The creation of biomimetic cell environments with micro and nanoscale topographical features resembling native tissues is critical for tissue engineering. To address this challenge, this study focuses on an innovative...The creation of biomimetic cell environments with micro and nanoscale topographical features resembling native tissues is critical for tissue engineering. To address this challenge, this study focuses on an innovative electrospinning strategy that adopts a symmetrically divergent electric field to induce rapid self-assembly of aligned polycaprolactone(PCL) nanofibers into a centimeter-scale architecture between separately grounded bevels. The 3D microstructures of the nanofiber scaffolds were characterized through a series of sectioning in both vertical and horizontal directions. PCL/collagen(type I)nanofiber scaffolds with different density gradients were incorporated in sodium alginate hydrogels and subjected to elemental analysis. Human fibroblasts were seeded onto the scaffolds and cultured for 7 days. Our studies showed that the inclination angle of the collector had significant effects on nanofiber attributes, including the mean diameter, density gradient, and alignment gradient. The fiber density and alignment at the peripheral area of the 45°-collector decreased by 21% and 55%, respectively, along the z-axis,while those of the 60°-collector decreased by 71% and 60%, respectively. By altering the geometry of the conductive areas on the collecting bevels, polyhedral and cylindrical scaffolds composed of aligned fibers were directly fabricated. By using a four-bevel collector, the nanofibers formed a matrix of microgrids with a density of 11%. The gradient of nitrogen-to-carbon ratio in the scaffold-incorporated hydrogel was consistent with the nanofiber density gradient. The scaffolds provided biophysical stimuli to facilitate cell adhesion, proliferation, and morphogenesis in 3D.展开更多
本文采用倾斜30°感应器的表面感应加热淬火工艺处理了Φ40 mm GCr15钢滚珠丝杠。金相观察和显微硬度测量结果表明,滚珠丝杠齿底部位的硬化层硬度及硬化层深度可以满足Φ40 mm规格滚珠丝杠的技术要求。因此,Φ40 mm规格以下的GCr15...本文采用倾斜30°感应器的表面感应加热淬火工艺处理了Φ40 mm GCr15钢滚珠丝杠。金相观察和显微硬度测量结果表明,滚珠丝杠齿底部位的硬化层硬度及硬化层深度可以满足Φ40 mm规格滚珠丝杠的技术要求。因此,Φ40 mm规格以下的GCr15钢滚珠丝杠可以采用倾斜感应器的表面感应加热淬火新工艺。展开更多
The microstructure and mechanical properties of steel/Al structure material produced by additive manufacturing （AM） was investigated in this work based on the cold metal transfer welding. The results show that the m...The microstructure and mechanical properties of steel/Al structure material produced by additive manufacturing （AM） was investigated in this work based on the cold metal transfer welding. The results show that the microstructure gradually changed from the steel side to the aluminum side. The microstructure in the steel layer consisted of vermiform like ferrite and anstenite structure, while in the aluminum layer the microstructure was constituted by c^-A1 grains and typical reticulate distributive Al-Si eutectic structure. Besides, a 7 y.m thickness Ni-Al intermetallic compound layer was emerged at the interface of nickel and aluminum layer. The maximum room-temperature tensile strength of the Steel-Al structure materials was found to be 54 MPa, the rupture morphology showed a brittle fracture characteristic.展开更多
基金financially supported by the Foundation of the Whitacre College of Engineering and the Office of Vice President for Research at Texas Tech University
文摘The creation of biomimetic cell environments with micro and nanoscale topographical features resembling native tissues is critical for tissue engineering. To address this challenge, this study focuses on an innovative electrospinning strategy that adopts a symmetrically divergent electric field to induce rapid self-assembly of aligned polycaprolactone(PCL) nanofibers into a centimeter-scale architecture between separately grounded bevels. The 3D microstructures of the nanofiber scaffolds were characterized through a series of sectioning in both vertical and horizontal directions. PCL/collagen(type I)nanofiber scaffolds with different density gradients were incorporated in sodium alginate hydrogels and subjected to elemental analysis. Human fibroblasts were seeded onto the scaffolds and cultured for 7 days. Our studies showed that the inclination angle of the collector had significant effects on nanofiber attributes, including the mean diameter, density gradient, and alignment gradient. The fiber density and alignment at the peripheral area of the 45°-collector decreased by 21% and 55%, respectively, along the z-axis,while those of the 60°-collector decreased by 71% and 60%, respectively. By altering the geometry of the conductive areas on the collecting bevels, polyhedral and cylindrical scaffolds composed of aligned fibers were directly fabricated. By using a four-bevel collector, the nanofibers formed a matrix of microgrids with a density of 11%. The gradient of nitrogen-to-carbon ratio in the scaffold-incorporated hydrogel was consistent with the nanofiber density gradient. The scaffolds provided biophysical stimuli to facilitate cell adhesion, proliferation, and morphogenesis in 3D.
基金supported by the National Natural Science Foundation of China(Grant No.51475104,51435004)the National Basic Research Program of China(2013CB035500)
文摘The microstructure and mechanical properties of steel/Al structure material produced by additive manufacturing （AM） was investigated in this work based on the cold metal transfer welding. The results show that the microstructure gradually changed from the steel side to the aluminum side. The microstructure in the steel layer consisted of vermiform like ferrite and anstenite structure, while in the aluminum layer the microstructure was constituted by c^-A1 grains and typical reticulate distributive Al-Si eutectic structure. Besides, a 7 y.m thickness Ni-Al intermetallic compound layer was emerged at the interface of nickel and aluminum layer. The maximum room-temperature tensile strength of the Steel-Al structure materials was found to be 54 MPa, the rupture morphology showed a brittle fracture characteristic.
