Fe_3O_4/SiO_2介孔组装纤维的制备及磁性能

以硝酸铁和正硅酸乙酯为原料,采用溶胶-凝胶法制备了Fe3O4/SiO2介孔组装纤维。当n（Fe）/n（Si）=0.13～0.23,n（H2O）/n（Si）=1.2～2.1时,溶胶体系的成纤性良好。利用TGA-DTA、IR光谱、XRD、SEM对介孔组装纤维进行了表征,结果表明介孔组装纤维表面光滑、致密,直径约为50μm,磁性颗粒约为50nm,镶嵌在无序凝胶网络的介孔中;SiO2主要以无定形态存在,铁以Fe3O4结构存在。利用VSM考察了纤维的磁性能,结果表明Fe3O4/SiO2介孔组装纤维比饱和磁化强度（σs）达11A.m2/kg,呈现良好的软磁特性。     

Three‐Dimensional Fabrication at Small Size Scales

Despite the fact that we live in a 3D world and macroscale engineering is 3D, conventional submillimeter‐scale engineering is inherently 2D. New fabrication and patterning strategies are needed to enable truly 3D‐engineered structures at small size scales. Here, strategies that have been developed over the past two decades that seek to enable such millimeter to nanoscale 3D fabrication and patterning are reviewed. A focus is the strategy of self‐assembly, specifically in a biologically inspired, more deterministic form, known as self‐folding. Self‐folding methods can leverage the strengths of lithography to enable the construction of precisely patterned 3D structures and “smart” components. This self‐assembly approach is compared with other 3D fabrication paradigms, and its advantages and disadvantages are discussed.

     

Construction of 3D Polymer Brushes by Dip‐Pen Nanodisplacement Lithography: Understanding the Molecular Displacement for Ultrafine and High‐Speed Patterning

Dip‐pen nanodisplacement lithography (DNL) is a versatile scanning probe‐based technique that can be employed for fabricating ultrafine 3D polymer brushes under ambient conditions. Many fundamental studies and applications require the large‐area fabrication of 3D structures. However, the fabrication throughput and uniformity are still far from satisfactory. In this work, the molecular displacement mechanism of DNL is elucidated by systematically investigating the synergistic effect of z extension and contact time. The in‐depth understanding of molecular displacement results in the successful achievement of ultrafine control of 3D structures and high‐speed patterning at the same time. Remarkably, one can prepare arbitrary 3D polymer brushes on a large area (1.3 mm × 1.3 mm), with <5% vertical and lateral size variations, and a patterning speed as much as 200‐fold faster than the current state‐of‐the‐art.     

三维石墨烯纳米球的制备及其在锂离子电池中的应用

采用直流电弧放电法制备出一种三维石墨烯纳米球材料。采用扫描电镜(SEM)、透射电镜(TEM)、拉曼光谱和X射线衍射光谱(XRD)等测试方法对三维石墨烯纳米球的形貌和结构进行了表征和研究。通过交流阻抗(EIS)、恒流充放电和循环稳定性测试等电化学测试手段来研究三维石墨烯纳米球作为锂离子电池负极材料的电化学性能。结果表明, 在电流密度为0.05 A/g下, 三维石墨烯纳米球作为锂离子电池负极材料的首次放电容量为485.9 mAh/g, 高于炭黑作负极的放电容量(401 mAh/g); 当电流密度为1 A/g时, 三维石墨烯纳米球负极材料仍然具有185.4 mAh/g的放电容量。在电流密度分别为0.5 A/g和2.5 A/g下, 充放电循环100次以后, 三维石墨烯纳米球的比容量几乎没有衰减, 这表明三维石墨烯纳米球作为锂离子电池的负极材料比炭黑具有更大的容量, 同时具有优异的循环稳定性。     

反铁磁层厚度对垂直磁各向异性钴/铂/铁锰多层膜磁性质的影响

在室温下用超高真空磁控溅射系统制备了一系列的Pt(4.0nm)/[Co(0.5nm)/Pt(0.3nm)]3-FeMn(tAFnm)多层膜样品,研究了反铁磁层厚度对于易轴垂直于样品表面的Co/Pt/FeMn多层膜磁性质的影响。在室温下利用样品的剩磁进行了X射线磁圆二色测量(XMCD),结果表明在铁磁/反铁磁界面有反铁磁层铁锰的净磁矩,这些净磁矩仅来自于铁元素。铁的磁矩倾向于垂直于膜面排列。磁测量结果表明,随着铁锰层厚度的增加,交换偏置场HEB增加直到饱和,而HC先增加,然后轻微减少,在tAF7.5nm以后,HEB和HC都几乎不变了。没有观察到磁锻炼效应。     

Interface‐Directed Self‐Assembly of Cell‐Laden Microgels

Cell‐laden hydrogels show great promise for creating engineered tissues. However, a major shortcoming with these systems has been the inability to fabricate structures with controlled micrometer‐scale features on a biologically relevant length scale. In this Full Paper, a rapid method is demonstrated for creating centimeter‐scale, cell‐laden hydrogels through the assembly of shape‐controlled microgels or a liquid–air interface. Cell‐laden microgels of specific shapes are randomly placed on the surface of a high‐density, hydrophobic solution, induced to aggregate and then crosslinked into macroscale tissue‐like structures. The resulting assemblies are cell‐laden hydrogel sheets consisting of tightly packed, ordered microgel units. In addition, a hierarchical approach creates complex multigel building blocks, which are then assembled into tissues with precise spatial control over the cell distribution. The results demonstrate that forces at an air–liquid interface can be used to self‐assemble spatially controllable, cocultured tissue‐like structures.     

汽车三维在线展示与虚拟试驾系统研究

目的针对在线汽车营销方式交互性、沉浸感差等问题,提升汽车网络化营销的交互体验性能。方法基于Unity3D平台,利用C#和My SQL数据库设计了汽车三维在线展示与虚拟试驾系统,采用显示层、应用层、数据层的三层体系结构,主要包含4个功能模块,分别为用户信息管理、汽车三维展示、虚拟试驾和试驾报告。依据SAEJ1100标准建立腿部空间测量模型,提出在虚拟试驾系统中腿部空间舒适性评价方法,并且基于实测数据构建虚拟试驾过程中的油耗预测模型。最终,建立较为真实的汽车试驾模型,同时确保试驾系统的流畅性和联机试驾的可操作性,实现系统的开发。实验验证系统的应用效果较好。结论汽车三维在线展示与虚拟试驾系统有效提高远程人机交互体验性能,为用户充分了解所选车型的特点和性能搭建了新型平台。     

Goosebumps‐Inspired Microgel Patterns with Switchable Adhesion and Friction

A substrate mimicking the surface topography and temperature sensitivity of skin goosebumps is fabricated. Close‐packed arrays of thermoresponsive microgel particles undergo topographical changes in response to temperature changes between 25 and 37 °C, resembling the goosebump structure that human skin develops in response to temperature changes or other circumstances. Specifically, positively charged poly[2‐(methacryloyloxy)ethyltrimethylammonium chloride] (PMETAC) brushes serve as an anchoring substrate for negatively charged poly(NIPAm‐co‐AA) microgels. The packing density and particle morphology can be tuned by brush layer thickness and pH of the microgel suspension. For brush layer thickness below 50 nm, particle monolayers are observed, with slightly flattened particle morphology at pH 3 and highly collapsed particles at pH above 7. Polymer brush films with thickness above 50 nm lead to the formation of particle multilayers. The temperature responsiveness of the monolayer assemblies allows reversible changes in the film morphology, which in turn affects underwater adhesion and friction at 25 and 37 °C. These results are promising for the design of new functional materials and may also serve as a model for biological structures and processes.