In this paper, a multi-frequency vibrational piezoelectric energy harvester (PEH) with a dual-microcantilever coupled structure based on the internal resonance effect is proposed. The device consists of a low-frequency cantilever and a high-frequency cantilever with an integer multiple of resonant frequencies connected by a clamped–clamped coupling beam. The internal resonant PEH (IR-PEH) is prepared by the microelectromechanical systems piezoelectric thick-film process based on the flexible thin metal substrate. The output performance of the proposed PEH device is greatly improved by taking advantages of the internal coupling structure and the piezoelectric thick-film microfabrication process. Under the excitation acceleration of 2 g, the maximum power output of IR-PEH reaches 424.6 μW at 190 Hz and 108.8 μW at 365 Hz, which increases by 35% of the power output due to the internal resonance coupling comparing with the PEH without the coupling effect. The corresponding power densities of IR-PEH reach 6.3 and 1.6 mW/cm3, respectively. This IR-PEH configuration induces the competitive advantages of good performance, wide bandwidth, and small volume, which can be potentially employed as a power source for low power wireless sensing nodes.

The evolution of artificial intelligence of things (AIoT) drastically facilitates the development of a smart city via comprehensive perception and seamless communication. As a foundation, various AIoT nodes are experiencing low integration and poor sustainability issues. Herein, a cubic-designed intelligent piezoelectric AIoT node iCUPE is presented, which integrates a high-performance energy harvesting and self-powered sensing module via a micromachined lead zirconate titanate (PZT) thick-film-based high-frequency (HF)-piezoelectric generator (PEG) and poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) nanofiber thin-film-based low-frequency (LF)-PEGs, respectively. The LF-PEG and HF-PEG with specific frequency up-conversion (FUC) mechanism ensures continuous power supply over a wide range of 10-46 Hz, with a record high power density of 17 mW/cm3 at 1 g acceleration. The cubic design allows for orthogonal placement of the three FUC-PEGs to ensure a wide range of response to vibrational energy sources from different directions. The self-powered triaxial piezoelectric sensor (TPS) combined with machine learning (ML) assisted three orthogonal piezoelectric sensing units by using three LF-PEGs to achieve high-precision multifunctional vibration recognition with resolutions of 0.01 g, 0.01 Hz, and 2° for acceleration, frequency, and tilting angle, respectively, providing a high recognition accuracy of 98%-100%. This work proves the feasibility of developing a ML-based intelligent sensor for accelerometer and gyroscope functions at resonant frequencies. The proposed sustainable iCUPE is highly scalable to explore multifunctional sensing and energy harvesting capabilities under diverse environments, which is essential for AIoT implementation.

Human-machine interfaces (HMIs) are the critical platforms for achieving effective and intuitive operations and control tasks between the user and machine. In this work, we propose a self-powered tactile sensing interface (STI) based on an array of bilayer single-electrode triboelectric nanogenerator (TENG) units. For each TENG unit, a pair of innovative, flexible materials, i.e., PET-PDMS and PTFE-PDMS, are arranged in a mosaic pattern, which can serialize the signal peaks and valleys, thus realizing the encoding of tactile sensing information and optimization of the wiring layout. This self-powered, signal-serialized and neatly wired STI can demonstrate the control of intelligent vehicles by detecting touch events.

苏州大学机电工程学院 苏州 215123； 2. 江苏省先进机器人技术重点实验室 苏州 215123

The development of Internet of Things (IoT) technology has greatly contributed to the development of smart cities, from smart homes to smart factories. The quality of human life is enriched by the comprehensive sensing and seamless communication of IoT devices in different spaces. As a foundation, wireless sensor networks, which currently consist of various fixed sensors, are experiencing sustainability and compatibility issues. Here, we report a broadband vibrational piezoelectric energy harvester (PEH) with frequency up-conversion (FUC) function, consisting of a high-frequency piezoelectric cantilever (HF-PC) with a resonant frequency of 214 Hz and a low-frequency stainless-steel cantilever (LF-SC) with a resonant frequency of 36 Hz, and the HF-PC is fabricated by MEMS PZT thick film technology. Under the excitation of external low-frequency vibration, the LF-SC at the bottom impinges on the HF-PC during its motion, and in this way converts the external low-frequency vibration into high-frequency piezoelectric cantilever vibration. The maximum output power of a single HF-PC is 521.5 ȝ: at 214 Hz and 1.0 g acceleration. On the other hand, the FUC-PEH is capable of achieving a maximum voltage output of 26.6 V over a drive frequency range of 26.2 Hz to 48.4 Hz, with an operating bandwidth of 22.2 Hz and a maximum output power of 775.3 μW. The output power is sufficient to power the Bluetooth temperature and humidity sensor, demonstrating the high power output and excellent charging capability of the FUC-PEH.

This paper proposed a high-performance magnetic-coupled nonlinear electromagnetic generator (MNL-EMG). A high-permeability iron core is incorporated to the coil. The strong coupling between the iron core and the vibrating magnets lead to significantly improved output power and a broadened operating bandwidth. The magnetic force of the iron core to the permanent magnets and the magnetic flux density inside the iron core are simulated, and the dimension parameters of the MNL-EMG are optimized. Under acceleration of 1.5 g, the MNL-EMG can maintain high output performance in a wide frequency range of 17~30 Hz, which is 4.3 times wider than that of linear electromagnetic generator (EMG) without an iron core. The maximum output power of MNL-EMG reaches 174 mW under the optimal load of 35 Ω, which is higher than those of most vibration generators with frequency less than 30 Hz. The maximum 360 parallel-connected LEDs were successfully lit by the prototype. Moreover, the prototype has an excellent charging performance such that a 1.2 V, 900 mAh Ni-MH battery was charged from 0.95 V to 0.98 V in 240 s. Both the simulation and experiments verify that the proposed bistable EMG device based on magnetic coupling has advantages of wide operating bandwidth and high output power, which could be sufficient to power micro electronic devices.