ABSTRACT
Recently, the multi-level interwoven structured micro/nano fiber membranes with coarse and fine overlaps have attracted lots of attention due to their advantages of high surface roughness, high porosity, good mechanical strength, etc., but their simple and direct preparation methods still need to be developed. Herein, the multi-level structured micro/nano fiber membranes were prepared novelly and directly by a one-step electrospinning technique based on the principle of micro-phase separation caused by polymer incompatibility using polystyrene (PS) and polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) as raw materials. It was found that different spinning fluid parameters and various spinning process parameters will have a significant impact on its morphology and structures. Under certain conditions (the concentration of spinning solution is 18 wt%, the mass ratio of PS to PVDF-HFP is 1:7, the spinning voltage is 30 kV, and the spinning receiving distance is 18 cm), the PS/PVDF-HFP membrane with optimal multi-level structured micro/nano fiber membranes could be obtained, which present an average pore size of 4.38 ± 0.10 µm, a porosity of 78.9 ± 3.5%, and a water contact angle of 145.84 ± 1.70°. The formation mechanism of micro/nano fiber interwoven structures was proposed through conductivity and viscosity tests. In addition, it was initially used as a separation membrane material in membrane distillation, and its performance was preliminarily explored. This paper provides a theoretical and experimental basis for the research and development of an efficient and feasible method for the preparation of multi-level micro/nano fiber membranes.
ABSTRACT
SiO2-MgO hybrid fibers (SMHFs) were fabricated by one-step electrospinning process, characterized, and evaluated in heavy metal adsorption, for the first time. High-pressure steam (HPS) pretreated SMHFs showed high specific surface area (SBET) and large number of surface basic sites accompanied by the crystallization of MgO. The SMHFs showed high affinities for Pb(II) and Cu(II) with the distribution coefficients Kd>100â¯L·g-1 (when pHâ¯>â¯4). Langmuir model and pseudo-second-order kinetic model described the experimental data well, and the maximum adsorption capacities of 787.9 and 493.0â¯mg·g-1 for Pb(II) and Cu(II) at 298â¯K were the highest among those of reported SiO2-MgO adsorbents. Thermodynamics indicated SMHFs had the spontaneous and physicochemical adsorption nature. SMHFs kept good capacities in the presence of interfering substances and retained their reusability. The SMHFs with the superiority of high efficiency, low cost, easy preparation and environmentally benign, have promising applications in wastewater treatment and relative fields.
ABSTRACT
Flexible membranes with excellent waterproofness and breathability have been strongly desired in wound dressing applications with the aim of providing both protection and comfort. Despite the advances in protective clothing using waterproof breathable materials, the construction of waterproof breathable membranes suited for wound dressing still faces huge challenges to eliminate the toxic solvent residue-related harm to health and improve the waterproof, breathable, and stretchable performance. In the current work, we developed a facile and versatile approach based on one-step electrospinning and an ethanol solvent system for producing skinlike waterproof and breathable polydimethylsiloxane (PDMS) embedded polyvinyl butyral (PVB) fibrous membranes. Benefiting from the addition of hydrophobic agent PDMS, a reduced maximum pore size and enhanced surface hydrophobicity were achieved, contributing to a maximum hydrostatic pressure of 54.32 kPa, which was about 4.0 times that of the PVB fibrous membrane. In addition, the obtained PVB/PDMS fibrous membranes exhibited a remarkable water vapor transmission rate of 8.98 kg m-2 day-1, and enhanced mechanical strength of 4.95 MPa. The developed fibrous membranes provided human skinlike functions, including blocking liquid water penetration inside, permitting water vapor transmission outside, and allowing for sufficient stretching at joint positions. Taken together, this work could contribute to a better design of health-friendly, waterproof, breathable, and stretchable wound dressing materials.
ABSTRACT
Guiding newly generated tissues in a gradient pattern, thereby precisely mimicking inherent tissue morphology and subsequently arranging the intimate networks between adjacent tissues, is essential to raise the technical levels of tissue engineering and facilitate its transition into the clinic. In this study, a straightforward electrospinning method (the tubing-electrospinning technique) was developed to create fibrous matrices readily with diverse gradient patterns and to induce patterned cellular responses. Gradient fibrous matrices can be produced simply by installing a series of polymer-containing lengths of tubing into an electrospinning circuit and sequentially processing polymers without a time lag. The loading of polymer samples with different characteristics, including concentration, wettability, and mechanical properties, into the tubing system enabled unique features in fibrous matrices, such as longitudinal gradients in fiber density, surface properties, and mechanical stiffness. The resulting fibrous gradients were shown to arrange cellular migration and residence in a gradient manner, thereby offering efficient cues to mediate patterned tissue formation. The one-step process using tubing-electrospinning apparatus can be used without significant modifications regardless of the type of fibrous gradient. Hence, the tubing-electrospinning system can serve as a platform that can be readily used by a wide-range of users to induce patterned tissue formation in a gradient manner, which will ultimately improve the functionality of tissue engineering scaffolds.