Designing rational structure is one of strategies as effective as supplementing proper materials for separator performance enhancement. Focusing on the nanofibrous separators that generally have high porosity but poor mechanical strength, in this work, we develop an architecture of orientation gradient along the thickness direction for polyacrylonitrile (PAN) nanofibrous membrane (OGP), which is facilely fabricated by sequential electrospinning with different collector rotating speeds. The obtained OGP separators not only share the advantages of PAN nanofibrous separator, such as high porosity, superior wettability and thermal stability, but also have considerable improvements in tensile strength and puncture resistance to compensate for its mechanical weakness. Meanwhile, when compared to the most commonly used nanofibrous separator with randomly oriented nanofibers , the OGP separators present more desirable lithium ion transport ability, including a larger amount of ions transported as well as a faster ion transport rate, thereby endowing the cell with superior cycling stability with a capacity retention 97.2% after 100 cycles at 0.5 C. Therefore, taking safety and battery performance into account, the as-prepared OGP nanofibrous membrane could be a promising separator candidate for lithium ion batteries .
Xu Gang,Ding Zhaozhao,Lu Qiang,Zhang Xiaoyi,Zhou Xiaozhong,Xiao Liying,Lu Guozhong,Kaplan David L
Gradient biomaterials are considered as preferable matrices for tissue engineering due to better simulation of native tissues. The introduction of gradient cues usually needs special equipment and complex process but is only effective to limited biomaterials. Incorporation of multiple gradients in the hydrogels remains challenges. Here, beta-sheet rich silk nanofibers (BSNF) were used as building blocks to introduce multiple gradients into different hydrogel systems through the joint action of crosslinking and electric field. The blocks migrated to the anode along the electric field and gradually stagnated due to the solution-hydrogel transition of the systems, finally achieving gradient distribution of the blocks in the formed hydrogels. The gradient distribution of the blocks could be tuned easily through changing different factors such as solution viscosity, which resulted in highly tunable gradient of mechanical cues. The blocks were also aligned under the electric field, endowing orientation gradient simultaneously. Different cargos could be loaded on the blocks and form gradient cues through the same crosslinking-electric field strategy. The building blocks could be introduced to various hydrogels such as Gelatin and NIPAM, indicating the universality. Complex niches with multiple gradient cues could be achieved through the strategy. Silk-based hydrogels with suitable mechanical gradients were fabricated to control the osteogenesis and chondrogenesis. Chondrogenic-osteogenic gradient transition was obtained, which stimulated the ectopic osteochondral tissue regeneration in vivo. The versatility and highly controllability of the strategy as well as multifunction of the building blocks reveal the applicability in complex tissue engineering and various interfacial tissues.
危险品化学品经营许可证（带存储）