Aluminum oxide (Al₂O₃) amorphous structure with short-range order and long-range disorder has presented promising applications in optical and optoelectronic devices. In this paper, the Al₂O₃ films with different thickness were prepared by atomic layer deposition (ALD) technology at 200°C in order to achieve amorphous structure. X-ray diffraction (XRD) and energy dispersive spectrum (EDS) results indicated that the Al₂O₃ films were amorphous structure and stable O/Al ratio. The surface topography investigated by atomic force microscopy (AFM) showed that the samples were smooth and crack-free. Spectroscopic ellipsometer (SE) measurements were operated to investigate the effect of thickness on the structure and optical properties of films with Tauc-Lorentz model. It is found that the band gap exhibits a steady value ~2.3 eV by the UV-VIS transmittance method, but the T-L model was ~3.0 eV. The refractive index and extinction coefficient are related to the variation of thickness and the samples surface quality of amorphous network structure in the thin films. The outstanding optoelectronic properties and facile fabrication of Al₂O₃ films amorphous structure can be extended to other similar oxides, which could display wide applications in various engineering and industrial fields.

Flexible sensors have been widely studied for use in motion monitoring, human‒machine interactions (HMIs), personalized medicine, and soft intelligent robots. However, their practical application is limited by their low output performance, narrow measuring range, and unidirectional force detection. Here, to achieve flexibility and high performance simultaneously, we developed a flexible wide-range multidimensional force sensor (FWMFS) similar to bones embedded in muscle structures. The adjustable magnetic field endows the FWMFS with multidimensional perception for detecting forces in different directions. The multilayer stacked coils significantly improved the output from the μV to the mV level while ensuring FWMFS miniaturization. The optimized FWMFS exhibited a high voltage sensitivity of 0.227 mV/N (0.5–8.4 N) and 0.047 mV/N (8.4–60 N) in response to normal forces ranging from 0.5 N to 60 N and could detect lateral forces ranging from 0.2–1.1 N and voltage sensitivities of 1.039 mV/N (0.2–0.5 N) and 0.194 mV/N (0.5–1.1 N). In terms of normal force measurements, the FWMFS can monitor finger pressure and sliding trajectories in response to finger taps, as well as measure plantar pressure for assessing human movement. The plantar pressure signals of five human movements collected by the FWMFS were analyzed using the k-nearest neighbors classification algorithm, which achieved a recognition accuracy of 92%. Additionally, an artificial intelligence biometric authentication system is being developed that classifies and recognizes user passwords. Based on the lateral force measurement ability of the FWMFS, the direction of ball movement can be distinguished, and communication systems such as Morse Code can be expanded. This research has significant potential in intelligent sensing and personalized spatial recognition.

Harvesting low-frequency vibration energy in the environment can provide electrical energy for mobile electronic devices. In this article, a bidirectional driving vibration energy harvester is presented based on the electromagnetic induction. The bidirectional driving component of the energy harvester converts the reciprocating linear motion driving energy into the unidirectional rotation. In addition, the two sets of generators are rectified first, and then connected in series to reduce the voltage rang, which is conducive to energy management and storage, and reduces energy loss. The results show that its average output power is 53.28 mW when the acceleration is 9 m/s ² . At a running speed of 8 km/h, the average output power of the energy harvester installed on the human torso is 41.07 mW. At the same time, it can provide real-time energy supply for temperature hygrometer, calculator, and Bluetooth module. It is a novel method for the harvest and utilization of vibration energy, and has great significance for solving the current energy long-term demand of electronic devices.

In response to the growing demand for high-sensitivity accelerometers in vector hydrophones, a piezoelectric MEMS accelerometer (PMA) was proposed, which has a four-cantilever beam integrated inertial mass unit structure, with the advantages of being lightweight and highly sensitive. A theoretical energy harvesting model was established for the piezoelectric cantilever beam, and the geometric dimensions and structure of the microdevice were optimized to meet the vibration pickup conditions. The sol-gel and annealing technology was employed to prepare high-quality PZT thin films on silicon substrate, and accelerometer microdevices were manufactured by using MEMS technology. Furthermore, the MEMS accelerometer was packaged for testing on a vibration measuring platform. Test results show that the PMA has a resonant frequency of 2300 Hz. In addition, there is a good linear relationship between the input acceleration and the output voltage, with V = 8.412a − 0.212. The PMA not only has high sensitivity, but also has outstanding anti-interference ability. The accelerometer structure was integrated into a vector hydrophone for testing in a calibration system. The results show that the piezoelectric vector hydrophone (PVH) has a sensitivity of –178.99 dB@1000 Hz (0 dB = 1 V/μPa) and a bandwidth of 20~1100 Hz. Meanwhile, it exhibits a good “8” shape directivity and consistency of each channel. These results demonstrate that the piezoelectric MEMS accelerometer has excellent capabilities suitable for use in vector hydrophones.

High-performance vector hydrophone that can acquire underwater acoustic vector information is crucial to the effectiveness of underwater target monitoring. In this paper, a novel piezoelectric MEMS vector hydrophone (PMVH) is proposed with d₃₁ working mode, which has a cross-beam integrated microsphere structure. The passive acoustic receiving unit has been integrated for a low-density microsphere instead of the ordinary cilium by increasing the sensing area of the receiving unit. Heterogeneous integrated preparation of high quality PbZr _0.52 Ti _0.48 O ₃ (PZT) thin film was realized on the cross-beam by sol-gel technology. The optimized geometric size of the sensitive structure was determined by simulation analysis. Based on the optimized parameters, the MEMS technology was employed to fabricate the hydrophone microdevices, and a prototype of the PMVH has been assembled. The PMVH is verified experimentally in a standing bucket wave calibration system. The experimental results show that compared to the bionic cilia MEMS vector hydrophone (CVH) the receiving sensitivity reaches up to -177.71 dB (re 1V/μPa) at 1000 Hz, which is higher than 19.3 dB,. Moreover, the bandwidth of the PMVH reaches 20Hz~1150Hz, which exhibits a satisfactory 8-shaped directivity. The results of this work pave a new way to development of piezoelectric hydrophone for underwater communications and acoustic monitoring.

Metal oxide semiconductors (MOSs) hold great promise for electronic devices such as gas sensors. The utilization of ZnO as a conductometric gas sensor material can be traced back to its early stages; however, its application has primarily been limited to high-temperature environments. A gas sensor based on highly porous and interconnected 3D networks of ZnO tetrapod (ZnO-T) micro-nano structures was fabricated via an easy chemical vapor deposition (CVD) method. Homemade instruments were utilized to evaluate the gas-sensing of the sample at room temperature. It exhibited good gas-sensing at room temperature, particularly with a response of up to 338.80% toward 1600 ppm ethanol, while also demonstrating remarkable repeatability, stability, and selectivity. Moreover, the unique gas-sensing properties of ZnO-T at room temperature can be reasonably explained by considering the effect of van der Waals forces in physical adsorption and the synergistic effect of carrier concentration and mobility. The aforementioned statement presents an opportunity for the advancement of gas sensors utilizing ZnO at room temperature.