The Internet of Things (IoT) relies heavily on wireless sensor network nodes, which integrate power, sensing, communication, and other functionalities. Traditional power sources like lithium and nickel-zinc batteries suffer from drawbacks like frequent charging needs, inflexibility, and environmental concerns, hindering the advancement of portable and sustainable IoT devices. Triboelectric nanogenerators (TENGs), which harvest mechanical energy through the coupling of the triboelectric effect and electrostatic induction, offer a sustainable and efficient alternative. While TENGs have advantages such as sustainability, high output, simple fabrication, and diverse material choices, their low energy conversion efficiency has limited their application in completely self-powered, real-time, continuous wireless multi-sensing microsystems. This research aims to address this limitation by developing a high-performance TEHNG to power such a system.

Existing literature highlights the advantages of TENGs for energy harvesting, including their sustainability, high output, simple fabrication, and diverse material selection. Research has focused on improving TENG efficiency through material optimization, microstructure design, and the exploration of composite energy conversion mechanisms. However, a significant gap remains in the development of fully self-powered, real-time wireless multi-sensing microsystems due to insufficient power generation from single-mechanism energy harvesters. This paper builds upon previous work by integrating multiple energy harvesting mechanisms and advanced circuit design to overcome this limitation.

This study developed a high-performance TEHNG based on a circular spring-cantilever structure. A PVC/PDMS triboelectric pair was chosen after experimental evaluation, exhibiting superior output compared to other material combinations (PTFE, PDMS, silicon rubber, PI, paper, PET, Sn, Al, and Cu). The electromagnetic component was optimized using a 10000-turn copper coil and a neodymium iron boron magnet (35 mm diameter, 4 mm height). Pyramid microstructures (13 µm width, 4 µm gap) were incorporated into the PDMS film to enhance the triboelectric output, significantly increasing surface area. The TEHNG integrates a power management module (PMM), an energy storage module (capacitors), a sensing signal processing module, and a microcontroller unit (MCU) on a PCB. Three sensors (temperature, pressure, and UV) were integrated into the system. The system's functionality was validated by demonstrating real-time wireless data transmission using Bluetooth, with the TEHNG as the sole power source. Detailed electrical characterizations of both the triboelectric and electromagnetic components were performed, analyzing output voltage, current, charge, and power under various conditions (different materials, microstructures, load resistances, and vibration frequencies).

The optimized TEHNG achieved a remarkable load power of 21.8 mW. The triboelectric component, using the optimized PVC/PDMS pair and microstructured PDMS, generated a peak-peak voltage of ~1180.0 V and a peak-peak current of 30.4 µA at 2 Hz. The maximum power output of the triboelectric part reached 3.32 mW at a load resistance of 28.5 MΩ. The electromagnetic component generated an average peak-peak voltage of ~28.0 V and a peak-peak current of 7.4 mA at 2 Hz, with a maximum power output of 18.48 mW at a load resistance of 3.90 kΩ (matching coil resistance). The combined output of both mechanisms provided sufficient power to operate the integrated multi-sensing system (total consumption: 1.019 mW) for continuous real-time wireless data transmission. The system successfully and continuously measured temperature, pressure, and UV levels, transmitting the data wirelessly via Bluetooth.

The high power output of the TEHNG, achieved through a combination of optimized materials, structural design (pyramid microstructures and spring-cantilever structure), and the integration of both triboelectric and electromagnetic energy harvesting mechanisms, successfully addresses the limitations of previous TENG-based systems. The demonstration of a fully self-powered, real-time wireless multi-sensing microsystem represents a significant advancement in the field of energy harvesting and IoT technology. This integrated approach shows great potential for replacing traditional batteries in various applications, reducing reliance on external power sources and enabling the development of truly autonomous and sustainable sensing systems. The successful real-time data transmission showcases the practicality of this technology for real-world applications.

This work successfully demonstrated a high-performance TEHNG capable of powering a fully integrated, self-powered wireless multi-sensing microsystem. The integration of triboelectric and electromagnetic energy harvesting, coupled with optimized materials and structural design, yielded a power output sufficient for real-time sensor operation and data transmission. This represents a significant step towards enabling a new generation of sustainable and autonomous IoT devices. Future research could explore further material optimizations, miniaturization of the system, and integration with more diverse sensor types.

While the TEHNG demonstrates high power output, the performance is dependent on the frequency and amplitude of the mechanical vibrations. The current system's performance under varying environmental conditions and long-term stability needs further investigation. The relatively large size of the current prototype could be a limitation for some applications; future miniaturization efforts would broaden its applicability.