E.S. Kim

University of Southern California

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Hongyu Yu

Hong Kong University of Science and Technology

Tzung K. Hsiai

University of California, Los Angeles

Mahsa Rouhanizadeh

Telesis Corporation (United States)

Lisong Ai

Edwards Lifesciences (United States)

S.J. Chen

Fujian University of Technology

Ann Lin

Cold Spring Harbor Laboratory

William C. Tang

University of California, Irvine

G. Soundararajan

University of Southern California

A. Jostes

Children's Hospital of Los Angeles

Yong Kyung Choe

Konkuk University

Cooperative Institutions

University of Southern California

Southern California University for Professional Studies

Children's Hospital of Los Angeles

University of California, Los Angeles

Georgia Institute of Technology

University of California System

Stanford University

National Taiwan University

Samueli Institute

Sensors (United States)

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Micromachined acoustic-wave liquid ejector

Journal of Microelectromechanical Systems (2001)

Dai Huang E.S. Kim

This paper describes the design and performance of micromachined, self-focusing acoustic-wave liquid ejector (AWLE) that requires no heat, nozzle, nor acoustic lens. The AWLE has a very simple device structure and is easy to fabricate. Three versions of AWLE have been designed, fabricated, and tested for an ink-jet printing application. Also developed are computer simulation and design aids that take into account the acoustic loss in water and the two-time wave reflections at the water-air and water-transducer interfaces. The AWLE has been observed to eject water droplets of about 5 /spl mu/m in diameter with radio frequency (RF) pulses of 5 /spl mu/s pulsewidth. Overall, the AWLE has been shown to be capable of improving the printing resolution and speed of ink-jet printing significantly.

Water jet

10.1109/84.946804

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Citations (88)

ACOUSTIC TRANSDUCERS BUILT ON EDGE-RELEASED MEMS STRUCTURES

1998 Solid-State, Actuators, and Microsystems Workshop Technical Digest (2010)

Sao‐Jie Chen Yong Kyung Choe E.S. Kim

This paper presents acoustic transducers built on edge-released MEMS structures, i.e., cantilever diaphragm and spiral-beam-supported diaphragm that are designed to release residual stress and also to avoid in-plane tension when bent.Sputter-deposited ZnO on the diaphragms is used as the piezoelectric thin film to sense and generate acoustic pressure.Typical diameter and thickness of the edge-released diaphragm are 1 mm and 1.6 µm, respectively.The maximum strain on the spiral-beam-supported diaphragm is about an order of magnitude larger than that of a cantilever diaphragm transducer for a given pressure level and diaphragm size.The spiral offers a higher sensitivity at the cost of a lower usable bandwidth and less tolerance on the fabrication process variation.

Diaphragm (acoustics)

10.31438/trf.hh2010.62

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Citations (2)

Piezoelectrically actuated dome-shaped diaphragm micropump

Journal of Microelectromechanical Systems (2005)

Guo‐Hua Feng E.S. Kim

This paper describes a piezoelectric micropump built on a dome-shaped diaphragm with one-way parylene valves. The micropump uses piezoelectric ZnO film (less than 10 /spl mu/m thick) to actuate a parylene dome diaphragm, which is fabricated with an innovative, IC-compatible process on a silicon substrate. Piezoelectric ZnO film is sputter-deposited on a parylene dome diaphragm with its C-axis oriented perpendicular to the dome surface. Two one-way check valves (made of parylene) are integrated with a piezoelectrically actuated dome diaphragm to form a multi-chip micropump. The fabricated micropump (10/spl times/10/spl times/1.6 mm/sup 3/) consumes extremely low power (i.e., 3 mW to pump 3.2 /spl mu/L/min) and shows negligible leak up to 700 Pa static differential pressure.

Diaphragm (acoustics)

Parylene

Dome (geology)

Diaphragm pump

Molding (decorative)

10.1109/jmems.2004.839331

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Citations (77)

Micromachined piezoelectric ultrasonic transducers on dome-shaped-diaphragm in silicon substrate

Cheol-Hyun Han E.S. Kim

We have successfully fabricated piezoelectric ultrasonic airborne transducers built on 1.5 /spl mu/m thick dome-shaped silicon-nitride diaphragm (2,000 /spl mu/m in radius, with a circular clamped boundary on a silicon substrate) with electrodes and a piezoelectric ZnO film. The key idea of fabricating such a large 3-D diaphragm ultrasonic transducer is in producing a large spherical etch front (2 mm in radius) in a 2 mm thick silicon substrate by an isotropic silicon etching with a 75 /spl mu/m thick tape as an etch mask. Also, we use a shadow mask during Al thermal evaporation in order to deposit (with a good step coverage) patterned electrodes over the sharp edge in the dome diaphragm. Flat-diaphragm transducers are also fabricated to demonstrate the effectiveness of a dome-shaped diaphragm for an ultrasonic transducer. Compared to the flat-diaphragm transducer, the dome transducer generates much higher sound output in 15-200 kHz range and this without distortion (unlike the flat-wrinkled-diaphragm transducer). The sound-pressure level at 50 mm away from the dome transducer is measured to be around 0.5 Pa at 145 kHz. The linearity of the dome transducer's response is also measured to be very good, as expected.

Diaphragm (acoustics)

Dome (geology)

10.1109/ultsym.1999.849205

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Citations (6)

MEMS shear stress sensors for microcirculation

Sensors and Actuators A Physical (2004)

G. Soundararajan Mahsa Rouhanizadeh Hongyu Yu Lucas DeMaio E.S. Kim

Fluidics

10.1016/j.sna.2004.07.005

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Citations (9)

Editorial Special Issue on Life Science Automation

IEEE Transactions on Automation Science and Engineering (2006)

M. Zhang Robin A. Felder E.S. Kim Burnell E. Nelson Beth L. Pruitt

10.1109/tase.2006.871475

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Citations (9)

Microelectromagnetic energy harvester with integrated magnets

Q. Zhang S.J. Chen Lukas Baumgartel Ann Lin E.S. Kim

This paper presents a microelectromagnetic power generator with integrated magnets that can be fabricated on silicon wafers in a batch process. The generator is fabricated by MEMS technologies and characterized at different vibration frequencies, amplitudes and load resistances. This compact generator occupies a volume of 15×13×0.4mm ³ , as no external permanent magnets are needed. Experimental results show that with a 20-turn spiral coil, the device can generate an induced electromotive force (EMF) of 0.27mV at a vibration frequency and amplitude of 350Hz and 10μm, respectively.

Electromotive force

10.1109/transducers.2011.5969859

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Citations (20)

10F-3 Self-Focused ZnO Transducers for Ultrasonic Biomicroscopy

Proceedings/Proceedings - IEEE Ultrasonics Symposium (2007)

Jonathan M. Cannata Jay A. Williams Qifa Zhou Hongyu Yu Lei Sun

A simple fabrication technique was developed to produce self-focused high frequency single element transducers with sputtered zinc oxide (ZnO) crystal films. The novelty of this technique lies in that the ZnO film can be sputtered directly onto a curved substrate. Two transducers were fabricated by sputtering an 18 mum thick ZnO layer on 2 and 3 mm diameter aluminum rods with ends shaped and polished to produce an f# equal to one. The aluminum rod served a dual purpose as the backing layer and positive electrode for the resultant transducers. A single 4 mum Parylene polymer matching layer was deposited on the transducers after housing and interconnect. The pulse-echo response for the 2 mm aperture transducer was centered at 109 MHz with a -6 dB bandwidth of 43%. A 3 mm aperture transducer produced a 96 MHz echo response with a 52% bandwidth. The measured insertion loss for the 2 mm aperture was 45 dB and the 3 mm aperture was 42 dB. A wire phantom and adult zebrafish were imaged to show the capability of the transducers.

Parylene

10.1109/ultsym.2007.241

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Citations (3)

HIGH FREQUENCY MICROMECHANICAL PIEZO ACTUATED DISK RESONATOR

1998 Solid-State, Actuators, and Microsystems Workshop Technical Digest (2004)

Le Yan Wei Pang Jian Wu William C. Tang E.S. Kim

This paper presents the design, simulation, fabrication and testing of a piezo transduced high frequency micromechanical resonator.The resonator is designed to operate in the wine-glass mode and the anchors are optimized to both suppress spurious modes and minimize the energy loss into the substrate.The resonator is fabricated with a simple 4-mask low temperature process from SOI wafer.The highest temperature during the process is 250°C, allowing post-COMS integration compatibility.A prototype resonator with measured diameter of 100 µm was tested in air using non-optimized experimental setup, with measured resonant peaks at 44.97 MHz and 138.5 MHz, which match the simulated result from Ansys©.The quality factor of 35 at 138.5 MHz is extracted, and is expected to be substantially higher if measured in vacuum with calibrated RF cables.

Q factor

Helical resonator

10.31438/trf.hh2004.96

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Citations (7)

Flexible Polymer Sensors for In Vivo Intravascular Shear Stress Analysis

Journal of Microelectromechanical Systems (2008)

Hongyu Yu Lisong Ai Mahsa Rouhanizadeh D. Patel E.S. Kim

Hemodynamic forces, specifically fluid shear stress, play an important role in the focal nature of arterial plaque formation known as atherosclerosis. We hereby developed biocompatible and flexible intravascular microelectromechanical systems sensor to measure real-time shear stress in the aortas of New Zealand white (NZW) rabbits. Titanium (Ti) and platinum (Pt) were deposited on silicon wafers and patterned to form the sensing elements. The polymer, parylene C, provided insulation to the electrode leads and flexibility to the sensors. Based on heat transfer principle, the heat dissipation from the sensors to the blood flow altered the resistance of the sensing elements, from which shear stress was calibrated. The resistance of the sensing element was measured at approximately 1.0 kOmega , and the temperature coefficient of resistance was at approximately 0.16%/ ^deg C. The individual sensors were packaged to the catheter for intravascular deployment in the aortas of NZW rabbits ( n = 5) . The sensor was capable of resolving spatial- and time-varying components of shear stress in the abdominal aorta. Computational fluid dynamic code based on non-Newtonian fluid properties showed comparable results within an acceptable range of experimental errors ( plusmn9%) for the maximal and minimal values in shear stress during one cardiac cycle. Therefore, we demonstrated the capability of biocompatible sensors for real-time shear stress measurement in vivo with a potential to advance the understanding between the blood flow and vascular disease.

Intravascular Ultrasound

10.1109/jmems.2008.927749

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Citations (55)