Recently, Professor Wu Hao's research group published a research paper titled Achieving Ultra High Power Output in Triboelectric Energy Harvesters by Torrent Like Charge Regulation in the internationally renowned journal Advanced Materials. This paper proposes a Torrent like charge regulation (TCR) strategy: accelerating charge transfer through a transistor like structure, while combining vascular biomimetic design to increase the total charge, achieving explosive output and obtaining an ultra-high instantaneous volume power density of 10 MW/m3. The electrical energy output is several orders of magnitude higher than previous reports. At the same time, this study replaced sliding friction with rolling friction to reduce friction losses and successfully achieved self powered wireless sensing based on shaking energy without the need for batteries.
With the advent of the Internet of Things era, collecting environmental kinetic energy (such as waves, raindrops, and wind energy) has become a feasible way for IoT devices to eliminate batteries and achieve self powering. However, due to the low and irregular frequency of these energy sources, their utilization is difficult. Therefore, various new micro nano energy harvesting technologies have emerged, including frictional nanogenerators, polarizable generators, piezoelectric generators, etc. These technologies generate electrical energy by inducing changes in material surface charge through mechanical motion. Despite their broad application prospects, they are all limited by issues such as low output charge and high internal impedance, which hinder their practical development.
On the one hand, the problem of low charge output can be solved through strategies such as material optimization, surface modification, and environmental control. However, these strategies often require additional charge preprocessing steps or strict environmental requirements, and are prone to charge decay in practical applications. On the other hand, to solve the problem of high internal resistance in devices, a planar transistor like structure nanogenerator was proposed in the early stage, which can significantly improve power output. However, the two-dimensional planar design of this structure requires close contact between the friction layers, resulting in significant wear and limiting its practical application. Therefore, it is of great significance to develop a practical energy harvester that combines high charge density, low output impedance, and low friction loss.
Researchers have adjusted the charge transfer speed from macroscopic motion control to electrical relaxation control by designing a transistor like structure, greatly accelerating charge transfer and reducing the internal resistance of the device from megaohms to kiloohms, effectively improving load power and electrical energy. On the other hand, researchers adopted a vascular biomimetic design by adding multiple charge vascular channels in the middle, resulting in a significant increase in the total charge output (see Figure 1). The combined effect of the two forms a torrent like charge control effect, achieving an ultra-high instantaneous volumetric power density of 10 MW/m3, and increasing the power output by multiple orders of magnitude compared to previous reports.
Figure 1. Design of TCR based energy harvester. (a) Schematic diagram of the transistor like switch structure inside the device. (b) Schematic diagram of charge channel structure in biomimetic plant vascular bundles. (c-d) Schematic diagram of working mechanism and physical photos (the device has a mass of 12.2 g, a diameter of 1.2 cm, and a length of 6 cm). (e) Output performance comparison: Control device 1 is a traditional friction nanogenerator device (without biomimetic design), control device 2 is a biomimetic friction nanogenerator device (without transistor like design), and an energy harvester based on TCR (with load resistance of 1 M Ω). (f) Comparison of output energy within half a working cycle (load 1 M Ω). (g) Comparison of instantaneous power density and charge density of this device with reported literature devices.
After optimizing the structural parameters of the device, the author team studied the output performance of TCR based energy harvesters under different working conditions. Figure 2 shows that the energy harvester can achieve an instantaneous peak power of approximately 74 W under a load of 1000 Ω, with a corresponding volumetric power density exceeding 10 MW/m3, and can easily light up 500 LED lights. In contrast, traditional devices with the same size cannot light up the same number of LED lights. Furthermore, this study used rolling friction instead of sliding friction to reduce friction losses, so its output performance did not degrade after a 9-month usage cycle.
Figure 2. Output performance of TCR based energy harvester. (a) The current curves of the device under loads of 1 M Ω, 4.7 M Ω, and 10 M Ω; (b) Comparison of energy output between TCR energy harvester and control 1 under different load resistance values; (c) The current and peak power density of the device as a function of load variation; (d) The current output of the device varies with the operating frequency; (e) The voltage and charge output of the device as a function of operating frequency; (f) The output performance of the device varies with the swing angle; (g) A physical photo of TCR energy harvester lighting up 400 LEDs; (h) Compare the output current of the same device after 9 months of use.
Figure 3 shows a completely battery free self powered wireless sensor based on shaking energy: firstly, the TCR energy collector is triggered by shaking, and under the combined effect of low impedance and high power density, the coil end connected to the TCR energy collector instantly triggers a violent electromagnetic field change, thereby transmitting high-power signals to a distance of 20 meters and being captured by a distant computer end. As a result, researchers have successfully constructed a battery free wireless transmission and communication system, demonstrating the broad prospects of TCR strategy in sustainable energy supply for IoT devices.
Figure 3 A wireless communication system application that completely eliminates the need for batteries. (a) Equivalent circuit diagram (integrating TCR energy harvester and coil as the transmitting end); (b) Under different transmission distances, voltage signals of reference device 1 and TCR energy collector are compared; (c) The signal waveform emitted by TCR energy harvester; (d) The waveform of the signal received by the oscilloscope at various transmission distances; (e) A physical photo of a wireless coding transmission system completely without batteries; (f) The waveform of the received signal displayed on the oscilloscope; (g) Receive signals SOS and 5; (h) A battery free wireless coding transmission system for computer visualization demonstration.
In summary, researchers have proposed a torrent style charge control strategy that not only increases the total amount and rate of charge transfer and reduces internal impedance, but also utilizes rolling friction to reduce friction losses, significantly improving the practicality of the device. The results showed that the volumetric charge density of the device reached 17 mC/m3, and the peak power density exceeded 10 MW/m3. Finally, the researchers successfully constructed a wireless transmission and communication system that does not require batteries.
Hong Hongxin, a doctoral student from South China University of Technology, and Yan Shushu, a master's student, are the first authors of the paper. Professor Wu Hao from South China University of Technology and Professor Wang Zhuangkai from Hong Kong Polytechnic University are the corresponding authors of this paper. This study was supported by the National Natural Science Foundation of China, the Guangdong Provincial Basic and Applied Basic Research Fund, and the Xiaomi Youth Talent Program.
Original link:
https://doi.org/10.1002/adma.202506136
