Factors affecting the sensitivity of electrostatic ultrasonic transducers

Hietanen, Joel; Mattila, Pentti; Stor-Pellinen, Jyrki; Tsuzuki, F.; Väätäjä, Heli; Sasaki, Ken; Luukkala, M.

doi:10.1088/0957-0233/4/10/018

Cited by 25 publications

(7 citation statements)

References 9 publications

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“…An 8 × 8-channel pMUT array was fabricated, as shown in figure 23, where each channel comprised 42 pMUT elements with a 1.8 MHz resonance frequency in air and a membrane diameter that was 100 µm wide. The pMUT on epitaxially grown γ-Al 2 O 3 (1 1 1) and SrRuO 3 layers exhibited sensitivity of 3.9 µV kPa −1 that was higher than 1.3 µV kPa −1 in a conventional pMUT on SiO 2 [90,91].…”

Section: Textured Pzt Pmutmentioning

confidence: 89%

Review of piezoelectric micromachined ultrasonic transducers and their applications

Jung

Lee

Kang

et al. 2017

J. Micromech. Microeng.

238

133

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In recent decades, micromachined ultrasonic transducers (MUTs) have been investigated as an alternative to conventional piezocomposite ultrasonic transducers, primarily due to the advantages that microelectromechanical systems provide. Miniaturized ultrasonic systems require ultrasonic transducers integrated with complementary metal-oxide-semiconductor circuits. Hence, piezoelectric MUTs (pMUTs) and capacitive MUTs (cMUTs) have been developed as the most favorable solutions. This paper reviews the basic equations to understand the characteristics of thin-film-based piezoelectric devices and presents recent research on pMUTs, including current approaches and limitations. Methods to improve the coupling coefficient of pMUTs are also investigated, such as device structure, materials, and fabrication techniques. The device structure improvements include multielectrode pMUTs, partially clamped boundary conditions, and 3D pMUTs (curved and domed types), where the latter can provide an electromechanical coupling coefficient of up to 45%. The piezoelectric coefficient (e31) can be increased by controlling the crystal texture (seed layer of γ-Al2O3), using single-crystal (PMN-PT) materials, or control of residual stresses (using SiO2 layer). Arrays of pMUTs can be implemented for various applications including intravascular ultrasound, fingerprint sensors, rangefinders in air, and wireless power supply systems. pMUTs are expected to be an ideal solution for applications such as mobile biometric security (fingerprint sensors) and rangefinders due to their superior power efficiency and compact size.

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Section: Textured Pzt Pmutmentioning

confidence: 89%

Review of piezoelectric micromachined ultrasonic transducers and their applications

Jung

Lee

Kang

et al. 2017

J. Micromech. Microeng.

238

133

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“…Experimentation by Hietenan et al [5] shows that reducing air gap between the membrane and the surface of the backplate has shown improvement on the sensitivity of the device in general.…”

Section: Air Gap Configurationmentioning

confidence: 99%

“…As a promising alternative to piezoelectric transducers especially in the field of non-destructive testing and evaluation (NDE), electrostatic ultrasonic transducers have its own challenges. In general electrostatic transducer offers certain advantage against the conventional piezoelectric transducers such as inherently wide bandwidth [1,2,3] and good matching to air due to the membrane's low acoustic impedance [4,5].…”

Section: Introductionmentioning

confidence: 99%

FLAUT: A mutual sensitivity improvement through matched pipe, cavity and thin plate resonance

Hamid

2021

Elektrika

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Electrostatic transducers promises a great potential in alternative to piezoelectric transducer based on certain advantages such as inherently wide bandwidth and good acoustic matching to air due to the membrane’s low acoustics impedance. There are two basic designs that are popular among electrostatic ultrasonic transducer developer – rigid backplate and micromachine backplate. This paper presents a methodology for improving the sensitivity of an air-coupled ultrasonic transducer by coupling the resonating thin plate, cavity and pipe in a single cell. The proposed device is termed Fluidically Amplified Ultrasonic Transducer (FLAUT) for an air-coupled application. Investigation of the concept of matched thin plate, cavity and pipe, of which the individual geometry is expected to mutually enhance one another. Analytical modelling is utilized to the matched thin plate, cavity and pipe. The analytical modelling identifies the required geometry for the FLAUT based on the matched operating resonant frequency of 25 kHz. At the end of the paper the prototype of FLAUT is presented where the device was fabricated using additive manufacturing process (3-D printing) which consist of a 50 µm Kapton thin film over a micro stereolithography designed backplate. Here aluminum is coated as the electrode utilizing the thermal evaporation process for both the Kapton film and the backplate. A laser interferometer is utilized to measure FLAUT thin plate displacement which indicates the device is running at 25 kHz fundamental mode. A 30 dB difference is also observed between the deformation velocity of the cavity active region and its surrounding.

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“…Several factors that have the same effect as observed in conjunction with grooved backplates, such as deviations in the position of the membrane against the backplate and backplate differences caused by fabrication tolerances, could remain unclear. Most capacitive transducers (those with grooved backplates) have a bandwidth of about 30% of the resonant frequency [5,9,11]. Means for bandwidth calculations can be found from among mechanisms that cause loading on the transducer at the resonant frequency.…”

Section: Acoustic Modelmentioning

confidence: 99%

Capacitive ultrasonic transducer with net backplate

Mattila

Stor-Pellinen

Ignatius

et al. 2000

Meas. Sci. Technol.

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A study is presented of the function of an air-coupled capacitive ultrasonic transducer with uniform net backplate. Net backplates are an easy, fast-to-assemble alternative to grooved backplates. The frequency responses of the transducers were measured and the resonance frequencies were estimated. A procedure to study the electrostatics of the transducer with net backplate geometry is described with calculations of surface charge density distribution, capacitance and sensitivity.

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Factors affecting the sensitivity of electrostatic ultrasonic transducers

Cited by 25 publications

References 9 publications

Review of piezoelectric micromachined ultrasonic transducers and their applications

Review of piezoelectric micromachined ultrasonic transducers and their applications

FLAUT: A mutual sensitivity improvement through matched pipe, cavity and thin plate resonance

Capacitive ultrasonic transducer with net backplate

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