Search

In this research, the Zn(C5H7O2)2·xH2O-based growth of ZnO micro/nanostructures in a low temperature, vapor-trapped chemical vapor deposition system was attempted to optimize structural and optical properties for potential biomedical applications. By trapping in-flow gas molecules and Zinc vapor inside a chamber tube by partially obstructing a chamber outlet, a high pressure condition can be achieved, and this experimental setup has the advantages of ease of synthesis, being a low temperature process, and cost effectiveness. Empirically, the growth process proceeded under a chamber condition of an atmospheric pressure of 730 torr, a controlled volume flow rate of input gas, N2/O2, of 500/500 Standard Cubic Centimeters per Minute (SCCM), and a designated oven temperature of 500 °C. Specifically, the dependence of structural and optical properties of the structures on growth duration and spatially dependent temperature were investigated utilizing scanning electron microscopy, X-ray diffraction (XRD), photoluminescence (PL), and ultraviolet-visible transmission spectroscopy. The experimental results indicate that the grown thin film observed with hexagonal structures and higher structural uniformity enables more prominent structural and optical signatures. XRD spectra present the dominant peaks along crystal planes of (002) and (101) as the main direction of crystallization. In addition, while the structures excited with laser wavelength of 325 nm emit a signature radiation around 380 nm, an ultraviolet lamp with a wavelength of 254 nm revealed distinctive photoluminescence peaks at 363.96 nm and 403.52 nm, elucidating different degrees of structural correlation as functions of growth duration and the spatial gradient of temperature. Transmittance spectra of the structures illustrate typical variation in the wavelength range of 200 nm to 400 nm, and its structural correlation is less significant when compared with PL.

In this research, the dynamic process of aggregation that forms microflower morphology in solution of lysozyme amyloid fibrils doped with spherical or spindle-like magnetic nanoparticles during the process of drying as well as their final microstructures were investigated. The prepared lysozyme amyloid fibrils as well as their mixtures with in-lab synthesized magnetic particles, which were prepared by adding the nanoparticles to the fibrils solution after the process of fibrillation was done, were characterized using brightfield trans-illumination-mode optical microscope, atomic force microscopy (AFM) and scanning electron microscope (SEM). Brightfield optical imaging bases upon photoabsorptive property of the fibrils-nanoparticle composites clearly reveals the morphological features in microscale, and additionally, for the in vivo, live action of the time-dependent process of self-assembly of such composites composed of fibrillary structure incorporated with magnetic particles was optically elucidated at ambient temperature. Moreover, while results of AFM reveal delicate and peculiar association of fibrils with magnetic nanoparticles of different shapes, SEM images illustrate a stark difference in fine detailed final morphology of microstructures associated with spherical and spindle-like nanoparticles. Our results indicated that the interaction between fibrils solution and the nanoparticles commence right after mixing, the dynamic process of forming dendritic structure resembling microflower morphology is on the order of minutes, and its final structure is highly dependent on the shape of magnetic nanoparticles.

This paper describes an optical system as the line beam shaper for an intra-oral scanning device. The line beam shaper needs to provide desired beam quality, including bean length, uniformity, line width and depth of focus while maintaining compact form factor. More specifically, the proposed optical system was demonstrated to use only the on-the-shelf lens element to resolve all the optical performance issue, and to lead to a versatile solution for varied specification.

Multi-layered micro/nanostructures enable the fine-tuning of spectral bandwidth induced by coherent interference of multi-scattering and refraction bounded by a motive of Fabry Perot etalon. In this paper a ZnO micro/nanostructured thin film device is grown on a 21 nm silver film-sputtered sapphire substrates (0001) and attempted to be complied as a transmission-mode white-light spectrum tuning device. In details, the growth of the structures as a function of temporal duration and the effects of deposition of a 21 nm silver film atop sapphire substrates to the structural and optical properties of ZnO structures are investigated. Results of SEM imaging reveals that the insertion of the silver film enables synthesis of round ZnO particles at micro or nanoscales depending on the duration of growth time as opposed to the floral pattern associated with plain sapphire substrates. Characterizing material crystallization by XRD spectra found one dominant and two minor peaks along the planes of crystallization (002), and (100) and (101), correspondingly. Also, the characteristic PL peak at 380 nm was confirmed when excited at 325 nm, and the intensity decreases as the duration of growth time increases. Finally, growth duration-dependent modulation of peak wavelength and spectral bandwidth of the continuum laser was demonstrated.

Elimination of virus-carrying insects, such as mosquitoes, by an efficient method is of primary importance to preventing the dissemination of infectious diseases and consequentially reducing the health and financial burden on human society. Research herein entails the design, characterization, and implementation of a structurally simple and cost-effective electro-optical system for mosquito-hunting, which is optimized with a system response time under 1.25 ms considering the average mosquito flight speed of 0.2777 m/s, capable of locating the free-flight adult mosquito and knocking it down, synchronously, without any post data-processing. Empirically, the visible-near-infrared absorption spectra of three mosquito species, namely, Culex piplens molestus, Aedes albopictus, and Armigeres subalbatus, were acquired to examine the disparity in photo-absorption property among different mosquito species and help determine an optimal wavelength for injuring the insects. Armigeres subalbatus, a natural transmission vector of filariasis to humans, was employed for the evaluation of the system's efficacy. By introducing a free-flight mosquito about 20 cm in front of an dichroic mirror that combines two optical beams for detection and eradication, a dynamically tracking photonic antenna with a maximal area of 45 mm by 39 mm can continuously track the insect and then knock it down by an instant exposure of a lethal beam with average energy ranging from 75 mJ to 155 mJ. Moreover, the dependence of the fate of the insects on the lethal beam energy dosage is statistically assessed. Overall, this research has successfully demonstrated the concept of the synchronizing scheme of identification and eradication with over 60% of mortality rate once the energy dosage is increased above 75mJ, and may be applicable to the control of other insects or avian animals.

A dental scanning system was developed using multiple light strips of DPSSL (Diode-Pumped Solid-State Laser) sources with a video capturing module of one CMOS camera. The laser line scanning method is less sensitive to the surface conditions of the materials for measurement compared with the structured light scanning method, and a multi-lines scanning design is used to improve the scanning efficiency. The study uses DPSSL lines to scan over the teeth models either by sequence or by sections, which determines the actual time spent. For an object within 100x100mm projective area, the scanning time is about 10 minutes with ±0.05 mm accuracy on a gypsum teeth model using sequential scanning. The results show high accuracy and efficiency scanning teeth models with multi-lines projecting module integrated within, and is possible for further improvement in the growing digital-dental industry.

As the progress of optical technologies, different commercial 3D surface contour scanners are on the market nowadays. Most of them are used for reconstructing the surface profile of mold or mechanical objects which are larger than 50 mm×50 mm× 50 mm, and the scanning system size is about 300 mm×300 mm×100 mm. There are seldom optical systems commercialized for surface profile fast scanning for small object size less than 10 mm×10 mm×10 mm. Therefore, a miniature optical system has been designed and developed in this research work for this purpose. Since the most used scanning method of such system is line scan technology, we have developed pseudo-phase shifting digital projection technology by adopting projecting fringes and phase reconstruction method. A projector was used to project a digital fringe patterns on the object, and the fringes intensity images of the reference plane and of the sample object were recorded by a CMOS camera. The phase difference between the plane and object can be calculated from the fringes images, and the surface profile of the object was reconstructed by using the phase differences. The traditional phase shifting method was accomplished by using PZT actuator or precisely controlled motor to adjust the light source or grating and this is one of the limitations for high speed scanning. Compared with the traditional optical setup, we utilized a micro projector to project the digital fringe patterns on the sample. This diminished the phase shifting processing time and the controlled phase differences between the shifted phases become more precise. Besides, the optical path design based on a portable device scanning system was used to minimize the size and reduce the number of the system components. A screwdriver section about 7mm×5mm×5mm has been scanned and its surface profile was successfully restored. The experimental results showed that the measurement area of our system can be smaller than 10mm×10mm, the precision reached to ±10μm, and the scanning time for each surface of an object was less than 15 seconds. This has proved that our system own the potential to be a fast scanning scanner for small object surface profile scanning.

A novel In0.3Ga0.7As0.99N0.01(Sb)/GaAs high-electron-mobility transistor has been successfully investigated for the first time by incorporating surfactant Sb atoms during the InGaAsN channel growth by molecular beam epitaxy (MBE). Superior stable thermal characteristics, including a thermal threshold coefficient (∂Vth/∂T) of -0.807 mV/K and a high-temperature linearity (∂GVS/∂T) of -0.053 mV/K, were achieved because of the improved crystalline quality and the enhanced carrier confinement capability of the In0.3Ga0.7As0.99N0.01(Sb)/GaAs heterostructure. The device also demonstrated a peak extrinsic transconductance (gm,max) of 94 (109) mS/mm at 450 (300) K.

Locally available manganese-coated sand, from packing and a by-product of the filtration process for water treatment plants in Taiwan, was found to be a low cost and promising adsorbent for the removal of Mn2+ from raw water. In this work, adsorption and desorption of Mn2+ in water have been studied by using batch techniques. The equilibrium adsorption level was determined to be a function of the solution pH, contact time and adsorbate concentration. The equilibrium adsorption capacity of Mn2+ was obtained by using a pseudo-Langmuir isotherm. Ion exchange is probably one of the major adsorption mechanisms for binding divalent manganese ions to the coated sand. The results provide a feasible hypothesis of adsorption mechanisms. This study also supplies significant plant operation capacity data for engineering design.

"Manganese-coated sand" is a type of silica medium coated with manganese oxides, formed from the sorption of manganese oxides during long-term filtration via the process of rapid sand filtration, followed by aeration in a water treatment plant. Locally available manganese-coated sand, both for packing and as a byproduct of filtration processes for water treatment plants in Taiwan, was found to be a low-cost and promising adsorbent for removal of Mn(2+) from raw water. This study was conducted to build the basic data for coating hydrated manganese oxide on the sand surface to utilize the adsorbent properties of the coating and the filtration properties of the sand. In this study, gas adsorption porosimetry and scanning electron microscopy analyses were used to investigate the surface properties of the coated layer. An energy dispersive X-ray (EDAX) technique of analysis was used to characterize metal adsorption sites on a manganese-coated sand surface. Results indicated that manganese-coated sand had more micropores and higher specific surface area, owing to attachment of manganese sand. Manganese ions penetrated into the micropores and mesopores of manganese oxide on a sandy surface; regeneration of manganese-coated sand could be achieved by soaking with pH2.0 acid solution. Results of EDAX analysis showed that the interfacial layer constructed the interface of manganese-coated sand. Acid and alkali resistance tests interpret a wide application range of pH for manganese-coated sand, and general temperature conditions do not affect the performance of this sand. Manganese-coated sand is potentially suitable for application as a packed bed for treatment of heavy metals from water. The results of this study can also benefit plant operational capacity data for engineering design.

This research used an ultra-membrane filtration system to divide raw water into four different organic groups with different molecular masses. The effects of each organic group on the quantity of disinfection by-products formed after a reaction with chlorine dioxide was investigated. The experimental results show that the four organic groups of different molecular masses were: 10 kD

Collagen, the main structural protein in vertebrates, possesses different structural organization that is responsible for specific functions of the tissues. Polarization dependence of the second harmonic generation (SHG) signal on spatial orientation of optically nonlinear materials, such as collagen, provides information on characteristic organization and architecture not available from intensity measurements alone. Here we describe a simple approach for determining both the azimuth and elevation angles of collagen fiber orientation in biological tissues. Azimuth angle of the fiber orientation is determined as an orthogonal angle to the laser polarization direction, when laser-induced total SHG signal is minimal, whereas the elevation angle is estimated from the ratio of the minimal SHG intensity to the intensity when laser polarization and fiber directions are parallel to each other. Using this approach pixel-resolved mapping of the spatial orientation of collagen fibers in tendon and cornea is demonstrated. The new approach may be used for analyzing of biological tissues in vivo. Spatial orientation mapping method provides additional information concerning fiber organization, and may be incorporated into nonlinear optical imaging systems.

Two generalized schemes for realizing grounded and floating imminance function simulators are proposed. A given real and rational voltage transfer function with lhe poles and zeros in the open left half-plane only can be converted into an immittance simulator. By suitably choosing the lwo-port network, both simulators can be integrated in current IC technology. The circuits do not require active componeni-matching. They perform well over a wide frequency range. Experimental results on these simulators are included.

This work reports for the first time a novel In0.2Ga0.8AsSb/GaAs heterostructure doped-channel field-effect transistor (DCFET) grown by the molecular beam epitaxy system. The interfacial quality within the InGaAsSb/GaAs quantum well of the DCFET device has been effectively improved by introducing surfactant-like Sb atoms during the growth of the Si-doped InGaAs channel layer. The improved device characteristics include the peak extrinsic transconductance (gm, max) of 161.5 mS mm−1, the peak drain–source saturation current density (IDSS, max) of 230 mA mm−1, the gate–voltage swing (GVS) of 1.65 V, the cutoff frequency (fT) of 12.5 GHz and the maximum oscillation frequency (fmax) of 25 GHz at 300 K with the gate dimensions of 1.2 × 200 µm2. The proposed design has also shown a stable thermal threshold coefficient (∂Vth/∂T) of −0.7 mV K−1.