一种局域共振型角式声子晶体梁

局域共振型声子晶体梁具有纵向振动带隙和横向振动带隙,一般而言,前者频率范围很窄而且衰减量极小,后者频率范围很宽并且衰减很强,二者往往不在同一频带,因此很难满足同一频带内的多维减振要求。针对这一问题,为充分利用横向振动带隙的宽频带强衰减特性,提出了一种局域共振型角式声子晶体梁,采用传递矩阵法进行了理论分析和数值求解,并进一步在有限元软件中做了仿真验证,结果表明该角梁能够通过纵波与横波的转换,使得三个自由度上的振动均能在同一频带内得到有效的衰减,从而一方面满足了工程上的多维减振需求,另一方面也拓展了声子晶体减振应用场合。     

一种基于光纤F-P腔的石墨烯谐振式压力传感器

谐振式传感器具有良好的重复性、分辨率和稳定性,全光纤谐振式微型传感器则集合了微纳结构与光纤传感特性两者的优点。石墨烯作为近年来发现的一种新型材料,具有良好的热学和力学特性,可以作为谐振式传感器中的敏感元件。本文提出了一种基于光纤F-P结构的石墨烯谐振式压力传感器,其兼具微机械传感器和光纤谐振器的优点,具有较高的谐振频率,在测量压力的实验中展现出良好的性能,压力灵敏度最高可达2. 93Hz/Pa,具有重要的应用价值。     

Variations in properties of atomic force microscope cantilevers fashioned from the same wafer

Variations in the mechanical properties of nominally identical V-shaped atomic force microscope (AFM) cantilevers sourced from the same silicon nitride wafer have been quantified by measuring the spring constants, resonant frequencies and quality factors of 101 specimens as received from the manufacturer using the thermal spectrum method of Hutter and Bechhoefer. The addition of thin gold coatings always lowers the resonant frequency but the corresponding spring constant can either increase or decrease as a result. The observed broad spread of spring constant values and the lack of correlations between the resonant frequency and spring constant can be attributed in part to the non-uniformity of composition and material properties in the thinnest dimension of such cantilevers which arise from the manufacturing process. The effects of coatings are dictated by the competing influence of differences in mass density and Young's modulus between the silicon nitride and the gold coating. An implication of this study is that cantilever calibration methods based on the assumption of uniformity of material properties of the cantilever in the thinnest dimension are unlikely to be applicable for such cantilevers.     

Modeling Piezoresistive Microcantilever Sensor Response to Surface Stress for Biochemical Sensors

This paper considers mechanical stress and strain in a piezoresistive cantilever sensor under surface stress loading, which is the loading condition that occurs in biochemical sensing applications. Finite element simulations examine the piezoresistor sensitivity due to changes in cantilever length, width, and thickness, and piezoresistor size, location, and depth. A few unexpected results are found. Unlike cantilevers designed for atomic force microscopy, cantilevers for biochemical sensing should be short and wide. While shallow piezoresistors offer good sensitivity, the piezoresistor may extend far into the thickness of the cantilever and still be quite effective. The paper concludes with comments on design guidelines for piezoresistive cantilever sensors.     

轴向拉力对微梁质量传感器精度和热弹性阻尼的影响

针对存在轴向拉力的矩形截面微梁谐振式质量传感器中的质量传感灵敏度、热弹性阻尼以及最小检测质量等问题进行了深入的研究。推导了质量传感器在存在轴向拉力情况下的检测灵敏度、热弹性阻尼以及最小检测质量的表达式。揭示了轴向拉力对质量传感器的工作性能的影响机理。结果表明:轴向拉力会提高质量传感灵敏度;轴向拉力会降低谐振器的热弹性阻尼;轴向拉力可以使得质量传感器捕获更微小的检测质量。     

Vibration energy harvester with sustainable power based on a single-crystal piezoelectric cantilever array

We designed and fabricated a bimorph cantilever array for sustainable power with an integrated Cu proof mass to obtain additional power and current. We fabricated a cantilever system using single-crystal piezoelectric material and compared the calculations for single and arrayed cantilevers to those obtained experimentally. The vibration energy harvester had resonant frequencies of 60.4 and 63.2 Hz for short and open circuits, respectively. The damping ratio and quality factor of the cantilever device were 0.012 and 41.66, respectively. The resonant frequency at maximum average power was 60.8 Hz. The current and highest average power of the harvester array were found to be 0.728 mA and 1.61 mW, respectively. The sustainable maximum power was obtained after slightly shifting the short-circuit frequency. In order to improve the current and power using an array of cantilevers, we also performed energy conversion experiments.     

非本征光纤法珀传感器的振动特性研究

针对光纤法珀(Fabry-Perot, FP)超声波传感器振动特性,将传感器薄板振动简化为具有集中参数的二阶振动,推导二阶振动方程的集中参数(力阻抗、等效质量、弹性系数、集中力),获得传感器共振频率、振幅灵敏度与结构参数设计关系。测试直径2.52 mm、厚度150 μm玻璃振动薄板在空气、水中的共振频率分别为205 kHz及115 kHz,水介质中共振频率振幅灵敏度约18 pm/Pa。制作的传感器可测试局放产生超声波的最小声压约1 Pa。     

约束阻尼板结构模态实验及阻尼特性研究

约束阻尼结构可在较宽的频带范围内抑制结构的振动,已在机械和交通等领域广泛应用。本文采用多输入多输出（MIMO）的锤击法,对一种约束阻尼板进行模态实验,参数识别得到其固有频率、振型及模态阻尼。通过模态实验和有限元结果的相互对比,验证了模态测试结果的可靠性。在此基础上,对敷设粘弹性阻尼的悬臂板结构进行了阻尼特性的研究,讨论了材料参数和结构参数对模态阻尼的影响,为结构的减振降噪及优化设计提供依据。     

基于调制FFT的谐振式SAW传感器快速频率估计算法

针对高动态环境下的谐振式声表面波（Surface Acoustic Wave,SAW）传感器快速精确频率估计,提出一种基于调制快速傅里叶变换（Fast Fourier Transform,FFT）的谐振式SAW传感器快速频率估计算法。对单次谐振式SAW传感器回波信号进行N点取样后进行调制FFT计算,获得回波信号频谱,然后利用最大谱线的两相邻谱线取代I_Rife算法频谱细化后的谱线对频率偏移因子进行估计,最后使用频率偏移因子对最大频谱频率进行修正。该算法较I_Rife算法不需要判断频率修正方向,减少了3N次复数乘法和4（N-1）次复数加法运算,频率估计均方根误差的平均值减小了26%。该算法在提高精度的同时,实现了对谐振式SAW传感器的快速频率估计。     

双腔负压法用于激波管动态压力校准

针对激波管中使用双腔负压法以获取微小阶跃压力进行了研究。使用北京长城计量测试技术研究所的100 mm激波管以及专门设计的附加装置,对绝压与微压传感器进行了校准实验,实验数据表明在激波管上使用双腔负压法与薄纸膜片能获得小于2 kPa的微小反射激波阶跃压力,上升时间与平台持续时间等各项指标也都符合国家检定规程的要求,扩展了现有激波管的技术能力。比较了不同静态压力和动态幅值情况下压力传感器激波管校准结果,谐振频率和阻尼比系数都随压力增大而增大,这在实际校准和使用中是一个值得注意的问题。     

压差型矢量传感器的方位估计性能

压差型矢量传感器具有结构简单、抗机械运动扰动性能强等优点,便于制作成浮标使用。提出了通用的矢量传感器整机测试的方位校准方法,在近似各向同性噪声场中验证了压差型矢量传感器声压、振速分量的独立性。海试浮标的拉距实验表明,压差型矢量传感器的方位估计精度达不到克拉美罗界（CRB）,实测精度大致比理论值降低3倍。     

Scanning infrared radiometer for measuring the air-sea temperature difference

We describe a vertically scanning infrared radiometer for measuring the air-sea temperature difference without disturbing the water skin layer. The radiometer operates with a single wavelength channel that is 1.1 mum wide, centered on 14.2 mum, on the short-wavelength edge of a CO(2) atmospheric absorption band. The resulting high atmospheric absorption enables calibration of the horizontal-viewing signal with an in situ air-temperature sensor. The signal at all other scan angles is measured relative to that at the horizontal, providing a differential air-sea temperature measurement that is nearly independent of calibration offsets that can be a problem with independent air- and water-temperature sensors. We show data measured on a ship in the Tropical Western Pacific Ocean during July 1999, which exhibit important discrepancies from in situ data using bulk air-and water-temperature sensors. These discrepancies illustrate important differences between bulk versus skin water temperature.     

Multiscale Hierarchical Design of a Flexible Piezoresistive Pressure Sensor with High Sensitivity and Wide Linearity Range

Flexible piezoresistive pressure sensors have been attracting wide attention for applications in health monitoring and human‐machine interfaces because of their simple device structure and easy‐readout signals. For practical applications, flexible pressure sensors with both high sensitivity and wide linearity range are highly desirable. Herein, a simple and low‐cost method for the fabrication of a flexible piezoresistive pressure sensor with a hierarchical structure over large areas is presented. The piezoresistive pressure sensor consists of arrays of microscale papillae with nanoscale roughness produced by replicating the lotus leaf's surface and spray‐coating of graphene ink. Finite element analysis (FEA) shows that the hierarchical structure governs the deformation behavior and pressure distribution at the contact interface, leading to a quick and steady increase in contact area with loads. As a result, the piezoresistive pressure sensor demonstrates a high sensitivity of 1.2 kPa⁻¹ and a wide linearity range from 0 to 25 kPa. The flexible pressure sensor is applied for sensitive monitoring of small vibrations, including wrist pulse and acoustic waves. Moreover, a piezoresistive pressure sensor array is fabricated for mapping the spatial distribution of pressure. These results highlight the potential applications of the flexible piezoresistive pressure sensor for health monitoring and electronic skin.     

Self-powered pressure sensor for ultra-wide range pressure detection

The next generation of sensors should be self-powered,maintenance-free,precise,and have wide-ranging sensing abilities.Despite extensive research and development in the field of pressure sensors,the sensitivity of most pressure sensors declines significantly at higher pressures,such that they are not able to detect a wide range of pressures with a uniformly high sensitivity.In this work,we demonstrate a single-electrode triboelectric pressure sensor,which can detect a wide range of pressures from 0.05 to 600 kPa with a high degree of sensitivity across the entire range by utilizing the synergistic effects of the piezoelectric polarization and triboelectric surface charges of self-polarized polyvinyldifluoride-trifluoroethylene (P(VDF-TrFE)) sponge.Taking into account both this wide pressure range and the sensitivity,this device exhibits the best performance relative to that of previously reported self-powered pressure sensors.This achievement facilitates wide-range pressure detection for a broad spectrum of applications,ranging from simple human touch,sensor networks,smart robotics,and sports applications,thus paving the way forward for the realization of next-generation sensing devices.Moreover,this work addresses the critical issue of saturation pressure in triboelectric nanogenerators and provides insights into the role of the surface charge on a piezoelectric polymer when used in a triboelectric nanogenerator.     

磁流变弹性体压缩模式动态力学性能测试

磁流变弹性体是一种新型的磁流变材料,已被成功地应用于变刚度器件设计中。为了评价磁流变弹性体材料性能,迫切需要建立一套磁流变弹性体性能测试系统。利用电磁振动台的线性扫频功能,采用激光位移传感器同步获取测试系统在不同磁感应强度下测试系统的激励与响应信号,通过系统的运动力学模型和相关理论计算,实现压缩模式下的磁流变弹性体刚度与阻尼性能的测试。该测试系统的建立为研制高性能的磁流变弹性体提供了动态压缩模式下的评价手段。     

Piezoelectric Vibration-Type Tactile Sensor Using Elasticity and Viscosity Change of Structure

We propose a new tactile sensor utilizing piezoelectric vibration. This tactile sensor has a high sensitivity, wide measurement range, pressure resistance, flexibility, and self-sensing function. This tactile sensor comprises two piezoelectric materials. One is used for the vibration of the sensor element and the other is used for the measurement of the change in mechanical impedance induced by an external force. We achieved the wide measurement range by implementing two ideas. One was to apply the external force to the sensor element through an elastic body and the other was to use two or more modes of vibration. Moreover, for the elastic body, it is preferable to use a material whose elasticity and viscosity are easily changed by an external force, such as a gel. In this study, first, this tactile sensor was analyzed, and then its characteristics were derived. The analytical results qualitatively corresponded to the experimental results. Next, a prototype tactile sensor was fabricated and evaluated. The evaluation results showed that this tactile sensor can measure a pressure of 2.5 Pa or less and a pressure of 10 kPa or more and its pressure resistance is 1 MPa or more.     

Parallel Signal Processing of a Wireless Pressure-Sensing Platform Combined with Machine-Learning-Based Cognition,Inspired by the Human Somatosensory System

Inspired by the human somatosensory system, pressure applied to multiple pressure sensors is received in parallel and combined into a representative signal pattern, which is subsequently processed using machine learning. The pressure signals are combined using a wireless system, where each sensor is assigned a specific resonant frequency on the reflection coefficient (S₁₁) spectrum, and the applied pressure changes the magnitude of the S₁₁ pole with minimal frequency shift. This allows the differentiation and identification of the pressure applied to each sensor. The pressure sensor consists of polypyrrole-coated microstructured poly(dimethylsiloxane) placed on top of electrodes, operating as a capacitive sensor. The high dielectric constant of polypyrrole enables relatively high pressure-sensing performance. The coils are vertically stacked to enable the reader to receive the signals from all of the sensors simultaneously at a single location, analogous to the junction between neighboring primary neurons to a secondary neuron. Here, the stacking order is important to minimize the interference between the coils. Furthermore, convolutional neural network (CNN)-based machine learning is utilized to predict the applied pressure of each sensor from unforeseen S₁₁ spectra. With increasing training, the prediction accuracy improves (with mean squared error of 0.12), analogous to humans' cognitive learning ability.     

Complementary metal oxide semiconductor cantilever arrays on a single chip: mass-sensitive detection of volatile organic compounds

The sensing behavior of polymer-coated resonant cantilevers for mass-sensitive detection of volatile organic compounds was investigated. Industrial complementary metal oxide semiconductor (CMOS) technology combined with subsequent CMOS-compatible micromachining was used to fabricate a single-chip system comprising the transducers and all necessary driving and signal-conditioning circuitry. An analytical model was developed to describe the mass-sensing mechanism of polymer-coated resonant cantilevers. The model was validated by measurements of various gaseous analytes. As an exemplary application, the quantitative analysis of a binary mixture using an array of four cantilevers is described. Experimental results are given for the concentration prediction of a mixture of n-octane and toluene. Finally, it was established that the limit of detection achieved with cantilever sensors is comparable to that of other acoustic wave-based gas sensors.     

新型力平衡微机械真空传感器研究

力平衡微机械真空传感器采用 ｐ＋＋硅自停止腐蚀技术和硅／玻璃键合技术制作,为了保持参考腔处在高真空状态,使用非蒸散吸气剂来吸附参考腔中的残余气体。研制了两种结构新型力平衡真空传感器,结果表明,采用力平衡模式工作可以扩展传感器的动态范围,灵敏度高。对力平衡电压与真空度的关系进行了研究,理论值与实测值符合得非常好。     

Spectral shift of damped harmonic vibrations and methods for compensation

Resonators, especially quartz devices, can be used as remote sensors. The signal they produce as pulse response consists of a damped harmonic vibration where the natural frequency contains the information about the measured quantity. Under the viewpoint of noise and interference the most efficient evaluation of the signal can be carried out in the frequency domain. For an undamped vibration the spectrum has a peak at the actual natural frequency. The problem is that the maximum of the spectrum of a damped vibration depends on uncertain parameters: damping and phase shift. In this paper several methods are discussed with which this effect can be eliminated, so that the natural frequency may be determined regardless of these parameters. Copyright © 1999 John Wiley & Sons, Ltd.