No abstract

Wearable sensors have recently attracted extensive interest not only in the field of healthcare monitoring but also for convenient and intelligent human–machine interactions. However, challenges such as wearable comfort, multiple applicable conditions, and differentiation of mechanical stimuli are yet to be fully addressed. Herein, we developed a breathable and waterproof electronic skin (E-skin) that can perceive pressure/strain with nonoverlapping signals. The synergistic effect from magnetic attraction and nanoscaled aggregation renders the E-skin with microscaled pores for breathability and three-dimensional microcilia for superhydrophobicity. Upon applied pressure, the bending of conductive microcilia enables sufficient contacts for resistance decrease, while the stretching causes increased resistance due to the separation of conductive materials. The optimized E-skin exhibits a high gauge factor of 7.747 for small strain (0–80%) and a detection limit down to 0.04%. The three-dimensional microcilia also exhibit a sensitivity of −0.0198 kPa–1 (0–3 kPa) and a broad detection range up to 200 kPa with robustness. The E-skin can reliably and precisely distinguish kinds of the human joint motions, covering a broad spectrum including bending, stretching, and pressure. With the nonoverlapping readouts, ternary inputs “1”, “0”, and “–1” could be produced with different stimuli, which expands the command capacity for logic outputs such as effective Morse code and intuitive robotic control. Owing to the rapid response, long-term stability (10 000 cycles), breathability, and superhydrophobicity, we believe that the E-skin can be widely applied as wearable devices from body motion monitoring to human–machine interactions toward a more convenient and intelligent future.

No abstract

Fine tuning the structure of bimetallic nanoparticles is critical toward understanding structure−activity relationships and further improving the catalytic performance in propane dehydrogenation (PDH). Excessive Fe species in the PtFe bimetallic catalysts promote carbon deposition leading to low propylene selectivity, and it remains challenging to synthesize welldefined PtFe catalysts while selectively eliminating the excessive Fe. Herein, we show that the formation of coke can be significantly inhibited by introducing CO 2 into the PDH over PtFe catalysts, where CO 2 effectively eliminates the active Fe(0) coking sites without changing the catalytic surface structure of the PtFe alloy. With a CO 2 /C 3 H 8 feeding ratio of 0.20, the Pt1Fe7/S-1 catalyst shows the highest propylene production rate and decreased amount of coke from 18.8 to 1.0 wt % compared with dehydrogenation without CO 2 . X-ray absorption spectroscopy, X-ray photoelectron spectroscopy, and 57 Fe Mossbauer results indicate that it is the oxidation of excessive unalloyed Fe species during the CO 2 -PDH reaction, instead of the reverse Boudouard reaction (CO 2 + C = 2CO), that significantly inhibits the carbon deposition. This work provides a promising strategy for tuning the structure of PtFe bimetallic catalysts under reaction conditions and improving the performance of the PDH reaction.

Three‐dimensional scaffolds like hydrogels can be employed as cell carriers for in vitro or in vivo colonization and have become a major research topic to replace damaged tissue. In the current study, a novel composite hydrogel composed of sodium alginate (SA) and platelet‐rich‐plasma (PRP) varying in blending ratios, cross‐linked with calcium ions, released from calcium carbonate‐D‐Glucono‐d‐lactone (CaCO3‐GDL) was successfully prepared. It was found that addition of PRP changed largely the physical properties and biological performance of the composite hydrogels, which was depending on the blending ratio. The gelation rate and swelling ratio of alginate hydrogels were significantly reduced by the addition of PRP, which produced also a more homogeneous gel structure. Field emission scanning electron microscopy (FE‐SEM) investigation confirmed the incorporation of PRP‐derived proteins in the hydrogel, where a porous structure with a pore size of 200–300 μm was found. On the other hand, an increase in surface roughness was observed after the addition of PRP. The compressive mechanical strength of SA/PRP composite hydrogel was enhanced in comparison to the pure SA gel. The composite hydrogels with the highest PRP content exhibited at a maximum compressive stress of 0.26 MPa a maximum strain of 55%, while the maximum compressive strain of pure SA hydrogels was only 45% at a stress of 0.08 MPa. It was also found that the in vitro degradation of the alginate gel was accelerated by the addition of PRP. In terms of cellular responses, all gels exhibited an excellent cytocompatibility. Indeed, the composite hydrogels supported bone marrow‐derived mesenchymal stem cells proliferation and their chondrogenesis with up‐regulation of chondrogenic marker genes Sox9 and Aggrecan. Overall, the present study suggests a great potential of SA/PRP composite hydrogels as cell carriers for cartilage tissue engineering.