IR imaging using uncooled microcantilever detectors

Uncooled bimaterial microcantilever detectors were fabricated and used to obtain infrared (IR) images of objects at temperatures ranging from room temperature to a few hundred degrees C. Images were obtained using both single 50 micro m x 50 micro m microcantilever IR detectors and arrays of microcantilever detectors. Thermal radiation from the target object was imaged onto the detector and the resulting temperature change caused microcantilever bending due to the bimaterial effect. This micromechanical bending was measured using two different non-contact optical readout techniques and IR images were obtained. A smaller size (20 micro m x 20 micro m) microcantilever IR detector was also used to capture IR images of near room temperature objects.     

THz焦平面连续波透射成像系统的成像面积及对比度

研究了THz辐射和THz焦平面器件的特性,分析了THz焦平面探测器连续波透射成像系统的能量传输过程。考虑大气衰减、器件限制等影响因素以及连续激光照射、目标场景与焦平面探测器之间的信号传递关系,推导出了连续波透射成像系统的成像面积及对比度两个重要的参量模型。然后设计并组建了连续波THz透射成像系统。根据所建模型分别对信封中的环三亚甲基三硝铵(RDX)粉末和塑料盒中的金属刀片两种不同被测物体的成像面积及对比度进行了计算。结果表明:基于理论推导的两种实例其最大成像面积可达4.74cm×6.32cm和3.534cm×4.712cm,图像对比度分别为0.242 2和0.306。与美国麻省理工学院(MIT)的成像系统进行了对比,该系统的成像面积为3cm×3cm或4cm×4cm,与本文推导结果处于同一数量级,由此验证了本文提出的模型和方法的合理性和有效性。     

Detection and differentiation of biological species using microcalorimetric spectroscopy

We report on the application of infrared (IR) microcalorimetric spectroscopy ( micro -CalSpec) to the identification and detection of trace amounts of biological species. Our approach combines principles of photothermal IR spectroscopy with ultrasensitive microcantilever (MC) thermal detectors. We have obtained photothermal IR spectra for DNA and RNA bases and for Bacillus Cereus (an anthrax simulant) in the wavelength range of 2.5-14.5 micro m (4000-690 cm(-1)). The measurements are accomplished by absorbing biological materials directly on a MC thermal detector. The main advantage of the developed micro -CalSpec is its unprecedented sensitivity as compared to any of the previously explored IR techniques, including FTIR and photothermal FTIR methods. Our results demonstrate that <10(-9)g of a biological sample is sufficient to obtain its characteristic micro -CalSpec spectrum that contains information-rich chemical (vibrational) signatures. This opens up a new opportunity to create inexpensive high-throughput analytical systems for biochemical detection.     

大面阵中波红外连续变焦光学系统设计

针对制冷式大面阵640×512凝视焦平面阵列探测器,设计了一套中波红外连续变焦光学系统。该系统由变焦系统和二次成像系统构成,包括7片透镜和2个反射镜组成的折叠光路。首先,根据变焦原理和专业光学设计软件给出了系统结构及其参数。然后,分析了系统的像质和冷反射效应。最后,验证了系统的性能指标。结果表明:该系统可以实现50～500mm的连续变焦,变焦过程中目标景物始终清晰可见;系统在耐奎斯特频率处的全视场光学传递函数大于0.35,全视场畸变小于2%,无冷反射现象;具有分辨率高、热灵敏度高、像质好、变焦轨迹平滑等特点,基本满足设计要求。     

A bi-material microcantilever temperature sensor based on optical readout

As one of the simplest MEMS sensors, microcantilever can sense temperature faster and more sensitively than traditional thermometers as its small size and low thermal mass. In this paper, an Au/SiNx bi-material microcantilever temperature sensor based on optical readout is presented. The deflection of the cantilever varies with the change of temperature due to the differences in thermal expansion coefficients between gold and silicon nitride. Then, the temperature could be accurately measured by detecting the deflection of the cantilever with optical lever method. By experiments, the theoretical model is verified and the temperature characteristics of the sensor are also determined. With a commercial microcantilever, the temperature resolution of the sensor is tested to be 0.02 K when 25 mm length of optical arm set. By optimizing the microcantilever parameters, the temperature resolution of the sensor could be 0.1 mK. High sensitivity makes it suitable for some special precise temperature measurements.     

大功率焦平面器件热控制研究

摘要：为了实现大功率焦平面器件的热控制,根据焦面组件的结构特点,通过仿真计算与试验相结合的方法,对大功率焦平面的热控设计进行了研究。首先,介绍了大功率焦平面器件的主要热设计要求,分析了大功率焦平面器件、小散热空间并安装在移动构件上的焦面组件热设计的特点。接着,利用I-DEAS有限元分析软件建立热分析计算模型,利用TMG模块进行分析计算。然后,进行试验验证,并根据试验给出了焦平面器件升温拟合曲线。最后,根据热设计实例提出如何合理的选择大功率焦平面器件的热控制方式。结果表明,50W大功率焦平面器件连续工作2min时,在有12℃冷源的情况下,能够控制焦平面器件小于35℃。满足焦平面器件设计要求。     

一种用于气体检测MEMS电容式红外发光强度探测器

文章提出了一种用于气体检测的MEMS电容式红外发光强度探测器。结合理论推导和仿真分析确定了该探测器的尺寸大小,并对其制作工艺流程做了叙述。它基于气体的红外吸收热效应,借助弹性薄膜的形变将热量变化转变为电容量变化,再经基于运算放大器的电容微传感器检测电路以电压信号输出。将它与环境气室采用MEMS技术一体化,能够得到体积小、精度高和可批量生产的气体检测装置。     

纳米硬度计研究多晶硅微悬臂梁的弹性模量

利用纳米硬度计通过微悬臂梁的弯曲试验来测量其力学特性是一种简便而有效的方法,具有很高的载荷分辨率,可精确测量微悬臂梁纳米级弯曲形变。运用该方法在研究微悬臂梁的弯曲形变过程中,必须考虑压头在微悬臂梁上的压入以及微悬臂沿宽度方向的挠曲。微悬臂梁采用普通的集成电路工艺(IC)制造。试验研究表明,多晶硅微悬臂梁的纯挠曲与载荷成很好的线性关系,呈现弹性变形,通过该线性关系可计算得到梁的弹性模量。测得的多晶硅微悬臂梁的弹性模量为156±(2.9%-6.3%)GPa。     

Effect of surface conjugation chemistry on the sensitivity of microcantilever sensors

Microcantilever sensors are an offshoot of atomic force microscopy and are useful tools for effectively detecting a target biomolecule. The recognition of the target molecule on the biosensor is based on the physical bending of the microcantilever, which is driven by a specific molecular interaction between the target molecule and the sensor surface. In this study, to enhance the sensitivity of the microcantilever sensor, the sensor surface was modified through a surface conjugation method using self-assembled monolayers (SAMs) and heterobifunctional cross-linkers. After the surface modification of the microcantilever sensor, the sensitivity for L-cysteine was recorded. The detection of L-cysteine was influenced by the active site and the molecular size of the cross-linked compound attached onto the surface of the microcantilever.     

Thermostatting of the RED-100 liquid-xenon emission detector

The thermal stabilization system of the RED-100 liquid-xenon two-phase emission detector for the experiment aimed at detecting the effect of coherent neutrino scattering off xenon nuclei has been tested. The system is based on thermosyphons (closed two-phase heat pipes) that are filled with nitrogen and use liquid nitrogen boiling at atmospheric pressure as a cooler. The system is capable of keeping the working medium of the RED-100 detector at a temperature of 167 K with a precision of <1 K.     

Analysis of fluid-structure interaction for predicting resonant frequencies and quality factors of a microcantilever on a squeeze-film

The dynamic behavior of a flexible microcantilever vibrating above a substrate such as the cantilever-based structure of a radio frequency microelectromechanical switch is strongly affected by the motion of gas between the microcantilever and the substrate. In this paper, parameter studies to investigate the effects of geometry, material properties of a microcantilever, and ambient pressure on the resonant frequencies and quality factors of the microcantilever are described. A Reynolds-equation-based continuum model is used to derive the gas force reflecting the gas rarefaction effect due to the size effect of MEMS packed at low ambient pressure. The frequency response function of an inertially-excited microcantilever is developed using the mode superposition method. One interaction parameter, including information on geometry, material properties of a microcantilever, and ambient pressure, is defined to investigate the fluidstructure interaction in a microcantilever vibrating on a squeeze-film. The quality factors of the first three bending modes increase with the decreasing interaction parameter. The changing trend of associated resonant frequencies depends on the order of the bending mode.     

Motion video image processing (MVIP) method for measuring microfluidic–structure interactions

In microsystem applications, many microstructures are submerged in fluid and their performances are directly influenced by the microfluidic–structure interactions. Characterizations of such interactions in microfluidic devices such as micropumps, microvalves, micro-viscometers, and biomedical related microfluidic chips, are essential to seek enhanced designs and design guidance. In this study, a hybrid microfluidic test chip with integrated microcantilever is fabricated on a polymer platform using soft lithography method for characterization of microcantilever–fluid interactions. A measurement technique based on the motion video image capture and processing (MVIP) is developed to measure the static and dynamic deflections of the microcantilever subjected to forces due to fluid within the microchannel. A peristaltic pump was used to generate fluid flows across the channel, which caused a pressure differential loading of the microstructure. The images of motion were processed to characterize the motion in terms of deflection, velocity and acceleration of the structure under different flow conditions. The validity of the proposed MIP method is illustrated through comparisons with finite element model of the microcantilever. The images acquired from the proposed MVIP method were further analyzed to estimate deflection mode shapes and natural frequencies of the microcantilever under fluid interactions.     

太赫兹冰云成像仪结构设计及耦合分析

太赫兹频段的微波探测仪对冰云的有效探测将极大地促进全球和局部气候研究,但成像仪内部空间狭小,结构设计难度较大,且单机布局紧凑、功耗较大,太空环境与太阳直照会使天线反射面结构变形,从而影响载荷电性能。文中对成像仪系统进行了详细的结构设计,运用有限元软件验证其在各试验工况下的力学特性,并对载荷温度进行在轨计算,将温度数据映射到模型中进行热变形计算,将结构热变形数据代入Grasp系统仿真。通过耦合分析,评估天馈系统结构热变形对其电性能的影响,结果表明电性能指标均满足设计要求。     

A scintillation strip detector for detection of thermal neutrons

A scintillation strip detector designed for precise experiments on the reflectometry of thermal neutrons is described. Test results obtained on the beam of a time-of-flight spectrometer have shown that the detector has a detection efficiency for thermal neutrons close to 100%, a lowered sensitivity to the neutron background, and a low level of intrinsic noise. The coordinate resolution of the detector can be varied in the range 1.5–0.1 mm. The strip is manufactured from a mixture of a ZnS(Ag) scintillator and a ⁶LiF neutron converter.     

Influence of the tip mass and position on the AFM cantilever dynamics: Coupling between bending,torsion and flexural modes

The effects of the geometrical asymmetric related to tip position as a concentrated mass, on the sensitivity of all three vibration modes, lateral excitation (LE), torsional resonance (TR) and vertical excitation (VE), of an atomic force microscopy (AFM) microcantilever have been analyzed. The effects of the tip mass and its position are studied to report the novel results to estimating the vibration behavior of AFM such as resonance frequency and amplitude of the microcantilever. In this way, to achieve more accurate results, the coupled motion in all three modes is considered. In particular, it is investigated that performing the coupled motion in analysis of AFM microcantilever is almost necessary. It is shown that the tip mass and its position have significant effects on vibrational responses. The results show that considering the tip mass decreases the resonance frequencies particularly on high-order modes. However, dislocating of tip position has an inverse effect that causes an increase in the resonance frequencies. In addition, it has been shown that the amplitude of the AFM microcantilever is affected by the influences of tip and its position. These effects are caused by the interaction between flexural and torsional motion due to the moment of inertia of the tip mass.     

Thermal buckling analysis in InSb focal plane arrays detector

When exploring the buckling mechanism in indium antimonide (InSb) detector, the global square checkerboard buckling pattern reappears in finite element simulation results. The contributions from the three layered materials to the deformations along the Z-direction are systematically analyzed. Analysis of results shows that the buckling deformation originated from the thermal difference between silicon readout integrated circuits (silicon-ROIC) and the intermediate layer directly above. Furthermore, the buckling pattern is determined by indium bumps array. After passing through the 10 μm intermediate layer, the deformation amplitude is significantly reduced from 2.23 μm to 0.24 μm. Afterwards, passing upward through the 10 μm InSb chip, the maximal deformation is further decreased to 0.09 μm.     

Microfabricated silicon dioxide cantilever with subwavelength aperture

We have developed a microfabricated SiO₂ cantilever with subwavelength aperture for scanning near-field optical microscopy (SNOM), to overcome the disadvantages of conventional optical fibre probes such as low reproducibility and low optical throughput. The microcantilever, which has a SiO₂ cantilever and an aperture tip near the end of the cantilever, is fabricated in a reproducible batch process. The circular aperture with a diameter of 100–150 nm is formed by a focused ion-beam technique. Incident light is directly focused on the aperture from the rear side of the cantilever using a focusing objective, and high optical throughput (10⁻² to 10⁻³) is obtained. The microcantilever can be operated as a SNOM probe in contact mode or in dynamic mode.     

双S弯结构应变计算与试验测量

双S弯结构是ITER馈线系统的重要组成部分,主要用来吸收电缆由于降温收缩造成的位移变形,为了确定该结构在一定位移载荷下的变形情况,基于能量原理,采用单位力法计算出该结构轴向各位置的轴力、弯矩和应变分布。通过数值模拟和试验测量,应变的理论计算值与数值模拟所得值和试验测量值的相对差值都很小。可以认为：运用该方法计算类似结构的轴力、弯矩和应变分布是可行的,计算结果具有较高的准确度。     

Optical microcantilever consisting of channel waveguide for scanning near-field optical microscopy controlled by atomic force

We develop a novel optical microcantilever for scanning near-field optical microscopy controlled by atomic force mode (SNOM/AFM). The optical microcantilever has the bent channel waveguide, the corner of which acts as aperture with a large tip angle. The resonance frequency of the optical microcantilever is 9 kHz, and the spring constant is estimated to be 0.59 N/m. The optical microcantilever can be operated in contact mode of SNOM/AFM and we obtain the optical resolution of about 200 nm, which is as same size as the diameter of aperture. We confirm that the throughput of optical microcantilever with an aperture of 170 nm diameter would be improved to be more than 10(-5).     

基于PSD的孔径测量系统设计

为了适应现代化生产和在线检测,提出了应用位置敏感探测器及激光三角法原理实现非接触内径测量的测量系统设计方案。分析了位置敏感探测器工作原理,系统测量原理,及电路原理和电路元件参数,实现了微弱电流的提取、放大、转换。整个测量系统的测量范围为1mm,采用加工精度为1μm、直径为90mm的内径标准件对测量系统进行精度校验,实验表明,在1mm测量范围内系统测量精度高于5%。