As a typical representative of micro/nano-textured silicon, black silicon has excellent light absorption properties and is gradually surfacing as a substitute for standard silicon in photoelectric devices. Black silicon overcomes the limitations of traditional silicon-based devices, which are unable to achieve infrared light detection at wavelengths >1100 nm and have low quantum efficiency and sensitivity in ultraviolet light detection. In this article, the recent theoretical and experimental breakthroughs in near-infrared and ultraviolet detection using black silicon are summarized in detail. First, black silicon and the techniques for its fabrication are introduced. Then, the application of enhanced black silicon photodetectors within or above the bandgap limit and black silicon fabricated using different methods in infrared detection is discussed. In principle, infrared detection using black silicon is achieved by jointly utilizing element doping, localized surface plasmon resonance effect, and heterojunction formation. In addition, the application of black silicon in ultraviolet detection is also introduced. Ultraviolet detection is realized by an induced junction and the self-built electric field between black silicon and aluminum oxide. Finally, the increasingly growing potential of black silicon in near-infrared and ultraviolet detection applications, such as infrared night vision imaging, signal detection, ultraviolet light intensity monitoring, and national defense early warning, is further discussed.

Recently, flexible iontronic pressure sensors (FIPSs) with higher sensitivities and wider sensing ranges than conventional capacitive sensors have been widely investigated. Due to the difficulty of fabricating the nanostructures that are commonly used on electrodes and ionic layers by screen printing techniques, strategies for fabricating such devices using these techniques to drive their mass production have rarely been reported. Herein, for the first time, we employed a 2-dimensional (2D) hexagonal boron nitride (h-BN) as both an additive and an ionic liquid reservoir in an ionic film, making the sensor printable and significantly improving its sensitivity and sensing range through screen printing. The engineered sensor exhibited high sensitivity (S_min> 261.4 kPa⁻¹) and a broad sensing range (0.05–450 kPa), and it was capable of stable operation at a high pressure (400 kPa) for more than 5000 cycles. In addition, the integrated sensor array system allowed accurate monitoring of wrist pressure and showed great potential for health care systems. We believe that using h-BN as an additive in an ionic material for screen-printed FIPS could greatly inspire research on 2D materials for similar systems and other types of sensors.

Quartz resonant pressure sensors have emerged as a promising technology for precise pressure measurements in a variety of applications such as aerospace, meteorological observation, and energy exploitation. These sensors are inherently compatible with digital techniques and provide high accuracy, high resolution, and good long-term stability over a wide pressure range. These excellent features can be tentatively attributed to the mechanical and electrical properties of quartz crystals. However, there are no reviews that delve into the mechanisms underlying the superior performance of such sensors, leading to a bottleneck in technological development. Accordingly, this paper reviews the key physical properties and effects of crystalline material that have driven sensor technology advances. In particular, it is gathered that crystal cuts significantly influence the operation and performance of the sensors. These cuts can be classified into three categories based on the sensitivity to the measurement: pressure-sensitive, temperature-sensitive, and frequency-reference cuts. We also summarize the mechanisms that govern the optimization of the crystal cuts and the effect of the combinations of different cuts on performance improvement. Additionally, the unique physical effects of quartz crystals are presented and their role in the sensor technology innovation is discussed in detail. Next, the different quartz resonant pressure sensing technologies available are classified according to the acoustic wave transmission method: surface acoustic wave, vibrating beam, and vibrating diaphragm types. We conclude this paper with an analysis of state-of-the-art sensor technologies, as well as a discussion on the status of the sensor industry and the latest technology trends.

In this work, a capacitive pH sensor consisting of Ta₂O₅ functional film is designed and fabricated by employing MEMS-based procedures. The Ta₂O₅ thin film has an amorphous microstructure, and its surface roughness is less than 3.17 nm. A signal processing circuit and a software filtering algorithm are also designed to measure the pH value, thus improving the detection accuracy and anti-interference ability. Good linearity (R² = 0.99904) and sensitivity (63.12 mV/pH) are recorded for the proposed sensing element in the range of pH 2~12. In addition, the sensor’s drift and hysteresis are equal to 5.1 mV and 5.8 mV, respectively. The enhanced sensing performance in combination with the facile miniaturization process, low fabrication cost, and suitability for mass production render the fabricated sensor attractive for applications where pH change measurements in a water environment are required.

Studies show that the detection of vector turbulence characteristics is of significant importance for further cognition of the marine turbulence mechanism. However, a succedent research process may be impeded by the detection dimensionality of existing marine turbulence sensors. In the present study, a vector high-resolution turbulence sensor (VHTS) is designed from a cilium-shaped structure. The designed VHTS is based on the bionic principle and the MEMS manufacturing technology. A systematic investigation is conducted to improve the VHTS and meet the stringent requirements in marine applications. The measuring sensitivity and natural frequency of the VHTS are balanced by performing theoretical analyses and numerical simulations. Moreover, the vector detection mechanism of the sensitive microstructure is analyzed. Then the designed VHTS is fabricated and encapsulated elaborately by MEMS processes and three-dimensional heterogeneous integration. The calibration experiments show that the sensitivity of the designed VHTS is up to 2.68×10-2 (V∙m∙s2)/kg. The vector verification testing exhibits the excellent orientation behaviors of the designed VHTS, indicating the feasibility of the VHTS to realize the detection of vector turbulence characteristics. The present study may provide a new opportunity for accurate observation and mechanism cognition of turbulence.

A mathematical model is necessary to analyze sensor performance and optimize its design. However, most of the existing models of piezoelectric micro-machined hydrophones are incomplete and too complex to understand. There has been no mathematical model for the sensitivity of piezoelectric hydrophones. To address this shortcoming, this paper proposes a mathematical model of a piezoelectric micro-machined hydrophone. The stresses in the piezoelectric layer and static displacement of the diaphragm under uniform sound pressure are derived. In addition, the resonant frequency and sensitivity of the hydrophone are analyzed. The finite element simulation is used to verify the validity of the proposed mathematical model. On the basis of the mathematical model and simulation, the diaphragm radius, top electrode area, and piezoelectric film thickness are optimized. Furthermore, the hydrophone is fabricated, and its morphology is observed. The impedance-frequency spectrum of the hydrophone is measured by HIOKI IM3536 LCR impedance analyzer. The tested resonant frequency is 0.5 MHz, which is relatively close to the calculated result of 0.537 MHz, so the validity of the proposed mathematical model is further validated. Also, the reason why the test result is less than the calculated result is explained. The effective electromechanical coupling coefficient derived from the impedance curve is 7.5%. The developed mathematical model can provide a useful guide for designing high performance piezoelectric micromachined hydrophone and make preliminary predictions of its characteristics.