Transparent capacitive micromachined ultrasonic transducers (CMUTs) for photoacoustic applications

Li, Zhenhao; Ilkhechi, Afshin Kashani; Zemp, Roger J.

doi:10.1364/oe.27.013204

Cited by 34 publications

(20 citation statements)

References 22 publications

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“…cMUTs have been researched for PAI applications with breakthroughs made in many aspects, such as two-dimensional (2D) cMUT arrays [ 161 , 162 , 163 ], transparent cMUTs [ 164 , 173 , 174 ], multiband cMUTs [ 165 , 166 , 167 ], and potential integration with endoscopes [ 168 ]. Most cMUTs have been studied and demonstrated on benchtop PAI systems.…”

Section: Cmutsmentioning

confidence: 99%

Section: Cmutsmentioning

confidence: 99%

“…Visible-light-transparent cMUTs were also developed [ 170 , 174 ]. By using a glass wafer as the substrate, a photo BCB polymer as the bonding agent, silicon nitride as the membrane material, and indium-tin-oxide (ITO) as the transparent electrodes, in 2019, Li et al presented cMUTs with a transparency of up to 82% in the visible range for PAI applications [ 174 ]. With this method, in 2020, Ilkhechi et al also developed transparent cMUT arrays for real-time PAI applications, showing an average transparency of 70% in the visible wavelength and up to 90% in the NIR range [ 170 ].…”

Section: Cmutsmentioning

confidence: 99%

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MEMS Ultrasound Transducers for Endoscopic Photoacoustic Imaging Applications

Wang

Yang

et al. 2020

Micromachines

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Photoacoustic imaging (PAI) is drawing extensive attention and gaining rapid development as an emerging biomedical imaging technology because of its high spatial resolution, large imaging depth, and rich optical contrast. PAI has great potential applications in endoscopy, but the progress of endoscopic PAI was hindered by the challenges of manufacturing and assembling miniature imaging components. Over the last decade, microelectromechanical systems (MEMS) technology has greatly facilitated the development of photoacoustic endoscopes and extended the realm of applicability of the PAI. As the key component of photoacoustic endoscopes, micromachined ultrasound transducers (MUTs), including piezoelectric MUTs (pMUTs) and capacitive MUTs (cMUTs), have been developed and explored for endoscopic PAI applications. In this article, the recent progress of pMUTs (thickness extension mode and flexural vibration mode) and cMUTs are reviewed and discussed with their applications in endoscopic PAI. Current PAI endoscopes based on pMUTs and cMUTs are also introduced and compared. Finally, the remaining challenges and future directions of MEMS ultrasound transducers for endoscopic PAI applications are given.

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Section: Cmutsmentioning

confidence: 99%

Section: Cmutsmentioning

confidence: 99%

Section: Cmutsmentioning

confidence: 99%

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MEMS Ultrasound Transducers for Endoscopic Photoacoustic Imaging Applications

Wang

Yang

et al. 2020

Micromachines

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“…The use of CMUTs for PAI has been researched for over a decade in mainly two types of application, the table top application with PACT and photoacoustic endoscopy. Various innovative ideas are being explored for PACT in areas such as 2D array [116,117,123,124], transparency [125,126,127], and multi-frequency [128,129,130]. In photoacoustic endoscopy, the designs being studied can be split into two different array configurations, phased [118,119] and ring arrays [120,121].…”

Section: Development Of Capacitive Micromachined Ultrasound Transdmentioning

confidence: 99%

Photoacoustic Imaging with Capacitive Micromachined Ultrasound Transducers: Principles and Developments

Chan

Zheng

Bell

et al. 2019

Sensors

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Photoacoustic imaging (PAI) is an emerging imaging technique that bridges the gap between pure optical and acoustic techniques to provide images with optical contrast at the acoustic penetration depth. The two key components that have allowed PAI to attain high-resolution images at deeper penetration depths are the photoacoustic signal generator, which is typically implemented as a pulsed laser and the detector to receive the generated acoustic signals. Many types of acoustic sensors have been explored as a detector for the PAI including Fabry–Perot interferometers (FPIs), micro ring resonators (MRRs), piezoelectric transducers, and capacitive micromachined ultrasound transducers (CMUTs). The fabrication technique of CMUTs has given it an edge over the other detectors. First, CMUTs can be easily fabricated into given shapes and sizes to fit the design specifications. Moreover, they can be made into an array to increase the imaging speed and reduce motion artifacts. With a fabrication technique that is similar to complementary metal-oxide-semiconductor (CMOS), CMUTs can be integrated with electronics to reduce the parasitic capacitance and improve the signal to noise ratio. The numerous benefits of CMUTs have enticed researchers to develop it for various PAI purposes such as photoacoustic computed tomography (PACT) and photoacoustic endoscopy applications. For PACT applications, the main areas of research are in designing two-dimensional array, transparent, and multi-frequency CMUTs. Moving from the table top approach to endoscopes, some of the different configurations that are being investigated are phased and ring arrays. In this paper, an overview of the development of CMUTs for PAI is presented.

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“…More importantly, they lack ultrasound excitation capabilities for applications that require combined ultrasound sensing and ultrasound tissue stimulation [16,17]. Recently, transparent capacitive micromachined ultrasonic transducers (CMUTs) were developed [18,19]. However, CMUTs need specialized front-end application-specific integrated circuits (ASICs), and involve a complicated fabrication process inside a cleanroom.…”

Section: Introductionmentioning

confidence: 99%

Optical-Resolution Photoacoustic Microscopy Using Transparent Ultrasound Transducer

Chen

Agrawal

Dangi

et al. 2019

Sensors

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The opacity of conventional ultrasound transducers can impede the miniaturization and workflow of current photoacoustic systems. In particular, optical-resolution photoacoustic microscopy (OR-PAM) requires the coaxial alignment of optical illumination and acoustic-detection paths through complex beam combiners and a thick coupling medium. To overcome these hurdles, we developed a novel OR-PAM method on the basis of our recently reported transparent lithium niobate (LiNbO 3 ) ultrasound transducer (Dangi et al., Optics Letters, 2019), which was centered at 13 MHz ultrasound frequency with 60% photoacoustic bandwidth. To test the feasibility of wearable OR-PAM, optical-only raster scanning of focused light through a transducer was performed while the transducer was fixed above the imaging subject. Imaging experiments on resolution targets and carbon fibers demonstrated a lateral resolution of 8.5 µm. Further, we demonstrated vasculature mapping using chicken embryos and melanoma depth profiling using tissue phantoms. In conclusion, the proposed OR-PAM system using a low-cost transparent LiNbO 3 window transducer has a promising future in wearable and high-throughput imaging applications, e.g., integration with conventional optical microscopy to enable a multimodal microscopy platform capable of ultrasound stimulation.

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Transparent capacitive micromachined ultrasonic transducers (CMUTs) for photoacoustic applications

Cited by 34 publications

References 22 publications

MEMS Ultrasound Transducers for Endoscopic Photoacoustic Imaging Applications

MEMS Ultrasound Transducers for Endoscopic Photoacoustic Imaging Applications

Photoacoustic Imaging with Capacitive Micromachined Ultrasound Transducers: Principles and Developments

Optical-Resolution Photoacoustic Microscopy Using Transparent Ultrasound Transducer

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