ABSTRACT
Microfluidic deprotonation approach is proposed to realize continuous, scalable, efficient, and uniform production of aramid nanofibers (ANFs) by virtue of large specific surface area, high mixing efficiency, strong heat transfer capacity, narrow residence time distribution, mild laminar-flow process, and amplification-free effect of the microchannel reactor. By means of monitoring capabilities endowed by the high transparency of the microchannel, the kinetic exfoliation process of original aramid particles is in situ observed and the corresponding exfoliation mechanism is established quantificationally. The deprotonated time can be reduced from the traditional several days to 7 min for the final colloidal dispersion due to the synergistic effect between enhanced local shearing/mixing and the rotational motion of aramid particles in microchannel revealed by numerical simulations. Furthermore, the cascade microfluidic processing approach is used to make various ANF colloidal aerogels including aerogel fibers, aerogel films, and 3D-printed aerogel articles. Comprehensive characterizations show that these cascade-microfluidic-processed colloidal aerogels have identical features as those prepared in batch-style mode, revealing the versatile use value of these ANFs. This work achieves significant progress toward continuous and efficient production of ANFs, bringing about appreciable prospects for the practical application of ANF-based materials and providing inspiration for exfoliating any other nano-building blocks.
ABSTRACT
Aerogels, as famous lightweight and porous nanomaterials, have attracted considerable attention in various emerging fields in recent decades, however, both low density and weak mechanical performance make their configuration-editing capability challenging. Inspired by folk arts, herein we establish a highly efficient twice-coagulated (TC) strategy to fabricate configuration-editable tough aerogels enabled by transformable gel precursors. As a proof of concept, aramid nanofibers (ANFs) and polyvinyl alcohol (PVA) are selected as the main components of aerogel, among which PVA forms a flexible configuration-editing gel network in the first coagulation process, and ANF forms a configuration-locking gel network in the second coagulation process. TC strategy guarantees the resulting aerogels with both high toughness and feasible configuration editing capability individually or simultaneously. Altogether, the resulting tough aerogels with special configuration through soft to hard modulation provide great opportunities to break through the performance limits of the aerogels and expand application areas of aerogels.
ABSTRACT
Hemostatic materials have played a significant role in mitigating traumatic injury by controlling bleeding, however, the fabrication of the desirable material's structure to enhance the accumulation of blood cells and platelets for highly efficient hemostasis is still a great challenge. In this work, directed assembly of poly(vinyl alcohol) (PVA) macromolecules covering the rigid Kevlar nanofiber (KNF) network during 3D printing process is utilized to fabricate hydrophilic, biocompatible, and mechanically stable KNF-PVA aerogel filaments for effective enriching blood components by fast water absorption. As such, KNF-PVA aerogel gauzes demonstrate remarkable water permeability (338 mL cm-2 s-1 bar-1 ), water absorption speed (as high as 9.64 g g-1 min-1 ) and capacity (more than ten times of self-weight), and ability to enrich micron-sized particles when contacting aqueous solution. All these properties favor efficient hemostasis and the resulting KNF-PVA aerogel gauzes significantly outperform the commercial product Quikclot Gauze (Z-Medica) during in vivo experiments with the rat liver laceration model, reducing the hemostasis time by half (60 ± 4 s) and the blood loss by two thirds (0.07 ± 0.01 g). These results demonstrate a robust strategy to design various aerogel gauzes for hemostasis applications.
Subject(s)
Hemostasis , Hemostatics , Rats , Animals , Hemostatics/pharmacology , Polyvinyl Alcohol/chemistry , Hemorrhage , Water , Printing, Three-DimensionalABSTRACT
The formation of hot spots is an effective approach to improve the performance of surface-enhanced Raman scattering (SERS). Silk nanoribbons (SNRs), with a height of about 1-2 nm, and Au nanoparticles (AuNPs) were assembled by electrostatic interactions to introduce sandwich hot spot structures. These sandwich structures were optimized by tuning the ratio of SNRs and AuNPs, resulting in strong SERS signals with a sensitivity of 10-13 M and enhancement factor (EF) of 5.8 × 106. Improved SERS spectrum uniformity with relative standard deviation (RSD) about 11.2% was also achieved due to the homogeneous distribution of these hot spot structures. The inherent biocompatibility of SNRs and facile fabrication processes utilized endowed the SERS substrates significant benefits toward biomedical applications, confirmed by cytocompatibility and improved SERS bioimaging capacity in vitro. The results of this study suggest the feasibility of forming high performance bioimaging systems through the use of naturally derived materials with special nanostructures.
