Capacitive micromachined ultrasonic transducers: Transmission evaluation with different membrane materials and dimensions

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Sudhanshu Tripathi ◽  
Rekha Agarwal ◽  
Rashmi Vashisth ◽  
Devraj Singh
Keyword(s):  
Resonant Frequency ◽  
Material Selection ◽  
Transmission Efficiency ◽  
Ultrasonic Transducers ◽  
Transduction Efficiency ◽  
Membrane Material ◽  
Structural Examination ◽  
Membrane Materials ◽  
Capacitive Micromachined Ultrasonic Transducers ◽  
Output Pressure

Abstract Capacitive micromachined ultrasonic transducers (CMUTs) are dominant in generating and receiving acoustic signals. CMUT transmission efficiency solely depends upon the membrane material utilized. This work presents the structural examination of receiving and transmitting characteristics of CMUT with divergent membrane materials, namely Silicon (Si), Silicon Nitride ( Si 3 N 4 {\mathrm{Si}_{3}}{\text{N}_{4}} ), Indium Phosphide (InP), Zinc Oxide (ZnO), and Polysilicon (Poly-Si). The analysis includes the membrane deflection, pull-in voltage, output pressure, resonant frequency and capacitance modification with variable DC voltage. It has been found that InP gives the pull-in voltage comparable to Si in the receiving mode and have more transduction efficiency in transmitting mode. Effect of dimensions of CMUT on pull-in voltage and resonant frequency are also discussed. The major contribution lies in the analytical and estimation study of CMUT for appropriate membrane material selection meant for transmission and reception in the field of pressure sensing application.

scholarly journals High-Efficiency Output Pressure Performance Using Capacitive Micromachined Ultrasonic Transducers with Substrate-Embedded Springs

Sensors ◽  
2018 ◽  
Vol 18 (8) ◽  
pp. 2520 ◽  
Author(s):  
Byung Lee ◽  
Amin Nikoozadeh ◽  
Kwan Park ◽  
Butrus Khuri-Yakub
Keyword(s):  
Lead Zirconate Titanate ◽  
High Efficiency ◽  
Transmission Efficiency ◽  
Ultrasonic Transducers ◽  
Parallel Plates ◽  
Displacement Efficiency ◽  
Average Volume ◽  
Capacitive Micromachined Ultrasonic Transducers ◽  
Output Pressure ◽  
Maximum Transmission

Capacitive micromachined ultrasonic transducers (CMUTs) with substrate-embedded springs offer highly efficient output pressure performance over conventional CMUTs, owing to their nonflexural parallel plate movement. The embedded silicon springs support thick Si piston plates, creating a large nonflexural average volume displacement efficiency in the operating frequency range from 1–3 MHz. Static and dynamic volume displacements of the nonflexural parallel plates were examined using white light interferometry and laser Doppler vibrometry. In addition, an output pressure measurement in immersion was performed using a hydrophone. The device showed a maximum transmission efficiency of 21 kPa/V, and an average volume displacement efficiency of 1.1 nm/V at 1.85 MHz with a low DC bias voltage of 55 V. The device element outperformed the lead zirconate titanate (PZT) ceramic HD3203, in the maximum transmission efficiency or the average volume displacement efficiency by 1.35 times. Furthermore, its average volume displacement efficiency reached almost 80% of the ideal state-of-the-art single-crystal relaxor ferroelectric materials PMN-0.33PT. Additionally, we confirmed that high-efficiency output pressure could be generated from the CMUT device, by quantitatively comparing the hydrophone measurement of a commercial PZT transducer.

CMUTs in Permanent Contact Operation for High Output Pressure

2015 ◽  
Author(s):  
Min-Chieh Ho ◽  
Maik Hoffmann ◽  
Alexander Unger ◽  
Kwan Kyu Park ◽  
Mario Kupnik ◽  
...  
Keyword(s):  
Large Cell ◽  
Ultrasonic Transducers ◽  
Contact Mode ◽  
Low Frequencies ◽  
Capacitive Micromachined Ultrasonic Transducers ◽  
Output Pressure ◽  
Acoustic Characterization ◽  
Displacement Profile ◽  
Gap Height ◽  
Transducer Surface

We present the operation of capacitive micromachined ultrasonic transducers (CMUTs) in permanent contact mode as an efficient transducer. The gap height of our transducers is chosen to be slightly smaller than the static deflection of the plate due to the pressure difference between the ambient and the vacuum cavity. Thus, the plates are in contact with the bottom of the cavities even with no dc bias applied. The devices were fabricated based on the thick box process. High-temperature assisted direct wafer bonding technique was used to fabricate devices with such large cell size (radii ∼ 2000 μm) featuring low frequencies ∼100–150 kHz. Extensive acoustic characterization was performed to demonstrate the behavior of such CMUTs in terms of displacement profile, output pressure and acoustic pitch-catch response. A maximum sound pressure of ∼145 dB (SPL) at the transducer surface is measured at 240 V dc and 10 V ac with 100 cycles of burst signal. This is a great improvement from conventional CMUTs (with deeper gap height, operating at 55 kHz), which requires 350 V dc and 200 V ac in order to achieve an output pressure of 129 dB (SPL) at the transducer surface. The results presented in this paper demonstrate that operating CMUTs in permanent contact mode indeed enhances the device output pressure, and provides a good candidate for efficient ultrasonic transducers.

Compensating Resonant Frequency via Adjusting Adjustable Coil Automatically

2019 ◽  
Vol 12 (5) ◽  
pp. 432-438
Author(s):  
Jin Xu ◽  
Yuting Zhao
Keyword(s):  
Resonant Frequency ◽  
Power Transmission ◽  
Reference Value ◽  
Transmission Efficiency ◽  
Theoretical Research ◽  
Future Research ◽  
Wireless Power ◽  
Wireless Power Transmission ◽  
Resonant Coupling ◽  
Transmission Distance

Background: Detuning is the main problem that affects the efficiency and transmission distance of the resonant coupling Wireless Power Transmission (WPT). The distance of load and the offset of the load position could cause serious detuning. Methods: This paper presents an adjustable coil in which inductance can be adjusted. Then a model of WPT was established that could compensate resonant frequency automatically using the adjustable coil. Next, the relationship between the primary resonant frequency and the transmission efficiency is analyzed from the circuit. The analysis proved that the design of the adjustable coil could improve the transmission efficiency of the WPT system. Finally, a prototype of WPT system was built. Results: The experimental results showed that WPT system with adjustable coil can improve the transmission efficiency which proves the theoretical research. At the same time, it has essential reference value for the future research of WPT. Conclusion: In this paper, aiming at the system detuning caused by some other factors, such as the position shift of the load during the wireless power transmission, an adjustable coil is proposed.

scholarly journals Filter lifetimes of different hemodiafiltration membrane materials in dogs: reevaluation of the optimal anticoagulant dosage

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Hiroko Yuzawa ◽  
Yousuke Hirose ◽  
Tomonori Kimura ◽  
Keisuke Shinozaki ◽  
Moe Oguchi ◽  
...  
Keyword(s):  
Clinical Practice ◽  
Activated Partial Thromboplastin Time ◽  
Target Range ◽  
Membrane Material ◽  
Actual Clinical Practice ◽  
Membrane Materials ◽  
Filter Membrane ◽  
Hemorrhagic Complications ◽  
Materials Used ◽  
Nafamostat Mesylate

Abstract Background In continuous renal replacement therapy (CRRT), administration of anticoagulants is necessary for achieving a certain level of filter lifetime. Generally, anticoagulant doses are controlled to keep activated partial thromboplastin time and other indicators within a certain target range, regardless of the membrane materials used for the filter. However, in actual clinical practice, the filter lifetime varies significantly depending on the membrane material used. The objective of this study was to demonstrate that the minimum anticoagulant dose necessary for prolonging the filter lifetime while reducing the risk of hemorrhagic complications varies depending on the type of membrane. Methods In three beagles, hemodiafiltration was performed with hemofilters using polysulfone (PS), polymethylmethacrylate (PMMA), and AN69ST membranes separately. The minimum dose of nafamostat mesylate (NM) that would allow for 6 h of hemodiafiltration (required dose) was investigated for each membrane material. Results The NM doses required for 6 h of hemodiafiltration were 2 mg/kg/h for the PS membrane, 6 mg/kg/h for the PMMA membrane, and 6 mg/kg/h for the AN69ST membrane. Conclusion For hemodiafiltration performed in beagles, the required NM dose varied for each filter membrane material. Using the optimal anticoagulant dose for each membrane material would allow for safer CRRT performance.

scholarly journals Encapsulation of Capacitive Micromachined Ultrasonic Transducers (CMUTs) for the Acoustic Communication between Medical Implants

Sensors ◽  
2021 ◽  
Vol 21 (2) ◽  
pp. 421
Author(s):  
Jorge Oevermann ◽  
Peter Weber ◽  
Steffen H. Tretbar
Keyword(s):  
Data Security ◽  
Ultrasonic Transducers ◽  
Surrounding Tissue ◽  
Center Frequency ◽  
Medical Implants ◽  
Research Groups ◽  
Capacitive Micromachined Ultrasonic Transducers ◽  
Polyether Ether Ketone ◽  
High Bandwidth ◽  
Ether Ketone

The aim of this work was to extend conventional medical implants by the possibility of communication between them. For reasons of data security and transmitting distances, this communication should be realized using ultrasound, which is generated and detected by capacitive micromachined ultrasonic transducers (CMUTs). These offer the advantage of an inherent high bandwidth and a high integration capability. To protect the surrounding tissue, it has to be encapsulated. In contrast to previous results of other research groups dealing with the encapsulation of CMUTs, the goal here is to integrate the CMUT into the housing of a medical implant. In this work, CMUTs were designed and fabricated for a center frequency of 2 MHz in water and experimentally tested on their characteristics for operation behind layers of Polyether ether ketone (PEEK) and titanium, two typical materials for the housings of medical implants. It could be shown that with silicone as a coupling layer it is possible to operate a CMUT behind the housing of an implant. Although it changes the characteristics of the CMUT, the setup is found to be well suited for communication between two transducers over a distance of at least 8 cm.

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