Mechanical and dynamic characteristics of double and single beam cantilevers for MEMS manipulation

Micro and millimeter-scaled cantilever beams are commonly used to apply and measure microforce and manipulate micro-objects, biological cells, and tissues. In manipulating micro-objects and actuating micro-devices by cantilever beams, sudden application and release of forces are typical, and subject to static and dynamic modes of operation. Therefore, the cantilever’s mechanical behavior and vibration characteristics are vital since they are also used in force sensors and probes. The dynamic behavior of the double beam cantilever (DBC) in micro and millimeter-scaled is explored by varying the length without changing the stiffness and compared with the single beam cantilever (SBC). The dynamic attributes such as mode shape, natural frequency, resonance, and response under the impulse force and Coulomb friction are evaluated numerically. This study will assist in selecting the appropriate type and length of cantilevers in micro and millimeter-scale to manipulate micro-objects, biological cells and tissues, and use in MEMS sensors.

     

The prediction of the impedance of the thorax to defibrillating current.

In this paper a technique for predicting thoracic impedance to defibrillator pulses is described. The impedance to low-current (1.0 mA) high-frequency (10-500kHz) sinusoidal current is used as an indicator of the impedance of the thorax to high-current, damped sinusoidal waveform pulses. Results from 71 dogs to which defibrillator shocks of 4 to 220 A peak current were applied show that thoracic impedance can be predicted by this method. This information indicates that it is possible to design a defibrillator that can automatically measure chest impedance prior to a defibrillation shock and deliver a predetermined peak current to the subject.     

Fast on-wafer electrical, mechanical, and electromechanical characterization of piezoresistive cantilever force sensors

Validation of a technological process requires an intensive characterization of the performance of the resulting devices, circuits, or systems. The technology for the fabrication of micro and nanoelectromechanical systems (MEMS and NEMS) is evolving rapidly, with new kind of device concepts for applications like sensing or harvesting are being proposed and demonstrated. However, the characterization tools and methods for these new devices are still not fully developed. Here, we present an on-wafer, highly precise, and rapid characterization method to measure the mechanical, electrical, and electromechanical properties of piezoresistive cantilevers. The setup is based on a combination of probe-card and atomic force microscopy technology, it allows accessing many devices across a wafer and it can be applied to a broad range of MEMS and NEMS. Using this setup we have characterized the performance of multiple submicron thick piezoresistive cantilever force sensors. For the best design we have obtained a force sensitivity Re(F) = 158μV/nN, a noise of 5.8 μV (1 Hz-1 kHz) and a minimum detectable force of 37 pN with a relative standard deviation of σ(r) ≈ 8%. This small value of σ(r), together with a high fabrication yield >95%, validates our fabrication technology. These devices are intended to be used as bio-molecular detectors for the measurement of intermolecular forces between ligand and receptor molecule pairs.     

A Digital Gate for Isolating the First and Second Waveforms in Cyclic Voltammetry

ABSTRACT

A circuit for gating the first one or two voltage waveforms passed to an electrochemical cell was designed, built, and tested. The device is independent of the voltage program stage and the potential or current control unit. Signals up to 1 kHz in frequency may be gated to the control amplifier stage and recording device. The voltage waveform can be initiated at any desired potential and in either the positive or negative direction. The response time of the switch is limited only by that of the mechanical relay used. Increased frequency response may easily be realized by replacing the mechanical relay with a FET controlled follower gate. The impedance of the device is essentially nil (0.150 ω) and it can gate any periodic or aperiodic voltage program up to 20 V peak-to-peak. The output current capacity is limited by the relay specifications; the current limit of the device described is 300 mA.     

A sensing and actuating transducer for measuring point impedance to moment

In dynamic testing of structures, rotational frequency response functions have been less utilized than its linear counterparts because no suitable moment generators and sensors for measuring moments and rotational motions are available. In this paper, a method and a new transducer for measuring point rotational impedance of structure is reported. The transducer contains two PZT bimorph cantilevers symmetrically attached to a solid base which is affixed to the measuring point of test structure. When the bimorph cantilevers are excited to vibrate out of phase with ac power, the transducer exerts a sinusoidal moment to the structure. To let the transducer measure rotational impedance simultaneously, a transducer model called “transduction matrix” is exploited. The matrix quantitatively relates the input voltage and current and the output moment and rotational velocity. Once the matrix is identified via tests and/or numerical simulation, the mechanical impedance at the output port can be evaluated from the electrical impedance measured at the input port of the transducer. To validate, the rotational impedance at a point of a beam was detected by the transducer and calculated by a finite element model. Comparisons of the results show that the proposed transducer fulfills the aimed measurement accurately.     

Control of a hybrid active-passive vibration isolation system

Precision vibration control is a major issue in nanotechnology. In particular, nano-precision measurement systems such as Atomic force microscopes (AFM) and Scanning probe microscopes (SPM) are sensitive to ground vibrations. The amplitude of a ground vibration is typically sub-micrometer and ground vibrations adversely affect both the precision and accuracy of these measuring equipment. Consequently, hybrid active-passive vibration isolation systems are typically used as they reduce ground vibrations. This paper presents a hybrid vibration isolation system composed of four spiral metal springs for passive isolation and eight voice coil motors for active isolation. H-infinite and Proportional–integral–derivative (PID) controllers are applied to its 6-DOF vibration control system using six velocity sensors to measure system vibrations. The transmissibility of the presented hybrid isolation system is in the range -10 to -48 dB at its passive resonance frequency and is at least -4 dB better than hybrid isolation systems employing acceleration sensors. The results of various tests conducted to verify the control performance of the developed system with a separately developed shaker indicate that it can serve as a bench-top device for precision measurement machines.     

Note: Piezoelectric strain voltage sensing at ultra-low frequencies

Piezoelectric sensors have emerged as a versatile tool for measurement of various quantities such as pressure, acceleration, strain, or force across many industrial applications. When mechanically strained, electric charges are produced inside a piezoelectric transducer. These charges result in an electric field that may be measured as a voltage difference between two electrodes, from which the strain can be inferred. To measure this voltage the sensor must be interfaced with an external device that would typically have a finite input impedance. This, together with the capacitive nature of the piezoelectric sensor, results in an inability to measure strain at low frequencies. We propose a method, based on using a varactor diode in an oscillator circuit, which can result in accurate measurements of the piezoelectric voltage at ultra-low frequencies. We demonstrate successful measurements at 1 mHz.     

温湿度传感器检定装置对比实验与分析

合理选取HMP45D温湿度传感器的检定装置对提高校准质量、节约校准成本具有重要意义。文中基于本单位现有的4台温湿度检定装置,通过大量的对比实验,分析了不同装置对HMP45D温湿度传感器校准质量的差异。结果表明：恒湿盐湿度发生器和DJM10型湿度检定箱具有较高的性价比,适合作为HMP45D温湿度传感器的检定装置。具体来说,恒湿盐湿度发生器适合HMP45D温湿度传感器的现场校准工作,而湿度检定箱更适合完成室内校准任务。     

A hardware-and-software package for multichannel studies of sound transmission in the human respiratory system

A setup for multichannel studies of sound vibration transmission in the human respiratory system is described. Accelerometers are used as sensors for recording signals on the surface of the chest. The setup records signals from 14 acoustic sensors. The studied frequency range is 80–1000 Hz. A program for visualizing signals, recorded on the chest surface, is designed. The setup is intended to record both natural respiratory sounds and artificial sounding signals transmitted to the chest surface. The advantage of the setup is the use of widespread universal devices.     

石英晶体自动调频设备的研发

研制了一种机电设备,涉及电子装置常用的音叉式石英晶片的机械加工技术领域,是一种利用砂轮对石英晶片的频率和阻抗进行自动调整的装置。该设备包括振动盘送料机构,机械手回转机构,砂轮磨削机构和测试分料机构,再辅以电气控制,形成了整个机械加工自动化控制系统。该装置不仅加工精度高,而且自动化程度高,提高了生产效率,使用效果好,取得了良好的社会经济效益。     

Transducer for mechanical impedance testing over a wide frequency range through active feedback

We describe a feedback-controlled active mechanical probe which can achieve a very low mechanical impedance, uniformly over a wide frequency range. The feedback produces a state of quasi-resonance which transforms the probe into a source of force used to excite an unknown load, resulting in a precise measurement of the real and imaginary components of the load impedance at any frequency. The instrument is applied to the determination of the mechanical impedance of a fingertip.     

Single HeLa and MCF-7 cell measurement using minimized impedance spectroscopy and microfluidic device

This study presents an impedance measurement system for single-cell capture and measurement. The microwell structure which utilizes nDEP force is used to single-cell capture and a minimized impedance spectroscopy which includes a power supply chip, an impedance measurement chip and a USB microcontroller chip is used to single-cell impedance measurement. To improve the measurement accuracy of the proposed system, Biquadratic fitting is used in this study. The measurement accuracy and reliability of the proposed system are compared to those of a conventional precision impedance analyzer. Moreover, a stable material, latex beads, is used to study the impedance measurement using the minimized impedance spectroscopy with cell-trapping device. Finally, the proposed system is used to measure the impedance of HeLa cells and MCF-7 cells. The impedance of single HeLa cells decreased from 9.55 × 10(3) to 3.36 × 10(3) Ω and the impedance of single MCF-7 cells decreased from 3.48 × 10(3) to 1.45 × 10(3) Ω at an operate voltage of 0.5 V when the excitation frequency was increased from 11 to 101 kHz. The results demonstrate that the proposed impedance measurement system successfully distinguishes HeLa cells and MCF-7 cells.     

Complex impedance measurements of calorimeters and bolometers: correction for stray impedances

Impedance measurements provide a useful probe of the physics of bolometers and calorimeters. We describe a method for measuring the complex impedance of these devices. In previous work, stray impedances and readout electronics of the measurement apparatus have resulted in artifacts in the impedance data. The technique allows experimenters to find an independent Thevenin or Norton equivalent circuit for each frequency. This method allows experimenters to easily isolate the device impedance from the effects of parasitic impedances and frequency dependent gains in amplifiers.     

A new impedance force control of a haptic teleoperation system for improved transparency

In this study, a new impedance force control model of a haptic device for teleoperation is developed and analyzed. A new contact force model for the haptic device and the human hand is provided. Movements of the human hand give additional force disturbances to the force control system. Disturbance force model by haptic dynamics and hand movements is fully analyzed and included in the control system design. An adaptive control scheme is proposed to improve system transparency by achieving good force tracking performance, while simultaneously compensating human hand disturbances and sensor noises. A separate reference model for every DOF is proposed to satisfy tracking performances. Adaptive control gains cover force tracking performance and compensates for human hand disturbances while providing robustness to sensor noises.

     

基于虚拟示波器的涡流应力测量装置研制

为将涡流阻抗法应用于金属构件应力的快速测量,基于改进的矢量伏安法,采用虚拟示波器技术,研制出一套测量参数可控的便携式阻抗测量装置。实验测试了信号平均次数、电路采样电阻等对涡流传感器阻抗-频率特性曲线测量精度的影响规律,在优化参数条件下,研制的阻抗测量装置与Agilent 4294a的测试结果较为一致,相对偏差在±5%范围。将便携式装置应用于金属杆件的涡流应力测量:先后对45号钢杆和LY12铝合金直杆进行拉伸实验,测量粘贴于直杆上涡流传感器的阻抗变化,回归分析得到阻抗变化率与拉力的直线拟合方程(拟合优度大于0.9)。实验结果表明,基于虚拟示波器的阻抗测量装置可以基于涡流测力原理,实现金属构件应力的快速、有效测量。     

Ear-jack port based one-way analogue communication for smart devices

As the wide spread of smart device, smartphone and tablet PC has led to various external device developments, there is a great need for efficient communication solution between devices. In this paper, a new method for one-way analogue communication using ear jack port is proposed. For one-way analogue communication, we mixed analogue signal with audible-frequency signal and then transmitted them by ear jack port. We also calibrated both impedance and frequency characteristics of each device. To verify the efficiency of the proposed communication method, an alcohol-breathalyzer was developed and its alcohol sensor data were successfully communicated via ear jack port.     

A preview approach to force control of robot manipulators

Automated assembly operations that utilize robots tend to constrain the robot's motion due to the task geometry. This constrained motion is termed compliant motion. Complaint motion can be actively controlled using a method of force feedback based upon servo-loop compensation, or it can be passively controlled by mechanical devices integrated into the robot structure. The “preview approach” to force control presented in this paper is a scheme based on predictive calculation of the contact forces that develop at the interface between mating parts. The preview approach utilizes predicted, present and past information to execute motion control. Contact forces are calculated using a mathematical model of the assembly process and are then used to control the compliant motion through suitable compensation torques. The control algorithm used here is more efficient than the standard methods that rely on data from force sensors and use no preview.     

基于声表面波器件的无源传感器的研究

利用声表面波器件的高频压电转换特性,研究设计了一种可实现无线访问的时间延迟型无源传感器,为提高回波信号的信噪比,在ＳＡＷ器件的设计中,采用了一种并联式的新型结构以替代传统的共线式结构。利用一套射频访问系统,本文重点针对器件的力敏特性进行了实验研究。实验表明,合理地设计器件中ＩＤ－Ｔａｇ与反射栅的参数,可稳定地测出器件上ＳＡＷ的传播参数,测量结果不受器件与访问系统间距离的影响,利用这一原理,可进上步     

不同电极结构的纯横向场激励压电传感器性能研究

横向场激励(lateral-field-excitation,LFE)压电传感器因其在液相测量中的优越特性而引起广泛关注.最近的研究表明LFE器件具有纯LFE、伪LFE和准LFE 3种不同的工作模式.为了研究不同电极结构的纯LFE器件的特性,文中在相同的铌酸锂晶体基板上制作了5种不同电极结构的纯LFE压电传感器,并进行了性能测试和对比分析.结果表明:两圈对称螺旋电极结构与单gap电极结构的LFE器件比另外3个LFE器件具有更高的Q值.当传感器从空气中移到水中和从水中移到NaCl溶液中时,谐振频率均减小,而当传感器被从水中移到异丙醇溶液中时,谐振频率增大,其中双间隔电极结构的LFE压电传感器谐振频率变化幅度最大.     

A programmable resuscitator for evaluation of CPR standards

Cardiopulmonary resuscitation (CPR) is the principal means for combating death caused by cardiac arrest in the prehospital setting. Adequate evaluation of CPR standards, however, requires exacting replication of both positive pressure ventilation and cardiac compression protocols over sufficient time periods to measure effects on arterial blood gases, hemodynamics, and intrapulmonary shunting. The programmable cardiopulmonary resuscitator studied provides for such highly controlled CPR protocols. It is developed from a cardiopulmonary resuscitator that has been adapted to accommodate a universal programmable timer. The programmable cardiopulmonary resuscitator permits independent changes in rate, duration, and sequence of both positive pressure ventilation and cardiac compression. Hence, it makes possible the simulation of one-rescuer and two-rescuer CPR standards, as well as the investigation of alternative CPR techniques.