Shearing interference microscope for step‐height measurements

A shearing interference microscope using a Savart prism as the shear plate is proposed for inspecting step‐heights. Where the light beam propagates through the Savart prism and microscopic system to illuminate the sample, it then turns back to re‐pass through the Savart prism and microscopic system to generate a shearing interference pattern on the camera. Two measurement modes, phase‐shifting and phase‐scanning, can be utilized to determine the depths of the step‐heights on the sample. The first mode, which employs a narrowband source, is based on the five‐step phase‐shifting algorithm and has a measurement range of a quarter‐wavelength. The second mode, which adopts a broadband source, is based on peak‐intensity identification technology and has a measurement range up to a few micrometres. This paper is to introduce the configuration and measurement theory of this microscope, perform a setup used to implement it, and present the experimental results from the uses of the setup. The results not only verify the validity but also confirm the high measurement repeatability of the proposed microscope.     

Impedance spectroscopy using maximum length sequences: application to single cell analysis

A maximum length sequence (MLS) is used to perform broadband impedance spectroscopy on a dielectric sample. The method has a number of advantages over other pulse-based or frequency sweep techniques. It requires the application of a very short sequence of voltage steps in the microsecond range and therefore allows the measurement of time-dependent impedance of a sample with high temporal resolution over a large bandwidth. The technique is demonstrated using a time-invariant passive RC network. The impedance of single biological cell flowing in a microfluidic channel is also measured, showing that MLS is an ideal method for high speed impedance analysis.     

基于微流控和酶比色的微创血糖连续检测仪

连续血糖检测对糖尿病的诊断与治疗具有十分重要的意义。本文设计了一种集成化、自动化的微创血糖连续检测仪器,该仪器通过微流控芯片透皮抽取组织液,利用单片机精确测量透皮抽取组织液的体积,并采用酶比色法检测组织液的葡萄糖浓度,利用组织液与血液的葡萄糖浓度相关性实现连续血糖检测。由于透皮抽取的组织液体积很小且分散在皮肤表面,为了便于收集,利用生理盐水对抽取出的组织液进行稀释,稀释后的组织液中葡萄糖浓度在3～50mg/dL。为了测量低浓度葡萄糖,实验选取了1～50mg/dL中的10个浓度的葡萄糖溶液进行吸光度测量,根据光谱数据与葡萄糖浓度建立吸光度模型,结果表明该酶比色检测方法在1～50mg/dL葡萄糖浓度内具有良好的线性度,测量相对标准偏差小于0.65%。该仪器能够实现自动化控制,为糖尿病的诊断提供依据,在微创血糖连续检测领域具有良好的应用前景。     

Explanation and correction of false step heights in amplitude modulation atomic force microscopy measurements on alkane films

We use a prototypical alkane film (n-C(32)H(66) or C32) adsorbed on a SiO(2) surface to compare step heights measured by amplitude modulation atomic force microscopy (AM-AFM) with those measured in the contact mode. The C32 film exhibits layers in which the molecules are oriented with their long axis parallel to the SiO(2) surface followed by partial layers of perpendicular molecules. We show that step heights measured in the AM and contact modes agree in all cases except where the step is between a surface formed by a layer of parallel molecules and one of perpendicular molecules. In this case, the AM mode gives a false step height that is as much as 20% lower than that measured in the contact mode and inferred from synchrotron X-ray specular reflectivity measurements. We propose that the weaker van der Waals forces between the AFM tip and a perpendicular layer compared to a parallel layer causes this discrepancy. We show how to correct the false step height by using the approximately linear relationship observed between phase angle (cantilever oscillation relative to the drive signal) and cantilever height measured in an approach curve.     

Measurement-based evaluation of optical pathlength distributions reconstructed from simulated differential interference contrast images

Recently a method was presented for reconstructing optical pathlength distributions (OPDs) from images of weak phase objects obtained by a conventional differential interference contrast (DIC) microscope. A potential application of this technique is the determination of the mass of biological objects: by integrating the optical pathlength over the projected surface of the image of an object, a measure of the dry mass, i.e. the total mass of all solid constituents present in the object, is obtained. To assess the possibilities of DIC microscopy for this application, simulations were performed on computer-generated DIC images of objects of various sizes, shapes and orientation angles. After reconstructing the OPDs from these images, the integrated optical pathlength of each of the test objects was determined, and compared with the expected results. The parameter settings used in the reconstruction algorithm were found to be very important in obtaining a reliable measurement. Using optimal parameter settings, errors in the integrated OPD could be limited to a few per cent for circular objects within the investigated size range. For non-circular objects, however, the orientation angle of the object relative to the lateral shift was found to influence the measured values. Ellipses with their long axes perpendicular to the shift direction had a significantly higher integrated OPD than ellipses orientated parallel to the shift. By adjusting the reconstruction parameters the effect could be limited, but complete elimination of the artefact was not possible within the parameter range investigated.     

纯金膜表面等离子增强的旋光效应

为了研究棱镜的磁光特性对系统光学响应的影响,测试了单个BK7棱镜在全内反射条件下的旋光角度谱以及BK7棱镜与金膜组合构成Kretschmann结构的旋光角度谱,并根据传统光学理论分析了光谱的成因.理论分析结果表明:在单个BK7棱镜构成的全内反射结构中,棱镜底部对p波和s波产生的反射系数差异是导致系统进入全内反射临界角之前产生较强旋光效应的主要原因;在BK7棱镜与金膜组合构成的Kretschmann结构中,棱镜的磁光特性使得光波到达金膜表面之前产生了较小的s光分量,金膜表面等离子共振激发削弱了p光振幅,两种因素结合产生了一种新的表面等离子共振增强磁光效应的物理机制.实验结果表明:Kretschmann模式下,26 nm厚金膜的表面旋光角最大为1.7°,克服了传统磁光克尔效应响应较弱的缺点.     

掺苝聚合物微球的制备及研究

为了获得高Q值激光器,利用光学微球谐振腔具有高Q值、低阈值和利于集成化等优点,制备了掺苝聚合物微球。通过改变实验试剂的用量,实现了对微球直径的控制。研究表明：所制备的微球表面光滑,形貌特征完好,是优良的回音壁腔体;在飞秒激光泵浦下,无论是单个微球还是聚集的微球都能激发出激光,具有良好的应用前景。     

Microfluidic channel depth determination with Tywman–Green interferometer

A microfluidic channel is fabricated on a silica wafer using reactive ion etching (RIE). The depth of the microfluidic channel has been measured using a surface profilometer and a Twyman–Green interferometer (TGI) setup. The TGI setup which mainly consists of a 660-nm wavelength He-Ne laser source, glass cube beam splitter and two prisms produced interference fringes based on the optical path difference between two interfering beams when the microfluidic channel is inserted into one of the beams. The TGI setup that was developed has shown high repeatability when measuring microfluidic channel depth and also eliminates back injection into the laser source and alignment criticality. The TGI setup applied a single photodiode to detect the shifting of the bright and dark fringe produced from the interference of the TGI. The depth of microfluidic channel obtained from the TGI is 1.79?±?0.31 μm using fringe shifting and intensity measurements, while according to the surface profilometer the depth of microfluidic channel obtained is 1.67?±?0.07 μm. The resolution of the TGI is 0.25 μm and can still go well below that depending on the wavelength of the laser source. This research describes the capability of the TGI to perform depth measurements on a microfluidic channel of a silica substrate which can also be improvised for other microscale devices and applications.     

High resolution electron energy loss spectroscopy oflow vapor pressure liquid lubricants: Fomblin Y and Z

Thin layers of perfluoropolyether lubricants Fomblin Y and Z havebeen deposited on a polycrystalline molybdenum surface andvibrational spectra have been measured by using high resolutionelectron energy loss spectroscopy. The vibrational spectra showstrong modes in the 155 meV range for Fomblin Y and Fomblin Zcharacteristic of CF₃ and CF₂ vibrationalmodes. Results from in situ and ex situ deposition of thelubricant on a differently prepared substrate suggest that thelubricant molecules condense on the surface forming a 300 Kmulti-layer structure.     

面向超分辨光学成像的浸没微球透镜控制

微球透镜配合传统光学显微镜可以采集到衍射极限以下的超分辨光学图像,为了精确控制微球透镜在样品表面的位置,同时扩大超分辨成像范围,提出了一种控制微球透镜的方法,结合多轴微动平台实现微球透镜的精确定位与成像扫描操作。通过光学仿真分析了微球透镜超分辨成像效果,并对精密微动平台进行了运动学分析。为了提高超分辨成像效果,将微球透镜浸没于液体介质中,并对在液体中运动的微球透镜进行力学分析。通过实验,清晰分辨出130nm(~λ/4)的蓝光光碟条纹间隙,证明了微球透镜具有超分辨成像能力,结果表明,微球透镜可以在传统光学显微镜的基础上进一步提高约3.52倍的放大倍数。通过控制微球透镜以5×10~(-6) m/s的速度在液体中按"S"型轨迹移动,实现了对一个视场内样品的超分辨成像,此控制方法可以精确控制微球透镜的运动,通过扫描的方式可以扩大微球透镜的观测范围,提高观测速度。     

采用傅里叶变换红外光谱对原材料进行质量检测

本文介绍了带有DialPath技术的ML分析仪,用户可以快速、准确地选择恰当的较长光程以满足检测低含量分析物的需求,并可以选择一个较短光程用于液体的总鉴定。与此同时,该技术操作简单并可以快速完成检测,同在较短光程使用衰减全反射一样。     

High pressure sample cell for total internal reflection fluorescence spectroscopy at pressures up to 2500 bar

Total internal reflection fluorescence (TIRF) spectroscopy is a surface sensitive technique that is widely used to characterize the structure and dynamics of molecules at planar liquid-solid interfaces. In particular, biomolecular systems, such as protein adsorbates and lipid membranes can easily be studied by TIRF spectroscopy. Applying pressure to molecular systems offers access to all kinds of volume changes occurring during assembly of molecules, phase transitions, and chemical reactions. So far, most of these volume changes have been characterized in bulk solution, only. Here, we describe the design and performance of a high pressure sample cell that allows for TIRF spectroscopy under high pressures up to 2500 bar (2.5 × 10(8) Pa), in order to expand the understanding of volume effects from the bulk phase to liquid-solid interfaces. The new sample cell is based on a cylindrical body made of Nimonic 90 alloy and incorporates a pressure transmitting sample cuvette. This cuvette is composed of a fused silica prism and a flexible rubber gasket. It contains the sample solution and ensures a complete separation of the sample from the liquid pressure medium. The sample solution is in contact with the inner wall of the prism forming the interface under study, where fluorescent molecules are immobilized. In this way, the new high pressure TIRF sample cell is very useful for studying any biomolecular layer that can be deposited at a planar water-silica interface. As examples, high pressure TIRF data of adsorbed lysozyme and two phospholipid membranes are presented.     

Super‐resolution optical microscopy based on scannable cantilever‐combined microsphere

We report an ingenious method of super‐resolution optical microscopy utilizing scannable cantilever‐combined microsphere. By scanning the microsphere over the sample surface in a cantilever‐combined microsphere‐sample contact state, super‐resolution images can be acquired at arbitrary sample regions through near‐field information collection by the microsphere. In addition, such a state can effectively reduce the possibility of breaking the cantilever and damaging the microsphere or sample surface. This work has developed a new method and technique of sub‐diffraction‐limit optical microscopy, and can be practically applied in various fields of micro/nanoscopy. Microsc. Res. Tech. 78:1128–1132, 2015. © 2015 Wiley Periodicals, Inc.     

An experimental study of micromilling parameters to manufacture microchannels on a PMMA substrate

Rapidly prototyping a polymer microfluidic device is a growing interest in the application fields of the disease detection, drug synthesis, and the environmental monitoring because of the benefits of the miniaturized platforms. Micromilling is one of the micromachining methods and it has been commonly used to manufacture polymer microfluidic devices. The advantages of using micromilling for polymer microfluidic devices include faster fabrication process, lower cost, easier user interface, and being capable of fabricating complicated structures, which make micromilling a perfect candidate in rapid prototyping polymer microfluidic devices for research idea testing and validation. This aim of this study is to understand the influence of each micromilling parameter to the surface quality, followed by the factor analysis to determine the optimal cutting conditions. The parameters included spindle speed, feed rate, depth of cut, and the selection of coolant (compressed air/oil coolant), and the milled surface quality was measured by a stylus profilemeter. Polymethyl methacrylate (PMMA) is the mainstream substrate material in the microfluidics due to its excellent optical property and popularity and is used as the target substrate. The experiment results showed that using the compressed air as a coolant can deliver a better surface quality than the oil coolant, and the smallest roughness achieved was 0.13 μm with the spindle speed of 20,000 rpm, feed rate of 300 mm/min, and the depth of cut of 10 μm. Factor analysis revealed that the depth of cut has the largest impact while the spindle speed has the minimized impact to the surface quality of a micromilled PMMA substrate. To further confirm the optimal cutting conditions, another 12 reservoirs were micromilled with the optimal cutting conditions and the average roughness is 0.17 μm with a stand deviation of 0.08 μm.     

Quantitative analysis of the number of antigens immobilized on a glass surface by AFM

To develop force measurements using an atomic force microscope (AFM) in a quantitative manner, it is necessary to estimate the number density of target molecules on a sample surface, and for this, the sensitivity of detection should be known. In this study, the AFM was used as a mechanical detector and an antigen and its antibody were used as a model to evaluate the sensitivity of detection. Antigens were immobilized on a glass surface and number density was estimated by monitoring optical absorbance due to product formation by the reaction of crosslinkers. The concentration of antigen was controlled by mixing control peptides. A microbead was used as a probe and antibodies were immobilized on the bead. AFM force measurements were then made for a range of number densities in the order of 10–10⁶ antigen molecules per square micrometer of surface and were compared to evaluate the sensitivity of detection. Our result establishes the reliability of estimating a number of molecules like receptors on the cell surface, and indicates that the AFM is useful as a mechanical detector with high sensitivity.     

离轴回转对称棱镜式头戴显示器目镜的研制

针对大曲率自由曲面棱镜在加工中存在表面粗糙度差的问题,本文采用离轴非球面面型研制了棱镜式虚拟显示目镜.目镜的3个光学表面都采用了回转对称的非球面面型,其加工精度比自由曲面高且加工难度大大降低.通过控制棱镜各表面的曲率、倾斜角度来实现短焦距和大视场并通过优化高次非球面系数校正像差.实验结果显示:研制的目镜其光瞳大小为6 mm,视场大小为55°;在30 lp/mm处,轴上视场的调制传递函数(MTF)值高于0.2,轴外视场的MTF值高于0.1,目镜的最大畸变量为-5.37％.棱镜的检测和试验结果表明:与自由曲面棱镜相比,采用非球面面型能够显著降低棱镜表面的粗糙度,避免图像重影现象,成像更为清晰,虚拟成像的目视效果得到了明显改善.     

Formation of type-II InAs/GaSb strained short-period superlattices for IR photodetectors by molecular beam epitaxy

The interaction of the GaSb(001) surface with fluxes of As₂, As₄, and Sb₄ molecules is studied using reflection high-energy electron diffraction. It is shown that As₂ molecules interact with a GaSb surface predominantly by an exchange mechanism, and As₄ molecules by the vacancy mechanism. It is established that for the reproducible generation of In-Sb heterointerfaces in InAs/GaSb superlattices, one needs to use a flux of As₄ molecules rather than As₂ molecules.     

Analysis of photonic crystal on LED extraction efficiency

Because of its very low light extraction efficiency (LEE),LED is limited to be widely used under the condition of the internal quantum efficiency which up to 90％.In order to fullfill the design of a mo...     

利用相位差异技术恢复宽带白光图像

研究了用于扩展目标成像的相位差异技术。该技术利用焦面和离焦面上的两幅图像之间的相位差异来估算波前相位畸变,同时对采集的图像进行恢复。设计了白光目标成像实验系统,用宽带白光作光源,在实验室搭建实验平台,模拟无穷远处目标和波前相位畸变。采用直角梯形分光棱镜将光路分为两个通道,在一台相机上同时采集两个通道像面上的图像,消除了相机不同产生的差异,极大地抑制了噪声对图像恢复的影响,分光后系统抗两个通道独立的高斯白噪声的能力为10%。实验结果显示恢复后的图像分辨率提高了19%,表明该技术是适合光电成像系统的图像恢复技术。