galloping harvester can be converted into a VIV harvester (and vice versa). Both numerical and experimental results are presented. First, the mathematical models are given; then, experimental tests validate the models and provide an insight into the phenomena; finally, numerical simulations extend the dissertation by providing a more in-depth analysis of the behavior of such harvesters. The results show that above the critical wind velocity, galloping harvesters are not affected by the amplitude and bandwidth of random base excitation. In contrast, VIV harvesters in the lock-in condition are affected by random base excitation, especially if the vibration amplitude is large and if its spectrum is concentrated in a narrow band centered about the resonance. Full article

Wireless sensors are vital for real-time condition monitoring of rotating machinery. Traditionally, these sensors depend on batteries, a solution that is neither eco-friendly nor cost-effective due to high maintenance. Vibration energy harvesting has emerged as a promising alternative for powering these sensors. Nevertheless, current energy harvesters commonly disregard high-frequency energy, which is weak but contains abundant condition-monitoring information. Moreover, the destructive interference between multiple vibration sources further attenuates the high-frequency energy. To address these limitations, this paper proposed a novel energy harvesting method based on a symmetrical gradient metamaterial beam (SGMB). The SGMB structure is designed to have multiple bands to enhance the high-frequency energy and diminish the destructive interference of flexural waves from two vibration sources. Multiple piezoelectric patches are integrated into SGMB to convert the dynamic stress into harvestable electrical power, enabling multi-band dual-source energy harvesting. Based on the rainbow trapping mechanism, the SGMB was first designed and optimized for desired frequency bands. Subsequently, the band characteristics and piezoelectric output performance were adjusted and validated through finite element simulation. Finally, experimental evaluations were conducted to validate the performance of the designed metamaterial. The results demonstrate that the SGMB provides multiple enhanced bands within the range from 1000 Hz to 3500 Hz and improves the energy harvesting efficiency by a factor over 100, which represents a breakthrough in developing self-powered and self-sensing wireless sensors. Full article

The increasing complexity of tall buildings demands higher performance in serviceability and resilience, particularly regarding airflow control to reduce vibration-inducing forces. On the other hand, harnessing wind energy in suburban environments remains a challenge for sustainable city planning. This study examines airflow around a tall building designed for vertical wind farming, incorporating passive flow-control balconies and a roof-mounted horizontal-axis wind turbine (HAWT). Using 3D-resolved flow simulations, we analyse configurations with a 3-blade HAWT placed at varying heights and combined with different balcony types. The results show that turbine height has a stronger influence on rotational performance and near-wake dynamics than balcony geometry, while the mid-wake depends primarily on the building itself. We also find that shorter turbines reduce material and maintenance costs while maintaining similar power output at 30 rpm, whereas taller turbines offer only marginal safety improvements at roof level. Overall, the prototypes demonstrate the feasibility of combining facade roughness with on-site wind harvesting to maximise energy capture without duplicating infrastructure in suburban contexts. Full article

Industrial workplaces, especially in vulnerable, hot, and arid developing countries, face major challenges in maintaining indoor comfort conditions due to the escalating problem of global temperature rise. This study investigates passive scenarios of adaptive retrofitting for a case study carpet and rug industrial plant in Cairo, Egypt to achieve indoor comfort conditions and energy efficiency. The research method included a Post Occupancy Evaluation (POE) for the operational phase of individual work units through measurements and simulations to investigate indoor thermal, visual, and acoustic comfort conditions as well as air quality concerns. Thus, the study presents a set of recommendations for building unit(s) and collectively for the entire facility by applying integrated application of building envelope enhancements; optimized opening design, thermal wall insulation and high-albedo (reflective) exterior coatings for wall and roof surfaces. Comparing the modified case to the base case scenario shows significant improvements. Thermal comfort achieved a 16% to 33% reduction in discomfort hours during peak summer, primarily through a 33% increase in air flow velocity and better humidity control. Visual comfort indicated improvements in daylight harvesting, with Daylighting Autonomy increasing by 47% to 64% in core areas, improving light uniformity and reducing glare potential by decreasing peak illuminance by approximately 25%. Thus, the combined envelope and system modifications resulted in a 60 to 80% reduction in monthly Energy Use Intensity (EUI). The effectiveness of the mitigation measures using acoustic insulation was demonstrated in reducing sound pollution transferring outdoors, but the high indoor sound levels require further near-source mitigation or specialized acoustic treatment for complete success. Eventually, the research method helps create a mechanism for measuring and controlling indoor comfort conditions, provide an internal baseline or benchmark to which future development can be compared against, and pinpoint areas of improvement. This can act as a pilot project for green solutions to mitigate the problem of climate change in industrial workplaces and pave the way for further collaboration with the industrial sector. Full article

Thin films have become indispensable in shaping the landscape of modern and future technologies, offering versatile platforms where properties can be engineered at the atomic to microscale to deliver performance unattainable with bulk materials. Historically evolving from protective coatings and optical layers, the field has advanced into a highly interdisciplinary domain that underpins innovations in microelectronics, energy harvesting, optoelectronics, sensing, and biomedical devices. In this review, a structured approach has been adopted to consolidate the fundamentals of thin film growth and the governing principles of nucleation, surface dynamics, and interface interactions, followed by an in-depth comparison of deposition strategies such as physical vapor deposition, chemical vapor deposition, atomic layer deposition (ALD), and novel solution-based techniques, highlighting their scalability, precision, and application relevance. By critically evaluating experimental studies and technological implementations, this review identifies key findings linking microstructural evolution to device performance, while also addressing the pressing challenges of stability, degradation pathways, and reliability under operational stresses. The synthesis of evidence points to the transformative role of advanced deposition controls, in situ monitoring, and emerging AI-driven optimization in overcoming current bottlenecks. Ultimately, this work concludes that thin film technologies are poised to drive the next generation of sustainable, intelligent, and multifunctional devices, with emerging frontiers such as hybrid heterostructures, quantum materials, and bio-integrated systems charting the future roadmap. Full article

Cymbal piezoelectric energy harvesters offer an effective platform for converting mechanical vibrations into electrical energy due to their ability to exploit both longitudinal (d₃₃) and transverse (d₃₁) piezoelectric coefficients. However, the design of flexible cymbal structures that ensure efficient stress transfer to polymer-based piezoelectric materials remains insufficiently explored. In this study, a bridge-like cymbal harvester incorporating polyvinylidene fluoride (PVDF) films as the active layer was designed, fabricated, and experimentally investigated. To support the design process and reduce the computational burden associated with evaluating multiple geometric configurations, we developed a novel machine learning methodology that integrates singular value decomposition (SVD) with metamodeling. This framework provides rapid predictions of resonance behavior and electrical response from key design parameters. The findings demonstrate the feasibility of PVDF-based cymbal harvesters for flexible energy harvesting applications and establish an efficient data-driven approach for guiding future design optimization. Full article