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A novel cell-stimulation system was fabricated using 10 × 29 piezoelectric micromachined ultrasonic transducer (pMUT) arrays for targeted ultrasonic cell stimulation. Both the diameter of a single pMUT element and the edge-to-edge gap were 120 μm, and the size of a pMUT array was 2.27 × 6.84 mm, to be placed at the bottom of a Transwell. The measured resonance frequency of a single pMUT element was 1.48 ± 0.13 MHz and the measured acoustic intensity of the pMUT array was 0.15 ± 0.03 MPa at 1 mm away from the transducer. A pMUT array was mounted on a print circuit board (PCB), which was designed in accordance with the size of a 12-well Transwell. The Transwell was placed on the PCB and wire bonding was performed to electrically connect the PCB and pMUT arrays. After wiring, the PCB and pMUT arrays were coated with 2.6-μm thick parylene-C to ensure biocompatibility and waterproofing. PC12 cells were used for ultrasonic cell stimulation tests to examine the proposed all-in-one low-intensity pulsed ultrasound stimulation system. Various stimulation times and duty cycles were used simultaneously for cell proliferation in a confined cell culture environment. All stimulation groups showed increased cell proliferation rates, in the range 138-166%, versus the proliferation rate of the control group.

In this research, piezoelectric micromachined ultrasonic transducer (pMUT) array was used for stimulation of mechanosensitive channel of HEK293T cells. The fabricated pMUT array was made by microelectromechanical system (MEMS) technology such as photo process, etching, sputtering, and sol-gel method. The resonance frequency and acoustic positive peak pressure were 2.07 MHz and 3.94 kPa, respectively. The proposed system can be used for ultrasonic stimulation and the result can be confirmed using fluorescence microscope by observing the cation changing in real-time. The cells were treated by fluorescence staining and transient receptor potential cation channel subfamily V member 1 (TRPV1) channel inserting. The Ca+ ion level of stimulated cell was changed by ultrasound. The result showed mechanosensitive channel was activated by ultrasound stimulation and observed influx of Ca+ ion in real-time.

Micro-electromechanical system (MEMS) technologies were used to develop a thickness-mode piezoelectric micromachined ultrasonic transducer (Tm-pMUT) annular array utilizing a lead magnesium niobate–lead zirconate titanate (PMN–PZT) single crystal prepared by the solid-state single-crystal-growth method. Dicing is a conventional processing method for PMN–PZT single crystals, but MEMS technology can be adopted for the development of Tm-pMUT annular arrays and has various advantages, including fabrication reliability, repeatability, and a curved element shape. An inductively coupled plasma–reactive ion etching process was used to etch a brittle PMN–PZT single crystal selectively. Using this process, eight ring-shaped elements were realized in an area of 1 × 1 cm2. The resonance frequency and effective electromechanical coupling coefficient of the Tm-pMUT annular array were 2.66 (±0.04) MHz, 3.18 (±0.03) MHz, and 30.05%, respectively, in the air. The maximum positive acoustic pressure in water, measured at a distance of 7.27 mm, was 40 kPa from the Tm-pMUT annular array driven by a 10 Vpp sine wave at 2.66 MHz without beamforming. The proposed Tm-pMUT annular array using a PMN–PZT single crystal has the potential for various applications, such as a fingerprint sensor, and for ultrasonic cell stimulation and low-intensity tissue stimulation.

In order to dissolve clots within blood vessels located in various parts of the human body with one sonothrombolysis application, the device employed should be able to control the focal depth where acoustic energy is focused. This paper presents such an ultrasound beamforming system with reconfigurable focal depth. It consists of an annular piezoelectric micromachined ultrasonic transducer (pMUT) array of 1 cm radius, and a beamforming unit that is composed of an ARM processor and a driving circuit. The measured peak intensity at the focal point of 13 mm is 1.35 W/cm2, and the average intensity of the −3 dB focal dimension from the peak intensity is 933 mW/cm. The proposed system operating at 1.21 MHz could be used for ultrasound-accelerated thrombolysis with an intensity that is above typical diagnostic levels at the focusing point, and also with a reconfigurable focusing depth.

A piezoelectric micromachined ultrasonic transducer (pMUT) is an ideal device for portable medical diagnosis systems, intravascular ultrasound systems, and ultrasonic cameras because of its favorable characteristics including small size, acoustic impedance matching with the body, low power consumption, and simple integration with the systems. Despite these advantages, practical applications are limited because of insufficient acoustic pressure of the pMUT caused by the thin active piezoelectric layer. Here, we report the fabrication of a thick piezoelectric Pb(Zr,Ti)O3 (PZT) film-based pMUT device having high deflection at low driving voltage using the granule spraying in vacuum (GSV) process. Pre-patterned high-density thick (exceeding 8 μm) PZT films were grown on 6-inch-diameter Si/SiO2/Ti/Pt silicon-on-insulator wafers at room temperature at a high deposition rate of ∼5 μm min−1. The fabrication process using the proposed GSV process was simple and fast, and the deflection of the pMUT exhibited a high...

Energy distribution under the human skin during ultrasound power transfer using a 15×15 MEMS transducer array with 2.2 MHz driving frequency is presented in this paper. When the surface pressure of the array element is 96 kPa, intensity at 2 mm under the skin is 0.96 W/cm2; intensity increases to 24 W/cm2 when the surface pressure increases to 0.48 MPa. In other words, the simulation results show that the larger the surface pressure, the larger the intensity. The simulated and the measured power density values at 7 mm in the vertical direction of the transducer surface in degassed water are 96.72 mW/cm2 and 94.08 mW/cm2, respectively. Temperature change due to ultrasound radiation on the skin is discussed, and the feasibility of ultrasonic power transfer for implantable medical devices specially implanted just underneath the skin is presented.

A double-photodiode feedback structure to extend the dynamic range (DR) of the CMOS active pixel sensor (APS) has been proposed in this paper. Since the proposed APS requires one additional photodiode and two additional nMOSFETs in comparison with a conventional 3-transistor (TR) APS, the size of pixel is slightly larger than that of conventional 3-TR APS. However, extension of the dynamic range is much easier than conventional methods by adjusting the reset voltage and photo current of the additional photodiode. The proposed APS exhibits a wide and variable dynamic range with high sensitivity at low illumination and low sensitivity at high illumination.

We design and fabricate segmented annular arrays (SAAs) using piezoelectric micromachined ultrasonic transducers (pMUTs) to demonstrate the feasibility of acoustic focusing of ultrasound. The fabricated SAAs have 25 concentric top-electrode signal lines and eight bottom-electrodes for grounding to enable electronic steering of selectively grouped ultrasonic transducers from 2393 pMUT elements. Each element in the array is connected by top-crossover-to-bottom metal bridges, which reduce the parasitic capacitance. Circular-shaped pMUT elements, 120 μm in diameter, are fabricated using 1 μm-thick sol–gel lead zirconate titanate on a silicon wafer. To utilize the high-density pMUT array, a deep reactive ion etching process is used for anisotropic silicon etching to realize the transducer membranes. The resonant frequency and effective coupling coefficient of the elements, measured with an impedance analyzer, yields 1.517 MHz and 1.29%, respectively, in air. The SAAs using pMUTs are packaged on a printed circuit board and coated with parylene C for acoustic intensity measurements in water. The ultrasound generated by each segmented array is focused on a selected point in space. When a 5 Vpp, 1.5 MHz square wave is applied, the maximum spatial peak temporal average intensity () is found to be 79 mW cm−2 5 mm from the SAAs' surface without beamforming. The beam widths (−3 dB) of ultrasonic radiation patterns in the elevation and azimuth directions are recorded as 3 and 3.4 mm, respectively. The results successfully show the feasibility of focusing ultrasound on a small area with SAAs using pMUTs.

A new design methodology and fabrication process for two-dimensional (2D) piezoelectric micromachined ultrasonic transducer (pMUT) arrays using a top-crossover-to-bottom (TCTB) structure was developed. Individual sensing and actuation of pMUT elements from a small number of connection lines was enabled by the TCTB structure, and the parasitic coupling capacitance of the array was significantly reduced as a result. A 32 × 32 pMUT array with a TCTB structure was fabricated, resulting in 64 connection lines over an area of 4.8 × 4.8 mm2. The top electrodes for each pMUT element were re-connected by metal bridging after bottom-electrode etching caused them to become disconnected. A deep reactive ion etching process was used to compactify the array. Each pMUT element was a circular-shaped K31-type ultrasonic transducer using a 1 µm thick sol–gel lead zirconate titanate (PZT: Pb1.10 Zr0.52 Ti0.48) thin film. To characterize a single element in the 2D pMUT array, the resonant frequency and coupling coefficient of 20 pMUT elements were averaged to 3.85 MHz and 0.0112, respectively. The maximum measured ultrasound intensity in water, measured at a distance of 4 mm, was 4.6 µW cm−2 from a single pMUT element driven by a 5 Vpp sine wave at 2.22 MHz. Potential applications for development of a TCTB-arranged 2D pMUT array include ultrasonic medical imaging, ultrasonic communication, ultrasonic range-finding and handwriting input systems.

In this paper, a highly sensitive gate/body-tied p-channel metal oxide semiconductor field effect transistor (PMOSFET)-type photodetector with an overlapping control gate is proposed. The proposed photodetector has an overlapping control gate that makes it possible to control the sensitivity of the proposed photodetector. This sensitivity controllability extends the dynamic range and provides a high sensitivity in a low-light environment. The body of the proposed gate/body-tied PMOSFET-type photodetector is connected to the floating gate, and the control gate is placed on top of the floating gate. The proposed device was fabricated using a 0.35 µm standard complementary metal oxide semiconductor (CMOS) process. The amplified photocurrent of the proposed device was more than 100 times larger than that of a conventional n+/p-sub photodiode with the same area. The area of the proposed photodetector is 3.8×4.4 µm2, which is 24% smaller than that of a conventional gate/body-tied PMOSFET-type photodetector with a transfer gate. Therefore, the proposed photodetector can be suitable for high-sensitivity active pixel sensors (APSs) because of its much higher responsivity than that of a conventional n+/p-sub photodiode.