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• We propose a tumbler-inspired electromagnetic harvester (T-EMH) for human motion. • We use the tumbler mechanism to transform irregular human motion energy. • The power of the T-EMH reaches 0.86 mW under the speed of 12 km/h. • T-EMH can harvest human motion energy and effectively power electronic devices. Harvesting energy from human motion to power portable electronic devices has attracted widespread attention. However, human motion energy is primarily concentrated in low-frequency range below 5 Hz, which makes it hard to capture with traditional approaches. In this work, a tumbler-inspired electromagnetic energy harvester (T-EMH) is designed to harvest human motion energy. The magnet is placed on the top of the tumbler structure, allowing for easy conversion of irregular human motion into electricity through the tumbler mechanism. A theoretical model is established to predict the energy harvesting performance of T-EMH. Both simulations and experiments were conducted to verify the low-frequency characteristics of T-EMH. The harvested maximum peak voltage is 0.6 V and the maximum average output power can reach 0.55 mW by adjusting the external load. Additionally, human motion tests substantiate T-EMH's capacity to generate a peak power output of 0.86 mW at a running speed of 12 km/h. These results emphasize the promising potential of T-EMH as an effective approach for capturing energy from human motion. [Display omitted] [ABSTRACT FROM AUTHOR]

• A tumbler-inspired electromagnetic ocean wave generator (T-EMG) is proposed. • The Halbach array is used to improve the low-frequency energy harvesting capacity. • T-EMG can harvest random and low-frequency ocean wave energy in offshore tests. • The maximum voltage is 3 V and the maximum average output power can reach 65 mW. Ocean wave is considered as one of most promising renewable energy sources due to the merits of wide distribution and high energy density. However, the low-frequency and large randomness characteristics make it hard to harvest. Here we report a tumbler-inspired electromagnetic generator (T-EMG) with a Halbach array to improve the low-frequency ocean wave energy harvesting performance. The theoretical model of the T-EMG is established. The amplitude-frequency relationship is derived. The simulations and experimental investigation are carried out. The maximum harvested voltage of 3 V with a lower frequency of 2.6 Hz is obtained, and the maximum average output power can reach 65 mW through adjusting the load and tumbler parameters. More significantly, the offshore tests in the East China sea were carried out and the experimental results showed that T-EMG can work effectively under ultra-low frequency (<1Hz) real ocean wave environments and achieve a maximum peak power of 120 mW, which could meet the requirement of low-power wireless sensors. In addition, the offshore tests also demonstrate the strong frequency adaptability of T-TMG that enables it to harvest random and low-frequency ocean waves efficiently. This work provides an effective solution to harvest low-frequency and random ocean wave energy and can be easily adapted to mechanical or aerospace engineering, etc. [ABSTRACT FROM AUTHOR]

• We derive the equation of motion of a tumbler on an arc surface. • The natural frequency of the tumbler on arc can be as low as 2.7 Hz. • The motion of the tumbler can be chaotic and periodic under different parameters. • Low frequency characteristic is beneficial for broadband vibration isolation. A tumbler oscillates around its geometric axis with a period under external disturbances. Due to the oscillation mechanism differs from traditional mass-spring-dampers, the dynamic response of tumblers is still a challenge. This work considers the dynamics behaviors of a tumbler on an arc surface. A tumbler prototype is designed and the corresponding equation of motion is derived according to the Lagrange's equation. Both the simulation and experimental efforts are performed to study the dynamics characteristics of the tumbler on an arc. The results demonstrate that the natural frequency of the tumbler can be 2.7 Hz, which is considerable to design low-frequency vibration devices in a new tunable perspective, such as vibration isolators or energy harvesters. The motion of the tumbler is periodic or quasi-periodic under a smaller excitation amplitude, and will be chaotic under a small damping. This work opens a window for the design and application of tumbler-inspired structures. [ABSTRACT FROM AUTHOR]