The influence of polypropylene fibers has been studied in different proportioning and fiber length to improve the performance characteristics of the lightweight cement composites. Fibers used in two different lengths (6mm and 12mm) and fiber proportions (0.15% and 0.35%) by cement weight in the mixture design. Hardened concrete properties such as: 7-and 28-day compressive strength, splitting tensile strength, flexural strength, water absorption, and shrinkage were evaluated. Fiber addition was seen to enhance the physical and mechanical properties of lightweight concrete. Compared to unreinforced LWC, polypropylene (PP) reinforced LWC with fiber proportioning 0.35% and 12 mm fiber length, caused 30.1% increase in the flexural strength and 27% increase in the splitting tensile strength. Increased fiber availability in the LWC matrix, in addition to the ability of longer PP fibers to bridge on the micro cracks, are suggested as the reasons for the enhancement in mechanical properties.

Cellulose, a natural, renewable, and environment friendly biopolymer, has been considered as a sustainable feedstock in the near future. However, only 0.3% of cellulose is today processed since it is not soluble in conventional solvents due to the strong hydrogen bonding network and highly ordered structure. Hence, the search of effective and eco-friendly solvents for cellulose dissolution has been a key pillar for decades. In the recent years, ionic liquids (ILs) have been proposed as green solvents for cellulose and have been applied for the production of cellulose-based fibers. This review aims to focus the attention toward fiber spinning methods of cellulose based on ILs, as well as recent progress in cellulose dissolution using ILs. Moreover, the development of cellulosic fibers blended with other biopolymers, and cellulose composites are presented. Finally, different applications of cellulose fibers and composites are summarized and discussed.

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Using cell-based engineered skin is an emerging strategy for treating difficult-to-heal wounds. To date, much endeavor has been devoted to the fabrication of appropriate scaffolds with suitable biomechanical properties to support cell viability and growth in the microenvironment of a wound. The aim of this research was to assess the impact of adipose tissue-derived mesenchymal stem cells (AD-MSCs) and keratinocytes on gelatin/chitosan/β-glycerol phosphate (GCGP) nanoscaffold in full-thickness excisional skin wound healing of rats. For this purpose, AD-MSCs and keratinocytes were isolated from rats and GCGP nanoscaffolds were electrospun. Through an in vivo study, the percentage of wound closure was assessed on days 7, 14, and 21 after wound induction. Samples were taken from the wound sites in order to evaluate the density of collagen fibers and vessels at 7 and 14 days. Moreover, sampling was done on days 7 and 14 from wound sites to assess the density of collagen fibers and vessels. The wound closure rate was significantly increased in the keratinocytes-AD-MSCsscaffold (KMS) group compared with other groups. The expressions of vascular endothelial growth factor, collagen type 1, and CD34 were also significantly higher in the KMS group compared with the other groups. These results suggest that the combination of AD-MSCs and keratinocytes seeded onto GCGP nanoscaffold provides a promising treatment for wound healing. (M.G.M.) and ar-bahrami@um.ac.ir (A.R.B.)

Electrospun polyvinylidene fluoride (PVDF) nanofibers have been widely used in the fabrication of flexible piezoelectric sensors and nanogenerators, due to their excellent mechanical properties. However, their relatively low piezoelectricity is still a critical issue. Herein, a new and effective route to enhance the piezoelectricity of PVDF nanofiber mats by electrospraying zinc oxide (ZnO) nanoparticles between layers of PVDF nanofibers is demonstrated. As compared to the conventional way of dispersing ZnO nanoparticles into PVDF solution for electrospinning nanofiber mats, this approach results in multilayered PVDF+ZnO nanofiber mats with significantly increased piezoelectricity. For example, 6.2 times higher output is achieved when 100% of ZnO (relative to PVDF quantity) is electrosprayed between PVDF nanofibers. Moreover, this new method enables higher loading of ZnO without having processing challenges and the maximum peak voltage of ≈3 V is achieved, when ZnO content increases up to 150%. Additionally, it is shown that the samples with equal amount of material but consisting of different number of layers have no significant difference. This work demonstrates that the proposed multilayer design provides an alternative strategy to enhance the piezoelectricity of PVDF nanofibers, which can be readily scaled up for mass production.

Piezoelectrics are one of the most important materials used for harvesting energies. Several piezoelectric nanostructures have been used to construct nanogenerators (NGs). Nanofibers made by piezo-polymers, especially polyvinylidene fluoride (PVDF) because of their high flexibility, biocompatibility, and low cost, have shown wonderful growth as the key materials for NGs. Despite these favorable properties, fabricated nanofibrous devices still has low efficiency and many studies have been conducted to characterize and improve the performance of the PVDF nanofibers. Here we tried to fabricate PVDF NG device based on align nanofibers to improve the NGs output, using two different methods rotary collector and applying magnetic field. Characteristics of these structures are evaluated utilizing X-ray diffraction, Fourier transform infrared, differential scanning calorimetry, and scanning electron microscopy. Electrical response of fabricated samples is measured through utilization of an impedance analyzer at room temperature. Results demonstrate that crystalline structure increases in both methods but sample fabricated by rotary collector in magnetic field has more improvement in their outputs. This result shows that in addition to the crystalline structure, nanofibers alignment and arrangement play important roles in piezoelectric properties of sample, as well as NG efficiency. These results teach us to establish engineering design rules for wearable power harvesting devices.

Piezoelectric nanogenerator based on a composite structure formed of Polyvinylidene Fluoride (PVDF) as the matrix and Barium Titanate BaTiO3 nanospherical after dissolving them in a solvent of Dimethyl Sulfoxide DMSO/Acetone in (1/3 v/v) then spanning it’s homogeneous solution on Aluminum foil. structural and morphology analyses that of fabricated nanofibers characterized by X-ray diffraction, Scanning Electron Microscope and the electrical output of piezoelectric membrane devices was measured by using oscilloscope. The electrical output of different samples were measured for the pure powder PVDF and for composite PVDF& BaTiO3. The highest PVDF composite piezoelectrically generated voltage for samples with BaTiO3 (20%PVDF & 25% BT) wt. %. where improved to 6 V in general the addition of BT Nc increases the piezoelectric response of electrospun PVDFnanofibers.

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