Moravec's paradox shows that low-level sensorimotor skills are more difficult than high-level reasoning in artificial intelligence and robotics. So simplifying every sensing unit on electronic skin is critical for endowing intelligent robots with tactile and temperature sense. The human nervous system is characterized by efficient single-electrode signal transmission, ensuring the efficiency and reliability of information transmission under big data conditions. In this work, we report a sensor based on a single-electrode piezoelectric nanogenerator (SPENG) by electrospun polyvinylidene fluoride (PVDF) nanofibers that can realize steady-state sensing of pressure integrating cold/heat sensing on a single unit. Piezoelectric signals appear as square wave signals, and the thermal-sensing signals appear as pulse signals. Therefore, the two signals can be acquired by a single unit simultaneously. The SPENG overcomes the shortcoming of electronic skins based on a single-electrode triboelectric nanogenerator (STENG), which can sense only dynamic movement and cannot sense temperature variations. The new sensor configuration uses a capacitor instead of the STENG's ground wire as a potential reference, allowing it to be used for truly autonomous robots. At the same time, the traditional advantages of polymer piezoelectric materials, such as flexibility, transparency, and self-powered advantages, have also been preserved.

Colorful nanofibrous membranes have attracted much attention for their visual varieties and various functionalities. In this article, a colored solution electrospinning process was used to fabricate colorful hydrophobic poly(vinyl butyral) (PVB)/cationic dye nanofibrous membranes (NFMs) successfully. The color and morphology of these as-spun nanofibrous membranes have been analyzed by colorimetry, spectroscopy, and scanning electron microscopy (SEM). It is shown that the as-spun colorful PVB-based membranes exhibit excellent level-dyeing property and color stability. Furthermore, the doping of cationic dye and the increase of dye concentration can decrease the diameter of the as-spun colored fibers, which results in better level-dyeing property and higher water contact angle more than 140°. The stained PVB fibrous membranes with excellent level-dyeing property and hydrophobicity are promising in some applications such as textiles, wallpapers, and anticorrosive coating/painting.Electronic supplementary materialThe online version of this article (doi:10.1186/s11671-016-1763-4) contains supplementary material, which is available to authorized users.

Humidity indicators based on composite polyamide 66/cobalt chloride (PA66/CoCl2) nanofibrous membranes (NFMs) were successfully fabricated by electrospinning. A series of NFMs with various weight percentage of CoCl2 to PA66 were prepared, and their humidity sensitivity based on color changing and quartz crystal microbalance (QCM) were studied. Due to the color change property of cobalt chloride, the as-spun composite NFMs show obviously macroscopic color change from blue to pink as relative humidity (RH) increasing from 12.4 to 97.2%. Moreover, the QCM detection showed a linear dependence on the RH changing and exhibited short response/recovery time (less than 65.4 s/11 s), small hysteresis (less than 11%), good reproducibility, and stability. Owing to the above double sensitive mechanism on RH, the PA66/CoCl2 composite NFM may show great potential applications from meticulous to coarse.Electronic supplementary materialThe online version of this article (doi:10.1186/s11671-017-2139-0) contains supplementary material, which is available to authorized users.

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The filtration of flying char particles from coal pyrolysis vapors plays a very important role in enhancing yields and quality of pyrolysis oil. In this work, the performance of coal pyrolysis flying char particles in a granular bed filter (GBF) was studied in cold model experiments. A filtration model was developed using a macroscopic phenomenological method that describes the filtration of the GBF. The polynomial expression of the relative filter coefficient (F) and the nonlinear expression of the relative pressure drop ratio (G) were applied in the new model. The unsteady state of granular filtration was captured, demonstrating that the GBF performance could be predicted by the new model. Effects of superficial gas velocity, thickness of granular layer, and dust mass concentration on collection efficiency and pressure drop were analyzed. An excellent performance of the GBF was obtained and the total collection efficiency could reach a span between 98% and 99.9%. In the case of lower dust mass concentration, the total collection efficiency and pressure drop were slightly affected by the increasing dust mass concentration. The optimal operating conditions of the GBF were obtained: a superficial gas velocity of 0.2–0.6 m/s and a granular layer thickness of 0.07–0.11 m.

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