Hydrophone Devices Research Articles

Suspended Graphene Hydroacoustic Sensor for Broadband Underwater Wireless Communications

Compared to terrestrial and airborne wireless communications using radio waves, underwater wireless communications encounter a longstanding challenge: the aqueous-medium seriously attenuates electromagnetic waves. As the only choice to this day, underwater wireless communication employing acoustic waves is still hindered by hydrophone device performance. Several shortcomings, such as the unsatisfactory response bandwidth and circuitry complexity, severely limit the popularization potential. To address these issues, a cohort study of a hydroacoustic sounder device made by suspended graphene is proposed in this article as a novel scenario for underwater wireless communications. By testing the sensor performance, we demonstrate a significant passband extension up to 192 kHz, which is competent to overcome the ubiquitous issue of spectrum scarcity in acoustic communications. The response sensitivity estimated at the level ~80 mS Pa-1 may enable the detection of weak signals down to the level ~0.1 dB. Besides, our suspended graphene sounder also provides a hardware simplification potential that automatically modulates acoustic wave excitations into radio frequency signals. The device deployment convenience may facilitate the incorporation of underwater wireless communications into telecommunication networks.

Induced Hall-Like Current by Acoustic Phonons in Semiconductor Fluorinated Carbon Nanotube

We show that Hall-like current can be induced by acoustic phonons in a nondegenerate, semiconductor fluorine-doped single-walled carbon nanotube (FSWCNT) using a tractable analytical approach in the hypersound regime (q is the modulus of the acoustic wavevector and is the electron mean free path). We observed a strong dependence of the Hall-like current on the magnetic field, H, the acoustic wave frequency, , the temperature, T, the overlapping integral, , and the acoustic wavenumber, q. Qualitatively, the Hall-like current exists even if the relaxation time does not depend on the carrier energy but has a strong spatial dispersion, and gives different results compared to that obtained in bulk semiconductors. For and , the Hall-like current is in the absence of an electric field and in the presence of an electric field at 300 K. Similarly, the surface electric field due to the Hall-like current is in the absence of an external electric field. In the presence of an external electric field, and for at 300 K. q and can be used to tune the Hall-like current and of the FSWCNT. This offers the potential for room temperature application as an acoustic switch or transistor, as well as a material for ultrasound current source density imaging (UCSDI) and AE hydrophone device in biomedical engineering.

Semiconductor Fluorinated Carbon Nanotube as a Low Voltage Current Amplifier Acoustic Device

Acoustoelectric effect (AE) in a non-degenerate fluorinated single walled carbon nanotube (FSWCNT) semiconductor was carried out using a tractable analytical approach in the hypersound regime , where q is the acoustic wavenumber and is the electron mean-free path. In the presence of an external electric field, a strong nonlinear dependence of the normalized AE current density , on ( is the electron drift velocity and is the speed of sound in the medium) was observed and depends on the acoustic wave frequency, , wavenumber q, temperature T and the electron-phonon interactions parameter, . When , decreases to a resonance minimum and increases again, where the FSWCNT is said to be amplifying the current. Conversely, when , rises to a maximum and starts to decrease, similar to the observed behaviour in negative differential conductivity which is a consequence of Bragg’s reflection at the band edges at T=300K. However, FSWCNT will offer the potential for room temperature application as an acoustic switch or transistor and also as a material for ultrasound current source density imaging (UCSDI) and AE hydrophone devices in biomedical engineering. Moreover, our results prove the feasibility of implementing chip-scale non-reciprocal acoustic devices in an FSWCNT platform through acoustoelectric amplification.

Low-Cost, Tiny-Sized MEMS Hydrophone Sensor for Water Pipeline Leak Detection

In this paper, we present an experimental investigation of a water pipeline leak detection system based on a low-cost, tiny-sized hydrophone sensor fabricated using the microelectromechanical system (MEMS) technologies. A 10 × 10 element arrayed MEMS hydrophone device with chip size of 3.5 × 3.5 mm $^2$ was used in the experiment. The hydrophone device is packaged with a customized on-board preamplification circuit using an acoustic transparent material. The overall package size of the MEMS hydrophone is $\Phi$ 1.2 × 2.5 cm. The packaged MEMS hydrophone achieves an acoustic sensitivity of −180 dB (re: 1 V/ $\mu$ Pa), a bandwidth from 10 Hz to 8 kHz, and a noise resolution of around 60 dB (re: 1 $\mu \text{Pa/}\sqrt{\text{Hz}}$ ) at 1 kHz. A section of ductile iron water pipeline with an internal diameter of 10 cm, wall thickness of 0.73 cm, and length of 30 m is constructed as the test bed for the water leak detection. Two different leak sizes with leak flow rates of about 30 and 180 L/min are designed along the pipe, which is pressurized at 3.2 bar. Analysis of the transient signals and spectrograms shows that the MEMS hydrophone can capture the key acoustic information of the water leak, i.e., identifying the leak and locating the leak position. The measurement results demonstrate the feasibility to construct an affordable, highly efficient, real-time, and permanent in-pipe pipeline health monitoring network based on the MEMS hydrophones due to their high performance, low cost, and tiny size.

Computational Modeling of Piezoelectric Foams

Piezoelectric materials, by virtue of their unique electromechanical characteristics, have been recognized for their potential utility in many applications as sensors and actuators. However, the sensing or actuating functionality of monolithic piezoelectric materials is generally limited. The composite approach to piezoelectric materials provides a unique opportunity to access a new design space with optimal mechanical and coupled characteristics. The properties of monolithic piezoelectric materials can be enhanced via the additive approach by adding two or more constituents to create several types of piezoelectric composites or via the subtractive approach by introducing controlled porosity in the matrix materials to create porous piezoelectric materials. Such porous piezoelectrics can be tailored to demonstrate improved signal-to-noise ratio, impedance matching, and sensitivity, and thus, they can be optimized for applications such as hydrophone devices. This article captures key results from the recent developments in the field of computational modeling of novel piezoelectric foam structures. It is demonstrated that the fundamental elastic, dielectric, and piezoelectric properties of piezoelectric foam are strongly dependent on the internal structure of the foams and the material volume fraction. The highest piezoelectric coupling constants and the highest acoustic impedance are obtained in the [3-3] interconnect-free piezoelectric foam structures, while the corresponding figures of merit for the [3-1] type long-porous structure are marginally higher. Among the [3-3] type foam structures, the sparsely-packed foam structures (with longer and thicker interconnects) display higher coupling constants and acoustic impedance as compared to closepacked foam structures (with shorter and thinner interconnects). The piezoelectric charge coefficients (d h), the hydrostatic voltage coefficients (g h), and the hydrostatic figures of merit (d hgh) are observed to be significantly higher for the [3-3] type piezoelectric foam structures as compared to the [3-1] type long-porous materials, and these can be enhanced significantly by modifying the aspect ratio of the porosity in the foam structures as well.

High sensitivity ultrasonic sensor for hydrophone applications, using an epitaxial Pb(Zr,Ti)O3 film grown on SrRuO3/Pt/γ-Al2O3/Si

A piezoelectric ultrasonic sensor has been fabricated using an epitaxial lead zirconate titanate, Pb(Zrx, Ti1−x)O3 (PZT) thin film, grown on an epitaxial SrRuO3/Pt/γ-Al2O3/Si substrate. The 3-μm thick PZT film was prepared by the sol–gel method. This sensor structure was very stable during the fabrication process after preparation of the PZT. The fabricated sensor offers a reception sensitivity of up to −243dB re 1V/μPa in the frequency range from 1 to 15MHz, which means that it has higher sensitivity than that of a conventional polyvinylidene fluoride (PVDF) hydrophone. The pressure field of a focused ultrasonic transducer was determined using this ultrasonic sensor. The measured pressure peak was in good agreement with the results derived from calculations. These results suggest that the fabricated ultrasonic sensor can be used as a high sensitivity hydrophone device.

Microfluidic amplification of ultrasound with application to MEMS hydrophones

Micro-electro-mechanical systems (MEMS) were used to fabricate a device with passive fluidic components that amplified the motion associated with ultrasonic waves in water. Two types of fluid components were etched in silicon, an acoustic horn, and an acoustic resonator. The fluid motion was detected by a small silicon diaphragm which moved with the sound wave. The diaphragm motion was measured with a laser Doppler vibrometer. Experiments were carried out for acoustic excitations in the frequency region of 0.5 to 5 MHz. Over this frequency range uniform thickness diaphragms were found to support multiple resonance modes and were found to be poor sensing surfaces. Composite diaphragms, with a stiff pedestal supported by compliant edge fixtures, provided a superior sensing surface. The motion of the diaphragm placed at the throat of an acoustic horn demonstrated broadband amplification with a gain of 6. An organ-pipe type resonator provided a narrow-band gain of 3. The horn and resonator structures could be incorporated into most types of MEMS hydrophone devices which use diaphragms to sense sound waves. [Work supported by DARPA.]

Development of novel polycrystalline materials on the basis of Sn2P2S6 for hydrophone applications

Polycrystalline textures, pressed powder and 0-3 composites on the basis of Sn2P2S6 have been prepared with the aim to identify an optimum polycrystalline form with high piezoelectric figure of merit which would offer the prospect of application in hydrophone devices. 0-3 Sn2P2S6/PVA (poly-vinyl alcohol) composite shows the highest hydrostatic piezoelectric voltage sensitivity (gh=210* 103Vm/N). The electromechanical coupling coefficients kt, kp and piezoelectric coefficient d33 for this composite were found to be 41%, 16% and 60 pC/N respectively. The dielectric properties of the materials studied, in particular the nature of the low frequency dielectric dispersion are discussed.

Composite hydrophone devices coupling piezoelectricity and tensegrity

The concept of tensegrity as conceived by Buckminster Fuller has been incorporated into a passive hydrophone device. Tensegrity is described as the physical phenomenon that produces a stable geometric structure using solid compressional elements arranged in tandem with flexible tensional cables. In the devices built by the authors, six PZT 5HTM bars acting as compressional elements in the tensegrity structure have been coupled with tensional bands of either polyaramid or carbon fiber. This stable system is then wrapped with an outer layer of either polyaramid or carbon fiber and rubber film to form a sealed device, which is referred to as a piezotensegritive device in this paper. The six bars are arranged in parallel electrical connectivity for all devices described. The resonant frequency for these devices ranged from 19.5 to 20.3 kHz depending on the material used for wrapping the piezoelectric bars. These devices were also tested in a hydrostatic environment to determine the relevant piezoelectric coefficients. For devices wrapped with carbon fiber, dh peaked at ∼6000 pC/N and gh at ∼ 275 mVm/N. For devices wrapped with polyaramid, dh peaked at ∼2000pC/N and gh at ∼ 100mVm/N. Sensitivities from—182–195 db ref. 1V/μPa were calculated for these devices.

Packaging MEM Sensor Arrays

AbstractMany applications of MEM sensors require hermetic or high vacuum packaging of sensor clusters. For example, multiple gyroscopes or accelerometers are fabricated on a single chip to improve alignment and stability of input axes or increase the dynamic range of instruments. Chemical sensors are fabricated as large arrays to both improve selectivity and increase the number of species that can be detected. Still larger arrays of sensors must be packaged for hydrophone and bolometer imaging devices. All of these applications place a demanding combination of requirements on the sensor package. The electrical outputs of the sensor array must be well isolated from each other as well as power and excitation signals, while parasitic capacitance is minimized. The package must also be capable of being evacuated and sealed to achieve a pressure of 5 millitorr with a leakage rate below 10−11 [Std cc sec−l]. Finally, the package must be compact and low cost to realize these same attributes of the MEM sensor. This paper describes a packaging approach that is based on low temperature cofired ceramic materials. This technology meets the packaging requirements of sensor arrays and is well suited to the research environment in which the sensor design is continually evolving.

Method of detecting sound in water using piezoelectric-polymer composites with 0–3 connectivity

First Page

Composite piezo wire hydrophone

Abstract Acomposite piezoelectric wire is made into a hydrophone device and the performance is tested in a standard underwater test facility in the frequency range 10 to 70 kHz. Its performance is comparable to that of standard Bruel & K hydrophone type 8103 in that frequency range. It has advantage of the continuous sensor element.

Transducer hydrophone with filled reservoir

A hydrophone device with one or more very small active spots located on a large continuous ferroelectric sheet, such as PVDF, overcomes many of the problems in prior art constructions associated with the high dielectric constant of various media in which the device is used. Additional improvements include increased signal to noise ratio and a sensitivity independent of the medium properties. The hydrophone device includes a piezoelectrically active sheet stretched and clamped on over the top of a hoop ring. A backing is attached to the back of the hoop ring. A low-dielectric material fills the space between the backing and the sheet. This material eliminates the capacitive loading effect which would otherwise be presented by the medium being probed.