基于双波长像面数字全息显微的微通道检测

针对微流控芯片通道三维形貌的可视化测量需求,搭建了一套反射式离轴双波长像面数字全息显微测量系统。首先,利用分辨率靶和标准样片对系统的横向、纵向分辨率和放大倍数进行标定实验,结果表明双波长全息显微系统在横向宽度及纵向深度测量中具有较好的准确性和可行性。然后,利用该系统分别对由PDMS材料制成的直通道、圆形小室结构微流控芯片以及硅基底微流控芯片通道进行三维形貌检测,并得到定量结果：直通道结构深度为48.6μm,宽度为75.8μm;圆形小室微通道深度为48.5μm,宽度为76.6μm;硅基底微流控芯片测量得到通道深度为61.6μm。上述结果与白光干涉仪的测量结果具有良好的一致性,说明双波长全息显微系统具有较高的可靠性和准确性,可为微流控芯片微通道检测提供新的成像检测方法。     

制备复合液滴的微尺度流动方法

微尺度流动能够一步到位地制备不同结构和功能、尺寸在微米量级的复合液滴.文章回顾了几种常见的基于复合液滴的微尺度流动方法,包括同轴电雾化、复合流动聚焦、微流控芯片、玻璃微毛细管等,并对各种技术的原理和进展进行了简要概括和分析.在这类流动中,不同种类的流体在一定的几何结构通道或外力场作用下平稳地拉伸成微细射流并最终破碎成复合液滴.在同轴电雾化和复合流动聚焦技术中,从毛细管流出的流体能够形成稳定的锥-射流结构,当外力作用改变时能够形成不同的流动模式.在微流控芯片和玻璃微毛细管技术中,流体被约束在固定管道内,不同管道构型下能够形成不同的流动形态.这些方法都采用纯物理机理,过程稳定、易于操作,制备的复合液滴粒径可控,单分散性好,微观结构可设计,在科学研究和工程实际中具有重要的应用价值.      

硅胶固载硅烷偶联剂的核磁共振波谱研究

通过核磁共振波谱对硅胶固载γ-胺丙基三甲氧基硅烷和γ-氯丙基三甲氧基硅烷的原料和中间产物进行表征. 原料硅胶核磁共振谱上存在与表面羟基相关的峰，但不是很明显；采用交叉极化方法测定的原料硅胶和固载胺丙基硅烷产物的交叉极化硅核磁共振谱极大提高了与表面羟基相联的硅谱峰的强度，进一步说明了硅胶表面的硅羟基反应比较完全；固 载γ-氯丙基三甲氧基硅烷产物的交叉极化硅核磁共振谱表明，在硅胶表面上已固载了氯丙基硅烷.     

用于微流控液滴检测的共焦激光诱导荧光检测系统

以发射波长为473nm的二极管泵浦激光器为激发光源,搭建适于微流控液滴检测的共聚焦激光诱导荧光检测系统.系统玻璃芯片采用简易加工技术加工而成.并用2%十八烷基三氯硅烷将微通道处理为具有强疏水性质.荧光素钠溶液在T形通道交叉处被十四烷剪切形成液滴,液滴流经检测点时被激光诱导荧光系统检测.荧光素钠的检出限为1.1×10<'...     

PDMS微流控芯片中焦耳热效应的数值研究

用数值模拟的方法对矩形通道微流控芯片中由于焦耳热效应而产生的温度场分布进行了分析.通过求解耦合的动量以及能量方程,得到了PDMS/PDMS芯片中温度场的瞬态发展过程.对稳定状态下不同缓冲溶液浓度,底片材质以及厚度的芯片中的温度场分布也做了比较和分析.结果表明,相比于PDMS/PDMS芯片,相同条件下PDMS/玻璃芯片中的焦耳热效应会减小很多,而缓冲溶液浓度以及芯片厚度对缓冲溶液的出口平均温度也有显著影响.最后提出了减小焦耳热效应的方法.     

硅纳米颗粒在碳纳米管表面生长的分子动力学模拟

采用分子动力学模拟方法研究了硅纳米颗粒在碳纳米管上的生长，并分析了这种复合材料的基本结构.研究表明，由于硅原子和碳纳米管之间的相互作用以及碳纳米管的巨大的表面曲率，硅原子在碳纳米管表面不是形成覆盖碳纳米管的二维薄膜，而是生成具有三维结构的硅纳米颗粒.小纳米颗粒的结构和无基底条件下生成的颗粒结构基本一致.对于大纳米颗粒，不同于无基底条件下形成的球状纳米晶体硅结构，硅纳米颗粒沿管轴方向伸长，其结构为类似于硅晶体的无定形网络结构. 关键词： 纳米颗粒 碳纳米管 硅 分子动力学模拟     

声学微结构的微流控声场的改进与优化*

受限于加工工艺,目前多数的声表面波微流控芯片,主要依靠普通的直通道调节细胞流速,从而控制微球在通道中的排列。但其形成的声场通常无法满足低能量、多功能的微流控需要。本文在普通声表面波微流控芯片的基础上,分别在频域和时域内构建声学微结构,并改变微结构阵列中铜柱间距,模拟仿真了微流控芯片输出端的电势,发现其输出端电压得到了明显的改善。当输入电信号频率在0-30MHz时,输出端电势增加约0.25V;在0-1000ns内,输出端电势增加0.015V左右;进而可以探索开发性价比更高的声波微流控芯片,针对病理检测等所存在的问题进行分析优化,提出新的细胞分离等技术。     

微流控SERS芯片及其生物传感应用

由于微流控芯片具有优异的集成性和灵活的可操作性,基于芯片上的检测方法被大量开发,发展十分迅速。其中,表面增强拉曼光谱（SERS）凭借其超高的灵敏度、独一无二的指纹谱和窄峰宽等特点成为一种广泛采用的检测手段。SERS微流控芯片集SERS检测技术与微流控芯片的优势于一体,一方面为SERS检测方法的重复性和可靠性提供了一个高效平台,另一方面推动了微流控芯片的功能拓展,在生物分子探测、细胞捕获乃至组织模拟等领域具有广阔的应用前景。本文在简要介绍SERS的原理及其生物传感应用的基础上,重点概述了SERS微流控芯片的构建及其在生物传感及检测中的应用,最后探讨了该研究方向存在的问题及发展方向。     

微流控芯片系统中测温及控温装置的研制

报道了一种结构简单、成本低、操作方便、应用于微流控芯片系统中温度测量及温度控制的装置。该系统以CCD摄像机、荧光显微镜及图像采集卡构成的非接触荧光指示剂测温装置,实现了微流体空间温度分布测量以及随时间变化的温度测量。提出了以透明氧化铟锡薄膜玻璃作为加热元件,采用PID控制算法的温度控制平台,稳态时温度控制精度可达到±0.1 ℃。采用该测温和控温装置研究了玻璃微流控芯片微通道内溶液温度在空间上和随时间的变化情况,结果表明该方法简单、有效,可达到μm级的空间分辨率和ms级的时间分辨率。     

高压作用下相分离液体玻璃转变的分子动力学研究

采用分子动力学模拟方法,研究了二元混合液体在不同外压作用下的相分离与玻璃转变过程,计算了相分离液体在玻璃转变过程中的结构和动力学特征.研究发现,外压会促进相分离的产生,并提高玻璃转变温度,会使β弛豫出现的温度更高、存在的时间更长,导致系统扩散性降低.同时还发现,相分离液体的玻璃转变过程存在微观不均匀现象. 关键词： 相分离 玻璃转变 分子动力学模拟 外压影响     

含羟基结构熔石英光电性质的第一性原理研究

熔石英是高功率激光装置中广泛使用的激光透镜材料,采用第一性原理结合平面波赝势方法,研究了熔石英材料中羟基结构的生成模式,系统计算了材料的电子态密度、差分电荷密度、原子电荷布居分布,分析了包含羟基熔石英材料的光学跃迁模式,研究结果表明:熔石英中的三配位硅原子缺陷在禁带中生成了两条缺陷能级,分别位于7.8和8.8 eV;研究还发现氢原子与五配位硅原子发生相互作用生成羟基结构,该反应还使三配位硅原子的杂化方式由sp~2变为sp~3,这种羟基结构会影响体系的电子结构,使原有的7.8和8.8ev缺陷能级消失,并在费米面上生成一条半占据态缺陷能级,引起激发能为6.2 eV的光学跃迁。     

Hydrogen adsorption on the silicon (001) surface and on a step on the (111) surface

Adsorption of atomic hydrogen on an ideal (001) silicon surface is investigated in the present paper. Saturation of one of the two dangling bonds of a silicon atom on this surface by hydrogen removes the interaction (hybridization) between them, resulting in the appearance of a bonding and an antibonding chemisorption state associated with the attacked dangling bond, and in the shift of the peak of the remaining unsaturated dangling bond to the energy typical of a surface state of the (111) surface. Further saturation leads to the disappearance of this peak from the energy spectrum. An analogous situation occurs for the silicon atom with two dangling bonds on a step on the (111) surface, when hydrogen is chemisorbed. Both examples testify to the local chemical nature of Shockley surface states in silicon.The authors thank A. N. Sorokin for useful discussions.     

Nanosphere dispersion on a large glass substrate by low dose ion implantation for localized surface plasmon resonance

Dispersing nanospheres on a large glass substrate is the key to fabricate noble metal nanostructures for localized surface plasmon resonance through dispersed nanosphere lithography. This article reports that by modifying the glass surface with low dose ion implantation and successively dip coating the surface with poly(diallyldimethyl ammonium chloride) (PDDA), polystyrene or silica nanospheres can be dispersed on a large glass substrate. Investigation shows that several kinds of ions, such as silicon, boron, argon, and arsenic, can improve the nanosphere dispersion on glass, attributed to the ion bombardment-caused silicon increment. Ion implantation imposes no surface roughness or optical loss to the glass substrate, thus this method is suitable for localized surface plasmon resonance application. Experiments show silicon ion implantation can best disperse the nanospheres. For the gold nanostructures obtained by obliquely evaporating 30 nm of gold film onto the polystyrene nanospheres, which are dispersed on a silicon ion implanted glass substrate, a localized surface plasmon resonance sensitivity of 242 nm/RIU is achieved.     

A quantum chemical study of ZrO2 atomic layer deposition growth reactions on the SiO2 surface

Zirconium oxide (ZrO₂) is one of the leading candidates to replace silicon oxide (SiO₂) as the gate dielectric for future generation metal-oxide-semiconductor (MOS) based nanoelectronic devices. Experimental studies have shown that a 1–3 monolayer SiO₂ film between the high permittivity metal oxide and the substrate silicon is needed to minimize electrical degradation. This study uses density functional theory (DFT) to investigate the initial growth reactions of ZrO₂ on hydroxylated SiO₂ by atomic layer deposition (ALD). The reactants investigated in this study are zirconium tetrachloride (ZrCl₄) and water (H₂O). Exchange reaction mechanisms for the two reaction half-cycles were investigated. For the first half-reaction, reaction of gaseous ZrCl₄ with the hydroxylated SiO₂ surface was studied. Upon adsorption, ZrCl₄ forms a stable intermediate complex with the surface SiO₂–OH^* site, followed by formation of SiO₂–O–Zr–Cl^* surface sites and HCl. For the second half-reaction, reaction of H₂O on SiO₂–O–Zr–Cl^* surface sites was investigated. The reaction pathway is analogous to that of the first half-reaction; water first forms a stable intermediate complex followed by evolution of HCl through combination of a Cl atom from the surface site and an H atom from H₂O. The results reveal that the stable intermediate complexes formed in both half-reactions can lead to a slow film growth rate unless process parameters are adjusted to lower the stability of the complex. The energetics of the two half-reactions are similar to those of ZrO₂ ALD on ZrO₂ and as well as the energetics of ZrO₂ ALD on hydroxylated silicon. The energetics of the growth reactions with two surface hydroxyl sites are also described.     

Surface enhanced spectroscopy with gold nanostructures on silicon and glass substrates

We compared the surface enhanced spectroscopy signal arising from dye molecules (methylene blue, crystal violet and octadecylrhodamine B) deposited on gold nanostructures fabricated onto two kinds of substrates: silicon wafer or glass. For any molecule and excitation wavelength, the observed signal was always higher on glass compared to silicon. This experimental result is confirmed by Finite-Difference Time Domain calculations: the enhancement in the electric field is much higher with gold nanoparticles on glass than on silicon, even if a thin oxide layer is present. These results clearly demonstrate that the nature of the substrate, independently of metallic nanoparticles, is important for the preparation of highly efficient SERS nanostructures.     

The chemisorption of hydrogen on silicon and silicon carbide (1 0 0) surfaces

The chemisorption of hydrogen onto semiconductor surfaces is examined. The hydrogen bonds to the dangling bond of a surface atom. These dangling bonds also dictate the reconstruction of the crystal surface. The chemisorbed hydrogen therefore modifies the reconstructed surface topology. In this work theoretical calculations of the surface structures of both covalent elemental silicon and polar silicon carbide are presented. The periodic MINDO method is employed to determine the topologies for the 2 × 1 reconstructed (1 0 0) surfaces. These topologies are obtained from the minimisation of the total energy, for silicon and silicon carbide films of 14 layer thickness, with respect to the atomic co-ordinates of the hydrogen adsorbate and the first four layers of the substrate. The results show that the formation of the hydrogen bond to the substrate leads to a general lengthening of the surface dimer bond. In addition, the buckling of the silicon dimer determined for silicon terminated SiC is removed by hydrogen chemisorption.     

Dispersion of nanospheres on large glass substrate by amorphous or polycrystalline silicon deposition for localized surface plasmon resonance

Nanosphere lithography is a cost-effective way to fabricate noble metal nanostructures for plasmonics. However, dispersing nanospheres on a large area of glass substrate is a difficulty encountered when transparent substrate is required in applications such as localized surface plasmon resonance or surface enhanced Raman spectroscopy. Because poly(diallyldimethyl ammonium chloride) (PDDA) on silicon surface introduces a force that can disperse nanospheres on silicon, in this article, we modify the glass surface through amorphous or polycrystalline silicon deposition and thus well disperse polystyrene or silica nanospheres over a glass area of more than 2 cm × 2 cm. Transmission loss of the glass substrate caused by amorphous or polycrystalline silicon deposition is analyzed with good agreement to experimental spectra, and localized surface plasmon resonance signals generated from the gold nanostructures fabricated on these substrates are measured and yield a sensitivity of 317 nm/RIU, which prove the feasibility and effectiveness of our method.     

基于芯-电子结合能偏移的碱金属中的表面、尺寸和热效应

还原氧化石墨烯是大规模生产石墨烯的前体;然而迄今为止,还原氧化石墨烯的电子结构还没有达成共识. 本文运用从头分子动力学方法研究羟基在石墨烯表面的吸附过程. 在吸附过程中,OH基团首先在位于两个碳原子桥位上方形成物理吸附络合物,然后翻越过渡态,最终被吸附在一个碳原子的顶位位点. 结果显示5×5石墨烯表面最多可以吸附6个羟基,表明石墨烯表面羟基的覆盖率约为12%. 计算结果还显示,负吸附能随着羟基吸附数目的增加而线性增加,带隙也随着羟基吸附数目的增加而线性增加.     

Model of laser-induced chemical etching of silicon in chlorine atmosphere

A mathematical model for the chemical etching of silicon in a chlorine atmosphere induced by laser irradiation is described. The model takes into account: dissociation of molecules having absorbed radiant energy into chlorine atoms and their diffusion onto the substrate surface, generation of photocarriers in the silicon substrate, kinetics of chlorine atom chemisorption on the silicon surface, chemical reaction of chemisorbed chlorine atoms with silicon atoms, and desorption of reaction products. The obtained results are compared with experimental data.     

飞秒激光改性6H-碳化硅晶体表面光电导增益现象研究

半绝缘6H型碳化硅(6H-SiC)具有高电阻率性质,在可见光照射下进行光电导测量时,通常光生电流很小;然而经过飞秒激光辐照改性之后,发现在可见光波段的光电导有明显的增益.本文利用紫外-可见-近红外吸收谱、X射线光电子能谱和发光光谱测量分析了激光改性之后碳化硅样品的光谱吸收、发射和晶体元素比例变化情况.分析认为碳化硅光电导增益的原因是飞秒激光辐照过程改变了碳化硅表面的硅碳元素的原子浓度比,形成新的物质结构形式,从而导致了表面光电导性能的提高.