As a new material, graphene shows excellent properties in mechanics, electricity, optics, and so on, which makes it widely concerned by people. At present, it is difficult for graphene pressure sensor to meet both high sensitivity and large pressure detection range at the same time. Therefore, it is highly desirable to produce flexible pressure sensors with sufficient sensitivity in a wide working range and with simple process. Herein, a relatively high flexible pressure sensor based on piezoresistivity is presented by combining the conical microstructure polydimethylsiloxane (PDMS) with bilayer graphene together. The piezoresistive material (bilayer graphene) attached to the flexible substrate can convert the local deformation caused by the vertical force into the change of resistance. Results show that the pressure sensor based on conical microstructure PDMS-bilayer graphene can operate at a pressure range of 20 kPa while maintaining a sensitivity of 0.122 ± 0.002 kPa⁻¹ (0–5 kPa) and 0.077 ± 0.002 kPa⁻¹ (5–20 kPa), respectively. The response time of the sensor is about 70 ms. In addition to the high sensitivity of the pressure sensor, it also has excellent reproducibility at different pressure and temperature. The pressure sensor based on conical microstructure PDMS-bilayer graphene can sense the motion of joint well when the index finger is bent, which makes it possible to be applied in electronic skin, flexible electronic devices, and other fields.

With advances in new materials and technologies, there has been increasing research focused on flexible sensors. However, in most flexible pressure sensors made using new materials, it is challenging to achieve high detection sensitivity across a wide pressure range. Although traditional silicon-based sensors have good performance, they are not formable and, because of their rigidity and brittleness, they are not suitable for fitting with soft human skin, which limits their application in wearable devices to collect various signals. Silicon nanomembranes are ultra-thin, flexible materials with excellent piezoresistive properties, and they can be applied in various fields, such as in soft robots and flexible devices. In this study, we developed a flexible pressure sensor based on the use of silicon nanomembranes (with a thickness of only 340 nm) as piezoresistive units, which were transferred onto a flexible polydimethylsiloxane (PDMS) substrate. The flexible pressure sensor operated normally in the range of 0–200 kPa, and the sensitivity of the sensor reached 0.0185 kPa⁻¹ in the low-pressure range of 0–5 kPa. In the high-pressure range of 5–200 kPa, the sensitivity of the sensor was maintained at 0.0023 kPa⁻¹. The proposed sensor exhibited a fast response and excellent long-term stability and could recognize human movements, such as the bending of fingers and wrist joints, while maintaining a stable output. Thus, the developed flexible pressure sensor has promising applications in body monitoring and wearable devices.

The miniaturization of low-frequency marine underwater acoustic detection systems presents new requirements for three-dimensional vector hydrophones. Inspired by fish lateral lines, we have introduced a biomimetic three-dimensional vector hydrophone. It features a microstructure with a monolithically integrated four-beam central block and cilium, capable of detecting underwater acoustic signals from three dimensions. Simulations were conducted to determine the natural frequencies and stress of the hydrophone, helping establish the structural parameters. The arrangement of piezoresistors on the four beams was meticulously designed to minimize inter-axis coupling. The hydrophone chip was fabricated using MEMS technology, followed by comprehensive testing. The hydrophone effectively operates within a detection frequency band of 20-500 Hz. The sensitivities for the three axes are -189 dB@500 Hz, -189.6 dB@500 Hz, and -200.9 dB@500 Hz (0 dB=1 V/μPa), respectively. The concave point depths are 30.4 dB, 29.8 dB, and 26.9 dB, with the voltage density of self-noise at -106 dB at 500 Hz. These results indicate that the biomimetic three-dimensional vector hydrophone holds promising prospects for low-frequency underwater acoustic detection applications.

Poly (vinylidene fluoride) (PVDF) hollow fiber membranes are prepared by modified TIPS from PVDF/triethyl phosphate (TEP) system. It is revealed by differential scanning calorimetry (DSC) that PVDF crystallization capacity increase with polymer content increasing. Additionally, crystallization behavior and crystal structure of PVDF in PVDF/TEP systems are investigated by scanning electron microscopy (SEM) and wide angle X-ray diffraction (WAXD). PVDF concentration has a remarkable effect on PVDF crystallization behavior. Dendritic pore structures are obvious when PVDF weight ratio is 30% in polymer/diluent solution. However, discernable spherulitic structures are obtained when PVDF weight ratio reaches to 35%.

The main frequency band of the radiated signals from ships is 20-500Hz, and also the main working frequency band of the Micro-Electro-Mechanical-System ( MEMS ) vector hydrophone. To improve sensitivity in this frequency band, this paper presents a nested package structure, which encapsulates the sensitive sections of the vector hydrophone with a mesh-like interior support and a sound-transparent cap. By COMSOL Multiphysics 6.0 simulation, the particle acceleration and intrinsic frequency of the hydrophone with different interior supports and sound-transparent cap are compared and analyzed. The simulation results show that the hydrophone encapsulated with nylon interior support and latex acoustic cap has higher acceleration, and its intrinsic frequency is 2285.1 Hz in air and 804.64 Hz underwater. The results of the testing indicate that the nested package hydrophone designed in this paper has a bandwidth of 10-800Hz, meeting the main working frequency band of the hydrophone. Additionally, the sensitivity of the hydrophone with latex encapsulation is increased by 7.8dB@100Hz than polyurethane encapsulation. The depth of the notch at 100Hz and 500Hz is more than 30dB, which indicates that the hydrophone has good dipole directivity. Compared with the traditional polyurethane-packaged hydrophone, the nested package structure can effectively improve the performance of the hydrophone.

To reduce the loss of the metal–insulator–metal waveguide structure in the near-infrared region, a plasmonic nanosensor structure based on a racetrack resonant cavity is proposed herein. Through finite element simulation, the transmission spectra of the sensor under different size parameters were analyzed, and its influence on the sensing characteristics of the system was examined. The analysis results show that the structure can excite the double Fano resonance, which has a distinctive dependence on the size parameters of the sensor. The position and line shape of the resonance peak can be adjusted by changing the key parameters. In addition, the sensor has a higher sensitivity, which can reach 1503.7 nm/RIU when being used in refractive index sensing; the figure of merit is 26.8, and it can reach 0.75 nm/°C when it is used in temperature sensing. This structure can be used in optical integrated circuits, especially high-sensitivity nanosensors.