Epileptic power supply in Sub-Saharan countries of Africa has warranted the use of power generators as an alternative source of power supply. Exhaust emission from these generators is associated with Polycyclic Aromatic Hydrocarbon (PAHs). Hence, this study focused on the determination of levels of PAHs in the emission of different brands of power generators used in Nigeria. Exhaust emissions of different power generators were sampled using a filter-sorbent sampling system with polyurethane foam (PUF) as an adsorbent material. Analysis of PAHs was carried out using a Gas Chromatograph coupled to a mass selective detector (GC- MS) operated on Electron Ionization (EI) mode. The results showed the ∑ PAHs range 14.91-26.0 μ g m - 3 . Bap was the most abundant of all the compounds with a concentration of 2.6 μ g m - 3 with a range of 2.08-3.07 μ g m - 3 . The Incremental Life Cancer Risk (ILCR) values of all the generator\'s emission sampled are higher than 10- 4 for both children and adult which indicate a high potential cancer risk from inhalation of emission from these generators while Hazard Quotient (HQ) values from all the power generating set in this study are all above 1 which indicated high associated non-carcinogenic. The study revealed the levels of PAHs associated with the emission of power generators in Nigeria.

As for the self-supporting composite films, it is significant to develop a structural design that allows for excellent flexibility while reducing the negative effect on thermoelectric (TE) properties. Herein, a robust, flexible TE film was fabricated by in situ chemical transformation and vacuum-assisted filtration without any organic solvents involved. The performance of the films was further optimized by adjusting the Ag/Te ratio and post-treatment methods. Owing to the semi-interpenetrating nanonetwork structure formed by AgxTe nanowires and bacterial cellulose, the obtained TE film displayed a high tensile strength of ∼78.4 MPa and a high power factor of 48.9 μW m-1 K-2 at room temperature. A slight electrical conductivity decrement of the TE film in flexible test (∼2% after 1000 bending cycles) indicates an excellent flexibility. Finally, a TE bracelet was assembled to harvest body heat energy, and a steady current of ∼2.7 μA was generated when worn on the wrist indoors. This work provides a reference for the structural design and practical application of flexible TE films.

High indoor humidity/temperature pose serious public health threat and hinder industrial productivity, thus adversely impairing the wellness and economy of the entire society. Traditional air conditioning systems for dehumidification and cooling involve significant energy consumption and have accelerated the greenhouse effect. Here, this work demonstrates an asymmetric bilayer cellulose-based fabric that enables solar-driven continuous indoor dehumidification, transpiration-driven power generation, and passive radiative cooling using the same textile without any energy input. The multimode fabric (ABMTF) consists of a cellulose moisture absorption-evaporation layer (ADF) and a cellulose acetate (CA) radiation layer. The ABMTF exhibits a high moisture absorption capacity and water evaporation rate, which quickly reduces the indoor relative humidity (RH) to a comfortable level (40-60% RH) under 1 sun illumination. The evaporation-driven continuous capillary flow generates a maximum open-circuit voltage (Voc ) of 0.82 V, and a power density (P) up to 1.13 µW cm-3 . When a CA layer with high solar reflection and mid-infrared (mid-IR) emissivity faces outward, it realizes subambient cooling of ≈12 °C with average cooling power of ≈106 W m-2 at midday under radiation of 900 W m-2 . This work brings a new perspective to develop the next-generation, high performance environmentally friendly materials for sustainable moisture/thermal management and self-powered applications.

Flexible thermoelectric (TE) generators have recently attracted increasing attention as they have the potential to power wearable devices using the temperature difference between the human body and the environment. Ag2S is recently reported to have plasticity near room temperature; however, it has very low electrical conductivity, leading to its poor TE property. Here, to improve the TE property, different amounts of Se (Se/Ag2S molar ratios being 0.4, 0.5, and 0.6) solid solution-substituted Ag2S films on a nylon membrane are prepared by combing wet-chemical synthesis, vacuum filtration, and hot-pressing. The film (Se/Ag2S molar ratio = 0.6) exhibits a better TE performance with a power factor of 477.4 ± 15.20 μW m-1 K-2 at room temperature, which is comparable to that of bulk Ag2S1-xSex. In addition, the film possesses excellent flexibility (only ∼5.4% decrease in electrical conductivity after 2000 times bending along a rod with a radius of 4 mm). The power density of a 6-leg TE generator assembled with the film is 6.6 W/m2 under a temperature difference of 28.8 K. This work provides a facile new route to Ag2S-based TE films with low cost, high TE performance, and ultrahigh flexibility.

This study proposed an energy harvester that combines an eccentric pendulum with Wiegand wires to harvest the kinetic energy of a rotating plate. The energy harvester converts the kinetic energy into electrical energy to power sensors mounted on the rotating plate or wheel. The kinetic model is derived from the Euler-Lagrange equation. The eccentric pendulum generates a swing motion from the direction variation of the centrifugal force and the gravitational force. The magnetic circuit is designed such that, during the swing motion, an alternating magnetic field is formed to induce the output voltage of the Wiegand wire. COMSOL software was used to simulate magnetic flux density and optimize the geometric parameters of magnets. Response surface methodology was used to formulate the output voltage model. Magnetic flux density affects output voltage dramatically. However, the output voltage is not sensitive to the gradient of magnetic flux density. The experimental results indicate that when the Wiegand wire is 14.2 mm from the magnet, the generation power is 0.118-1.15 mW, in a speed range of 240-540 rpm. When the Wiegand wire is 7.0 mm from the magnet, the generation power is 0.741-1.06 mW, in a speed range of 480-660 rpm.

In this work, we developed a facile method to fabricate low-cost, flexible, and high-thermoelectric-performance n-type Ag2Se1-xSx@(Ag2S1-ySey/S) composite film on a nylon membrane. The composite film was prepared by first performing wet-chemical synthesis of the S-doped Ag2Se powder, then vacuum-assisted filtration of the powder on a nylon membrane, and finally hot-pressing. Transmission electron microscopy (TEM) observation and energy-dispersive system (EDS) analysis of the film revealed that the film had a porous network-like microstructure, in which Ag2Se1-xSx sub-micron grains formed the skeleton and are coated by a ∼15 nm thick layer of S-rich Ag2S1-ySey nanograins mixed with an S amorphous phase. The film showed a power factor of ∼954.7 μW·m-1·K-2 at 300 K and superior flexibility (94.4% of the original electrical conductivity was preserved after bending 2000 times around a rod with a radius of 4 mm). Moreover, a six-leg flexible thermoelectric generator was assembled with the film and produced a maximum power of 6.67 μW (corresponding power density ∼14.8 W/m2) at a temperature difference of 38.7 K. This work reveals a novel approach to explore high-performance and low-cost flexible thermoelectric devices suitable for room-temperature applications.

Herein, we fabricated an Ag/Ag2Se composite film on a flexible nylon membrane with a high power factor and excellent flexibility. First, Ag nanoparticles and multiscale Ag2Se nanostructure composite powders were prepared by wet chemical synthesis using Se nanowires, silver nitrate, and l-ascorbic acid as raw materials, followed by vacuum-assisted filtration of the composite powders on a porous nylon membrane and then hot pressing. The optimized composite film shows a very high power factor of 1860.6 μW m-1 K-2 (with a corresponding electrical conductivity of 3958 S cm-1) at room temperature. The composite film retains 93.3% of the original electrical conductivity after 1000 bending cycles around a rod with a diameter of 8 mm. At a temperature difference of 27 K, an 8-leg thermoelectric prototype device assembled with the optimized composite film generates a maximum power of 7.14 μW with a corresponding power density of 8.74 W m-2. This work provides a new strategy to synthesize flexible thermoelectric films with both a high power factor and high electrical conductivity.

Bi-Sb-Te-based semiconductors possess the best room-temperature thermoelectric performance, but are restricted for application in the wearable field because of their inherent brittleness, rigidity, and nonscalable manufacturing techniques. Therefore, how to obtain thermoelectric materials with excellent thermoelectric properties and flexibility through the batch production process is a serious challenge. Here, we report the fabrication of flexible p-type thermoelectric Ag-modified Bi0.5Sb1.5Te3 films on flexible substrates using a facile approach. Their optimized power factors are ∼12.4 and ∼14.0 μW cm-1 K-2 at 300 and 420 K, respectively. These high-power factors mainly originate from the optimized carrier transport of the composite system, through which a high level of electrical conductivity is achieved, whereas a remarkably improved Seebeck coefficient is simultaneously obtained. Bending tests demonstrate the excellent flexibility and mechanical durability of the composite films, and their power factors decrease by only about 10% after bending for 650 cycles with a bending radius of 5 mm. A flexible thermoelectric module is designed and constructed using the optimized composite films and displays a power density of ∼1.4 mW cm-2 at a relatively small ΔT of 60 K. This work demonstrates the potential of inorganic thermoelectric materials to be made on flexible/wearable substrates for energy harvesting and management devices.

Transpiration is the process by which water is carried in plants from the roots to the leaves where evaporation takes place. Here, we report a transpiration driven electrokinetic power generator (TEPG) that exploits capillary flow of water in an asymmetrically wetted cotton fabric coated with carbon black. Accumulation of protons induced by the electrical double layer formed at the solid (carbon black)/liquid (water) interface gives rise to potential difference between the wet and dry sides. The conductive carbon black coating channels electrical current driven by the pseudostreaming mechanism. A TEPG of 90 mm × 30 mm × 0.12 mm yields a maximum voltage of 0.53 V, maximum current of 3.91 μA, and maximum energy density of 1.14 mWh cm-3, depending on the loading of the carbon black. Multiple TEPGs generate enough power to light up a light-emitting diode (20 mA × 2.2 V) or charge a 1 F supercapacitor.

An implantable power generation system driven by muscle contractions for supplying power to active implantable medical devices, such as pacemakers and neurostimulators, is proposed. In this system, a muscle is intentionally contracted by an electrical stimulation in accordance with the demands of the active implantable medical device for electrical power. The proposed system, which comprises a small electromagnetic induction generator, electrodes with an electrical circuit for stimulation and a transmission device to convert the linear motion of the muscle contractions into rotational motion for the magneto rotor, generates electrical energy. In an ex vivo demonstration using the gastrocnemius muscle of a toad, which was 28 mm in length and weighed 1.3 g, the electrical energy generated by the prototype exceeded the energy consumed for electrical stimulation, with the net power being 111 µW. It was demonstrated that the proposed implantable power generation system has the potential to replace implantable batteries for active implantable medical devices.