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The continuous progress made in wearable energy harvesting technology is delivering sophisticated devices with increasing power outputs, which are possible to provide sustainable energy supply for body sensors to achieve energy-autonomous wireless sensing systems. This paper reports the development and characterisation of a wearable energy harvesting powered wireless sensing system with system-level strategies to address the challenges in energy harvesting, power conditioning, wireless sensing and their integration into a system. The system comprises four parts: (1) a magnetically plucked wearable knee-joint energy harvester (Mag-WKEH) to scavenge energy from knee-joint motions during human walking, (2) a power management module (PMM) with a maximum power point tracking (MPPT) function, (3) an energy-aware interface (EAI) for dealing with the mismatch between the energy generated and demanded, and (4) an energy-aware wireless sensor node (WSN) for data sensing and transmitting. Experiments were performed with a human subject wearing the system and walking on a treadmill at different speeds. The experimental results showed that as the walking speed increased from 3 to 7 km/h, the power output of the Mag-WKEH increased from 1.9 ± 0.12 to 4.5 ± 0.35 mW, and the generated power was able to power the WSN to work at duty cycles from 6.6 ± 0.36% to 13 ± 0.5% with an active time of 2.0 ± 0.1s. In each active time, the WSN was able to sample 482 readings with an interval of 10 ms from the sensors and transmit all data to a base station at a distance of 4 m. [ABSTRACT FROM AUTHOR]

A compact, springless, easy-to-process kirigami-inspired TENG (KI-TENG) is developed. The frequency responses of the KI-TENG under the influence of mass, acceleration, and initial distance are investigated in detail to optimize its structural design. Moreover, the TENG coupled with the kirigami structure could collect ultra-wide-band vibration energy and as a sensor measuring acceleration. [Display omitted] • A compact and springless kirigami-inspired TENG (KI-TENG) is developed. • The frequency response characteristics of the KI-TENG are investigated. • The KI-TENG can harvest ultra-wide-band vibration energy from 2 to 49 Hz. • The output of the KI-TENG at different vibration tilt angles is explored. • The KI-TENG can effectively monitor acceleration changes from 1 to 9 m/s2. Triboelectric Nanogenerators (TENGs) based on spring-assisted structures play a central role in scavenging vibrational energy that is widely available in the natural environment. However, they suffer from difficulties in adjusting the stiffness and bonding the springs to the triboelectric layer. Here, a kirigami-inspired TENG (KI-TENG) with a kirigami structure is demonstrated, which can be used as an ultra-wide-band vibrational energy harvester and self-powered acceleration sensor. The triboelectric layer of the KI-TENG can be easily processed into the kirigami structure with one or two-degree-of-freedom by laser cutting technology. The frequency responses of the KI-TENG under the influence of mass, acceleration, and initial distance are investigated in detail to optimize the structural design. With optimized structural parameters, the KI-TENG can not only harvest broadband vibration energy from 2 to 49 Hz in vertical vibration state but also obtain high output performance over a wide frequency range in horizontal vibration state. Moreover, the KI-TENG can be used as a sensor measuring acceleration from 1 to 9 m/s2. This work demonstrates a compact TENG coupled with the kirigami structure for energy harvesting and active sensing, which has great prospects in intelligent plants, artificial intelligence, and the internet age. [ABSTRACT FROM AUTHOR]