Flexible tactile sensors have promising applications at the field of intelligent robotics. However, manufacturing flexible tactile sensors with excellent stability and high sensitivity remain a great challenge. In the present work, polyvinylidene fluoride (PVDF)-based nanofibers are prepared by electrospinning loaded with Fe ₃ O ₄ nanoparticles (NPs). X-ray diffraction (XRD) and attenuated total reflection fourier transform infrared spectroscope (ATR-FTIR) results indicate that the addition of Fe ₃ O ₄ NPs promotes the generation of β-phase in PVDF polymer, which greatly improves piezoelectric properties of composite nanofibers. Simultaneously, a flexible piezoelectric tactile sensor with cilia-inspired structures (PTSCS) based on PVDF/Fe ₃ O ₄ nanofibers is proposed, which consists of the substrate with cilia structures, Ag electrodes, composite nanofiber membrane and nanofiber protective layer. The PTSCS demonstrates a higher output voltage compared to sensors with bump and planar structures, which also exhibits high robustness, with a stable output after 30000 cycles of vibration testing. More importantly, the PTSCS demonstrates superior performance in recognizing surface texture and temperature of objects. The flexible PTSCS has potential use in areas such as intelligent soft robotics and material recognition.

High-density seismic array method has attracted enormous interest in geophysical methods, and it is an advanced seismic observation technology which is of great significance in oil and gas resource detection and underground space exploration. However, designing a portable sensor node that prolongs the lifetime and equips wireless monitoring system to improve construction efficiency has been still a challenge for the high-density seismic array method. In this paper, a portable energy-efficient wireless sensor node and a hybrid communication system that content themselves with complex terrain, large-scale and reliable transmission are proposed to tackle the restrictions of high-density seismic survey. A Wi-Fi communication system based on the star network structure at the core network layer and a ZigBee communication system based on wireless multi-hop structure in the extended network layer form the hybrid communication system. In order to balance the energy of nodes in the extended network and prolong the network lifetime, this paper proposes a multi-hop variable weight routing method (MVWRM). The method selects the cluster-head node and the multi-hop route by changing the weight of the residual energy of the node and the weight of the distance at different periods. Then, a series of simulations and experiments are carried out for verification. The experiments show that the proposed sensor node suggest good performance in equivalent noise level (0.8μV@500Hz, PGA = 1), total harmonic distortion (124dB). Simulation results and performance analysis validate that the effectiveness of the proposed MVWRM can extend about 10% of the node lifetime.

Poly(vinylidene fluoride) (PVDF) has been a kind of particularly attractive piezoelectric materials for its excellent piezoelectric property. Due to its light weight, impedance characteristic is very similar to water, and good mechanical flexibility, PVDF piezoelectric film is very suitable for the field of hydrophones. Although the piezoelectric ceramic hydrophone has been widely used, but due to the disadvantage of high inherent frequency and fragile characteristics of the piezoelectric ceramics slice, the development of the piezoelectric hydrophone is limited. The application of PVDF piezoelectric film has solved many problems encountered in the use of piezoelectric ceramics. In this article, the classification of hydrophone is briefly introduced at first, and then the current status of hydrophone research is involved. And then, by analyzing the electrical equivalent model of the PVDF piezoelectric sensitive unit, the signal conditioning circuit of the PVDF piezoelectric hydrophone is summarized as well. After that, the current status of PVDF hydrophone research is discussed. Finally, a summary of all the work listed in this article is given and an outlook of PVDF hydrophone is proposed.

The microtremor survey method (MSM) has the potential to be an important geophysical method for identifying the strata velocity structure and detecting the buried fault structures. However, the existing microtremor exploration equipment has been unable to satisfy the requirements of the MSM, which suffers from low data accuracy, long measurement time, and blind acquisition. In this study, we combined a 2 Hz moving coil geophone with advanced acquisition systems to develop a new integrated energy-efficient wireless sensor node for microtremor exploration. A high-precision AD chip and noise matching technology are used to develop a low-noise design for the sensor node. Dynamic frequency selection technology (DFS) and dynamic power management technology (DPM) are used to design an energy-efficient mode. The data quality monitoring system solves the closed technical flaws between the acquisition systems and the control center via 4G wireless monitoring technologies. According to the results of a series of in situ tests and field measurements, the noise level of the system was 0.7 μV@500 Hz with 0 dB attenuation and 220 mW power consumption of the system in the autonomous data acquisition mode. Therefore, it provides substantial support for the effective data acquisition over long measurement durations in microtremor exploration processes. The applicability of the system is evaluated using field data, according to which the integrated energy-efficient wireless sensor node is convenient and effective for MSM.

The subject of the studies presented in this paper is the fabrication of electrochemical geophone, especially the electrochemical transducer with symmetrical four-electrode cell by FPCB process technology. The geophone assembled by transducer, dumbbell-shaped tube, highly-flexible membranes, electrolyte solution and signal-amplification circuit, is calibrated using a standard vibration platform, and the results show a good consistency of each geophone parameters. Coupled with low cost, the electrochemical geophone by FPCB shows a good potential application prospect.