基于电纺直写的图案化微纳结构喷印技术

研究了利用电纺直写技术进行图案化微纳结构可控喷印沉积的方法,该方法利用喷头与收集板之间的稳定直线射流来实现有序纳米纤维的直写制造。分析了电纺直写射流在静止收集板和移动收集板上的沉积行为;探究了工艺参数对电纺直写微纳结构定位误差的影响规律。实验显示:在内部应力和电荷排斥力的作用下,射流会产生弯曲螺旋从而引导纳米纤维在静止收集板上逐层叠加形成三维微结构;提高收集板运动速度可克服射流螺旋鞭动,获得无螺旋结构的直线纳米纤维。根据设计图形分别电纺直写了方波、多圈矩形纳米纤维图案,分析了直写图案尺寸与设计图案尺寸间的误差。结果显示:电纺直写纤维图案定位误差随着收集板运动速度、喷头至收集板距离、施加电压、收集板运动距离的升高而增加;优化实验条件和试验参数,电纺直写微纳结构定位误差可优于10μm。实验验证了微纳结构图案的精确喷印沉积有助于提高电纺直写技术的控制水平。     

熔体电纺直写系统设计与实现

静电纺丝是通过静电拉伸聚合物溶液或熔体来制造微/纳米纤维的一种高效途径。熔融电纺纤维因其原生细胞外基质纳米尺度的性质和结构特征,已经被研究用作组织工程支架。为了改进现有的熔体电纺直写装置的不足以及缩短数控系统开发周期,基于近场电纺技术开发了一套熔体电纺直写系统。采用工业计算机和固高运动控制卡形式搭建了电纺直写系统硬件平台。在Windows 7上采用vs2010作为开发平台,编写了一套人机界面友好的控制软件。介绍了系统的控制方案和软件流程图。最后通过图案化的沉积实验验证了电纺直写系统的可行性,为系统的相关研究提供指导。     

溶剂挥发对静电纺丝纳米纤维支架直径与沉积的影响

为实现静电纺丝纳米纤维生物支架的可控制备,实验研究了不同溶剂挥发速度对聚己酸内酯(Polycaprolactone,PCL)纳米纤维直径和纤维沉积面积的影响。首先,使用挥发速度不同的溶剂分别配制相同浓度的PCL纺丝溶液,在外加电压为15kV,纤维接收距离为12cm的条件下进行静电纺丝;然后,利用钨灯丝扫描电镜测量所制备的纳米纤维直径和沉积面积,并使用最小二乘法拟合计算实验数据,推导出溶剂挥发速度与纤维直径和纤维沉积面积的比例关系。结果表明,随着溶剂挥发速度的增加,纳米纤维的平均直径从98nm(标准偏差为21.14nm)上升到205nm(标准偏差为38.83nm),溶剂挥发速度与纤维直径的比例关系为:d∝N0.25i;纤维的沉积面积从143cm2下降到35cm2,溶剂挥发速度与纤维沉积面积的比例关系为:S∝N-0.18i。实验结果和建立的比例关系式能够为纳米纤维生物支架的可控制备提供可靠的数据基础和理论指导。     

磁性电纺丝明胶纳米纤维支架的制备与表征

采用静电纺丝法,以Fe3O4纳米粒子为磁性填料、明胶为基体,制备出磁性电纺丝明胶纳米纤维支架,SEM观察发现所制备的电纺丝纤维支架具有连续、光滑、直径分布均匀的纤维形貌,XRD与FT—IR分析验证了磁性电纺丝明胶纳米纤维支架中Fe3O4的存在,VSM发现磁性电纺丝明胶纳米纤维支架具有超顺弱磁性,TEM证实了磁性电纺丝明胶纳米纤维支架中Fe3O4纳米粒子以团聚形式存在,提示我们应进一步研究Fe3O4纳米粒子表面修饰与改性,以提高其分散性。本研究制备的磁性电纺丝明胶纳米纤维支架为进一步应用于生物医学工程领域奠定了基础。     

静电纺丝制备有序纳米纤维的研究进展

静电纺丝法是目前制备纳米纤维最直接最有效的方法,有序排列的纳米纤维具有独特的光、电、磁等性质,但是静电纺丝法所制备的纳米纤维杂乱无章的无纺结构限制了静电纺丝在许多领域的应用.文章介绍了静电纺丝的基本原理,综述了目前制备有序纳米纤维的一些有代表性的方法,并分析了各自的优缺点.     

基于韦森堡效应的旋转多针头式静电纺丝

文中研究了用静电纺丝法批量制备纳米纤维的方法.基于韦森堡效应的原理,圆盘的旋转使溶液沿转轴爬升,从而为静电纺丝连续供液,由此设计了一种装置.纺丝头是由固定在圆盘上的针尖阵列组成的.圆盘的旋转使针尖蘸取爬升的溶液,在针尖和收集板间高电压的作用下制备出直径较小(200~800 nm)、比较均一的整齐的纤维.随着针数量和圆盘转速的增加,纤维的产率呈增加的趋势,产率可达3.3 g/h.纤维直径随着溶液浓度的增加而增加,但会随着圆盘转速以及电极至收集板之间的距离的增加而减小.     

鞘气聚焦电纺射流喷射的电学特性

开展了鞘气聚焦高效率纺丝射流喷射的研究。搭建了带有微弱电流检测模块的鞘气聚焦电纺喷射实验平台,讨论了鞘气约束作用下纺丝射流的流变与运动行为,结合理论模型分析了鞘气供气压强等工艺参数对纺丝电流的作用规律。实验显示:鞘气聚焦促进了射流的拉伸细化,降低了射流喷射临界启动电压,减小了纳米纤维的直径、提高了电纺纳米纤维的均匀性。当供气压强由0kPa上升到50kPa时,射流喷射平均临界启动电压由10.2kV降低至2.9kV;施加电压为4kV时,经4.4s产生峰值为532nA的冲击电流,稳定喷射阶段纺丝电流为300~500nA。鞘气聚焦还减小了射流直径和表面电荷密度,纺丝电流减小至没有鞘气聚焦时纺丝电流的1/7;纺丝电流随着鞘气压强、喷头至收集板距离的增加而降低,随着施加电压和溶液质量百分数的增加而增大。得到的结果表明:鞘气聚焦抑制了射流喷射过程的电荷干扰,减小了纺丝射流直径,提高了静电纺丝的稳定性。该方法为改善静电纺丝技术的控制水平提供了新的途径。     

方波脉冲电压下电喷印技术的实验研究

基于电流体动力学原理的电喷印技术是一种用于制造微纳尺度三维结构的喷印技术,可以在喷头不易堵塞的基础上实现亚微米和纳米级分辨率的高精度图案化,对电喷印施加脉冲电压可以实现按需喷印。通过实验得出方波脉冲电压对于喷印的影响规律,其中频率越大,沉积液滴直径越小;频率不变,电压幅值或入口压力增大都会使沉积液滴直径增大;而增大电压或气压值,可以提高液滴最大释放频率。最终获得了频率为300 Hz和平均直径为52.3μm的液滴,确立了较为理想的喷印工艺条件。     

微机电可调硅基三族氮化物光栅

将静电梳齿微驱动器与三族氮化物光栅集成,获得了利用静电梳齿微驱动器调节光栅周期的硅基三族氮化物光栅。首先,以硅基三族氮化物基片为基础,设计了微机电可调光栅,光栅的设计周期为1.1μm,设计线宽为0.8μm。然后,利用严格耦合波分析法研究了横向磁场模式下可调光栅的光学响应特性;研究显示改变光栅周期和占空比,光栅的谐振波峰出现了明显偏移。最后,介绍了结合电子束光刻、三族氮化物干法刻蚀和深硅刻蚀技术制备微机电可调三族氮化物光栅的方法。严格耦合波分析和实验表明:制备的微机电可调三族氮化物光栅具有良好的质量;在静电驱动器上施加电压,可将光栅的谐振波峰由1.345μm调节至1.40μm,满足了利用微机电技术调节三族氮化物光栅光学响应特性的要求。     

电纺氧化锌纳米纤维乙醇、丙酮气敏传感器

研究了用静电纺丝技术制造微纳气体传感器的方法。采用PVP（Polyvinyl Pyrrolidone）/Zn（Ac）₂和PEO（Polyoxyethylene ）/Zn（Ac）₂两种混合溶液作为原料,通过电纺喷射获得了复合前驱体纳米纤维;在空气中加热至500℃去除聚合物,并使Zn（Ac）₂受热分解、氧化获得ZnO纳米纤维;利用X射线衍射术（XRD）对ZnO纳米纤维进行成分表征;最后实验检测了ZnO纳米纤维气敏传感器对乙醇和丙酮气体的传感特性。结果显示：以PVP/Zn（Ac）₂、PEO/Zn（Ac）₂复合纳米纤维为前驱体制得的ZnO纳米纤维平均直径分别为308 nm、184 nm;这种纳米纤维经加热氧化可获得高纯度ZnO纳米纤维;在室温条件ZnO纳米纤维气敏传感器对目标气体传感响应时间小于1 s,其传感灵敏值随着气体浓度的增大而升高。另外,以PEO/Zn（Ac）₂为前驱体制得的ZnO纳米纤维表面粗糙、比表面积大,具有较高的传感灵敏值,对于乙醇、丙酮两种目标气体的最高灵敏值分别为215.69和118.13。得到的结果表明：静电纺丝技术的引入为半导体微纳气敏传感器的集成制造提供了有效的方法。     

Fabrication of patterned single-walled carbon nanotube films using electrophoretic deposition

Thin films of chemically functionalized single-walled carbon nanotubes (SWNTs) were fabricated by using a direct current (dc) electrophoretic deposition method. SWNTs were shortened and then functionalized with acid chloride group to combine with the amine group-terminated gold substrate. Silica nanospheres with a diameter of about 190nm were arrayed on gold substrate to pattern a thin SWNT film. Periodically patterned SWNT film was eventually produced and would be used in potential applications like electron emitters and large surface area electrodes.     

Nanofabrication of arbitrary patterns by nano plastic forming and etching (NPFE)

In this paper, flexibility of nano plastic forming and etching, an ultra-high resolution nanofabrication process developed recently by the authors, in terms of fabrication of arbitrary patterns as well as applicability to various work materials is demonstrated. First, a thin layer of nickel (Ni) is deposited on a silicon (Si) substrate. Then, it is directly patterned by nano plastic forming. Next, the patterned Ni mask is slightly etched by direct current sputter etching to transfer the pattern into the entire mask thickness and expose the surface of the substrate in the individual patterned areas. Afterward, the pattern is transferred onto the substrate by reactive ion etching. Finally, the remained Ni layer is removed from the substrate, and nanostructures fabricated on the surface of the substrate are revealed. Fabrication of grid patterns with various pitch settings on the surface of Si substrates is demonstrated. The experimental results indicate that the depth and width of the nanostructures can be controlled by the etching time. Also, it is confirmed from the results that the depth and width are not influenced by the pitch setting.     

球笼式等速万向节结构轻量化设计

为了实现球笼式等速万向节的结构轻量化设计,以球笼式等速万向节最大接触应力、接触总变形和塑性变形为依据,分别对钢球数量为6和8的两种结构的球笼式等速万向节进行了初步研究.对球笼式等速万向节的主要结构尺寸即钢球中心圆直径与钢球直径之比、万向节外径与内套花键分度圆直径之比,以及球笼式等速万向节的偏心距与钢珠中心圆半径之比进行了优化选择和比较.研究结果初步表明,对于球笼式等速万向节,当钢球数量由6增加为8时,由于钢球直径的减小,不但其外形尺寸可以减小12%、质量可以减少近20%,而且万向节的承载能力反而可以得到少许提高.因此,增加球笼式等速万向节的钢球数量是实现其结构轻量化设计的一种有效方法.     

Lift-off patterning of thin Au films on Si surfaces with atomic force microscopy

We studied a new lift-off process of thin Au film on silicon surfaces in nanometer-scale, combining anodic oxidation patterning with AFM, deposition of Au thin film on the patterned substrate and chemical etching processes of the Si oxide underneath the Au film. For Au films of thickness of 2-5 nm, the Au films on the Si oxide patterns were left unbroken and bent down to stick to Si surface after the removal of the oxide by the chemical etching. For an Au film of 1 nm in thickness, it was possible to lift-off the Au film on oxide patterns of the lines and dots in nanometer-scale using Si oxide as a sacrificial mask.     

使用目标多特征识别的纳米纤维制造在线监测系统

针对电纺丝成型纳米级纤维工艺中因供料速度与电压值不匹配而出现的不稳定现象-流涎,提出了基于目标多特征识别的纳米纤维制造在线检测系统来提高纳米纤维成型质量的稳定性并实现纤维直径的可控性.首先,使用工业CCD对喷头出口处的泰勒锥进行连续图像采集,并对其进行锐化、滤波、阈值分割等预处理;然后,用目标多特征识别算法对泰勒锥的周长、面积和锥高等特征进行识别,实现对泰勒锥的形态和大小实时判别;最后,以判别结果作为控制系统的反馈信号,实时在线调节供料模块或电源模块驱动供料速度与电压达到匹配.实验结果表明,当电压为8 kV,系统能在0.43 s后达到稳定,从而维持泰勒锥形状稳定,无流涎现象,得到直径均匀的纳米纤维.提出的方法有效地解决了电纺纳米纤维直径不均匀和不可控制的难题.     

An investigation of the effect of laser deposition parameters on characteristics of multilayered 316 L deposits

A potential problem in applying the direct laser deposition (DLD) technique to material fabrication is the effect that subsequent deposited layers have on reheating previous laser deposition layers. Most of the previous investigations examined the effect of the laser deposition parameters on the microstructure and mechanical properties of a single layer. This work focused on the effect of the laser parameters of subsequent layers on the microstructure and mechanical properties of the deposited layers to select proper parameters and characterize the effect. The microstructure morphology and property values are affected by the varied parameters. This leads to some tempering and aging effects in the steels. The microstructure of the top layer was equiaxed, while the near substrate region was fine dendritic. Typically, both of the travel speed and power of the laser show the significant effects on microstructure and hardness.     

Stencil mask methodology for the parallelized production of microscale mechanical test samples

A new methodology to parallelize the production of micromechanical test samples from bulk materials is reported. This methodology has been developed to produce samples with typical gage dimensions on the order of 20-200 μm, and also to minimize the reliance on conventional focused ion beam fabrication methods. The fabrication technique uses standard microelectronic process methods such as photolithography and deep-reactive ion etching to create high aspect ratio patterned templates-stencil masks-from a silicon wafer. In the present work, the stencil mask pattern consists of a linear row of tensile samples, where one grip of each sample is integrally attached to the bulk substrate. Once fabricated, the stencil mask is placed on top of a pre-thinned substrate, and the pattern and substrate are co-sputtered using a broad ion beam milling system, which ultimately results in the transfer of the mask pattern into the substrate. The methodology is demonstrated using a Si stencil mask and a polycrystalline Ni foil to manufacture an array of metallic micro-tensile samples.