World Congress on Biosensors 2014

World Congress on Biosensors 2014
Biosensors 2014

Wednesday, 2 May 2012

Just Published: Sensors & Actuators A: Physical


A new issue of this journal has just been published. To see abstracts of the papers it contains (with links through to the full papers) click here:
Selected papers from the latest issue:

Fiber Bragg grating-tuned feedback laser flow sensor system

02 May 2012, 09:43:12
Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 179
Kyung-Rak Sohn
In this paper, a fiber Bragg grating (FBG) air flow sensor system using an all-fiber feedback laser is proposed. The operating principle of the feedback laser is based on the mode-locking mechanism between a Sagnac loop multi-grid filter and a tunable FBG <!-- no-mfc -->sing<!-- /no-mfc -->le-wavelength filter. A shift in the lasing wavelength is attributed to the change in the heat energy of the coil heater. This is because the flow sensor depends on the variations in the heat energy of the coil heater surrounding the FBG, thereby causing a shift in the Bragg wavelength owing to a thermo-optic effect. In order to investigate the spectral response as a function of the flow speed of air, a simple and cost-effective intensity-based demodulation technique using a micro-optic band-pass filter is demonstrated. The flow sensitivity of the sensor system was 0.7dB/(l/min) within a linear region.

Design and fabrication of SMS fiber refractometer for liquid

02 May 2012, 09:43:12
Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 179
R.X. Gao, W.J. Liu, Y.Y. Wang, Q. Wang, F. Zhao, S.L. Qu
Single-mode/multi-mode/single-mode (SMS) fibers are optimally designed and fabricated as high sensitivity (∼4.6×10−6) refractometer sensors for liquid. It is shown that the width of multimode fiber is a key factor in the performance of as-fabricated refractometer sensor, which can be effectively controlled in the fabrication process by monitoring the output power of SMS fiber during wet acid etching process. The experimental results match quite well with the numerical simulation results. As-fabricated refractometer sensor shows promising potential applications in precisely monitoring the refractive index of liquid in chemical and biomedical fields.

A GaAs MEMS for AFM and spin injection

02 May 2012, 09:43:12
Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 179
Steve Arscott, Emilien Peytavit, Dominique Deresmes, Thomas Dargent, Duong Vu, Alistair C.H. Rowe, Daniel Paget
We investigate the mechanical and electrical properties of tip-less, GaAs micro-cantilevers on silica supports that are fabricated using a novel assembly approach. The resulting device is compatible with an atomic force microscope (AFM) and takes advantage of the electronic and optical properties of GaAs as well as the mechanical properties of silica. Mechanically, their resonant frequency and quality factor, as well as their AFM imaging capabilities (lateral resolution ∼10–20nm), are comparable to commercial silicon cantilevers despite the absence of micromachined tip. In the same AFM-like configuration, they can also function as novel spin-polarized electron injectors under excitation by a circularly polarized laser from the rear. Surface nitridation of the cantilever and deposition of a hydrophobic thin polymer film on the sample surface are found to stabilize the injected photocurrent, making them potentially useful for a variety of fundamental and applied investigations in atmosphere.

A review of tactile sensing technologies with applications in biomedical engineering

02 May 2012, 09:43:12
Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 179
Mohsin I. Tiwana, Stephen J. Redmond, Nigel H. Lovell
Any device which senses information such as shape, texture, softness, temperature, vibration or shear and normal forces, by physical contact or touch, can be termed a tactile sensor. The importance of tactile sensor technology was recognized in the 1980s, along with a realization of the importance of computers and robotics. Despite this awareness, tactile sensors failed to be strongly adopted in industrial or consumer markets. In this paper, previous expectations of tactile sensors have been reviewed and the reasons for their failure to meet these expectations are discussed. The evolution of different tactile transduction principles, state of art designs and fabrication methods, and their pros and cons, are analyzed. From current development trends, new application areas for tactile sensors have been proposed. Literature from the last few decades has been revisited, and areas which are not appropriate for the use of tactile sensors have been identified. Similarly, the challenges that this technology needs to overcome in order to find its place in the market have been highlighted.

Biosensor platform based on stress-improved piezoelectric membrane

02 May 2012, 09:43:12
Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 179
Xu Lu, Qiushi Guo, Zhuo Xu, Wei Ren, Z.-Y. Cheng
A new design as piezoelectric membrane is introduced to improve the performance of a diaphragm based biosensor platform. In the design, stress is introduced into the diaphragm by a vacuum chamber and makes it work as membrane with a higher sensitivity and a higher Q factor. The mass sensitivity of stress-improved membrane was investigated and an effective mass approach is used to simulate the sensitivity of the device for a point mass load. Piezoelectric membranes with different sizes have been built using PVDF piezo-polymers. These devices were characterized in air and in water. The experimental results are consistent with the theoretical simulation and indicate that the device in liquid can have a higher Q factor than that in air. A theoretical model, which is a sphere executing translatory oscillations in viscous fluid, was used to analyze the Q factor in liquid environment. The results indicated that the large Q factor in liquid can be attributed to the relative large effective mass of membrane in liquid environment.

Responsivity and noise of a wire-bonded CMOS micro-fluxgate sensor

02 May 2012, 09:43:12
Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 179
Chih-Cheng Lu, Yu-Ting Liu, Fang-Yu Jhao, Jen-Tzong Jeng
This paper presents a dual-core (Vacquier-type) micro-fluxgate magnetic sensor fabricated on a silicon chip based on standard CMOS technology. The silicon chip is 2.5mm×2.5mm in dimension, and the micro-fluxgate sensor occupies the area of 2.5mm×1.8mm. The sensor consists of magnetic cores, planar pick-up coils, bottom excitation coils (CMOS Al interconnections) and upper excitation coils (wire-bonding Al wires). The micro-solenoid excitation coils consisting of aluminum bonding wires and CMOS metallic layers can generate out-of-phase excitation magnetic fields strong enough to saturate the two magnetic cores. It was found that the sensor's sensitivity can be optimized and the field noise spectral density can be minimized by adjusting the excitation current as well as the excitation frequency. The maximum responsivity of 8.1V/T occurs at the second harmonic when the excitation frequency is 110kHz; however, the minimum magnetic field noise is found to be 2.6nT/√Hz at 1Hz under 20-kHz excitation. In comparison with other miniature planar fluxgates with similar dimensions reported to date, our device has a relatively low field noise spectral density.

Low-humidity sensing properties of PAMAM dendrimer and PAMAM–Au nanoparticles measured by a quartz-crystal microbalance

02 May 2012, 09:43:12
Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 179
Pi-Guey Su, Wen-Hau Tzou
Low-humidity sensing performance of generation 1 amine terminated polyamidoamine (PAMAM) dendrimer (G1-NH2), generation 5 amine terminated PAMAM dendrimer (G5-NH2) and G5-NH2–Au nanoparticles (G5-NH2–AuNPs) thin films were investigated by using a quartz crystal microbalance (QCM). The formation of AuNPs was characterized by UV–vis spectrophotometer. The characterizations of the thin films were analyzed by atomic force microscopy (AFM). Water vapor molecules adsorbed onto the G5-NH2–AuNPs thin film had a larger frequency shift than the G1-NH2 and G5-NH2 thin films. Adsorption dynamic analysis, molecular mechanics calculation (association constant), was applied to elucidate how number of amine surface functional groups of PAMAM dendrimer and doped AuNPS in PAMAM dendrimer increase the sensitivity to low-humidity.

Thick film resistors on stainless steel as sensing elements for strain sensor applications

02 May 2012, 09:43:12
Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 179
Zongyang Zhang, Min Jin, Sheng Liu
In this paper, thick film resistors (TFRs, R8241, Heraeus) on 430 stainless steel (SS) substrate for strain sensor applications are investigated. TFRs are screen printed and fired on dielectrics-on-430SS substrate by thick film technology. Microstructure analysis shows that no interaction or evidence for new phase can be detected at the interface between TFRs and dielectrics-on-430SS, which indicates the compatibility of the dielectrics and TFRs. Further experiments also show the excellent insulativity and robust bonding between the dielectrics layer and 430SS substrate. Meanwhile, temperature coefficients of resistivity (TCRs), gauge factors (GFs) and noise indices (NI) of TFRs are measured. Finally, thick film technology based steel pressure sensors (SPS) are fabricated by screen printing and firing four TFRs on a machined circular diaphragm and then the TFRs are connected in a Wheatstone bridge configuration. Preliminary tests show that the sensors exhibit a sensitivity of 4.68mV/V full-scale (FS) with 0.1% FS linearity and 0.15% FS hysteresis and 0.15% FS repeatability. Moreover, the thermal zero drifts and thermal sensitivity drifts of the sensors in the whole temperature range (−40°C to +125°C) are less than 2.5% FS.

A polymer foil non-contact IR temperature sensor with a thermoresistor integrated on the back of a vertically configured thermopile

02 May 2012, 09:43:12
Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 179
Fang Mao, Mikael Lindeberg, Klas Hjort, Lena Klintberg
A very thin non-contact IR temperature sensor has been fabricated in a polymer foil. A thermoresistor was placed in the isothermal back-layer of a vertical configured IR-sensor. The IR-sensor is a thermopile consisting of through-the-foil thermocouple legs in a flexible polyimide foil, and the integration of a thermoresistor to one of its surfaces enables use of the sensor for non-contact temperature measurements. The size of the sensor is 3mm×3mm and the thickness is less than 0.2mm. The sensor can easily be surface mounted to printed circuit boards. An ion track technique followed by lithographically controlled electroplating of nanowires and thin film deposited interconnects are used to fabricate the infrared sensor. The thin film nickel thermoresistor was fabricated using evaporation. Layers of Parylene C was used for electric insulation and protection to improve environmental stability. In the temperature range of 20–55°C, the thermoresistor shows good linearity. Some initial decrease in resistance was seen at 105°C whereafter the resistance stabilized. The IR temperature sensor was characterized, and for temperatures near room temperature a simple linear equation using the voltage response and temperature of the thermoresistor as the only input parameters was curve fitted to the experimental data. The difference between the measured and the calculated object temperature is less than 0.5°C using a confidence level of 95%.

Flexible microfluidic normal force sensor skin for tactile feedback

02 May 2012, 09:43:12
Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 179
Ruben D. Ponce Wong, Jonathan D. Posner, Veronica J. Santos
Robotic applications often require robust tactile sensing capabilities on curved surfaces, such as artificial fingertips. Flexible tactile sensors could be conformally wrapped around curved digits and could enhance grip by cushioning impacts and increasing the effective contact area during grasp. Flexible microfabricated devices that use thin film or solid electrical components are susceptible to failure due to cracking and fatigue. Conductive fluids have been used as transduction media, electrical connections, and in resistance-based pressure and bend sensors. In this work, a flexible and multilayer capacitive microfluidic normal force sensor is developed with a 5×5 taxel array. The sensor uses liquid metal-filled microfluidic channels as the capacitive plates and conductive interconnects. The sensor is microfabricated using soft lithography microfabrication techniques and consists of multiple layers of PDMS microchannels filled with the liquid metal alloy Galinstan and air pockets that modify the mechanical and electrical properties of the sensor. A single taxel is calibrated for normal forces ranging from 0 to 2.5N, is shown to provide repeatable measurements of static uniaxial loads, and follows the loading and unloading phases of low-frequency dynamic loads (0.4–4Hz). The sensor prototype has a spatial resolution on the order of 0.5mm, performs reliably when wrapped around a surface having a curvature similar to that of a human finger (1.575cm−1), and has been shown to tolerate curvatures as high as 6.289cm−1. The deformable liquid capacitive plates and heterogeneous PDMS-air dielectric medium can be designed to tune the sensor's sensitivity and range. The sensor prototype provides greater sensitivity at low loads, a feature which can be exploited for robotic applications in which light touch is important.

Investigation on standing wave vibration of the imperfect resonant shell for cylindrical gyro

02 May 2012, 09:43:12
Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 179
Xiang Xi, Yulie Wu, Xiaomei Wu, Yi Tao, Xuezhong Wu
Standing wave vibration is the basic working mode for most vibratory shell gyros. In this paper, the standing wave vibration of the imperfect resonant shell for cylindrical gyro is investigated. The stability of the vibration is analyzed by building the imperfect ring model. Theoretical result shows that the offset of the vibration axis, which gives rise to the zero bias of the gyro, is affected synthetically by the frequency split, exciting force and damping coefficient. FEM simulation is employed to give a study of the vibration process of the imperfect shell. In addition, the factors which may affect the offset of the standing wave vibration are analyzed quantitatively. Experiments were set up to validate these influence factors by using vibration measurement equipments. Experimental results show that the frequency split affects the vibration offset significantly. The exciting force and damping coefficient have slight effect on the standing wave vibration. Simulated and measured results are in close agreement.

Geomagnetic sensors based on Metglas/PZT laminates

02 May 2012, 09:43:12
Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 179
D.T. Huong Giang, P.A. Duc, N.T. Ngoc, N.H. Duc
A potential geomagnetic-field sensor is proposed on the basis of an optimal 2D configuration of magnetoelectric Ni-based Metglas/PZT laminates. This sensor can perfectly serve to measure both the strength and the orientation of the earth's magnetic field. An incredibly high ME-voltage response of 0.871V/Oe to the geomagnetic field with a resolution of 3×10−4 Oe has been achieved for composite laminates with a size of 15mm×1mm. With respect to the field inclination, an angular sensitivity of 3.86×10−3 V/degree and an angular resolution of 10−1 degree have been determined. This simple and low-cost magnetic-field sensor is promising for applications not only as novel smart compasses and in global positioning devices, but also as magnetic biosensors.

Carbon nanotube polymer coatings for textile yarns with good strain sensing capability

02 May 2012, 09:43:12
Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 179
Rui Zhang, Hua Deng, Renata Valenca, Junhong Jin, Qiang Fu, Emiliano Bilotti, Ton Peijs
In this study, a commercially available Spandex multifilament yarn was coated with a thermoplastic polyurethane/carbon nanotube (TPU/CNT) conductive polymer composite (CPC), and conductive elastic yarns with good strain sensing ability were achieved with equivalent CNT concentrations as low as 0.015wt.%. The resistance per meter coated yarn decreased with increasing CNT concentration in the CPC coating, while in the case of a homogeneous coating, the CPC concentration in the coating solution did not have a significant effect on the resistance per meter coated yarn. Upon cyclic loading, the strain sensing behaviour showed partial recovery of resistance in the first loading cycle, while good reversibility was observed a number of cycles, giving these materials good potential as sensors for smart textiles.

Magnetic flux vertical motion modulation for 1/f noise reduction of magnetic tunnel junctions

02 May 2012, 09:43:12
Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 179
Mengchun Pan, Jiafei Hu, Wugang Tian, Dixiang Chen, Jianqiang Zhao
Magnetic tunnel junctions (MTJs) have larger magnetoresistance ratio and higher magnetic sensitivity than other magnetoresistive structures, whereas their 1/f noise is also larger. To reduce the 1/f noise and improve the low frequency detection capability of MTJ sensors, some magnetic flux modulation schemes based on MEMS flux concentrators have been put forward, and several prototypes with gap-changed modulation (GCM) were fabricated by Army Research Laboratory (ARL). Presently, the problem of low magnetic modulation efficiency in GCM is still an obstacle for MTJ sensors with a resolution of pico-Tesla. In this paper, a novel magnetic flux modulation called vertical motion modulation (VMM) is proposed. In VMM, a modulation film driven by a MEMS actuator vibrates vertically above the air gap of the flux concentrator and the MTJs in the air gap detect an AC magnetic field with a DC bias. Theoretically the modulation efficiency of VMM can exceed 30% when the air gap varies from 30μm to 70μm. A preliminary prototype sensor with VMM was fabricated and its modulation efficiency achieves 17.4%. It is expected that the modulation efficiency of MTJ magnetic sensors with VMM can surpass 30% through modifying the sizes and improving the magnetic permeability of modulation films.

Gas sensing properties of RF magnetron sputtered MgIn2O4 thin films

02 May 2012, 09:43:12
Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 179
B. Anuradha, C. Sanjeeviraja
MgIn2O4 thin films have been deposited on glass substrates by RF magnetron sputtering technique and their sensing characteristics were investigated in this study. The experimental results showed that the MIO exhibited high sensitivity and selectivity for the detection of ethanol. The gas-sensitive behavior of RF sputtered MIO thin films can be altered by varying the fabrication parameters like the sputtering power, substrate temperature. In particular, the sensitivity can be increased. The thickness of MIO films was measured by Mitutoyo SJ-301 surface roughness tester. The morphology, composition and crystal structure were investigated by using SEM, EDAX and XRD. Hall measurements showed n-type conductivity with electron mobility value 6.9cm2/(Vs) and carrier concentration of 1.40×1018 cm−3.

Direct analog-to-microcontroller interfacing

02 May 2012, 09:43:12
Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 179
Lars Bengtsson
This paper will demonstrate how signals from analog sensors can be directly interfaced to any digital embedded system even though they may not be equipped with an on-chip ADC (Analog-to-Digital Converter), comparator or OP amp (Operational Amplifier). With only two resistors and one capacitor, we will present a solution that allows analog voltages to be measured directly using only a few digital I/O-pins. The digital target system requirements are minimized and limited to only two digital I/O-pins (with tri-state capability). No ADC, comparators, timers or capture modules are necessary. The extremely modest hardware requirements make it a suitable solution also for CPLDs/FPGAs (Complex Programmable Logic devices/Field Programmable Gate Arrays). Since this solution will allow even the simplest embedded system to be interfaced to analog voltage sensors, it has the potential of reducing design costs considerably. The proposed design is for DC or low-frequency signals and compared to other similar solution, this design needs no embedded analog blocks at all.

The synthesis of poly(vinyl cinnamates) with light-induced shape fixity properties

02 May 2012, 09:43:12
Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 179
Haiyan Du, Junhua Zhang
Poly(vinyl cinnamates) (PVCi) with different degrees of substitution (DS) are synthesized by esterifying hydroxyl of poly(vinyl alcohol) (PVA) with carboxyl of p-chloro-substituted cinnamic acid. The grafted polymer has photosensitive property and presents photocrosslinking due to the photodimerization between pendant cinnamate groups, which affords PVCi sample photo induced shape fixity properties. That is to say PVCi sample having original shape could be deformed into a temporary shape under extra load followed by irradiating it under ultraviolet (UV) light of 360nm. What interesting is the shape fixity has strong relationship with DS. Unfortunately, the deformed sample cannot recover its original shape under UV light of 254nm. The reason behind the macroscopic shape change has been studied. And the effect of DS on the grafted polymer structure and properties has been studied by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and UV spectra.

PMN-PT–PZT composite films for high frequency ultrasonic transducer applications

02 May 2012, 09:43:12
Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 179
Hsiu-Sheng Hsu, Vatcharee Benjauthrit, Fan Zheng, Rumin Chen, Yuhong Huang, Qifa Zhou, K. Kirk Shung
We have successfully fabricated x(0.65PMN-0.35PT)–(1− x)PZT (xPMN-PT–(1− x)PZT), where x is 0.1, 0.3, 0.5, 0.7 and 0.9, thick films with a thickness of approximately 9μm on platinized silicon substrate by employing a composite sol–gel technique. X-ray diffraction analysis and scanning electron microscopy revealed that these films are dense and creak-free with well-crystallized perovskite phase in the whole composition range. The dielectric constant can be controllably adjusted by using different compositions. Higher PZT content of xPMN-PT–(1− x)PZT films show better ferroelectric properties. A representative 0.9PMN-PT–0.1PZT thick film transducer is built. It has 200MHz center frequency with a −6dB bandwidth of 38% (76MHz). The measured two-way insertion loss is 65dB.

Characterization of inverted pyramidal hollow cathode microplasma devices operating in reactive gases for maskless scanning plasma etching

02 May 2012, 09:43:12
Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 179
Li Wen, Zhen Yuan, Leili Cheng, Hai Wang, Jiaru Chu
In the cantilever-based microplasma etching system proposed by our group, the stable discharge characteristics of microplasma device in reactive gases is the foundation of the maskless scanning etching of material. In this paper, the cantilever probe integrated with 100μm2 inverted pyramidal hollow cathode microplasma device and nano-aperture at the hollow tip is successfully fabricated. The electrical and optical characteristics of the dc-driven microplasma devices operating in SF6, CHF3 reactive gases and their mixtures with Ar at different gas pressure are investigated. The etching profile and etching rate for silicon in SF6 microplasma exported from the nano-aperture are simulated to predict the etching effect under maskless microplasma etching system. The results of this paper may lay a foundation for upcoming experiments of maskless scanning plasma etching of silicon and its compounds, and also have implications in microplasma material processing in reactive gases using other devices configuration.

Power-generation performance of lead-free (K,Na)NbO3 piezoelectric thin-film energy harvesters

02 May 2012, 09:43:12
Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 179
Isaku Kanno, Tomoharu Ichida, Kazuhiko Adachi, Hidetoshi Kotera, Kenji Shibata, Tomoyoshi Mishima
We fabricated piezoelectric energy harvesters with lead-free (K,Na)NbO3 (KNN) thin films and compared their power-generation performance with that of Pb(Zr,Ti)O3 (PZT) thin film energy harvesters. The KNN and PZT thin films were deposited on Pt/Ti/Si substrates by rf-magnetron sputtering. The transverse piezoelectric properties of the KNN and PZT films were essentially the same, e 31,f ∼−11C/m2. The peak average output power of the unimorph cantilevers of KNN/Si and PZT/Si were 1.1 and 1.0μW, respectively. Thus, the performance of lead-free KNN thin films as a piezoelectric energy harvester is comparable to that of PZT films.

Frequency-tunable soft composite antennas for wireless sensing

02 May 2012, 09:43:12
Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 179
Qing-Yuan Tang, Yong-Mei Pan, Y.C. Chan, K.W. Leung
In this study, flexible and uniform multiwall carbon nanotube embedded polydimethylsiloxane (PDMS) sheets were prepared using a vacuum filtration and transfer process. The resistance of the sheets and microstructures were investigated for the fabrication of ideal probe-fed and microstrip-fed patch antennas. Simulation results showed that the resonance and gain of an antenna were affected by the conductivity of the patch significantly. The return loss and gain are acceptable when a conductivity of 105 S/m is used. The stretchability test indicated that a gold-coated sheet was more stable than a pristine sheet. Its resistance has a change of 0.5% only, with a displacement of 2500μm. The frequency-tuning capability was demonstrated using an air inflatable microstrip-fed patch antenna. The working frequency can be tuned by 6.5% with a displacement of 1500μm, which was higher than that of previously reported MEMS bridge and electrostatic force tunable antennas. This is the first time that a frequency tunable antenna fabricated by PDMS/carbon nanotube is reported. The optimization methods for this type of antenna are discussed and some potential applications such as remote wireless pressure sensors are proposed.

Temperature-sensitive chemical cell based on Nickel (II) phthalocyanine-tetrasulfonic acid tetrasodium salt

02 May 2012, 09:43:12
Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 179
Zubair Ahmad, Shahino Mah Abdullah, Khaulah Sulaiman
An organic compound Nickel (II) phthalocyanine-tetrasulfonic acid tetrasodium salt (NiTSPc) has been studied as a potential material for a solution based temperature sensor. Using NiTSPc, an ITO/NiTSPc solution/ITO chemical cell has been made and characterized in the temperature range of 20–85°C. This sensor works on the principle of change in the resistance and capacitance of the chemical cell caused by the temperature variation. Good response/recovery and small hysteresis have been attained. The proposed sensor is aimed to evolve towards highly sensitive organic temperature sensor in a specific temperature range.

A compact dielectric elastomer tubular actuator for refreshable Braille displays

02 May 2012, 09:43:12
Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 179
P. Chakraborti, H.A. Karahan Toprakci, P. Yang, N. Di Spigna, P. Franzon, T. Ghosh
Electroactive polymer actuators stimulated by appropriate levels of electric field are particularly attractive for human-assist devices such as Braille. The development of a full page refreshable Braille display is very important for the integration of the visually impaired into the new era of communication. In this paper, development of a compact dielectric elastomer actuator suitable for Braille application is reported. The actuators are fabricated from commercially available silicone tubes. The tube has been rendered mechanically anisotropic through asymmetric levels of applied pretension in circumferential and axial directions in order to direct the actuation strain in the axial direction of the actuator. Key performance parameters, such as displacement, force, and response time of the actuator are investigated. The test results demonstrate the potential of the compact, lightweight, and low cost dielectric elastomer as actuators for a refreshable full page Braille display.

RF/baseband co-design of switching receivers for multiband microwave energy harvesting

02 May 2012, 09:43:12
Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 179
Alessandra Costanzo, Aldo Romani, Diego Masotti, Nicola Arbizzani, Vittorio Rizzoli
The paper addresses a new integrated design of RF/Microwave receivers and conversion systems for energy harvesting to be adopted in ultra-low power density environments. Such systems can be very useful in typical humanized scenarios in the presence of existing wireless systems with power densities as low as a few μW/cm2. Despite of the scarce RF power available, energy usable to extend battery life or to self-power low-duty cycle electronics may be scavenged by highly efficient receivers and power converter circuits designed in a unique design process. A multi-band antenna is used as the RF power receiver. Its rigorous frequency-dependent equivalent circuit in the presence of incident fields, simultaneously radiated in several bands, is used in the joint design of a rectifier stage and of a boost converter that can dynamically track the maximum power point. This is obtained by a new simulation platform combining SPICE-like time-domain models of dispersive multiport components with the transient analysis of the storage and control sub-systems. The system operation is fully measured in a practical application and predicted and measured stored energy and system efficiency are discussed. As preliminary results the converter is realized by discrete components, but a significant reduction in power consumption is expected by an integrated circuit design.

Electrostrictive bending actuators: Modeling and experimental investigation

02 May 2012, 09:43:12
Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 179
Mickaël Lallart, Claude Richard, Pisan Sukwisut, Lionel Petit, Daniel Guyomar, Nantakan Muensit
Electroactive polymers (EAPs) have become of great interest for energy conversion because of their flexibility, manufacturability and low production cost. Hence, such materials present promising application potentials in the fields of actuation (e.g., artificial muscles, micropumps, …). The purpose of this paper is to present the modeling of devices using EAPs in quasi-static flexural solicitations. Based on the mechanical and electromechanical analyses of a structure equipped with such materials, the actuation abilities of such systems will be assessed. In order to illustrate the proposed principles, the approach will be applied to two particular structures consisting in a cantilever beam and a clamped–clamped beam with the active material in the middle.

Design and characterization of miniature piezoelectric generators with low resonant frequency

02 May 2012, 09:43:12
Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 179
Ziping Cao, Jinya Zhang, Hiroki Kuwano
In this study, both materials selection and device configuration design were considered for developing miniature piezoelectric generators with low resonant frequency. Instead of single crystal Si, stainless steel (SUS) was chosen as the substrate of AlN thin films owing to its higher fracture toughness, which made it possible that millimeter-scale generators had resonant frequency of less than 100Hz. The device configuration including the aspect ratio (the length of the cantilever to the width of the cantilever) and the thickness ratio (the substrate layer to the AlN film layer) were analyzed for optimizing transverse electromechanical coupling coefficient of generators. Using AlN thin films deposited on stainless steel, millimeter-scale generators were fabricated and their vibration energy harvesting performance was characterized. Output power and resonant frequency of the devices are, respectively, 5.130μW and 69.8Hz when they were vibrated at 1g acceleration and connected with 0.7MΩ electric loading.

A model for the energy harvesting performance of shear mode piezoelectric cantilever

02 May 2012, 09:43:12
Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 179
L. Zhou, J. Sun, X.J. Zheng, S.F. Deng, J.H. Zhao, S.T. Peng, Y. Zhang, X.Y. Wang, H.B. Cheng
The electrical model with the piezoelectric constitutive equations of d 15 mode and the single degree of freedom model are combined to describe the energy harvesting performance of shear mode piezoelectric cantilever, and the proposed model is used to simulate the frequency dependence of the output peak voltage and power. To verify the validity, the previous experimental parameters of the shear mode piezoelectric cantilever with 0.71Pb(Mg1/3Nb2/3)O3–0.29PbTiO3 single crystal and brass shim are chosen to evaluate the energy harvesting performance as the example, and the frequency dependence of the output peak voltage and output power is in good agreement with the previous experiment. The results are also compared with the ANSYS numerical solutions, which reveal acceptable agreement. The effects of the material properties and geometrical dimensions on the energy harvesting performance are discussed to provide some useful guidelines to the design of piezoelectric energy harvesting devices.

Large stroke and nanometer-resolution giant magnetostrictive assembled actuator for driving segmented mirrors in very large astronomical telescopes

02 May 2012, 09:43:12
Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 179
Bin-tang Yang, De-hua Yang, Peng-you Xu, Yu-dong Cao, Zhi-qiang Feng, Guang Meng
High-precision-positioning technology with nanometric resolution plays a vital role in driving segmented mirrors in very large astronomical telescopes (VLAT). Current positioning actuators in VLAT are generally based on hydraulic technology, flexible-hinge principle and motor-reducer approaches. Although these actuators have their own merits in their specific applications, they cannot satisfy the high-precise-positioning requirements in active and adaptive optics because of their inherent drawbacks such as hydraulic leakage, lagging, solid friction and insufficient accuracy. To improve the performance of actuators and meet the needs for positioning resolution and accuracy in active and adaptive optics in VLAT, this paper presents the design and implementation of a giant magnetostrictive assembled actuator (GMAA). The actuator features stable nano-resolution positioning, large stroke, instant response, and high load capacity. The design is based on a combination of dual level, i.e. coarse and fine drive regimes. A new large stroke, nanometric positioning GMAA is realized. In this paper the integrated design of the actuator, the control system and the test results from the prototype are presented. The test results prove not only the capacity and positioning accuracy of the actuator in large strokes, but also the effectiveness of the control system and the control method. The tests performed on a single GMA show that when its stroke is 0.6mm, its positioning accuracy may reach to ±30nm and the GMAA positioning accuracy may reach up to ±90nm. The tests performed on the entire GMAA verify that it is able to perform a stroke of 2.2mm with approximately 60nm of displacement resolutions when 600N of external load is applied.

A new acoustic transducer with a pressure-deformed piezoelectric diaphragm

02 May 2012, 09:43:12
Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 179
Andrew S. Wixom, Michael J. Anderson, David F. Bahr, Dylan J. Morris
A new design for wide-band acoustic transducers is described. Radial tension is applied to a thin piezoelectric diaphragm with conductive electrodes on the upper and lower surface. One side of the diaphragm is pressurized, elastically deforming the diaphragm into a slightly curved shape. The in-plane static tension is modulated by applying a time-dependent voltage across the electrodes of the piezoelectric diaphragm. The tension modulation causes transverse displacement oscillations of the diaphragm. This actuation takes place in spite of the fact that the piezoelectric diaphragm does not contain a passive elastic layer, which is necessary for actuation by flexure in planar diaphragms. A theoretical quasi-static model using hexagonal symmetry for the piezoelectric material was developed to predict the electromechanical actuation mechanism, and the mode for optimal operation in non-resonant conditions. Piezoelectric diaphragms were fabricated from PVDF film of nominal thickness 40μm into circular diaphragms 1cm in diameter. For the pressure-deformed transducers fabricated from PVDF film, displacement amplitudes of 9–14.5nm/V were observed, and the maximum displacement amplitude took place at the applied tension and static pressure predicted by the model. Additional measurements with conventional flexure-type transducers containing a diaphragm consisting of a layer of PZT and a passive elastic material fabricated using MEMS processes were performed to compare with the transducers fabricated from PVDF film. The displacement amplitude per unit electric field measured for the transducers fabricated from PVDF film was comparable to those measured from conventional PZT flexure-type transducers, despite the fact that the piezoelectric coupling coefficient for PVDF was approximately 100 times smaller than that for PZT.

Effective hydraulic resistance of actuator nozzle generating a periodic jet

02 May 2012, 09:43:12
Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 179
V. Tesař
Because of nonlinearity of characteristics of nozzles, their effective hydraulic resistance when generating periodically pulsating jet is higher than the steady-flow value. Author investigated this effect in experiments with a nozzle supplied with superposed steady flow and a pulsation generated by piston-type pulsator, and found deviations from the predictions based on mere nonlinearity. The disagreement is explained by fluid accumulation due to its compressibility in the actuator cavity upstream from the nozzle. Two mathematical models of the periodic accumulation processes were set up. The experimental data are located between the results of these models. The final outcome of this study is a law of universal validity for design of actuators with periodic flows in nozzles.

Nanoforce estimation based on Kalman filtering and applied to a force sensor using diamagnetic levitation

02 May 2012, 09:43:12
Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 179
Emmanuel Piat, Joël Abadie, Stéphane Oster
Nanoforce sensors based on passive diamagnetic levitation with a macroscopic seismic mass are a possible alternative to classical Atomic Force Microscopes when the force bandwidth to be measured is limited to a few Hertz. When an external unknown force is applied to the levitating seismic mass, this one acts as a transducer that converts this unknown input into a displacement that is the measured output signal. Because the under-damped and long transient response of this kind of macroscopic transducer cannot be neglected for time-varying force measurement, it is then necessary to deconvolve the output to correctly estimate the unknown input force. The deconvolution approach proposed in this paper is based on a Kalman filter that use an uncertain a priori model to represent the unknown nanoforce to be estimated. The main advantage of this approach is that the end-user can directly control the unavoidable trade-off that exists between the wished resolution on the estimated force and the response time of the estimation.

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