The bottleneck of the miniaturized electromagnetic vibration energy harvester (EVEH) device is the limited output voltage and power. Commonly reported mV-level AC output of the EVEHs cannot be rectified and used. In this work, we report a cost-effective EVEH device based on batch-fabricated flexible springs and coils. At an acceleration of ±1 g peak-to-peak amplitude (±9.8 m s−2), a maximum output peak-to-peak voltage of 1.57 V and an output power of 91.8 μW are measured, at a frequency of 66 Hz. The output voltage of the EVEH is successfully rectified, amplified (passively) and used to charge a supercapacitor.

This paper presents a compact electromagnetic vibrational energy harvester (EVEH) with tunable resonance frequency. The resonance frequency of the EVEH is tuned by adjusting the axial stress in the flexible polymeric springs, which is realized by physically pulling and pushing the springs. The stress tuning functionality is realized with a compact structure with small volume. The total frequency tuning range of the proposed EVEH is 56 Hz (74 Hz–130 Hz), which is 64% of the natural resonance frequency of the EVEH (88 Hz). It is found that the tensile stress increases the resonance frequency of the EVEH, while the compressive stress firstly reduces the resonance frequency and then increases the resonance frequency due to buckling.

The novel g-C3N4–DAPhen adsorbent was synthesized for the selective adsorption of palladium from high level liquid waste.

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