Surface Acoustic Wave Element Research Articles

Diffraction-based acoustic manipulation in microchannels enables continuous particle and bacteria focusing

Acoustic fields have shown wide utility for micromanipulation, though their implementation in microfluidic devices often requires accurate alignment or highly precise channel dimensions, including in typical standing surface acoustic wave (SSAW) devices and resonant channels. In this work we investigate an approach that permits continuous microscale focusing based on diffractive acoustics, a phenomenon where a time-averaged spatially varying acoustic pressure landscape is produced by bounding a surface acoustic wave (SAW) transducer with a microchannel. By virtue of diffractive effects, this acoustic field is formed with the application of only a single travelling wave. As the field is dictated by the interplay between a propagating substrate-bound wave and a channel geometry, the pressure distribution will be identical for a given channel orientation regardless of its translation on a SAW substrate, and where small variations in channel size have no substantive effect on the pressure field magnitude or overall particle migration. Moreover, in the case of a channel with dimensions on the order of the diffractive fringe pattern spacing, the number of focusing positions will be identical for all channel orientations, with acoustic radiation forces pushing suspended particles to the channel edges. We explore this highly robust particle manipulation technique, determining two distinct sets of streaming and acoustic radiation dominant concentration positions, and show the continuous focusing of polystyrene 1 μm and 0.5 μm diameter particles and fluorescently labeled E. coli bacteria cells at flow rates exceeding those of previous microfluidic implementations for micron and submicron sized particles.

Analysis on Characteristics of ZnO Surface Acoustic Wave with and without Micro-Structures.

In this paper, we fabricate a surface acoustic wave (SAW) device with micro-structures on a zinc oxide (ZnO) thin film and measure its signal response. The manufacturing processes of the SAW device include the fabrication of micro-structures of a SAW element and its interdigital transducer by silicon micro-machining and the fabrication of a thin film of ZnO by RF magnetron sputtering. We, then, measure the SAW properties. This research investigates the properties of sputtered thin films for various amounts of O2/(Ar + O2) using Zn and ZnO targets. Regardless of target, the growth rate of the ZnO thin film decreases as the oxygen content increases. When the SAW is sputtered ZnO thin film using 30% oxygen, the digital signal of the SAW has better performance. The measurement signal of the SAW with micro-structures is similar to that without micro-structures.

Pressure sensor device with surface acoustic wave elements

Thickness of a pressure-detecting piezoelectric substrate ( 2 ) that is thinner than that of a supporting piezoelectric substrate ( 3 ) and that has a surface acoustic wave element for pressure detection ( 7 a ) on its lower surface is mounted on the supporting piezoelectric substrate ( 3 ) having a surface acoustic wave element for reference ( 4 a ) on its upper surface. A sealing member ( 5 ) is provided between the supporting piezoelectric substrate ( 3 ) and the pressure-detecting piezoelectric substrate ( 1 ). The surface acoustic wave element for pressure detection ( 7 a ) and the surface acoustic wave element for reference ( 4 a ) can be disposed in a space (S) enclosed with the pressure-detecting piezoelectric substrate ( 1 ) and the sealing member ( 5 ). It is possible to provide a small-sized pressure sensor device ( 1 ) that can perform temperature compensation and that has high reliability.

Surface acoustic wave element

A surface acoustic wave element according to the present invention has a structure including a hard layer containing a composition component essentially consisting of at least one of diamond and a diamond-like carbon film [2], a piezoelectric layer formed on the hard layer [4], a silicon dioxide (SiO₂) [5] layer formed on the piezoelectric layer, and electrodes combined with the piezoelectric layer to perform electro-mechanical conversion. The surface acoustic wave element having the above structure according to the present invention has a larger electro-mechanical coupling coefficient and a higher surface acoustic wave propagation velocity than those of a conventional surface acoustic wave element having no silicon dioxide layer, thereby obtaining a surface acoustic wave element operated in a high-frequency range. In particular, the electro-mechanical coupling element is increased. The silicon dioxide (SiO₂) layer is an electric insulator and rarely reacts with moisture or an acid. The silicon dioxide layer can protect the piezoelectric layer and the electrodes from an external environment, thereby providing a surface acoustic wave element having good high-frequency characteristics and a high resistance to environment.

Surface acoustic wave element and electronic equipment provided with the element

A surface acoustic wave element 1 includes a substrate 2 , an intermediate layer and a piezoelectric layer 4 laminated on the substrate 2 , an IDT 5 disposed on the piezoelectric layer 4 , a pair of reflectors 6 and 7 arranged on both sides of the IDT 5 , and a protective layer 8 provided so as to cover the IDT 5 and the reflectors 6 and 7 . The IDT 5 , that is each of the electrode 5 a and 5 b , has a plurality of electrode fingers 51 juxtaposed with a prescribed spacing and the reflectors 6 and 7 have respectively a plurality of reflecting bodies 61 and 71 . Further, the pitch Pr of the reflecting body of each reflector 6 and 7 is set to be smaller than the pitch Pt of the electrode finger of the IDT 5 and the ratio Pr/Pt is preferably set to be in the range of 0.7 to 0.9995. According to the surface acoustic wave element 1 , the impedance characteristic and the insertion loss can be improved. Furthermore, electronic equipment having such surface acoustic wave element is provided.

Method of manufacturing potassium niobate single crystal thin film, surface acoustic wave element, frequency filter, frequency oscillator, electronic circuit, and electronic apparatus

A method of manufacturing potassium niobate single crystal thin film on a single crystal substrate that epitaxially grows orthorhombic potassium niobate single crystal at a temperature near room temperature at a high deposition rate. A surface acoustic wave element, frequency filter, frequency oscillator, electronics circuit, and electronic device employ the thin film manufactured by the method, and are high in k 2 , wideband, downsized, and economical in power consumption. The method includes the steps of coating liquid drops of a potassium niobate solution on a SrTiO 3 single crystal substrate by a liquid drop emission method, and precipitating potassium niobate single crystal layer by epitaxial growth from the liquid drops.

Passive saw-based hydrogen sensor and system

A hydrogen detecting system is characterized by a passive surface acoustic wave (SAW) sensor. The sensor includes a piezoelectric substrate having a self assembled monolayer arranged on at least a portion of the substrate to create a hydrophobic surface. A palladium nanocluster thin film is deposited on the monolayer and an interdigital SAW transducer is disposed upon the piezoelectric substrate for conversion of an RF signal into an acoustic wave and vice versa. At least one additional SAW element is also disposed on the substrate and spaced from the SAW transducer. The SAW element receives a signal from the SAW transducer and produces a response signal. The response signal is modified by the palladium nanocluster film due to a change in conductivity of the palladium nanocluster film upon exposure to hydrogen. This change in the response signal is measured by an interrogator, and yields a measure of the hydrogen concentration to which the sensor was exposed.

Surface acoustic wave element, electric signal processing apparatus using the surface acoustic wave element, environment evaluating apparatus using the electric signal processing apparatus, and analyzing method using the surface acoustic wave element

A surface acoustic wave element includes a single crystal base which has an annular surface formed by at least one portion of a spherical surface, and an exciting unit which excites a surface acoustic wave propagating along the annular surface. An electric signal processing apparatus includes the surface acoustic wave element, an input portion which inputs a predetermined signal to the exciting unit so that the wave is excited, a detecting unit which detects the propagating wave, and an output portion which outputs a signal corresponding to the wave detected by the detecting unit. An environment evaluating apparatus includes the processing apparatus, and a processing portion which evaluates an environment around the base, based on at least one of a frequency of the signal outputted by the processing apparatus, an intensity thereof, and time elapsing from a signal input time to a signal output time from the processing apparatus.

Surface acoustic wave element, surface acoustic wave device, surface acoustic wave duplexer, and method of manufacturing surface acoustic wave element

A surface acoustic wave element includes a thin film electrode composed of monocrystal aluminum disposed on a piezoelectric substrate. At least one metal of Cu, Ta, W, and Ti is segregated in the thin film electrode composed of monocrystal aluminum. In this surface acoustic wave element, segregation of Cu or the like occurs in the thin film electrode. Such segregation is effective to reduce the occurrence of cracks on the piezoelectric substrate during ultrasonic wave connection for flip chip mounting. That is, because the occurrence of cracks on the piezoelectric substrate is reduced, tolerance against the ultrasonic vibration is advantageously improved in the surface acoustic wave element.

Elastic wave apparatus

A surface acoustic wave apparatus is configured to avoid destruction from static electricity. The surface acoustic wave apparatus includes a piezoelectric substrate; a surface acoustic wave element having at least one interdigital electrode made up of a conductive film on the piezoelectric substrate; and a thin film electrically connected between terminals connecting to electrode fingers of the interdigital electrode, the thin film showing varistor characteristics formed on the piezoelectric substrate.

Surface acoustic wave element, frequency filter, oscillator, electronic circuit, and electronic instrument

A surface acoustic wave element includes a single crystal substrate; a buffer layer formed by a crystal film that is formed on top of the single crystal substrate; and a piezoelectric thin film having a hexagonal system or a trigonal system crystal structure that is formed on top of the buffer layer. The surface acoustic wave element has an improved performance by improving the film quality of the piezoelectric thin film. In addition, because a semiconductor device can be formed on the single crystal substrate, the surface acoustic wave element can be integrated with the semiconductor device. Moreover, leakages of surface acoustic waves into the single crystal substrate are prevented. There are also provided a frequency filter, an oscillator, an electronic circuit, and an electronic instrument that are provided with this surface acoustic wave element.

Surface acoustic wave device and method of adjusting a temperature characteristic of the same

The invention miniaturizes a surface acoustic wave device on which a plurality of surface acoustic wave elements are disposed and connected together in parallel on a plate, and provides a good temperature characteristic in a wide temperature range. A surface acoustic wave device according to the invention includes a plurality of surface acoustic wave elements disposed on a main surface of a quartz plate cut out with a Euler angle at (0°, 113° to 135°, +/−(40 to 49)°). Surface acoustic waves have propagation directions “ψ” which are different each other. When the Euler angle is set at (0°, θ, ψ), it is possible to reduce differences in each propagation direction by setting each propagation angle so as to satisfy a formula: ψ=0.3295θ+3.3318°+/−1.125°. This makes it possible to decrease the angle among the surface acoustic wave elements, and thereby miniaturizes the surface acoustic wave elements.

Piezoelectric vibration gyro-sensor

The present invention provides a piezoelectric vibration gyro-sensor utilizing Coriolis force that includes a tuning fork type vibrator in which two rectangular-columnar arms and a base to support the lower end of the arms are integrated; drive electrodes formed on two rectangular-columnar arms; and IDT electrodes of a surface acoustic wave element formed on two arms. Two pairs of the drive electrodes are provided on each rectangular-columnar arm, in which each of the pairs of drive electrodes face each other, and each pair of the drive electrodes are arranged in parallel on the rectangular-columnar arm at a given distance. The IDT electrodes of the surface acoustic wave element are provided between the drive electrodes at the lower end of the rectangular-columnar arms.

Application of principal component analysis and artificial neural networks to recognize the individual VOCs of methanol/2-propanol in a binary mixture by SAW multi-sensor array

This work reports on the performance of a volatile organic compounds (VOCs) identification system based on a surface acoustic wave (SAW) multi-sensor array with four acoustic sensing elements, developed in dual configuration as multiplexed two-port resonator 433.92 MHz oscillators and a reference SAW element, in order to recognize the different individual components in a binary mixture of VOCs such as methanol (CH 3OH) and 2-propanol (C 3H 7OH), in the range 20–140 and 5–70 ppm, respectively. The SAW sensors, operating at room temperature, have been specifically coated by sensing thin films belonging to various chemical classes such as arachidic acid (fatty acids), carbowax (stationary phases), triethanolamine (amines), acrylated polysiloxane (polysiloxanes) to ensure cross-sensitivity towards VOCs under test. By using the relative frequency change as the output signal of the SAW multi-sensor array with an artificial neural network (ANN), a recognition system has been realized for the identification of tested VOCs. The features extraction from output signals of the SAW multi-sensor array, exposed to the binary component mixture of methanol and 2-propanol, has been also performed by pattern recognition techniques such as principal component analysis (PCA). The feedforward multi-layer neural network with a hidden layer and trained by a back-propagation learning algorithm has been implemented in order to classify and identify the tested VOCs patterns. Both the normalized responses of four SAW sensors array and the selected principal components (PCs) scores have been used as inputs to the multi-layer perceptron ANN by resulting in a 100% success recognition rate with the four SAW sensors normalized responses and with the first two principal components scores of the original data of the primary matrix. The different strategies used to recognize the VOCs patterns by the ANNs such as the ‘Leave-one-out’ method and ‘Training-and-Test’ method are discussed. Our experimental results have evidenced that the proposed binary vapor mixture classifier based on the electronic nose system, developed by inexpensive and poorly selective chemical SAW sensors, is highly effective in the identification of tested VOCs of methanol and 2-propanol. Moreover, the combination of PCA, as data pre-processing technique, and ANN, as patterns classification technique, provides a rapid and accurate recognition method of the individual components in the tested binary mixture of methanol and 2-propanol.

Implementing wavelet transform with SAW elements

In the design of the finger-overlap envelope according to the envelope of wavelet function, it is concluded that the pulse-response function of the interdigital transducer (IDT) for surface acoustic wave (SAW) is identical to the wavelet function. SAW type of the wavelet-transform element is manufactured. A new method of using two wavelet-transform elements to manufacture the reconstruction element of the wavelet transform is proposed. The sources of the element error are analyzed, and the methods for reducing the error are put forward. SAW type of the wavelet transformation element and its reconstruction element have the following three characteristics: (i) the implementing methods of the wavelet transform element and its reconstruction element are simple, and free of complicated mathematical algorithms of the wavelet, transform; (ii) because one of SAW element is fast, the response velocities of SAW type of the wavelet transform element and its reconstruction element are also fast; (iii) the costs of the wavelet transform element and its reconstruction element are low, so the elements may be manufactured in a large quantity.

Micromechanical precision pressure sensor incorporating SAW delay lines

We have developed a wireless surface acoustic wave (SAW) pressure sensor operating in the pressure range of 0 Pa to 250 kPa. In order to minimize the temperature sensitivity the pressure sensor is made of on an all-quartz package (AQP), which has been designed with the Finite Element Method. The package of the pressure sensor consists of a diaphragm and a cover, both made of conventional Y-cut quartz. A blind-hole was structured into the sensor cover. By attaching the cover and the diaphragm with an epoxy-adhesive, this blind-hole forms a closed cavity. The SAW element is a reflective delay line (RDL), working at 434 MHz. The RDL consists of ten reflectors and extends over the whole diaphragm. The pressure is determined by evaluating the change of the carrier phase shifts of the reflected impulses at the reflectors. We show that it is possible to minimize the temperature sensitivity and to achieve good linearity by proper positioning of the SAW reflectors. The measurements of the SAW pressure sensor show a deviation from linearity of less than ±0,7%. The temperature dependence is almost negligible in the range from-20°C to 100°C. The objective of this paper is to provide a deeper insight into the behaviour of SAW propagation on pre-stressed substrates. To do so, we start with investigating the behavior of SAWs on stress-free substrates followed by an analysis of SAW propagation on pre-stressed substrates. Further, the requirements on suitable substrate materials for the AQP are specified. Finally, we take advantage of the method of differences to compensate for the temperature dependence of our pressure sensor.

Strain effect in surface acoustic wave elements with a piezoelectric acoustic line and sensors based on this effect

Strain effect in surface acoustic wave elements with a piezoelectric acoustic line and sensors based on this effect

Comparison between BAW and SAW sensor principles

A comparison is given between piezoelectrically excited bulk acoustic wave (BAW) and surface acoustic wave (SAW) elements with respect to their primary sensitivity functions and principal capabilities for sensor applications. The importance of mode purity for high dynamic range sensors is emphasized. Characteristic sensor examples are reviewed, and the special demands on the electronics for BAW and SAW elements in the sensor field are described (e.g., cable problem, wireless SAW sensors). For a fair evaluation, a performance figure, SQ, defined as the product of reduced sensitivity S and resonator Q-value, is introduced. The potential of alternative piezoelectric materials for future sensor developments is discussed briefly.

A new SO 2 sensor system with SAW and IDC elements

Applying new transducer principles on well known indicator materials improves the performance of the whole system, especially the humidity interference. A well known SO 2-sensitive material (heteropolysiloxane, NND/PTMS) was tested with a SAW (surface acoustic wave, surface transverse wave mode (STW)) transducer and an interdigital capacitor (IDC) device. Due to a different relative sensitivity of the coated IDC and SAW devices to SO 2 and humidity, we were able to reduce the overall cross-sensitivity of the system to humidity significantly. The combination of these two different types of transducers, in case of need extended with other transducers, increases the performance of the sensor system.

Detection of food poisoning bacteria involves contacting foodstuff with surface acoustic wave element having antibodies attached to surface : Oki Electric Ind. Co. Ltd JP-05034349, 9 February 1993

Chocolate confectionery fillings are generally regarded as microbiologically stable. The stability of these fillings is largely due to the general practice of adding either alcohol or preservatives. Consumer demands are now stimulating producers to move away from adding alcohol or other preservatives to their confectionery fillings and instead to search for innovative formulations. Such changes in composition can influence the shelf life of the product and may lead to spoilage by xerophilic fungi. The aim of this study was to test whether the production environment of Belgian chocolate confectionery factories and common ingredients of chocolate confectioneries could be potential sources of contamination with xerophilic fungal species. In the factory environment, the general and strictly xerophilic fungal spore load was determined using an RCS Air Sampler device in combination with DG18 and MY50G medium, respectively. Four basic ingredients of chocolate confectionery fillings were also examined for fungal spore levels using a direct plating technique. Detected fungi were identified to species level by a combination of morphological characterization and sequence analysis. Results indicated a general fungal spore load in the range of 50–250 colony forming units per cubic meter of air (CFU/m3 air) and a more strict xerophilic spore load below 50 CFU/m3 air. These results indicate rather low levels of fungal spores present in the factory environment. The most prevalent fungi in the factory environment were identified as Penicillium spp., particularly Penicillium brevicompactum. Examination of the basic ingredients of confectionery fillings revealed nuts to be the most likely potential source of direct contamination. In nuts, the most prevalent fungal species identified were Eurotium, particularly Eurotium repens.