Abstract: This paper applies the MEMS technology to design and fabricate a micro-bubble generator by a piezoelectric actuator. Coupled with a nickel nozzle plate, an annular piezoelectric ceramic was utilized as the primary structure of the generator. In operations, the piezoelectric element deforms transversely under an electric field applied across the thickness of the generator. The surface of the nozzle plate can expand or contract because of the induction of radial strain, resulting in the whole structure to bend, and successively transport oxygen micro-bubbles into the blood flow for enhancing the oxygen content in blood. In the tests, a high magnification microscope and a high speed CCD camera were employed to photograph the time evolution of meniscus shape of gaseous bubbles dispensed from the micro-bubble generator for flow visualization. This investigation thus explored the bubble formation process including the influences of inlet gas pressure along with driving voltage and resonance frequency on the formed bubble extent.
Abstract: This paper presents the design and fabrication of a
novel piezoelectric actuator for a gas micro pump with check valve
having the advantages of miniature size, light weight and low power
consumption. The micro pump is designed to have eight major
components, namely a stainless steel upper cover layer, a piezoelectric
actuator, a stainless steel diaphragm, a PDMS chamber layer, two
stainless steel channel layers with two valve seats, a PDMS check
valve layer with two cantilever-type check valves and an acrylic
substrate. A prototype of the gas micro pump, with a size of 52 mm ×
50 mm × 5.0 mm, is fabricated by precise manufacturing. This device
is designed to pump gases with the capability of performing the
self-priming and bubble-tolerant work mode by maximizing the stroke
volume of the membrane as well as the compression ratio via
minimization of the dead volume of the micro pump chamber and
channel. By experiment apparatus setup, we can get the real-time
values of the flow rate of micro pump and the displacement of the
piezoelectric actuator, simultaneously. The gas micro pump obtained
higher output performance under the sinusoidal waveform of 250 Vpp.
The micro pump achieved the maximum pumping rates of 1185
ml/min and back pressure of 7.14 kPa at the corresponding frequency
of 120 and 50 Hz.
Abstract: Optical biosensors have become a powerful detection
and analysis tool for wide-ranging applications in biomedical research,
pharmaceuticals and environmental monitoring. This study carried out
the computational fluid dynamics (CFD)-based simulations to explore
the dispersion phenomenon in the micro channel of an optical
biosensor. The predicted time sequences of concentration contours
were utilized to better understand the dispersion development occurred
in different geometric shapes of micro channels. The simulation results
showed the surface concentrations at the sensing probe (with the best
performance of a grating coupler) in respect of time to appraise the
dispersion effect and therefore identify the design configurations
resulting in minimum dispersion.
Abstract: The objective of this study is to conduct computational
fluid dynamic (CFD) simulations for evaluating the cooling efficacy
from vegetation implanted in a public park in the Taipei, Taiwan. To
probe the impacts of park renewal by means of adding three pavilions
and supplementary green areas on urban microclimates, the simulated
results have revealed that the park having a higher percentage of green
coverage ratio (GCR) tended to experience a better cooling effect.
These findings can be used to explore the effects of different greening
modifications on urban environments for achieving an effective
thermal comfort in urban public spaces.
Abstract: This paper reports a novel actuating design that uses
the shear deformation of a piezoelectric actuator to deflect a
bulge-diaphragm for driving an array microdroplet ejector. In essence,
we employed a circular-shaped actuator poled radial direction with
remnant polarization normal to the actuating electric field for inducing
the piezoelectric shear effect. The array microdroplet ejector consists
of a shear type piezoelectric actuator, a vibration plate, two chamber
plates, two channel plates and a nozzle plate. The vibration, chamber
and nozzle plate components are fabricated using nickel
electroforming technology, whereas the channel plate is fabricated by
etching of stainless steel. The diaphragm displacement was measured
by the laser two-dimensional scanning vibrometer. The ejected
droplets of the microejector were also observed via an optic
visualization system.
Abstract: This research studies the electroplating of zinc coating
in the zinc chloride bath mixed with supercritical CO2. The sodium
fluoride (NaF) was used as the bath additive to change the structure
and property of the coating, and therefore the roughness and corrosion
resistance of the zinc coating was investigated. The surface
characterization was performed using optical microscope (OM), X-ray
diffractometer (XRD), and α-step profilometer. Moreover, the
potentiodynamic polarization measurement in 3% NaCl solution was
employed in the corrosion resistance evaluation. Because of the
emulsification of the electrolyte mixed in Sc-CO2, the electroplated
zinc produced the coating with smoother surface, smaller grain, better
throwing power and higher corrosion resistance. The main role played
by the NaF was to reduce the coating’s roughness and grain size. In
other words, the CO2 mixed with the electrolyte under the supercritical
condition performed the similar function as brighter and leveler in zinc
electroplating to enhance the throwing power and corrosion resistance
of the coating.
Abstract: This paper aims to present the design, fabrication and test of a novel piezoelectric actuated, check-valves embedded micropump having the advantages of miniature size, light weight and low power consumption. This device is designed to pump gases and liquids with the capability of performing the self-priming and bubble-tolerant work mode by maximizing the stroke volume of the membrane as well as the compression ratio via minimization of the dead volume of the micropump chamber and channel. By experiment apparatus setup, we can get the real-time values of the flow rate of micropump, the displacement of the piezoelectric actuator and the deformation of the check valve, simultaneously. The micropump with check valve 0.4 mm in thickness obtained higher output performance under the sinusoidal waveform of 120 Vpp. The micropump achieved the maximum pumping rates of 42.2 ml/min and back pressure of 14.0 kPa at the corresponding frequency of 28 and 20 Hz. The presented micropump is able to pump gases with a pumping rate of 196 ml/min at operating frequencies of 280 Hz under the sinusoidal waveform of 120 Vpp.
Abstract: The main objective of this article is to present the semi-active vibration control using an electro-rheological fluid embedded sandwich structure for a cantilever beam. ER fluid is a smart material, which cause the suspended particles polarize and connect each other to form chain. The stiffness and damping coefficients of the ER fluid can be changed in 10 micro seconds; therefore, ERF is suitable to become the material embedded in the tunable vibration absorber to become a smart absorber. For the ERF smart material embedded structure, the fuzzy control law depends on the experimental expert database and the proposed self-tuning strategy. The electric field is controlled by a CRIO embedded system to implement the real application. This study investigates the different performances using the Type-1 fuzzy and interval Type-2 fuzzy controllers. The Interval type-2 fuzzy control is used to improve the modeling uncertainties for this ERF embedded shock absorber. The self-tuning vibration controllers using Type-1 and Interval Type-2 fuzzy law are implemented to the shock absorber system. Based on the resulting performance, Internal Type-2 fuzzy is better than the traditional Type-1 fuzzy control for this vibration control system.
Abstract: This paper investigates experimental studies on
vibration suppression for a cantilever beam using an
Electro-Rheological (ER) sandwich shock absorber. ER fluid (ERF) is a
class of smart materials that can undergo significant reversible changes
immediately in its rheological and mechanical properties under the
influence of an applied electric field. Firstly, an ER sandwich beam is
fabricated by inserting a starch-based ERF into a hollow composite
beam. At the same time, experimental investigations are focused on the
frequency response of the ERF sandwich beam. Second, the ERF
sandwich beam is attached to a cantilever beam to become as a shock
absorber. Finally, a fuzzy semi-active vibration control is designed to
suppress the vibration of the cantilever beam via the ERF sandwich
shock absorber. To check the consistency of the proposed fuzzy
controller, the real-time implementation validated the performance of
the controller.
Abstract: Natural ventilation has played an important role for
many low energy-building designs. It has been also noticed as a
essential subject to persistently bring the fresh cool air from the
outside into a building. This study carried out the computational fluid
dynamics (CFD)-based simulations to examine the natural ventilation
development of a work area in a public building. The simulated results
can be useful to better understand the indoor microclimate and the
interaction of wind with buildings. Besides, this CFD simulation
procedure can serve as an effective analysis tool to characterize the
airing performance, and thereby optimize the building ventilation for
strengthening the architects, planners and other decision makers on
improving the natural ventilation design of public buildings.