Design,fabrication and characterization of micro flow sensor inspired by biological hair cell

Design, fabrication and characterization of micro flow sensor were investigated based on the inspiration of biological hair cell in a nature. The micro scale artificial hair cell sensor was designed as considering two parts; first the high aspect ratio cilium structure which works as a hair cell of fish and second the mechanoreceptor structure where the drag force by flow are actually measured. Parameters of cilium structure were designed based on static modelling as follow: 300 μm diameter and 2 mm height. The high aspect ratio cilium structure was precisely fabricated using a hot embossing process with the developed separated micro mold system prepared by LIGA (from the German Lithographi, Galvanoformung, Abformung) process. The mechanoreceptor was formulated with a force sensitive resistor with four symmetric electrodes to analyze the direction and the magnitude of target flow. Performance of assembled sensor was characterized using the prepared water channel. Flow velocity was sensed with the magnitude of signal and the direction of flow was distinguished by analyzing the signals from four mechanoreceptors.     

A silicon resonant sensor structure for Coriolis mass-flowmeasurements

We present the first mass-flow sensor in silicon, based on the Coriolis-force principle. The sensor consists of a double-loop tube resonator structure with a size of only 9×18×1 mm. The tube structure is excited electrostatically into a resonance-bending or torsion vibration mode. A liquid mass flow passing through the tube induces a Coriolis force, resulting in a twisting angular motion phase shifted and perpendicular to the excitation. The excitation and Coriolis-induced angular motion are detected optically. The amplitude of the induced angular motion is linearly proportional to the mass flow and, thus, a measure thereof. The sensor can be used for measurement of fluid density since the resonance frequency of the sensor is a function of the fluid density. The measurements show the device to be a true mass-flow sensor with direction sensitivity and high linearity in the investigated flow range of as low as 0-0.5 g/s in either direction. A sensitivity of 2.95 (mV/V)/(g/s) and standard deviation for the measured values of 0.012 mV/V are demonstrated     

A wireless powered fully integrated SU-8-based implantable LC transponder

In this work, we report a SU-8-based fully integrated miniaturized inductively powered LC transponder for generic implantable wireless sensor applications. It consists of a 1 mm diameter octagonal spiral inductor and a micro fabricated MIM (metal insulator metal) capacitor. Polyvinylidene Fluoride–Trifluoroethylene (PVDF–TrFE) copolymer is applied as a dielectric material for the capacitor fabrication due to its high dielectric constant. The 1 mm diameter, 154 nH spiral inductor is built on top of the capacitor. The capacitor and the inductor are in parallel connection through SU-8 via holes. SU-8 is used as a packaging material due to its biocompatibility, and also it serves as an insulator between the capacitor and the spiral inductor. The operating frequencies of the LC tanks are decided by the sizes of the capacitors (45 × 45, 55 × 55, 95 × 95 and 100 × 100 μm), and measured operating frequency range is from 385 to 485 MHz. The fabricated LC tanks are held to the power transmitting coil coaxially at distances of 2, 5, 7 and 10 mm, and rectified induced voltage at the LC tank is 8.5 V with 29 dBm input power at a 5 mm distance.     

A micro PDMS flow sensor based on time-of-flight measurement for conductive liquid

Transdermal extraction of interstitial fluid (ISF) offers an attractive method for non-invasive blood glucose monitoring. In order to calculate blood glucose concentration accurately, precise volume measurement of transdermally extracted ISF is required due to human skin’s varying permeability. In this paper, we presented a novel flow sensor fabricated from polydimethylsiloxane (PDMS), designed to measure the volume of conductive liquid. The flow sensor consists of two pairs of metal electrodes, which are fabricated in the PDMS channel. The volume of liquid is measured utilizing the time-of-flight of the two electrode pairs’ resistance while the liquid is flowing through the flow sensor. 1–14 μL normal saline solution was measured, the flow sensor measured volumes correlate very well (R ² = 0.9996 and R ² = 0.9975 for vacuum pump and syringe pump situations respectively) with the actual volumes. And the coefficient of variation for 10 times 10 μL normal saline solution measurement is 0.0077 (vacuum pump) and 0.0381 (syringe pump), respectively. The demonstrated flow sensor provides excellent functionality for conductive liquid.     

Improved micro fluxgate sensor with double-layer Fe-based amorphous core

A rapid manufacturing process for the micro solenoid fluxgate sensor integrating multilayer amorphous ribbon core has been established, which combines the micro assembling method and the MEMS technologies. We select Fe-based amorphous soft magnetic ribbons for core materials and have fabricated the micro fluxgate sensors by MEMS technologies, with single-layer core and double-layer core respectively. The micro fluxgate sensors with double-layer core show the advantageous to that with single-layer core and exhibit sensitivity of 1089.2 V/T at excitation current of 120 mA rms, wide linear range of ?900 to 900 μT and power consumption of 24.48 mW. The noise power density of the single core fluxgate sensor is 2.48nT/Hz^1/2@1 Hz.     

Safety-monitoring-type wide-range detectable contact sensor system using ultrasonic waves and viscoelastic tubing

In physical human–robot interaction, a contact sensor is fundamentally required for robots to sense contact with humans and to take appropriate safety measures. This paper proposes a wide-range detectable contact sensor system with a safety monitoring function that uses an ultrasonic wave and a silicone rubber tube. The appropriate threshold voltage for generating a monitoring pulse signal is calculated using the estimation equation derived on the basis of the propagation characteristics of ultrasonic waves in straight and curved tubes. By comparing the periodic time between the generated monitoring signals and self-diagnostic signals, the proposed contact detection algorithm detects both contact due to tube deformation and failure of a sensor system including a stack fault. An experiment investigating the relationship between tube deformation by pushing force and the loss of peak voltage of an ultrasonic wave reveals that the sensor system can detect contact when the tube is deformed by 8 mm.     

A printed circuit board capacitive sensor for air bubble inside fluidic flow detection

This paper presents a three-electrode capacitive fluidic sensor for detecting an air bubble inside a fluidic channel such as blood vessels, oil or medical liquid channels. The capacitor is designed and fabricated based on a printed circuit board (PCB). The electrodes are fabricated by using copper via structure through top to bottom surface of the PCB. A plastic pipe is layout through the capacitive sensor and perpendicular to the PCB surface. Capacitance of sensor changes when an air bubble inside fluidic flow cross the sensor. The capacitance change can be monitored by using a differential capacitive amplifier, a lock-in amplifier, filter and an NI acquisition card. Signal is processed and calculated on a computer. Air bubble inside the liquid flow are detected by monitor the unbalance signal between the three electrode potential voltages. Output voltage depends on the volume of the air bubble due to dielectric change between capacitor’s electrodes. Output voltage is up to 53 mV when an 2.28 mm³ air bubble crosses the sensing channel. Air bubble velocity can be estimated based on the output pulse signal. This proposed fluidic sensor can be used for void fraction detection in medical devices and systems; fluidic characterization; and water–gas, oil–water and oil–water–gas multiphase flows in petroleum technology. That structure also can apply to the micro-size for detecting in microfluidic to monitor and control changes in microfluidic channels.     

Design and analysis of a z-axis tuning fork gyroscope with guided-mechanical coupling

This paper presents design and analysis of a z-axis tuning fork gyroscope. The sensor is designed to reduce noises and improve the sensitivity by using a drive coupling spring in the lozenge shape. The in-phase sensing mode is suppressed by using a self-rotation ring. The designed sensor prioritizes anti-phase driving and sensing modes. The frequencies of anti-phase driving and sensing modes are far from those of parasitic ones. The design also enables the sensing mode to decouple from the driving one, which is considered to decrease vibration-induced error. The proposed sensor structure is analyzed by finite element method. The simulated frequencies of the driving and sensing modes are 9.9 and 10.0 kHz, respectively, which show the bandwidth of sensor of 100 Hz. The frequency difference between the driving and sensing modes and the parasitic ones is obtained to be 50 %. The optimized gap between electrodes leads to the determination of the number of the sensing capacitor fingers and consequently the suitable dimension parameters of the whole device. The sensor performance in the time domain and the frequency domain having the transient response to a given rotation rate is also simulated showing the linear dependence of capacitance change on angular velocity. As a result, the sensitivity of the sensor is evaluated to be 11 fF/°/s.     

Two-axis micro fluxgate sensor on single chip

We present a two-axis micro fluxgate sensor on single chip for electronic compassing function. To measure X- and Y-axis magnetic fields, functional two fluxgate sensors were perpendicularly aligned and connected each other. The fluxgate sensor was composed of square-ring shaped magnetic core and solenoid excitation and pick-up coils. The solenoid coils and magnetic core were separated by benzocyclobutane which had high insulation and good planarization characters. Copper coil patterns of 10 μm width and 6 μm thickness were electroplated on Ti (300 Å)/Cu (1,500 Å) seed layers. 3 μm thick Ni_0.8Fe_0.2 (permalloy) film for the magnetic core was also electroplated under 2,000 gauss. Excellent linear response over the range of ?100 μT to +100 μT was obtained with the sensitivity of ～280 V/T. Actual chip size was 3.1×3.1 mm². The sine and cosine signals of two-axis fluxgate sensor had a good function of azimuth compass.     

Fabrication of micro-capacitive inclination sensor by resin molding

Capacitive inclination sensors have the advantage that they can easily provide a linear analog output with respect to inclination. Although inclination sensors featuring this advantages are already commercially available, they are generally too large. We fabricated a micro-capacitive inclination sensor by a combination of a resin forming method and a mold. Electrodes of the sensor are 40 μm in a gap and 12 mm² in area. The sensor detects difference of capacitance, which varies with movement of silicone oil accompanying with inclination of the sensor. Since the dimensions of the sensing region are 5 × 5 × 3 mm³ this inclination sensor is expected to be widely used in fields where efficient and reliable position control is a primary factor to be considered. The use of resins is also expected to contribute to a reduction in the costs of materials. We successfully fabricated a micro inclination sensor as a molded product. In future, we will wire up the device to complete this inclination sensor, and will then conduct performance evaluations. If techniques using resin-molded parts are introduced to the low-cost mass-production of Micro Electro Mechanical Systems devices, the range of applications will further expand to new areas of technology and industry.     

A dual-axis MEMS capacitive inertial sensor with high-density proof mass

This paper reports a novel dual-axis microelectromechanical systems (MEMS) capacitive inertial sensor that utilizes multi-layered electroplated gold. All the MEMS structures are made by gold electroplating that is used as a post complementary metal-oxide semiconductor (CMOS) process. Due to the high density of gold, the Brownian noise on the proof mass becomes lower than those made of other materials such as silicon in the same size. The single gold proof mass works as a dual-axis sensing electrode by utilizing both out-of-plane (Z axis) and in-plane (X axis) motions; the proof mass has been designed to be 660 μm × 660 μm in area with the thickness of 12 μm, and the actual Brownian noise in the proof mass has been measured to be 1.2 \({\upmu}{\text{G/}}\sqrt {\text{Hz}}\) (in Z axis) and 0.29 \({\upmu}{\text{G/}}\sqrt {\text{Hz}}\) (in X axis) at room temperature, where 1 G = 9.8 m/s². The miniaturized dual-axis MEMS accelerometer can be implemented in integrated CMOS-MEMS accelerometers to detect a broad range of acceleration with sub-1G resolution on a single sensor chip.     

Silicon cantilevers with piezo-resistive measuring bridge for tactile line measurement

In this article a variety of applications of a microelectromechanical system (MEMS) including a cantilever with an integrated piezo-resistive bridge is described. With the low-noise integrated piezo-resistive bridge a resolution in the nanometer range is possible. This sensor obtains a typical resolution in the vertical displacement of 2 nm (due to noise floor Δf = 1.6 kHz). Due to the low spring constant of D = 1 to 10 N/m, measurements with contact forces of <100 μN can be realized. This allows a non-destructive examination of polymer structures. Furthermore, the sensor is characterized by a high eigenfrequency (>2.7 kHz), a slight mass (≈0.1 mg) and a measuring velocity of up to 10 mm/s. The important applications of the MEMS cantilever are fast inline control of building panels, measurement of optical structures, inside measurement of fuel injection nozzle micro holes. Furthermore, it is possible to provide different tip geometries (e.g. cone or ball) at the end of the cantilever for an ideal surface measurement.     

超声波式预警器的研制

在超声波预警器的研制中,选用双角度超声波传感器并在其前端加套筒。传感器阵列的激励采用循环扫描调制触发信号,其接收信号经过AGC放大、鉴频等处理,在-75°～75°视角、1.5～10.5m空间范围内,这种预警器对人体闯入能够进行准确、可靠报警。     

Catheter sensor system for in-situ breathing and optical imaging measurements at airway in inside of lung

A catheter sensor system composed of a tube flow sensor with a medical basket forceps and an optical fiberscope was systemized for in-situ measurements in the airway in the lung system. The tube flow sensor was produced by assembling the sensor film containing two heaters onto the tube surface, and the basket forceps was installed into the inside space of the tube sensor. The assembled tube flow sensor with the basket forceps was inserted into the tube and was fixed at the center of the tube by expanding the basket. The flow detection characteristics of the tube flow sensor were experimentally evaluated. A calibration equation based on King’s law was derived from the sensor output vs. flow velocity curve, and a sufficiently short response time of 60 ms was obtained for the breathing measurements in a rabbit and a person. Finally, the tube flow sensor with the basket forceps and the optical fiberscope was systemized into a single tube with the diameter of 5.0 mm for in-situ measurements in the airway. The developed system successfully detected both a breathing airflow waveform and an optical image inside the airway in the rabbit.

     

Analysis and experiment of transient filling flow into a rectangular microchannel on a rotating disk

In order to predict the time-dependent behaviors of the moving front in lab-on-a-CD systems or centrifugal pumping, an analytical expression and experimental methods of centrifugal-force-driven transient filling flow into a rectangular microchannel in centrifugal microfluidics are presented in this paper. Considering the effect of surface tension, and neglecting the effect of Coriolis force, the velocity profile, flow rate, the moving front displacement and the pressure distribution along the microchannel are characterized. Experiments are carried out using the image-capturing unit to measure the shift of the flow in rectangular microchannels. The flow characteristics in rectangular microchannels with different cross-sectional dimensions (200, 300 and 400 μm in width and 140, 240 and 300 μm in depth) and length (18 and 25 mm) under different rotational speed are investigated. According to the experimental data, the model can be more reasonable to predict the flow displacement with time, and the errors between theoretical and the experimental will decrease with increasing the cross-section size of the microchannel.     

Microfabrication of thin film temperature sensor for cryogenic measurement

In this paper, thin film Pt temperature microsensor in the temperature range of 10–100 K for cryogenic engineering applications is proposed and researched. The sensor is designed with two structures, and they are obtained by micro fabrication technology. The sensors are annealed in different conditions. The degree crystallization and grain size are analyzed by X-ray diffraction and SEM for both as-deposited and annealed sensors. The resistance dependency on temperature test result shows that when temperature is larger and smaller than 50 K, the average temperature coefficient resistance (TCR) of rectangular shape sensor could achieve 3,118 ppm/K and above 257 ppm/K, respectively. Meanwhile, TCR of circular shape sensor is 2,778 ppm/K and above 249 ppm/K, respectively. The good thermal cycle stability is observed. After three cycles between 10 and 100 K, the maximum resistance variation values are 0.0034 and 0.0137 %, which correspond to 0.0082 and 0.061 K temperature shift for the rectangular and circular sensors, respectively. The ΔT/T (%) of rectangular and circular sensors is performed with the magnetic field up to 6T in the temperature range of 10–100 K, and they are within the range of ?19.84 to 0.137 and ?2.18 to 11.33 for rectangular and circular sensors,respectively. The impedance test shows that the sensors have the same electric properties under direct current and alternating current condition.     

High aspect ratio metal micro and nano pillars for minimal footprint MEMS suspension

Vertical nano and micro pillars perpendicularly rising from a substrate offer two lateral translatory–rotatory degrees of freedom. Electroforming allows their production as small footprint integrated suspension elements of micro to nano scale. This paper demonstrates the design of a novel inertial sensor concept with acceleration sensor and gyroscope function using only one inertial mass. Experimental results using UV Direct LIGA with AZ 125 nXT show the feasibility of a technology demonstrator with a copper micro pillar of 400 μm length and 40 μm diameter. Further work using x-ray Direct LIGA is scheduled for the production of the pillar with a length of 100 μm and a diameter of 3–6 μm. Fabrication concepts and pilot tests show promising possibilities for miniaturization towards nano scale pillars for minimal footprint suspension in MEMS.     

集成微流体测控芯片的研制

设计、研制了集成有微泵、微沟道、微流量传感器、温度传感器的微流体测控芯片.采用有限元软件ANSYS模拟分析了将其作为冷却芯片时微沟道的散热作用,分析确定了芯片上各元件的结构.该集成芯片为硅-玻璃结构,在硅片上,利用ICP法刻蚀无阀微泵泵体和微沟道;在7740玻璃片上,以溅射、剥离法制作微流量和温度传感器;图形精确对准后硅/玻璃以静电键合方法封接.无阀微泵采用压电元件驱动.测试结果表明:集成芯片具有冷却功能,循环水的流速最大可达25.4mm/s.     

用于油库安全监测的气体传感器研究与设计

研究并设计了一种用于油库安全监测的气体传感器.传感器中气体敏感元件是利用直流磁控溅射法制备的Al掺杂ZnO薄膜.此薄膜对汽油等有机蒸汽有较高的敏感性和较短的响应(恢复)时间.当油气浓度较大时(大于1%),输出信号的变化仍较大.本传感器采用MAX197芯片,可以同时采集多个气敏元件的模拟信号并进行12位高精度A/D转换,利用无线收发模块F05C、J04E进行数据的无线传输.传感器拥有ACM12864液晶显示模块,方便数据显示.     

Distributed duty cycle control for delay improvement in wireless sensor networks

Dynamically adjusting the time duration of a node to stay active in one data collection period, i.e., duty cycle, is an efficient strategy to save energy and prolong the lifetime of network. In this paper, we propose a novel Adaptation Duty Cycle Control (ADCC) scheme based on feedback signals for wireless sensor networks (WSNs) which can reduce to-sink data transmission delay while lifetime is also improved. In ADCC, every node adaptively adjusts its duty cycle by comparing its own energy consumption with the largest energy consumption of the entire packet delivery flow, which is stored in a feedback ACK packet generated by sink node. Since in WSNs, a huge number of sensor nodes in the area far from the sink node have much remaining energy when network dies, even up to 90 %, these nodes have much larger duty cycles in ADCC compared with previous schemes, therefore the data transmission delay can be reduced to a great extent. Additionally, ADCC provides a largest-energy notification mechanism in order to determine the appropriate duty cycle of nodes in each data collection flow according to the application-dependent requirements. Comparing with the Wake on Idle, Dual-QCon and the Same Duty Cycle (SDC) schemes, ADCC can reduce the delay by more than 59.5 % under the same network lifetime, or increase the lifetime by 32.8 %–63.4 % under the same delay requirements, while also increase energy efficiency as much as 43.1 %.