Utilizing Surface Acoustic Wave Research Articles

Surface acoustic wave platform integrated with ultraviolet activated rGO-SnS2 nanocomposites to achieve ppb-level dimethyl methylphosphonate detection at room-temperature

Dimethyl methylphosphonate (DMMP) is commonly used as an alternative for demonstrating to detect sarin, which is one of the most toxic but odorless chemical nerve agents. Among various types of DMMP sensors, those utilizing surface acoustic wave (SAW) technology provide notable advantages such as wireless/passive monitoring, digital output, and a compact, portable design. However, key challenges for SAW-based DMMP sensors operated at room temperature lies in simultaneous enhancement of sensitivities and reduction of detection limits. In this study, we developed a binary material strategy by combining reduced graphene oxide (rGO) and tin disulfide (SnS2) with (100)-facets orientation as sensing layers of SAW device for DMMP detection utilized at room temperature. Ultraviolet (UV) light was applied to activate the sensitive film and reduce the sensor's response time. The developed SAW DMMP sensor demonstrated a superior sensitivity (−1298.82 Hz/ppm), a low detection limit of 50 ppb, and a hysteresis below 1.5%, along with fast response/recovery time (39.2 s/28.4 s), excellent selectivity, long-term stability and repeatability. The formation of shrub-like rGO-SnS2 heterojunctions with abundant surface defects and large specific surface areas, high-energy (100) crystalline surfaces of SnS2, and photogenerated carriers generated by UV irradiation were pinpointed as the crucial sensing mechanisms. These factors collectively enhanced adsorption and reaction dynamics of DMMP molecules.

Synthesis and Characterization of High‐Quality Ta2O5 Nanoparticles for Highly Selective SAW‐Based DUV Sensor and Corona Detection Application

AbstractIn recent times, significant progress is made in the development of solar‐blind deep‐ultraviolet (DUV) photodetectors (200–280 nm) due to their potential applications for military and civil purposes. In this study, the development of a novel solar‐blind DUV photodetector based on tantalum pentoxide (Ta2O5) nanoparticles (NPs) utilizing Surface Acoustic Wave (SAW) sensor integrated with Interface electronics is reported for the first time. The 3‐D Ta2O5 NPs surface morphology, crystallinity, and defect state level is discussed using various analytical techniques, including scanning electron microscope (SEM), X‐ray diffraction (XRD), and spectrophotometer. The developed 3‐D Ta2O5 NPs based photodetector exhibits high sensitivity to 254 nm DUV irradiation (5 µW cm−2), demonstrating excellent photoresponse characteristics. The performance parameters including highest sensitivity, fast response/recovery time are measured as 1621.1 ppm (mW cm−2)−1, 3.7s/19.8s, respectively. Subsequent analysis demonstrates the stability and repeatability of the photodetector, enabling its potential to real time corona discharge detection. With its inherent advantages, the current DUV photodetector utilizing Ta2O5 NPs exhibits great potential for future applications in DUV optoelectronics.

Enhanced sensitivity of langasite-based surface acoustic wave CO gas sensor using highly porous Ppy@PEDOT:PSS hybrid nanocomposite

The potential usage of the nano-porous Ppy@PEDOT:PSS hybrid organic nanocomposite polymers has been widely explored in various applications fields. However, the study of Ppy@PEDOT:PSS based room temperature (RT) CO gas sensing utilizing surface acoustic wave (SAW) sensor is still at infancy. Herein, we report a langasite (LGS) based RT CO SAW gas sensor using Ppy@PEDOT:PSS hybrid organic nanocomposite polymer. The Ppy@PEDOT:PSS/LGS SAW sensor exhibited high sensitivity of ~9.38 KHz positive frequency shift (∆f) as compared to the pristine PEDOT:PSS/LGS SAW (~1.76 kHz negative ∆f) sensor with a short response/recovery times (121 s/138 s), good reproducibility, excellent selectivity and low detection limit (~231 ppb) towards CO (100 ppm) gas at RT. Interestingly, our experimental findings demonstrated that the Ppy@PEDOT:PSS/LGS SAW sensor exhibited the positive ∆f which was attributed to the enhanced elastic loading and decrease in the electrical conductivity under CO gas ambient, whereas the PEDOT:PSS/LGS SAW showed negative ∆f, which was due to the mass loading effect. Moreover, the impressive CO gas sensing performances were attributed to the, high porosity, large surface area, abundant OH and amine functionalizing groups. In addition the synergetic effect of the p-p hybrid heterojunction, which can act as active surface sites that further improving the CO gas molecules absorption, and thus leading to the massive changes in elastic stiffness and the electrical conductivity of the Ppy@PEDOT:PSS film. The scientific findings of this work offers a versatile platform to develop high performance hybrid organic polymer nanocomposites based SAW gas-sensing applications.

Versatile platform for performing protocols on a chip utilizing surface acoustic wave (SAW) driven mixing.

We present and demonstrate a dextrous microfluidic device which features a reaction chamber with volume flexibility. This feature is critical for developing protocols directly on chip when the exact reaction is not yet defined, enabling bio/chemical reactions on chip to be performed without volumetric restrictions. This is achieved by the integration of single layer valves (for reagent dispensing) and surface acoustic wave excitation (for rapid reagent mixing). We show that a single layer valve can control the delivery of fluid into, an initially air-filled, mixing chamber. This chamber arrangement offers flexibility in the relative volume of reagents used, and so offers the capability to not only conduct, but also develop protocols on a chip. To enable this potential, we have integrated a SAW based mixer into the system, and characterised its mixing time based on frequency and power of excitation. Numerical simulations on the streaming pattern inside the chamber were conducted to probe the underlying physics of the experimental system. To demonstrate the on-chip protocol capability, the system was utilised to perform protein crystallization. Furthermore, the effect of rapid mixing, results in a significant increase in crystal size uniformity.

Surface Acoustic Wave-Based Microfluidic Coagulation Device for Monitoring Anticoagulant Therapy.

An universal coagulation test that reliably detects prolonged coagulation times in patients, regardless of which anticoagulant is administered, is not yet available. The authors developed a novel, miniaturized device utilizing surface acoustic waves (SAW) to detect clotting, and used it to develop a novel universal microfluidic coagulation test. Results from this assay were compared with results from standard coagulation assays to detect classical anticoagulants (unfractionated heparin, argatroban) and direct oral anticoagulants (dabigatran, rivaroxaban). The SAW-clotting time (SAW-CT) of this novel device was prolonged in a dose-dependent manner for heparin, argatroban, dabigatran, and rivaroxaban, comparable to standard assays. The authors confirmed the clinical utility of this device in a small patient population admitted to a stroke unit. Preliminary clinical data prove the suitability of the SAW-CT in patients receiving warfarin, rivaroxaban, or dabigatran. The device could be particularly useful as a point-of-care test to assess whole blood coagulation (e.g., in stroke units or in other emergency settings).

Enhancement of acousto-optical coupling in two-dimensional air-slot phoxonic crystal cavities by utilizing surface acoustic waves

A phoxonic crystal is a periodically patterned material that can simultaneously localize optical and acoustic modes. The acousto-optical coupling in two-dimensional air-slot phoxonic crystal cavities is investigated numerically. The photons can be well confined in the slot owing to the large electric field discontinuity at the air/dielectric interfaces. Besides, the surface acoustic modes lead to the localization of the phonons near the air-slot. The high overlap of the photonic and phononic cavity modes near the slot results in a significant enhancement of the moving interface effect, and thus strengthens the total acousto-optical interaction. The results of two cavities with different slot widths show that the coupling strength is dependent on the slot width. It is expected to achieve a strong acousto-optical/optomechanical coupling in air-slot phoxonic crystal structures by utilizing surface acoustic modes.

Measurements of Streams Agitated by Fluid Loaded SAW-devices Using a Volumetric 3-component Measurement Technique (V3V)

Utilizing surface acoustic waves (SAW) to induce tailored fluid motion via the acoustic streaming requires detailed knowledge about the acoustic bulk wave excitation. For the first time, the Defocus Digital Particle Image Velocimetry is used to measure the fluid motion originating from a fluid loaded SAW-device. With this flow measurement technique, the acoustic streaming-induced fluid motion can be observed volumetrically, which is attractive not only for application, but also for simulation in order to gain deeper insights regarding three-dimensional acoustic effects.

Spatially resolved acoustic spectroscopy for rapid imaging of material microstructure and grain orientation

Measuring the grain structure of aerospace materials is very important to understand their mechanical properties and in-service performance. Spatially resolved acoustic spectroscopy is an acoustic technique utilizing surface acoustic waves to map the grain structure of a material. When combined with measurements in multiple acoustic propagation directions, the grain orientation can be obtained by fitting the velocity surface to a model. The new instrument presented here can take thousands of acoustic velocity measurements per second. The spatial and velocity resolution can be adjusted by simple modification to the system; this is discussed in detail by comparison of theoretical expectations with experimental data.

Enhanced surface acoustic wave atomization via amplitude modulation

Recent developments in the miniature chip-based microfludic nebulization platform utilizing surface acoustic wave (SAW) atomizer for inhalation therapy offers distinct advantages over other conventional nebulizers. Such efficient hand-held nebulizer system also requires the optimization of the usage of available power systems in the simplest manner. Here, amplitude modulation (AM) is presented as a simple yet effective means of optimizing the power requirement. SAWs are nano meter order amplitude acoustic waves that originate as a result of the application of an alternating current onto a pair of single-phase unidirectional transducers patterned on a piezoelectric substrate. The effect of the AM at modulation frequencies of 500 Hz, 1 kHz, 5 kHz, 10 kHz, 20kHz and 40 kHz sinusoidal signals, on shear-sensitive biomolecules such as plasmid DNA and antibody molecules are shown to be minimal. Energy savings of around 40% can be obtained with more efficient atomization achieved with AM less than 10 kHz. Together with these advantages, AM having little effect of the mean aerosol diameter; particularly important when therapies are to be targeted for the deep lung regions, holds great promise for its use in the SAW nebulizers for non-invasive inhalation therapy. Acknowledgements are dedicated to Asthma Foundation Victoria (Australia).

Wireless Remote 2-D Strain Sensor using SAW Delay Line

AbstractTwo-dimensional (2-D) strain sensor utilizing surface acoustic wave (SAW) devices is demonstrated. SAW devices offer many attractive features for applications as chemical and physical sensors. In this paper, a novel SAW strain sensor that employs SAW delay lines has been designed. Two crossed delay lines were used to measure the two-dimensional strain. A wireless sensing system is also proposed for effective operation of the strain sensor.

Electronic weighing apparatus utilizing surface acoustic waves using sensors operating at different frequencies, having temperature compensation, and a push oscillator

A weighing apparatus includes a SAW oscillator and a “push oscillator” to force the SAW oscillator into a desired mode of operation. A SAW temperature oscillator and a thermistor are also provided. The frequency of the “push oscillator” is made immune to temperature changes by generating it via a mixer mixing the SAW temperature oscillator with an adjustable fixed frequency oscillator. Long term stability of the SAW temperature oscillator is achieved by periodic calibration with the thermistor.

Acoustic-wave-based voltage sensors

Acoustic-wave-based voltage sensors utilizing surface acoustic wave (SAW) delay lines are reviewed. A SAW oscillator that consists of a SAW delay line and an amplifier connected between input and output interdigital transducers (IDTs) can be used as a SAW-based voltage sensor, when a d.c. or a.c. voltage is applied on the SAW propagation path in the piezoelectric substrate. The voltage sensors detect an applied voltage as a fractional change of oscillation frequency. there are two electrode configurations for applying a voltage to the substrates on which the SAW propagates. One is to apply a voltage perpendicular to the surface of the substrate, and the other is to apply it parallel to the surface of the substrate and perpendicular to the propagation direction of the SAW. The former configuration is used in a sensor having a ZnO thin film on Si and a sensor utilizing a Lamb wave, as well as in a sensor utilizing a Rayleigh wave on LiNbO 3 plates, whereas the latter is used in a sensor with SAW waveguides.

Focus detection method utilizing surface acoustic wave

Method for detecting a focus condition of an imaging optical system by using a surface acoustic wave device is disclosed. A light receiving element array formed by a plurality of light receiving elements receives a light flux transmitted through at least a part of an image formed by the imaging optical system. Then, outputs of said light receiving elements are processed on real time by means of a Fourier transform device including a surface acoustic wave device, a convolver, etc. so as to derive an image sharpness and/or an image lateral shift, both of which are used for a focus detection. Therefore, as compared with a conventional focus detection method, it is possible to perform the focus detection in a fast and accurate manner by a simple and small construction.

Acousto-optic isolator

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Experimental investigation of the acoustooptic interaction in a waveguide interferometer

An experimental investigation was made of the transfer characteristics and signal readout efficiency of devices utilizing surface acoustic waves. The investigation was carried out using a strip optical waveguide interferometer. A prototype of this interferometer was made from a YZ-cut lithium niobate substrate. Electrodes were used for electrooptic correction of ihe initial phase shift between the optical waves in the interferometer arms and an opposed-comb transducer was employed to excite acoustic waves. The results should be useful in the development of signal

A new type of pressure sensor utilizing surface acoustic waves

Abstract Mechanical strain effect experiments on a 103 MHz Y-Z LiNbO3 surface acoustic waves (SAW) transducer with 3 cm electrode distance have been made. The phase shift was 40 degrees at −90 × 10−6 strain and quite linear with strain. Optimum design considerations for a SAW pressure sensor consisting of a clamped edge piezoelectric diaphragm with two sets of interdigital electrodes have been made. The optimum positions for the electrodes were determined. Deflection of the diaphragm under pressure retards the phase for one set and advances the phase for the other set. The maximum phase shift and cancellation of thermal expansion effects results by measuring the phase difference between the two sets. The maximum phase shift and cancellation of thermal expansion effects results by measuring the phase difference between the two sets.