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As the most commonly used additive manufacturing technology, fused deposition modeling (FDM) still faces some technical issues caused by temperature change-induced unsteady thermal stress and warpi...

In this work, a functionalized polycaprolactone (PCL) composite fiber combining calf-type I collagen (CO) and natural drug usnic acid (UA) was prepared, in which UA was used as an antibacterial agent. Through 3D near-field electrospinning, the mixed solution was prepared into PCL/CO/UA composite fibers (PCUCF), which has a well-defined perfect arrangement structure. The influence of electrospinning process parameters on fiber diameter was investigated, the optimal electrospinning parameters were determined, and the electric field simulation was conducted to verify the optimal parameters. The addition of 20% collagen made the composite fiber have good hydrophilicity and water absorption property. In the presence of PCUCF, 1% UA content significantly inhibited the growth rate of Gram-positive and negative bacteria in the plate culture. The AC-PCUCF (after crosslinking PCUCF) prepared by crosslinking collagen with genipin showed stronger mechanical properties, water absorption property, thermal stability, and drug release performance. Cell proliferation experiments showed that PCUCF and AC-PCUCF had no cytotoxicity and could promote cell proliferation and adhesion. The results show that PCL/CO/UA composite fiber has potential application prospects in biomedical dressing.

A novel nanocellulose - microcrystalline cellulose complex (NCMC) with special hierarchical structure has been prepared by grafting nanocellulose (NC) onto the surface of microcrystalline cellulose (MCC) via different silane coupling agents in this paper. The cellulose complex was easier to separate and purify from the solution in the preparation process than nanocellulose due to its large size, and was used to reinforce polylactic acid (PLA) as 3D printing materials through a melt-blending process. The results showed that NCMCs prepared by different silane coupling agents had different surface morphologies. Nanocelluloses formed a network structure on the surface of KH-550 treated NCMC, while a spherical structure wrapped by nanocellulose was formed on the surface of KH-560 treated NCMC, and KH-570 treated NCMC was the nanocellulose network with a small amount of irregular silica impurities. The mechanical properties, crystallinity of polymer and thermal stability of NCMC/PLA composites are obviously improved by adding a small amount of NCMC. Compared to pure PLA, the tensile strength, bending strength and elongation at break of the NCMC/PLA composites were increased by 40.3%, 84.1% and 34.3%, respectively. It is because NCMC had higher specific surface area and more complex surface structure than MCC, that led to more thorough grafting reaction on polylactic acid during high temperature extrusion blending process. The DSC results also showed that a small amount of NCMC could promote the crystallization of PLA as 3D printing materials. Besides, NCMC/PLA composites did not block the printing nozzle in continuous 3D printing, and the printed products had better appearances. The obtained materials are environmentally friendly, renewable and ideal for 3D printing.

To promote natural waste resource utilization, a novel biocomposite, composed of waste crab shells and poly (lactic acid) matrix, was developed by combining chemical treatment and 3D printing. A crab shell powder (ISCSP) with an abundant porous structure and a high specific surface area was obtained by treatment with hydrochloric acid and sodium hydroxide. Importantly, under the optimal printing parameters determined by the finite element analysis, test samples, and porous bones were successfully printed using CSP/PLA composites by a commercial fused deposition modeling (FDM) 3D printer. The morphology, mechanical and thermal properties, antibacterial properties, and biocompatibility of the CSP/PLA composites were then assessed. Our results revealed that the tensile strength and flexural strength of the ISCSP/PLA composites reached 58.71 and 90.11 MPa, which were 28.6 % and 28.8 % higher than that of pure PLA, respectively. The glass transition and melting temperatures of the composites remained similar to those of pure PLA. Interestingly, the addition of CSP increased PLA crystallinity, which could be attributed to the nucleation effect of CSP in the system. The antibacterial activity of the PLA-1.5ESCSP composite samples against Escherichia coli (E. coli) was greater than 99 %. More importantly, the live/dead assay showed that the CSP/PLA composites possessed excellent biocompatibility. Therefore, the developed CSP/PLA biocomposites are potential feedstocks for 3D printing in bone tissue engineering and may be used as graft substitutes in reparative and reconstructive surgery. They are especially beneficial due to their superior mechanical and thermal properties, excellent antibacterial activities, and significant biocompatibility.

Public health safety issues have been plaguing the world since the pandemic outbreak of coronavirus disease (COVID-19). However, most personal protective equipments (PPE) do not have antibacterial and anti- toxicity effects. In this work, we designed and prepared a reusable, antibacterial and anti-toxicity Polyacrylonitrile (PAN) based nanofibrous membrane cooperated with Ag/g-C