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Flexible wearable sensors with excellent electric response and self-powered capability have become an appealing hotspot for personal healthcare and human–machine interfaces. Here, based on triboelectric nanogenerator (TENG), a flexible self-powered tactile sensor composed of micro-frustum-arrays-structured polydimethylsiloxane (PDMS) film/copper (Cu) electrodes, and poly(vinylidenefluoride–trifluoroethylene) (P(VDF-TrFE)) nanofibers has been demonstrated. The TENG-based self-powered tactile sensor can generate electrical signals through the contact-separation process of two triboelectric layers under external mechanical stimuli. Due to the uniform and controllable micro-frustum-arrays structure fabricated by micro-electro-mechanical system (MEMS) process and the P(VDF-TrFE) nanofibers fabricated by electrostatic spinning, the flexible PDMS-based sensor presents high sensitivity of 2.97 V kPa−1, stability of 40,000 cycles (no significant decay), response time of 60 ms at 1 Hz, low detection pressure of a water drop (~4 Pa, 35 mg) and good linearity of 0.99231 in low pressure region. Since the PDMS film presents ultra-flexibility and excellent-biocompatibility, the sensor can be comfortably attached on human body. Furthermore, the tactile sensor can recognize various types of human body movements by the corresponding electrical signals. Therefore, the as-prepared TENGs are potential on the prospects of gesture detection, health assessment, human-machine interfaces and so on.

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.

Hydrophone, serving as a part of sonar, has a significant effect on the performance of acoustic sensors such as frequency characteristics and sensitivity, however, some limitation such as high cost and complexity in SOI manufacturing technique hinder the industrial application of hydrophones. Therefore, a novel Micro-Electro-Mechanical Systems (MEMS) piezoelectric vector hydrophone based on PZT (lead zirconate titanate) film has been adopted in obtaining vector information of underwater sound field. The piezoelectric hydrophone sensor was analyzed, designed and fabricated with PZT-on-Si substrate, and the structure consists of a four-cantilevers and an acoustics columnar cilium fixed on the center micro mass. According to the simulation results, the piezoelectric films are optimally distributed at the tip of the four beams, where the maximum strain locates. Finally, the piezoelectric vector hydrophone was characterized by comparative calibration experiments in a standing wave bucket. This passive MEMS piezoelectric hydrophone has the characteristics of receiving sensitivity with −189.3 dB at 920 Hz (0dB = 1 V/μPa) and a typical directional pattern of "8" shape, low noise output and high dynamic test range, which is suitable for high precision passive underwater detection.