This paper proposes an impact-based micro piezoelectric energy harvesting system (PEHS) working with the frequency up-conversion mechanism. The PEHS consists of a high-frequency straight piezoelectric cantilever (SPC), a low-frequency S-shaped stainless-steel cantilever (SSC), and supporting frames. During the vibration, the frequency up-conversion behavior is realized through the impact between the bottom low-frequency cantilever and the top high-frequency cantilever. The SPC used in the system is fabricated using a new micro electromechanical system (MEMS) fabrication process for a piezoelectric thick film on silicon substrate. The output performances of the single SPC and the PEHS under different excitation accelerations are tested. In the experiment, the normalized power density of the PEHS is 0.216 μW·g⁻¹·Hz⁻¹·cm⁻³ at 0.3 g acceleration, which is 34 times higher than that of the SPC at the same acceleration level of 0.3 g. The PEHS can improve the output power under the low frequency and low acceleration scenario.

With the rapid development of wireless communication and micro-power technologies, smart wearable devices with various functionalities appear more and more in our daily lives. Nevertheless, they normally possess short battery life and need to be recharged with external power sources with a long charging time, which seriously affects the user experience. To help extend the battery life or even replace it, a non-resonant piezoelectric–electromagnetic–triboelectric hybrid energy harvester is presented to effectively harvest energy from low-frequency human motions. In the designed structure, a moving magnet is used to simultaneously excite the three integrated energy collection units (i.e., piezoelectric, electromagnetic, and triboelectric) with a synergistic effect, such that the overall output power and energy-harvesting efficiency of the hybrid device can be greatly improved under various excitations. The experimental results show that with a vibration frequency of 4 Hz and a displacement of 200 mm, the hybrid energy harvester obtains a maximum output power of 26.17 mW at 70 kΩ for one piezoelectric generator (PEG) unit, 87.1 mW at 500 Ω for one electromagnetic generator (EMG) unit, and 63 μW at 140 MΩ for one triboelectric nanogenerator (TENG) unit, respectively. Then, the generated outputs are adopted for capacitor charging, which reveals that the performance of the three-unit integration is remarkably stronger than that of individual units. Finally, the practical energy-harvesting experiments conducted on various body parts such as wrist, calf, hand, and waist indicate that the proposed hybrid energy harvester has promising application potential in constructing a self-powered wearable system as the sustainable power source.

With the continual increasing application requirements of broadband vibration energy harvesters (VEHs), many attempts have been made to broaden the bandwidth. As compared to adopted only a single approach, integration of multi-approaches can further widen the operating bandwidth. Here, a novel two-degree-of-freedom cantilever-based vibration triboelectric nanogenerator is proposed to obtain high operating bandwidth by integrating multimodal harvesting technique and inherent nonlinearity broadening behavior due to vibration contact between triboelectric surfaces. A wide operating bandwidth of 32.9 Hz is observed even at a low acceleration of 0.6 g. Meanwhile, the peak output voltage is 18.8 V at the primary resonant frequency of 23 Hz and 1 g, while the output voltage is 14.9 V at the secondary frequency of 75 Hz and 2.5 g. Under the frequencies of these two modes at 1 g, maximum peak power of 43.08 μW and 12.5 μW are achieved, respectively. Additionally, the fabricated device shows good stability, reaching and maintaining its voltage at 8 V when tested on a vacuum compression pump. The experimental results demonstrate the device has the ability to harvest energy from a wide range of low-frequency (<100 Hz) vibrations and has broad application prospects in self-powered electronic devices and systems.

Tactile sensors, due to their unique advantages of high sensitivity, flexibility, and stability, have received increasing attention from researchers worldwide and hold great promise for application to a variety of fields, particularly electronic skin. However, the majority of tactile sensors are limited in their ability to meet the demand of their application to multi-variable tests due to their single-functionality. To address this issue, in this paper, we introduce a novel type of array pressure/temperature composite tactile sensor that functions without any interference. The pressure sensor is a capacitive pressure sensor with carbon-filled polydimethylsiloxane (PDMS) serving as the intermediate dielectric layers. The temperature sensor, which is placed on the top of the pressure sensor with the two elements closely attached to each other, is a T-shaped thermocouple sensor fabricated by magnetron sputtering. PDMS filled with carbon materials has been shown to perform well overall in experiments. The sensor’s sensitivity is 85.5%/N within a pressure range of 0–2 N and 23.9%/N within a pressure range of 0–10 N, while the hysteresis is around 9.1%. Practical experiments are conducted to test the prepared device, and finally, the designed hardware circuit is connected to the IPC.

Dissolvable polymeric microneedles have gained significant attention in recent years as a promising transdermal drug delivery method due to their simple fabrication and lack of medical waste after use. However, traditional polymeric microneedles possess several notable drawbacks, including insufficient mechanical strength, difficulty in effectively penetrating the skin barrier, limited drug loading capacity affecting therapeutic outcomes, and uncontrollable drug release rates leading to unstable efficacy. In this paper, a conductive polymer microneedle with an adjustable dissolution rate is proposed. The dissolution rate of microneedles can be adjusted by controlling the current so as to control the drug release rate and realize the controlled drug release truly. The PVA-Ag and PVP-Ag lidocaine-loaded microneedles demonstrated good puncture performance and nearly complete dissolution within 10 min in a simulated body fluid environment. The dissolution rate was significantly accelerated under electrical stimulation. The microneedles showed good biocompatibility, and under the application of a 3 V voltage, the drug delivery efficiency of PVP-Ag lidocaine microneedles reached 85% within 5 min, while PVA-Ag lidocaine microneedles achieved up to 90%.