Sensors (Surface Acoustic Waves)

In this paper, finite element method is used for modeling of 433MHz one port SAW resonator. The simulation process performed using COMSOL in 2D models. Impedance, admittance and scattering parameters for SAWR with 2 electrodes are predicted. The equivalent circuit parameters of one port SAW resonator extracted from FEM results which considered as a contribution.

One significant challenge facing biosensor development is packaging. For surface acoustic wave based biosensors, packaging influences the general sensing performance. The acoustic wave is generated and received thanks to interdigital transducers and the separation between the transducers defines the sensing area. Liquids used in biosensing experiments lead to an attenuation of the acoustic signal while in contact with the transducers. We have developed a liquid cell based on photodefinable epoxy SU-8 that prevents the presence of liquid on the transducers, has a small disturbance effect on the propagation of the acoustic wave, does not interfere with the biochemical sensing event, and leads to an integrated sensor system with reproducible properties. The liquid cell is achieved in two steps. In a first step, the SU-8 is precisely patterned around the transducers to define 120 µm thick walls. In a second step and after the dicing of the sensors, a glass capping is placed manually and glued on top of the SU-8 walls. This design approach is an improvement compared to the more classical solution consisting of a pre-molded cell that must be pressed against the device in order to avoid leaks, with negative consequences on the reproducibility of the experimental results. We demonstrate the effectiveness of our approach by protein adsorption monitoring. The packaging materials do not interfere with the biomolecules and have a high chemical resistance. For future developments, wafer level bonding of the quartz capping onto the SU-8 walls is envisioned.

This paper gives an overview on the system development of a wireless surface acoustic wave (SAW) temperature measurement application in high-speed high-voltage motors. The measurement location of interest is on the rotor in the vicinity of the copper squirrel cage. To fit the sensor in a 4 mm bore, a custom packaging with outer dimensions of 10.0 3.1 2.0 mm 3 has been developed. For the purpose of interrogation a mechanically robust metal slot antenna has been designed to withstand rotation speeds up to 15 000 rpm. As the sensor interacts only during a very short time of a few 100 s with the reader antenna a fast frequency modulated continuous wave (FMCW) reader was developed. The reader operates in the ISM band of 2.4 GHz and achieves a typical sweep time for data acquisition of 100 s. The sensor system has been tested both in test bed and real engine conditions and performed stable read outs, although in the real engine signal behavior is disturbed by reflections and possibly electromagnetic field bursts caused by the power converter. Index Terms-Antenna design, frequency modulated continuous wave radar, packaging, surface acoustic wave sensor, temperature measurement. Alfred Binder received the M.Sc. degrees from the Johannes

A proposed schematic design for surface acoustic wave resonator (SAWR) is introduced in this paper. A simplified equivalent model for both one and two port 433MHz SAWR is built. Scattering parameters of the proposed design is extracted and compared with a commercial one of the same resonant frequency. Advanced system design tool is nominated to give the main parameters like Impedance and Admittance with their real and imaginary response. The insertion loss predicted mathematically and recorded from simulation then compared with the measured value. The proposed design tool introduced adequate results with minimum hardware procedure specifications.

A contactless torque sensor based on four one-port SAW resonators on quartz substrates working in the 430-437 MHz frequency range is presented in the paper. Design of the sensor allows full compensation of the bending effect. A single stationary interrogation unit is used to measure resonant frequencies of all four resonators attached to the rotating shaft. The interrogation method is based on a pulsed excitation of the natural oscillations and their subsequent spectral analysis. The achieved standard deviation of the measured frequency difference is sufficient for EPAS applications in automotive industry.

We report lithium niobate (LiNbO3) surface acoustic wave (SAW) transducers with the smallest linewidth and the highest resonant frequency. A record 30 nm wide, 200 nm period  nanofabricated metallic structure on non-conductive LiNbO3 enables a frequency exceeding 14 GHz. At higher frequencies, greater data throughputs and improved sensor sensitivity are enabled. A systematic study of SAW devices from lamda =200-800 nm is presented taking into account crystal orientation, device design, patterning strategies, and resonant modes. The device performance metrics such as frequency, Q-factor, insertion loss, and coupling coefficient are measured in detail and these metrics are also found to exceed the results of other recent state-of-the-art devices, when compared.

A contactless torque sensor, based on four one-port SAW resonators on quartz substrates working in the 430-437 MHz frequency range, is presented in this paper. The design of the sensor allows full compensation of the bending effect. A single stationary interrogation unit is used to measure resonant frequencies of all four resonators attached to the rotating shaft. The interrogation method is based on a pulsed excitation of the natural oscillations and their subsequent spectral analysis. The achieved standard deviation of the measured frequency difference is sufficient for electrical power assisted-steering applications in the automotive industry.

The present paper describes a novel approach to evaluate the mass sensitivity of a Love wave (LW) sensor. A ZnO/XY LiNbO3 delay line based device with a sensing film was modeled and simulated applying the 3D-Finite Element Method (FEM). The radio frequency signal delays due to the thickness changes induced to the sensing film were registered and measured at the output Interdigital Transducer (IDT). The time delays were associated with phase shifts to determine the phase sensitivity of the sensor. A phase sensitivity of 600 [cm 2 /g] was obtained, which is in good agreement with literature.

Karakteristik dari komponen tapis berbasis SAW adalah tanggapan frekuensi akan berubah
jika elektroda yang terdapat pada komponen tersebut terpapar suatu gas. Pada penelitian
ini telah berhasil dibuat sensor gas berbasis  surface acoustic wave dengan memodifikas
tapis analog berfrekuensi dasar 46Mhz. Karakteristik frekuensi resonansi yang berubah saat
menyerap gas menghasilkan pola tanggapan yang berbeda untuk setiap jenis gas.
Pergeseran frekuensi tersebut akan dihitung oleh pencacah frekuensi 32 bit dan diakuisis
oleh mikrokontroler.  Data pola tanggapan sensor  yang berbeda-beda tersebut akan d
proses oleh komputer dengan menggunakan algoritma jaringan syaraf tiruan untuk
mengidentifikasi jenis gas. Hasil pengujian menunjukkan bahwa jaringan saraf tiruan dapat
dilatih untuk mengenali beragam gas dengan tingkat keberhasilan 99%.

In the current paper, mono and multi EBG structures for wider bandwidth are presented. For every EBG mentioned in this paper, metallic patches of regular shapes are selected as unit elements and these patches are altered to get additional inductance and capacitance which provides lower cut-off frequency and large bandwidth. The surface wave attenuation of EBG structures are juxtaposed with conventional EBG of mushroom type. The variation of transmission response due to unit element size, via diameter and distance
between unit elements is shown. Out of these proposed EBG’s the square patch is small, the fractal EBG
has wider bandwidth. The square patch with mono disconnected loop type slot and the fractal are multi
band. The designing of microwave circuits and the antennas can be done using these EBGs.

Analysis and knowledge are required in order to obtain awareness and understanding of sensory data, sound in this case, to process what we perceive and to derive some meaning.
It is possible to capture small details in the environment and take them all in to see the whole.
The aim of my research is to explore the connections between sound and perception through the decoding of physics rules, cultural aspects, and parameters contained in sound. This research is about looking for something in a focused and systematic way, to create a new knowledge through active experimentation and also interpretation of new sound sensations.
This project explores listening to “noise” to develop a new attitude to understanding sounds and music in order to arrive at a new way of thinking that helps the listeners understand the shapes of sound through analytic investigation. This research could be a help for designers, city planners, musicians, artists and those who want to experience new perceptions. My thesis project will support these goals and my conclusion will discuss the objectives proposed in this paper.

Love Wave (LW) surface acoustic wave (SAW) devices have demonstrated higher sensitivity in the detection of biorelevant molecules in liquid media than the traditional quartz crystal microbalance (QCM). One of the main issues when dealing with Love wave (LW) based biosensors is the fluidic aspect, since the surface on top of the Interdigital transducers (IDTs) has to be isolated from liquids, otherwise the electric signal is greatly attenuated. A user-friendly flow cell for LW biosensors was fabricated and tested. The fabricated cell allows a fast and easy installation and replacement of the sensor. Friendly-usability and robustness are two central features of the fabricated LW flow cell. Mechanical, thermal, electrical and chemical requirements are considered. Piezoelectric substrate AT-cut quartz Z propagating 350 µm thick Guiding layer SiO 2 3 µm thick Interdigital transducers (IDTs) 100 aluminum double-fingers pairs Shear horizontal Particle displacement Sensing area Gold Structure of the fabricated LW sensor

This work investigates the mechanical and dielectric properties of an ion-selective membrane based on PDMS:PEG:valinomycin, with a view to creating practical geometries for high performance ion sensing in a variety of real world settings including healthcare, food industry and agriculture. We focus effort on measuring physical changes in the membrane that can be detected with simple sensors. First a dynamic mechanical analyser instrument was used to determine the effect of potassium ions on the real and imaginary bending storage modulus, loss tangent, glass transition temperature, temperature coefficient of millimeter sized PDMS samples. Second, a microwave dielectric analyser with a coaxial probe fixture was applied to the same sample to isolate dielectric shifts associated with ion uptake, namely the real and imaginary permittivities. These perturbation measurements performed for PDMS, PDMS:PEG and PDMS:PEG:V samples, provide strong evidence that alternatives to traditional electrochemical sensing devices can easily be constructed. Thus a plethora of new acoustic and capacitive sensing geometries arise. Thus there is the opportunity to integrate membranes into quartz crystal microbalance, surface acoustic wave and single-sided capacitance sensors. Some suggestions on suitable dimensions, aspect ratios, operating frequencies are provided.

Surface acoustic wave (SAW) transducers are a well-established component used in numerous sensors, communications, and electronics devices. In this work, the authors report a systematic study of 320–800 nm period lithium niobate SAW interdigitated transducers (IDTs) corresponding to resonant frequencies in the 4–12 GHz range. An optimized SAW design and a nanofabrication process flow were developed, which enabled superior device performance in terms of frequency, signal losses, and electromagnetic coupling. The influence of the device alignment on the substrate crystal planes, in addition to
the IDT period and electrode design, is found to have a significant impact on various process metrics. As an example, two identical SAW transducers fabricated perpendicular to each other may have a resonant frequency difference approaching 1 GHz, for the same harmonic mode. These and other trends are presented and discussed.

Pada penelitian ini dilakukan karakterisasi divais SAW dan beberapa material polimer yang memiliki karakteristik berbeda terhadap paparan uap yang mudah menguap. Respon dari uap organik terhadap parameter lingkungan yakni temperatur dan kelembaban relatif  diteliti dari purwarupa sistem instumentasi. Sistem instrumentasi tersebut terdiri dari sebuah deret osilator SAW terlapis polimer, sebuah osilator SAW referensi, rangkaian pengkondisi sinyal dan pencacah frekuensi, suatu pengkonsisi awal ruang pengujian uap serta sebuah pompa udara

This review presents a deep insight into the Surface Generated Acoustic Wave (SGAW) technology for biosensing applications, based on more than 40 years of technological and scientific developments. In the last 20 years, SGAWs have been attracting the attention of the biochemical scientific community, due to the fact that some of these devices -Shear Horizontal Surface Acoustic Wave (SH-SAW), Surface Transverse Wave (STW), Love Wave (LW), Flexural Plate Wave (FPW), Shear Horizontal Acoustic Plate Mode (SH-APM) and Layered Guided Acoustic Plate Mode (LG-APM) -have demonstrated a high sensitivity in the detection of biorelevant molecules in liquid media. In addition, complementary efforts to improve the sensing films have been done during these years. All these developments have been made with the aim of achieving, in a future, a highly sensitive, low cost, small size, multi-channel, portable, reliable and commercially established SGAW biosensor. A setup with these features could significantly contribute to future developments in the health, food and environmental industries. The second purpose of this work is to describe the state-of-the-art of SGAW biosensors for the detection of pathogens, being this topic an issue of extremely importance for the human health. Finally, the review discuses the commercial availability, trends and future challenges of the SGAW biosensors for such applications.

Many Automatic Identification (Auto-ID) technologies such as bar codes, magnetic stripes, Optical Character Recognition (OCR) and Electronic Article Surveillance (EAS) security tags are in existence. However, they are limited by a variety of constraints on them such as limited object rate of scan, need for Lineof-Sight (LOS) operation, very small interrogation range and poor accuracy in complex environments. Research has accordingly grown rapidly in recent years into the development of robust identification or tracking mechanisms. Radio Frequency Identification (RFID) technology using readers and RFID tags, whether passive, semi-passive or active in nature, has been deemed to be a promising candidate. Silicon based IC tags are quite popular. However, some alternative RFID technologies have also been on the rise. In particular, another special type of tag based on Surface Acoustic Wave (SAW) design also has a great potential for deployment in future identification fields due to its ruggedness against harsh conditions, metallic environments, interference, small and low cost and is being thoroughly reviewed, which is ignored in other survey papers. While other chipless RFID systems based on conductive ink, ink-tattoo and others do exist, negative aspects such as inability to survive in extreme weather, larger tag size and limited data storage capacity have severely impacted the penetration of such tags in the RFID market. Therefore, the scope of this survey article does not include chipless RFID tags. This article instead provides a comparative survey of silicon based IC and SAW based tags, which has attracted much attention from both academia and industry. The underlying characteristics, principles, advantages, and limitations of such tags are thoroughly discussed, and relevant research work followed by frequency of operation and other parameters are elaborated. This article undertakes a thorough investigation into the evolution of RFID technology and comparison into the current trend in silicon based IC and SAW based RFID tags and provides a comparison across many metrics, such as read range, tag size, tag power, availability of tag power, lifespan and more importantly, cost and security. It discusses active and passive tags under silicon based IC and SAW technology. Finally, the article reviews recent advances and provides potentials, open challenges and future research directions in such RFID tags.

A Love Wave (LW) immunosensor was developed for the detection of carbaryl pesticide. The experimental setup consisted on: a compact electronic characterization circuit based on phase and amplitude detection at constant frequency; an automated flow injection system; a thermal control unit; a custom-made flow-through cell; and Quartz /SiO 2 LW sensors with a 40 μm wavelength and 120 MHz center frequency. The carbaryl detection was based on a competitive immunoassay format using LIB-CNH45 monoclonal antibody (MAb). Bovine Serum Albumin-CNH (BSA-CNH) carbaryl hapten-conjugate was covalently immobilized, via mercaptohexadecanoic acid self-assembled monolayer (SAM), onto the gold sensing area of the LW sensors. This immobilization allowed the reusability of the sensor for at least 70 assays without significant signal losses. The LW immunosensor showed a limit of detection (LOD) of 0.09 μg/L, a sensitivity of 0.31 μg/L

A one-port SAW resonator with a non-uniform strained substrate is studied both experimentally and theoretically. Apart from the expected variation of the resonant frequency due to static strain and noticeable variation of the resonant value of S11 the emergence of a parasitic mode is also observed. Modelling explain this phenomenon and helps to predict a reduction of the sensitivity to strain due to its non-uniformity.

The propagation of shear horizontal surface acoustic waves (SHSAWs) in an inhomogeneous magnetoelectro-
elastic (MEE) half-space with 6-mm symmetry is studied. By virtue of both the direct approach and Strohformalism,
the dispersion relations corresponding to two general cases of material properties variation are obtained.
In the first case, it is assumed that all material properties involving the MEE properties and density vary similarly
in depth, whereas, the second case considers identical variation for the MEE properties, which differs from the
variation of the density. The non-dispersive SHSAW velocities pertinent to the homogeneous MEE media are
obtained under eight different surface electromagnetic boundary conditions as the limiting cases of the current
study. The dispersion curves corresponding to eleven inhomogeneity profiles of practical importance are presented
in an effective dimensionless format, and the effects of different types of inhomogeneity functions describing the
composition of the functionally graded magneto-electro-elastic (FGMEE) half-space on the dispersion relation are
discussed.

A wireless passive SAW sensor based on three one-port resonators and capable of simultaneous torque and temperature measurement is presented. The sensing element is made on Y+34° cut quartz substrate and the resonant frequencies are in the range from 433 to 437 MHz. Interrogation of the sensor is performed through an RF rotary coupler by short RF pulses. A microprocessor in the interrogation unit analyses the spectrum of SAW responses and calculates a temperature compensated torque value. Experimental results show that the temperature measurement error is within ±1° at any angle of the shaft and the torque measurement error does not exceed ±1% of full scale within the range from -40° to +125°C.

Surface acoustic waveguides have found an application for (bio)chemical detection. The mass modification due to surface adsorption leads to measurable changes in the propagation properties of the waveguide. Among a wide variety of waveguides, the Love mode device has been investigated because of its high mass sensitivity. The acoustic signal launched and detected in the waveguide by electrical transducers is accompanied by an electromagnetic wave; the interaction of the two signals, easily enhanced by the open structure of the sensor, creates interference patterns in the transfer function of the sensor. The interference peaks are used to determine the sensitivity of the acoustic device. We show that electromagnetic interferences generate a distortion in the experimental value of the sensitivity. This distortion is not identical for the two classical instrumentation of the sensor that are the open and the closed loop configurations. Our theoretical approach is completed by the experimentation of an actual Love mode sensor operated under liquid conditions and in an open loop configuration. The experiment indicates that the interaction depends on frequency and mass modifications.

One significant challenge facing biosensor development is packaging. For surface acoustic wave based biosensors, packaging influences the general sensing performance. The acoustic wave is generated and received thanks to interdigital transducers and the separation between the transducers defines the sensing area. Liquids used in biosensing experiments lead to an attenuation of the acoustic signal while in contact with the transducers. We have developed a liquid cell based on photodefinable epoxy SU-8 that prevents the presence of liquid on the transducers, has a small disturbance effect on the propagation of the acoustic wave, does not interfere with the biochemical sensing event, and leads to an integrated sensor system with reproducible properties. The liquid cell is achieved in two steps. In a first step, the SU-8 is precisely patterned around the transducers to define 120 µm thick walls. In a second step and after the dicing of the sensors, a glass capping is placed manually and glued on top of the SU-8 walls. This design approach is an improvement compared to the more classical solution consisting of a pre-molded cell that must be pressed against the device in order to avoid leaks, with negative consequences on the reproducibility of the experimental results. We demonstrate the effectiveness of our approach by protein adsorption monitoring. The packaging materials do not interfere with the biomolecules and have a high chemical resistance. For future developments, wafer level bonding of the quartz capping onto the SU-8 walls is envisioned.

One significant challenge facing biosensor development is packaging. For surface acoustic wave based biosensors, packaging influences the general sensing performance. The acoustic wave is generated and received thanks to interdigital transducers and the separation between the transducers defines the sensing area. Liquids used in biosensing experiments lead to an attenuation of the acoustic signal while in contact with the transducers. We have developed a liquid cell based on photodefinable epoxy SU-8 that prevents the presence of liquid on the transducers, has a small disturbance effect on the propagation of the acoustic wave, does not interfere with the biochemical sensing event, and leads to an integrated sensor system with reproducible properties. The liquid cell is achieved in two steps. In a first step, the SU-8 is precisely patterned around the transducers to define 120 µm thick walls. In a second step and after the dicing of the sensors, a glass capping is placed manually and glued on top of the SU-8 walls. This design approach is an improvement compared to the more classical solution consisting of a pre-molded cell that must be pressed against the device in order to avoid leaks, with negative consequences on the reproducibility of the experimental results. We demonstrate the effectiveness of our approach by protein adsorption monitoring. The packaging materials do not interfere with the biomolecules and have a high chemical resistance. For future developments, wafer level bonding of the quartz capping onto the SU-8 walls is envisioned.

Three different directional wave sensors were compared in 2001and 2002 at a coastal location in 56 m water depth off the Atlantic French coast. Both of them are directional buoys: a Datawell wave rider (MK II) and a Triaxys (Axys technologies), while the third one is a bottom mounted ADCP (WH-sentinel autonomous, from RD Instruments, working at 300KHZ).
The comparisons are based on the Datawell wave rider as a reference since it is the oldest and best known and validated system.
Correlations for significant wave heights, mean periods and peak parameters (period and directions) are respectively very good, good and poor. The agreement is always better between the two surface buoys than between the Datawell buoy and the bottom mounted ADCP. However, the ADCP also provides current profiles in the water column.
For the ADCP results are rather similar for significant wave heights as obtained by surface tracking or with orbital velocities. For the wave period the mean wave period seems to be underestimated by 1 second while the bias for the peak period is only from 0.1 second.
Discrepancies for wave parameters seem to be mostly located at low frequencies (f<0.1 Hz) for the Triaxys buoy and at high frequencies for the ADCP.

Possible ways of reducing calibration complexity are considered for a non-contact passive torque and temperature sensor based on three one-port SAW resonators working at 433-437 MHz. A spread of sensor characteristics is investigated and it is shown that dynamic calibration curves differ considerably from the static ones not allowing accelerated temperature variation during calibration. A simplified procedure is suggested using correction of generic calibration parameters based on individual sensor calibration only in one or two temperature points.

A water quality monitoring application often requires the deployment of Internet of Things (IoT) sensors over a wide water body with communication links among them to transmit, receive the data, and then uplink it to the cloud for further analytics. Deployment of this kind requires battery-assisted IoT sensors which require monitoring the battery level and replacement when necessary. It is thus desirable to have battery-free sensortags and a suitable communication infrastructure to obtain data. In this paper, a system that facilitates obtaining sensed data, like pH, through passive sensor-tags based on Surface Acoustic Wave (SAW) technology and a cellular code-reuse scheme based reader infrastructure is proposed. The reader in each cell is able to read multiple sensor-tags simultaneously, which itself has been a challenge. The SAW sensor tags are appropriately proposed to be designed to be orthogonal to allow simultaneous detection and the cell range of reader-SAW sensor-tags communication is sought to be further enhanced through a resonant loading of Interdigital Transducer (IDT) based reflectors.

Many Automatic Identification (Auto-ID) technologies such as bar codes, magnetic stripes, Optical Character Recognition (OCR) and Electronic Article Surveillance (EAS) security tags are in existence. However, they are limited by a variety of constraints on them such as limited object rate of scan, need for Line-of-Sight (LOS) operation, very small interrogation range and poor accuracy in complex environments. Research has accordingly grown rapidly in recent years into the development of robust identification or tracking mechanisms. Radio Frequency Identification (RFID) technology using readers and RFID tags, whether passive, semi-passive or active in nature, has been deemed to be a promising candidate. Silicon based IC tags are quite popular. However, some alternative RFID technologies have also been on the rise. In particular, another special type of tag based on Surface Acoustic Wave (SAW) design also has a great potential for deployment in future identification fields due to its ruggedness against harsh conditions, metallic environments, interference, small and low cost and is being thoroughly reviewed, which is ignored in other survey papers. While other chipless RFID systems based on conductive ink, ink-tattoo and others do exist, negative aspects such as inability to survive in extreme weather, larger tag size and limited data storage capacity have severely impacted the penetration of such tags in the RFID market. Therefore, the scope of this survey article does not include chipless RFID tags. This article instead provides a comparative survey of silicon based IC and SAW based tags, which has attracted much attention from both academia and industry. The underlying characteristics, principles, advantages, and limitations of such tags are thoroughly discussed, and relevant research work followed by frequency of operation and other parameters are elaborated. This article undertakes a thorough investigation into the evolution of RFID technology and comparison into the current trend in silicon based IC and SAW based RFID tags and provides a comparison across many metrics, such as read range, tag size, tag power, availability of tag power, lifespan and more importantly, cost and security. It discusses active and passive tags under silicon based IC and SAW technology. Finally, the article reviews recent advances and provides potentials, open challenges and future research directions in such RFID tags. INDEX TERMS RFID tracking/identification, surface acoustic wave (SAW), interdigital transducer (IDT), silicon based integrated circuit (IC) RFID tags, near field, far field communication.

We investigated the mass sensitivity of Love mode SAW biosensors by experimental and theoretical techniques. A first experimental approach is based on the analysis of the dispersion curve of the sensor. which helps to determine by derivation a value of the mass sensitivity. In order to obtain the dispersion curve, we have performed a chemical wet etching procedure which enables the continuous monitoring of the transfer function during the etching of the entire guiding layer. A second experimental approach is ...

The artificial properties in two dimensional electromagnetic structures (2D-EBGs), such as PMC and Band
Reject Region are investigated for a proposed structure of square shaped mushroom. The radiation
characteristics of monopole antenna over this 2D-EBG is tested by considering two cases. During first
case monopole antenna is made to operate within band rejection region. Second case monopole antenna
made operate outside the band rejection range. The obtained results during first case is showing
enhancement in operating band width and smoother radiation pattern. In second case the effect is null and
2D-EBG resembles like conventional plane reflector. The simulated results are presented.

Radio Frequency Identification (RFID) technology using readers and ID tags has been deemed to be a promising candidate compared to bar codes, QR codes and others due to Non Line of Sight (NLOS) operability, bulk readability, and longer read range. Silicon based Integrated Circuit (IC) active and passive RFID tags are quite popular. However, such tags are constrained by several factors such as inability to operate under hazardous conditions, less cost efficient, susceptibility towards electromagnetic interference and poor accuracy in metallic environments. To combat such effects, a special type of passive tag called Surface Acoustic Wave (SAW) RFID tag, which possess a very high potential due to its robustness against the above mentioned effects, has received a lot of attention among the researchers. A very popular approach called Open Circuit/Short Circuit (OC/SC) using a strip reflector design to design unique codes has been in existence and can provide a range of 2.4 m on average. Nevertheless, this range is not sufficient to be considered for a remote interrogation RFID system for many long range RFID applications. This paper uses a different reflector design for Ultra Wide Band (UWB) SAW RFID tags based on Inductive Resonant Loading (IRL) where an inductor is loaded across the reflecting IDT. Simulation results show that there is a 15 dB improvement in reflected power using this design which corresponds to an extended range of up to 9.6 m. Such tags can prove to be very useful in various identification applications leading to a better detection of the tags that are located roughly 10 meters away from the RFID reader.

A scalable surface-acoustic-wave- (SAW-) based cantilevered device for portable bio-chemical sensing applications is presented. Even in the current, proof-of-principle implementation this architecture is shown to outperform commercial quartz–crystal microbalances in terms of sensitivity. Adhesion of analytes on a functionalized surface of the cantilever shifts the resonant frequency of a SAW-generating transducer due to the stress-induced variation of the speed of surface acoustic modes. We discuss the relevance of this approach for diagnostics applications based on miniaturized devices.

We present results from an instrument combining surface acoustic wave (SAW) propagation and surface plasmon resonance (SPR) measurements. The objective is to use two independent methods, the former based on adsorbed mass change measurements and the latter on surface dielectric properties variations, to identify physical properties of protein layers, and more specifically their water content. We display mass sensitivity calibration curves using electrodeposition of copper leading to a sensitivity in liquid of 150±15 cm 2 /g for the Love mode device used here, and the application to monitoring biological processes. The extraction of protein layer thickness and protein to water content ratio is also presented for S-layer proteins under investigation. We obtain respectively 4.7±0.7 nm and 75±15%.

An atomic resolution ultra-high sensitivity surface acoustic wave (SAW) biosensor for DNA sequences and cells detection is proposed. Interdigitated transducers (IDTs) fabricated on LiNbO3 substrate achieve a high quality factor (Q) of over 4000 at a frequency of 6.4GHz (third-order harmonic mode) using an optimized design and process. The biosensor shows excellent linear responses to target DNA in the range from 1μg/ml to 1ng/ml with a high sensitivity of 6.7×10-16g/cm2/Hz, hence the difference of a single hybridized DNA base can also be distinguished. With such a high mass resolution, the biosensor is capable of quantitative detection of living cancer cells. The frequency responses of single mouse mammary adenocarcinoma (EMT6) cell and mouse fibroblast (3T3) cell are studied. The interferences in the experiments show insignificant influence on the frequency shift, which verifies the high selectivity of the biosensor. The biosensor is also able to repeat the sensing ability after rough cleaning, therefore cost reduction is achieved from the recycling process in practical applications. The detection limit is defined from the noise analysis of the device, atomic resolution is realized according to the calculation, thereby initiating a potential tool for high-precision medical diagnoses and phenomena observation at the atomic-level.

A compact microfiber-based acoustic vibration sensor is demonstrated using microfiber knot resonator (MKR) structure, which is fabricated by flame brushing technique. It is observed that the extinction ratio of the resonant spectrum of the knot resonator is linearly proportional to the vibration amplitude. This is attributed to the interruption of the effective coupling of the MKR which is correlated with the exposed vibration force. It is also shown that the resonant wavelength shifts by about 0.19 nm as the normalized vibration energy is increased from 0 to 10%. The performance of the sensor is then further investigated by monitoring the fast Fourier transform (FFT) of the signal when the MKR is exposed to various vibration frequencies as a narrowband 1545 nm laser is injected into the MKR. In the spectra of the signals, the frequency of the applied vibration is clearly shown as it has the highest magnitude followed by the accompanying harmonics. This holds true for all vibration frequencies. © 2013 Wiley Periodicals, Inc.

http://onlinelibrary.wiley.com/doi/10.1002/mop.27526/abstract 
http://onlinelibrary.wiley.com/doi/10.1002/mop.27526/abstract;jsessionid=C4E82672F24D93ACEED00934537C4E5B.f01t02?deniedAccessCustomisedMessage=&userIsAuthenticated=false

Piezoelectric quaru crystals capable of generating ultrasonic shear waves have long been used to detect mass changes that result from deposition of metal layers, using the Sauerbrey equation to relale the observed changes in resonant frequenry to the corresponding changes in mass. More recently such crystals have been employed in