Two essential oils were isolated from discarded perfume lemon and leaves (Citrus limon (L.) Burm. F.) by hydro-distillation with good yield (0.044% for perfume lemon and 0.338% for leaves). Their biological activities were evaluated against five selected bacterial strains and Aedes albopictus (Ae. albopictus, Diptera: Culicidae). Chemical composition indicated that both essential oils were rich in essential phytochemicals including hydrocarbons, monoterpenes and sesquiterpene. These constituents revealed some variability among the oils displaying interesting chemotypes (R)-(+)-limonene (12.29–49.63%), citronellal (5.37–78.70%) and citronellol (2.98–7.18%). The biological assessments proved that the two essential oils had similar effect against bacterial (inhibition zones diameter ranging from 7.27 ± 0.06 to 10.37 ± 0.15 mm; MICs and MBCs ranging from 1.6 to 6.4 mg/mL); against Ae. albopictus larvae (LC50 ranging from 384.81 to 395.09 ppm) and adult mosquito (LD50 ranging from 133.059 to 218.962 μg/cm2); the activity of the two chemotypes ((R)-(+)-limonene and citronellal): larvae (LC50 ranging from 267.08 to 295.28 ppm), which were all presented in dose-dependent manners. Through this work, we have showcased that recycling and reusing of agriculture by-products, such as discarded perfume lemon and leaves can produce eco-friendly alternatives in bacterial disinfectants and mosquito control product.
Herein, a piezoelectric vibration energy harvester (PVEH) using liquid as an energy-capturing medium is proposed to simultaneously achieve ultralow frequency, low intensity, and multidirectional vibration energy harvesting in a horizontal plane, which is difficult to realize using traditional PVEHs. The proposed harvester comprises a cylindrical container with a certain liquid, a piezoelectric cantilever beam, ropes, and floater-lever arrays. The experimental results indicate that the proposed harvester with a single floater-lever can generate 9.8 μW under an ultralow frequency (2.6 Hz) and a low intensity vibration excitation (0.03 g), and the normalized power density is 8.89 μW/(cm3 g2 Hz). Under a multidirectional vibration excitation (360° in the horizontal plane) with frequencies below 3 Hz and an acceleration of 0.03 g, the two proposed harvesters with three and four floater-levers indicate a maximum output power (Pmax) deviation of 24.92% and 28.31%, respectively, and an angle bandwidth of 360° (using 2/2Pmax as the standard). All the experimental results indicate that the proposed PVEH is highly promising as an energy supply of wireless sensor networks distributed in ultralow frequency, low intensity, and multidirectional applications.
Though numerous piezoelectric vibration energy harvesters (PVEHs) have been designed and investigated to provide power supply for wireless sensors or wearable devices, it remains a challenge for traditional PVEHs to work effectively in an environment of low frequency, low acceleration and multidirectional vibrations. This work presents a PVEH using a low-frequency energy-capturing resonant system formed by a rolling ball in a hemispherical shell and driven by a rope. Due to the symmetry of the sphere, the ball can be excited at multiple directions in 3D space, and the piezoelectric beam can be pulled by the ball through a rope in multiple directions. Thus, the efficient multidirectional energy harvesting under low frequency (< 10 Hz) and ultralow intensity (< 0.1 g) vibrations could be realized. A mass-spring-damper equivalent model was built to understand the operation mechanism of the proposed PVEH. The results show that the proposed PVEH has a potential to collect energy in any direction in 3D space, and could achieve a good angle bandwidth with 360° for φ and 240° for β under the excitation of a = 0.04 g, f = 6.8 Hz with the acceleration defined in the spherical coordinate system. The developed PVEH can generate 6.5 μW under a low-intensity excitation (0.03 g), and the normalized power density can reach 22.63 μW/(cm3g2Hz). Moreover, the minimum start-up acceleration analysis of the proposed PVEH indicates that the PVEH can capture multidirectional energy from vibrations as low as 0.01 g. In addition, both simulation and experimental study on rope redundancy and ball mass show that they can be used to adjust the device performance easily without structure re-fabrication. Overall, this study demonstrates a new mechanism that could effectively harvest low frequency, ultralow intensity and multidirectional vibration
In this work, a mechanical model of a rope-driven piezoelectric vibration energy harvester (PVEH) for low-frequency and wideband energy harvesting was presented. The rope-driven PVEH consisting of one low-frequency driving beam (LFDB) and one high-frequency generating beam (HFGB) connected with a rope was modeled as two mass-spring-damper suspension systems and a massless spring, which can be used to predict the dynamic motion of the LFDB and HFGB. Using this model, the effects of multiple parameters including excitation acceleration, rope margin and rope stiffness in the performance of the PVEH have been investigated systematically by numerical simulation and experiments. The results show a reasonable agreement between the simulation and experimental study, which demonstrates the validity of the proposed model of rope-driven PVEH. It was also found that the performance of the PVEH can be adjusted conveniently by only changing rope margin or stiffness. The dynamic mechanical model of the rope-driven PVEH built in this paper can be used to the further device design or optimization.
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