基于随机共振的纳米碳管气体传感器的研究

基于气体电晕放电原理,利用纳米碳管独特的物理结构和尖端发射效应,提出了一种新型的纳米碳管离子型气体传感器.采用阳极氧化铝模板法生长的定向纳米碳管阵列所构成的传感器,纳米碳管和电极是一体的,简化了器件结构和工艺.在外加直流电压激励下,纳米碳管顶部形成很强的非均匀电场,在电压相对低的情况下能很容易地电离气体,根据气体的击穿电压和放电电流来实现对单一气体和确定性混合气体的检测.为了提高检测混合气体的灵敏度,创新地在检测回路中引入随机共振发生装置,有效地提高了混合气体浓度检测的范围.实验中还分析了温度、湿度对传感器的影响,对该传感器的性能也作了评价.实验结果表明该传感器具有选择性好、体积小、响应时间快、灵敏度高、稳定性好,室温操作等优点,而且实现方便,操作简单,有较大的实用价值.     

纳米孔单分子传感器电导特性有限元分析

主要从纳米孔结构角度,考虑生物分子在纳米孔内的位阻效应影响.运用有限元模拟方法分别模拟了3类常见纳米孔的电导,并比较了3种不同纳米孔在检测纳米杆通过纳米孔时的相对堵塞电流值大小.研究了纳米杆上带有亚结构时,在3种纳米孔内的电流堵塞效应的差异.研究方法有助于进一步理解纳米孔结构对检测生物分子的影响.     

纳米碳化硅/硅纳米孔柱阵列湿敏性能研究

以硅纳米孔阵列(Si-NPA)为衬底,采用化学气相沉积法分别制备了SiC纳米颗粒/Si-NPA(nc-SiC/Si-NPA)和SiC纳米线/Si-NPA(nw-Si/Si-NPA)复合体系,并对其表面成分和形貌、室温湿敏性能进行了表征.实验结果表明,nc-SiC/Si-NPA和nw-SiC/Si-NPA均对水蒸气表现出...     

纳米Fe3O4表面聚合接枝的XPS分析

采用在纳米Fe3O4颗粒表面通过引入过氧基因引发甲基丙烯酸甲酯(MMA)聚合的方法,在纳米Fe3O4颗粒表面接枝了PMMA.采用傅立叶红外光谱(IR-FT)检测粉体表面官能团,采用X射线光电子能谱(XPS)检测粉体表面化学键变化,采用高分辨透射电镜(HRTEM)观察改性后粉体的表观形貌.结果表明纳米Fe3O4呈球形,颗粒间团聚不明显,在纳米Fe3O4表面成功地包覆了PMMA,PMMA以化学接枝的方式结合在Fe3O4颗粒表面.     

纳米金与二茂铁在葡萄糖传感器中的相互作用

针对纳米金颗粒修饰的葡萄糖生物传感器对葡萄糖的响应电流随着工作电压的下降快速下降的问题,进一步利用电子媒介体二茂铁对其进行修饰,并选用丝网印刷电极研究了纳米金颗粒和二茂铁之间的相互作用。实验结果表明:二茂铁有效地降低了纳米金颗粒修饰的葡萄糖生物传感器响应电流的下降值,纳米金颗粒降低了电子媒介体二茂铁的氧化还原反应电位,并且,纳米金颗粒与电子媒介体二茂铁在葡萄糖生物传感器中表现协同增效效应。     

随机栅长变化引起纳米MOSFET失配模型

随着CMOS技术进入纳米工艺,随机栅长变化成为影响集成电路性能和成品率最重要因素之一.文中分析并验证了纳米MOS器件随机栅长变化导致电流增益因子与阈值电压的之间的相关性及失配解析关系式,并以此为基础,结合偏差传递理论实现了22 nm工艺MOSFET电流失配模型.仿真实验结果表明,该模型揭示了短沟道效应导致的器件阈值电压变化改变了载流子有效迁移率,进而影响电流增益因子及器件电流的规律,精确地估计了随机栅长变化导致的电气参数统计变化特性.     

蜂巢基底纳米颗粒SEM图像分析方法研究

分析了蜂巢形基底上纳米颗粒SEM图像的特征,阐明了纳米颗粒特征值提取所遇到的问题。借助形态学滤波、直方图均衡、颗粒分析等图像处理方法,解决了图像二值化处理后纳米颗粒图像上的大孔洞、粘连颗粒影响粒径提取等问题。给出了蜂巢形基底上纳米颗粒SEM图像处理算法,实现了占空比、粒径分布等纳米颗粒特征值提取的目标,为进一步对纳米器件的参数进行定量评价和改进奠定了基础。     

基于纳米金、铁氰化镍纳米颗粒共修饰的电流型甲胎蛋白免疫传感器的研究

该文通过铁氰化镍纳米颗粒和纳米金之间的化学作用及强的吸附作用,利用纳米金良好的生物兼容性和强烈的吸附作用固定甲胎蛋白抗体,最后用牛血清白蛋白封闭非特异性吸附位点,从而制备了一种新型的用于检测甲胎蛋白的电流型免疫传感器.在优化条件下,该传感器分别在1.0到10.0ng/mL和10.0到200.0 ng/mL两个浓度范围内对甲胎蛋白展示了良好的线性响应关系,检出限为0.2 ng/mL.     

基于光导电渗流的碳纳米颗粒自动化装配仿真

研究碳纳米自动化装配优化问题.50nm碳纳米颗粒的自动化装配,在工业领域中有广泛的应用价值.光电子镊器件的光导电渗流操作方法,可用于纳米尺度自动化装配中.为此,首次通过建立光导电渗流等效电路模型,得到有效装配的交流电源的频率范围.可通过有限元仿真软件Comsol Multiphysics 3.5a,进行了光导电渗流自动化装配50nm碳纳米颗粒的仿真.仿真结果证明,选择合适的频率,可以利用光导电渗流方法实现50nm碳纳米颗粒的自动化富集、装配.从而从理论上解决了光导电渗流可应用于纳米尺度自动化装配系统中,并将为实现碳纳米颗粒的三维器件和纳米传感器提供理论依据.     

纳米金修饰铂金电极固载白喉抗原免疫传感器的研究

该文报道了一种制作电流型白喉抗原免疫传感器的方法.用金纳米颗粒吸附白喉抗原,采用聚乙烯醇缩丁醛(PVB)为辅助固定抗原膜基质将其固定在铂金电极的表面,制成白喉抗原免疫传感器.根据抗原抗体特异性结合形成的免疫复合物使电极敏感膜有效扩散面积减小,电流减少的特性,实现对白喉抗体的定量检测.该传感器对白喉抗体检测的线性范围是2...     

基于纳米孔读取的 DNA 存储发展与展望

现代社会正处于数据爆炸的时代,全球对数据存储的需求已经远远超过了已有的存储能力。DNA 是一种天然的遗传信息载体,可实现稳定、高效、低功耗的数据存储。目前的 DNA 存储过程主要分为 6 个环节：编码、写入、保存、检索、读取、解码。纳米孔测序技术被广泛应用于读取 DNA 中所存储的信息。该文系统性地介绍了纳米孔分子检测技术的原理和发展历史,及其在 DNA 存储中的应用。此外,该文总结了机器学习在纳米孔检测技术中的应用,着重介绍了结合机器学习的新型纳米孔检测技术。该文为纳米孔检测技术的发展提供了新方向,也为新型实用化 DNA 存储系统的发展奠定了基础。     

Fabrication of Cylindrical Nanopores and Nanopore Arrays in Silicon-On-Insulator Substrates

Electron-beam lithography and reactive ion etching were used to process silicon-on-insulator substrates for the fabrication of single cylindrical high-aspect-ratio solid-state nanopores and high-packing-density nanopore arrays. Minimum pore diameters of 40 nm were readily achieved with a high yield. The electrolyte concentration dependence of ion transport through single nanopores was measured for pores with diameters ranging from 40 to 140 nm. Measured single-nanopore conductances in high salt concentrations were compared to a simple model using a cylindrical resistance path and bulk solution conductivity. Electrochemical impedance spectroscopy was used to study the ac response of the device.     

Incorporating ionic size in the transport equations for charged nanopores

Nanopores with fixed charges show ionic selectivity because of the high surface potential and the small pore radius. In this limit, the size of the ions could no longer be ignored because they occupy a significant fraction of the pore and, in addition, they would reach unrealistic concentrations at the surface if treated as point charges. However, most models of selectivity assume point ions and ignore this fact. Although this approach shows the essential qualitative trends of the problem, it is not strictly valid for high surface potentials and low nanopore radii, which is just the case where a high ionic selectivity should be expected. We consider the effect of ion size on the electrical double layer within a charged cylindrical nanopore using an extended Poisson–Boltzmann equation, paying special attention to (non-equilibrium) transport properties such as the streaming potential, the counter-ion transport number, and the electrical conductance. The first two quantities are related to the nanopore selectivity while the third one characterizes the conductive properties. We discuss the nanopore characteristics in terms of the ratio between the electrolyte and fixed charge concentrations and the ratio between the ionic and nanopore radii showing the experimental range where the point ion model can still be useful. Even for relatively small inorganic ions at intermediate concentrations, ion size effects could be significant for a quantitative estimation of the nanopore selectivity in the case of high surface charge densities.     

Pressure-driven water flow through hydrophilic alumina nanomembranes

We present an experimental study that focuses on pressure-driven flow of distilled water through γ alumina membranes with 5, 10 and 20 nm pore radii. The nanopore geometry, pore size and porosity are characterized using scanning electron microscopy images taken pre- and post-flow experiments. Comparisons of these images have shown reduction in the pore size, which is attributed to precipitation of hydroxyl groups on alumina surfaces. Measured flowrates compared with the Hagen–Poiseuille flow relations consistently predict 2.2 nm reductions in the pore size for three different membranes. This behavior can be explained by the formation of a thick stick layer of water molecules over hydroxylated alumina surfaces, evidenced by water droplet contact angle measurements that exhibit increased hydrophilicity of alumina surfaces. Other possible effects of the mismatch between theory and experiments such as unaccounted pressure losses in the system or the streaming potential effects were also considered, but shown to be negligible for current experimental conditions.     

Simulation of transport and extravasation of nanoparticles in tumors which exhibit enhanced permeability and retention effect

Determining the factors that influence the delivery of sub-micron particles to tumors and understanding the relative importance of each of these factors is fundamental to the optimization of the particle delivery process. In this paper, a model that combines random walk with the pressure driven movement of nanoparticles in a tumor vasculature is presented. Nanoparticle movement in a cylindrical tube with dimensions similar to the tumor's blood capillary with a single pore is simulated. Nanoparticle velocities are calculated as a pressure driven flow over imposed to Brownian motion. The number and percentage of nanoparticles leaving the blood vessel through a single pore is obtained as a function of pore size, nanoparticle size and concentration, interstitial pressure, and blood pressure. The model presented here is able to determine the importance of these controllable parameters and thus it can be used to understand the process and predict the best conditions for nanoparticle-based treatment. The results indicate that the nanoparticle delivery gradually increases with pore size and decreases with nanoparticle size for tumors with high interstitial fluid pressure (in this work we found this behavior for head and neck carcinoma and for metastatic melanoma with interstitial pressures of 18 mmHg and 19 mmHg, respectively). For tumors with lower interstitial fluid pressure (rectal carcinoma with 15.3 mmHg) however, delivery is observed to have little sensitivity to particle size for almost the entire nanoparticle size range. Though an increase in nanoparticle concentration increases the number of nanoparticles being delivered, the efficiency of the delivery (percentage of nanoparticles delivered) is found to remain closely unaffected.     

Droplet microfluidic preparation of au nanoparticles-coated chitosan microbeads for flow-through surface-enhanced Raman scattering detection

An integrated microfluidic device was fabricated to enable on-chip droplet forming, trapping, fusing, shrinking, reaction and producing functional microbeads for a flow-through single bead-based molecule detection. Dielectrophoresis (DEP) force was used to transport target polymer droplets into different predefined microwells, where the droplets were fused through electrocoalescence to form a new one with a desired diameter. In a continuous water loss process with water diffusion to oil phase, the polymer droplet was shrunken and solidified to form a polymer microbead. For a demonstration, Au nanoparticles-coated chitosan microbeads were in situ fabricated through droplet trapping, fusion and shrinking, followed by synthesis of Au nanoparticles on the microbead surface via a photoreduction process. The produced Au nanoparticle/chitosan microbead embedded in the microwell resulted in a highly sensitive, flow-through surface-enhanced Raman scattering (SERS) detection of Rhodamine 6G (R6G). This work successfully demonstrates an integrated droplet based lab-on-a chip and its application to fabricate an extremely high-throughput single bead based detection platform.     

基于过程现场总线技术的振动检测系统

针对当前振动检测系统延迟大、传感网络可控性差、检测精度低等问题,提出了一种基于过程现场总线（Profibus）技术的振动检测系统。首先,在每个检测设备节点处实现卡尔曼滤波、快速傅里叶变换（FFT）等复杂计算,使网络负载与传输大量原始振动数据的传统方案相比降低了约95%,缩短了网络传输时间和工作站的计算时间,提高了系统的实时性和计算能力。然后,采用Profibus协议实现对振动检测设备网络的管理和数据传输,保证了传感网络的稳定性和可控性;并且,在振动检测节点设备上使用高精度振动传感器,在检测节点上对振动数据进行滤波等处理,检测精度高达0.0039 mg。此外,自主设计开发了Profibus协议从站,方便检测设备的功能定制与二次开发;在检测节点设备上采用RT-Thread嵌入式系统内核实现资源分配与任务调度,提高了实时性和可靠性。实验结果表明,所提系统可以快速地对振动现场的原始振动数据进行数据处理并把处理后的数据传输到工作站电脑,实时性高。同时,振动检测设备组成的Profibus网络可以实时显示节点的状态信息,若有网络故障能够及时提醒,网络的可控性好。     

基于动态阈值的可信度加权协作频谱感知

为了提升受阴影衰落等因素影响下的协作频谱感知性能, 采取了一种改进的基于动态阈值和可信度相结合的协作频谱感知方法。该方法利用各认知用户的检测信噪比对检测可信度较低的认知用户进行过滤, 各认知用户根据检测信噪比设定一个适合自身的动态阈值进行能量感知, 融合中心结合各单节点感知结果和分配的传输可信度作出最终判决。仿真结果表明, 在检测信道和传输信道均受到阴影衰落等因素严重影响下, 与单纯的动态阈值协作感知和传统的可信任度协作感知方法相比, 该方法能获得较高的检测概率。     

飞机起落架收放系统性能仿真与故障分析

由于飞机前起落架与主起落架收放方向不同导致前起落架更容易受气动阻力影响而产生收放不到位等故障.对此利用AMEsim对某型飞机前起落架进行建模仿真,并通过建立起落架机械模型完成作动筒受力分析,将一些单一因素和混合因素分别注入到模型中对起落架收放性能进行仿真实验.实验结果表明,单一因素中油泵泄漏、作动筒限流阀阻塞、作动筒内...     

基于机器视觉的多孔材料缺陷检测

针对多孔材料在生产工艺中易出现阻塞和缺角等缺陷,本文设计了一种基于机器视觉的多孔材料表面缺陷检测方法,通过对目标区域的有效分割、模糊度检测、形态学处理和分析等技术手段,实现了该类材料的表面缺陷的快速定位和特征分析.经实验检测,本文算法的准确性和检测效率可以满足工业生产实时检测需求.