Dr. Minshul Shin, Assistant Professor, earned his PhD in Mechanical Engineering at The Tufts University in 2012. He has conducted research in the area of microelectricalmechanical systems (MEMS) and nanotechnology, including design and fabrication of micro/nano structure, robots, sensors and actuators.
Areas of Expertise (5)
MEMS and Nanotechnology
Tufts University: Ph.D.
University of Alabama at Birmingham: M.A.
University of Alabama at Birmingham: B.S.
M. Shin et al.
A micromachined array of 168 nickel-on-glass capacitive ultrasound transducers was used to demonstrate a long range Doppler velocity measurement system. By using an electroplated nickel on glass process, the total capacitance of the chip was reduced to 65 pF, resulting in a high signal to noise ratio and allowing an operable range of 1.5 m. The range is limited by room reverberation level, rather than electronic noise. The sensor array operates at a 180 kHz resonant frequency to achieve a half-angle −3 dB beamwidth of 6° with a 1 cm2 die. The cMUT array was characterized using laser Doppler vibrometry (LDV), beampattern measurements, range testing, and the ability to measure the velocity of a moving plate. The sensor is capable of measuring the velocity of a moving reflector with a resolution of 6 cm/s, at an update rate of 0.016 s, and with a range of 1.5 m (3 m round trip).
M. Shin et al.
A micromachined floating element array sensor was designed, fabricated, and characterized. The sensor chip is 1 cm2 and includes 16 separate sensor groups in a 4 by 4 array with a pitch of approximately 2 mm. The device was fabricated using four layers of surface micromachining including copper and nickel electroplating. A capacitance to digital converter IC was used to measure the differential capacitance change resulting from flow forces. The achieved resolution is limited by white noise with a level of 0.24 Pa/√Hz, and linearity is demonstrated to >13 Pa. Experimental characterization in three different duct height laminar flow cells allowed independent determination of the sensitivity to shear stress and pressure gradient. The sensor chip with half the elements acting in parallel has a sensitivity of 77.0 aF/Pa to shear and −15.8 aF/(Pa/mm) to pressure gradient. Pressure gradient sensitivity is found to be an important contributor to overall output, and must be accounted for when calibrating floating element shear stress sensors if accurate measurements are to be achieved. This work is the first demonstration of a shear sensor array on a chip with independent pressure gradient sensitivity calibration.
M. Shin et al.
This paper describes the design, fabrication, modeling, and characterization of a small (1 cm2 transducer chip) acoustic Doppler velocity measurement system using microelectromechanical systems capacitive micromachined ultrasound transducer (cMUT) array technology. The cMUT sensor has a 185 kHz resonant frequency to achieve a 13° beam width for a 1 cm aperture. A model for the cMUT and the acoustic system which includes electrical, mechanical, and acoustic components is provided. Furthermore, this paper shows characterization of the cMUT sensor with a variety of testing procedures including Laser Doppler Vibrometry (LDV), beampattern measurement, reflection testing, and velocity testing. LDV measurements demonstrate that the membrane displacement at the center point is 0.4 nm/V2 at 185 kHz. The maximum range of the sensor is 60 cm (30 cm out and 30 cm back). A velocity sled was constructed and used to demonstrate measureable Doppler shifts at velocities from 0.2 to 1.0 m/s. The Doppler shifts agree well with the expected frequency shifts over this range.
M. Shin et al.
The design, fabrication, modeling and characterization of a small (1 cm2 transducer chip) acoustic Doppler velocity measurement system using a capacitive micromachined nickel on glass ultrasound transducer array technology is described. The acoustic measurement system operates in both transmit and receive mode. The device consists of 168 0.6 mm diameter nickel diaphragms, and operates at approximately 180 kHz. Computational predictions suggest that in transmit mode the system will deliver an 11 degree -3dB beamwidth ultrasound. Characterization of the cMUT sensor with a variety of testing procedures including acoustic testing, Laser Doppler Vibrometry (LDV), beampattern test, reflection test, and velocity testing will be shown. LDV measurements demonstrate that the membrane displacement at center point is 0.1 nm/V2 at 180 kHz. During beampattern testing, the measured response was 0.1 mVrms at the main lobe with 90 kHz drive at 20 Vpp (frequency doubling causes the acoustics to be at 180 kHz). The maximum range of the sensor is 1.7 m. Finally, a velocity sled was constructed and used to demonstrate measureable Doppler shifts at velocities from 0.2 m/s to 0.8m/s. Doppler shifts are clearly seen as the velocity changes.
M. Shin et al.
Polydimethylsiloxane (PDMS) posts with a diameter of 80 μm were used to measure the shearing forces at the wafer-pad interface during chemical mechanical planarization (CMP). Measurements are made at 10 kHz with measurable forces between 40 and 400 μN. The structures were polished using a stiff, ungrooved pad and 3 wt % fumed silica slurry at velocities of 0.3 and 0.6 m/s and average wafer-pad normal load of 5.0 and 9.1 kPa. Due to the small fraction of the pad that contacts the wafer, the local microscale forces can be much larger than the global average force might suggest. Observed lateral forces on the structures averaged, in time, between 230 and 310 μN with RMS deviations of the force about the mean between 47 and 64 μN. The faster polishing case shows a 30% higher mean force, and a 20% reduction in the RMS variation of force. Little change is seen in the force characteristics when increasing from 5.0 to 9.1 kPa downforce. A mathematical model is developed to interpret these forces, allowing estimation of the local pad properties. The model suggests that 5000 asperity contacts are present per square millimeter, asperity lateral stiffness is 0.3 N/m, and asperity slip-off force is 19 μN.