Strong and tough chitin hydrogel constructed by dehydration and rehydration strategy

As a renewable,biocompatible,biodegradable soft material,chitin hydrogels have better advantages in stability,antibacterial activity,antifouling,cost,immunogenicity,and so on than most polymer hydrogels.However,compared with other widely used polymer hydrogels with high strength and toughness,the practical applications of chitin-based hydrogels have been limited by their weak mechanical properties,such as cartilage repair and meniscus replacement.Here,we present the design and fabrication of chitin hydrogels with excellent mechanical strength and toughness by a dehydration and rehydration strategy.By sequential dehydration and rehydration processes,the crystalline domains in the chitin hydrogels can be properly controlled.With optimized crystallinity,the elastic modulus of the chitin hydrogels exceeds all previously reported values,and the fracture toughness is even comparable to some synthetic polymer hydrogels,while maintaining a high-water-content of about 80 wt.%.At the same water content,the mechanical properties of the chitin hydrogels are positively correlated with the hydrogel crystallinity,which proves that the change of mechanical properties of hydrogels is not simply dependent on weight concentration.The hydrogels can be further strengthened by incorporating other biopolymers that are intrinsically weak,which makes the hydrogels promising for applications in fields such as cartilage repair and meniscus replacement.Moreover,the hydrogels enable loading and release of water-soluble and poorly water-soluble drugs.This highly extendable strengthening and toughening strategy of chitin and chitin-based biopolymer hydrogels paves the way for their widely applications.

Strong and Tough TPU Fibers with Orientedly Aligned CNTs Reinforced by Amorphous ZrO_(2)

High strength and high toughness are vital for fibers’engineering applications,but are hard to simultaneously achieve.Herein,we synthesize a carbon nanotube(CNT)-thermoplastic polyurethanes(TPU)fiber reinforced by an amorphous ZrO_(2)layer through the wet-spinning method.The amorphous ZrO_(2)layer is in-situ grown on the surface of CNT and the hybrid nanowires are orientedly aligned with TPU to form the ternary fiber.The fiber possesses an excellent combination of high strength(84.6 MPa)and toughness(126.7 MJ/m^(3)),which is outstanding when compared with previously reported CNT-TPU fibers.The pull-out of nanowires attributed to the oriented alignment structure and the enhanced interface and restriction of deformation obtained from the amorphous ZrO_(2)layer are considered as the primary strengthening and toughening mechanisms.We anticipate that our fiber synthesis strategy gives a new path to design strong and tough fibers.

Recent developments in artificial spider silk and functional gel fibers

It is highly desirable to develop fiber materials with high strength and toughness while increasing fiber strength always results in a decrease in toughness.Spider silk is a natural fiber material with an excellent combination of high strength and toughness,which is produced from the spinning dope solution by gelation and drawing spinning process.This encourages people to prepare artificial fibers by mimicking the material,structure,and spinning of natural spider silk.In this review,we first summarized the preparation of artificial spider silk prepared via such a gelation process from different types of materials,including nonrecombinant proteins,recombinant proteins,polypeptides,synthetic polymers,and polymer nanocomposites.In addition,different spinning approaches for spinning artificial spider silk are also summarized.In the third section,some novel application scenarios of the artificial spider silk were summarized,such as artificial muscles,sensing,and smart fibers.

通过给桑蚕喂食稀土离子改性的饲料制备高强高韧的蚕丝纤维

蚕丝纤维具有优异的生物相容性和良好的力学性能,但以简单且大规模的方式生产强韧的蚕丝纤维仍是一项重大挑战.本文报道了一种通过给桑蚕喂食稀土离子改性桑叶饲料以制备强韧蚕丝纤维的方法.所得蚕丝纤维具有显著提高的拉伸强度和韧性,其平均值分别为0.85±0.07 GPa和156±13 MJ m^(-3),且最大值达到0.97±0.04 GPa和188±19 MJ m^(-3),这些性能接近蜘蛛牵引丝(自然界最强的丝纤维之一)的拉伸强度和韧性.研究结果表明,稀土离子(La^(3+)或En^(3+))成功掺入蚕丝纤维并与其形成相互作用.稀土离子减小了蚕丝纤维的直径,降低了其内部结晶组分的含量并提升了取向度.这些相互作用与结构演变同时提升了蚕丝纤维的强度和韧性.该研究提出了一种简单、可扩展且有效的生产超强韧丝纤维的策略,制备的蚕丝纤维有望应用于个人防护和航空航天等需要轻质结构材料的领域.