Browsing by Author "Chen, Sheng-Chieh"

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A Novel Multifilter PM(10)-PM(2.5) Sampler (MFPPS)
(2011-01-01)
Liu, Chun-Nan
;
Chen, Sheng-Chieh
;
Tsai, Chuen-Jinn
;
環境工程研究所
;
Institute of Environmental Engineering
A novel multifilter PM(10)-PM(2.5) sampler (MFPPS) that enables the collection of four PM(10) and four PM(2.5) samples simultaneously has been developed and tested. The MFPPS uses a PM(10) impactor as the inlet and operates at 33.4 L/min. After the inlet, the aerosol flow is divided half by a Y-type fitting. Half of the flow is directed into four PM(10) filter cassettes, while the other half is directed into four PM(2.5) filter cassettes after the aerosols are further classified by a PM(2.5) impactor. An active flow control system consisting of two mass flow controllers (MFCs), one for PM(10) and the other for PM(2.5), is used to fix the total flow rate of 16.7 L/min for four PM(10) or four PM(2.5) channels based on the ambient pressure and temperature. To ensure flow rate uniformity through each of the four PM(10) or four PM(2.5) filter cassettes, an orifice is assembled behind each of the filter cassettes to increase the pressure drop, such that the flow rates of eight sampling lines are nearly equal using just two MFCs. The MFPPS was calibrated in the laboratory for particle collection efficiency curves first. Then, the ambient PM concentrations were compared with those of other two collocated FRM samplers, the dichotomous PM(10) and the EPA WINS PM(2.5) sampler in the field study. Calibration results showed the cutoff aerodynamic diameters of the PM(10) and PM(2.5) impactors were 9.8 +/- 0.1 and 2.5 +/- 0.05 mu m, respectively. Field comparison results indicated PM(10) and PM(2.5) concentrations agreed well with the other two PM samplers.
A Novel Multifilter PM10-PM2.5 Sampler (MFPPS)
(2011-01-01)
Liu, Chun-Nan
;
Chen, Sheng-Chieh
;
Tsai, Chuen-Jinn
;
環境工程研究所
;
Institute of Environmental Engineering
A novel multifilter PM10-PM2.5 sampler (MFPPS) that enables the collection of four PM10 and four PM2.5 samples simultaneously has been developed and tested. The MFPPS uses a PM10 impactor as the inlet and operates at 33.4 L/min. After the inlet, the aerosol flow is divided half by a Y-type fitting. Half of the flow is directed into four PM10 filter cassettes, while the other half is directed into four PM2.5 filter cassettes after the aerosols are further classified by a PM2.5 impactor. An active flow control system consisting of two mass flow controllers (MFCs), one for PM10 and the other for PM2.5, is used to fix the total flow rate of 16.7 L/min for four PM10 or four PM2.5 channels based on the ambient pressure and temperature. To ensure flow rate uniformity through each of the four PM10 or four PM2.5 filter cassettes, an orifice is assembled behind each of the filter cassettes to increase the pressure drop, such that the flow rates of eight sampling lines are nearly equal using just two MFCs. The MFPPS was calibrated in the laboratory for particle collection efficiency curves first. Then, the ambient PM concentrations were compared with those of other two collocated FRM samplers, the dichotomous PM10 and the EPA WINS PM2.5 sampler in the field study. Calibration results showed the cutoff aerodynamic diameters of the PM10 and PM2.5 impactors were 9.8 +/- 0.1 and 2.5 +/- 0.05 mu m, respectively. Field comparison results indicated PM10 and PM2.5 concentrations agreed well with the other two PM samplers.
A parallel plate wet denuder for acidic gas measurement
(2008-08-01)
Tsai, Chuen-Jinn
;
Lin, Guan-Yu
;
Chen, Sheng-Chieh
;
環境工程研究所
;
Institute of Environmental Engineering
A parallel plate wet denuder (PPWD) was designed and tested for acidic gas absorption in this studY. The PPWD is composed of two fi-osted glass plates coated with nano-TiO? particles. The gap of the plates is 4 inin, the active sinjace is 7.5 cut in width and 15 cin in height. The DI water is,flowing downward along the sulf ces to form a icn forni tvaterfilm to absorb the gas.flowing uptvard along the gap. The gas absorption efficiency and nienzory eft ct were tested using test gases of HF (3.573.80 ppb), HCl (0.48-15.63 pph), and HN03 (8.43-20.92 ppb) generatedfi-oni per"leation tubes at the flow rate of 5-10 Llinin, scrubbing DI water flow rate oj'].O n?Llnlilll plate, and PH = 6.8 -_ 0.3. The experiment was also conducted for HF and HCl with scrubbing water PH value ol'3.08 and 4.10 to examine the ffcct of PH oil the absorption efficiency. The experimental data at different.flow rates match with the theoretical values ver ' N7 well assuming peifect absorption condition (it the water filin when the scrubbing water PH = 6.8 +/- 0.3. The absorption efficiency of the three gases at the sampling flow rate of 5 Llinin was nearly 100% when the scrubbing water PH value was 6.8 +/- 0.3, but was ' found to decrease slightl ' v when the PH value of scrubbing tvater was reduced from 6.8 to 3.08, which indicates slight inodification of' peifect absorption condition at the water filin. The meniory cffect test showed that the rise time was 15 to 25 min and the fiall tinie was 10 to 25 iniiijbi- the three gases. Good un ft)rniit_v Qfthe tvater filin was observed during the 9-day ainbient air sampling for HF, 110, and HNO,, which indicates the applicabilitly (the present PPWD for ambient air sampling. (c) 2008 American Institute of Chemical Engineers.
An axial flow cyclone to remove nanoparticles at low pressure conditions
(2007-01-01)
Chen, Sheng-Chieh
;
Tsai, Chuen-Jinn
;
環境工程研究所
;
Institute of Environmental Engineering
In this study, the axial flow cyclone used in Tsai et al. (2004) was further tested for the collection efficiency of both solid (NaCl) and liquid (OA, oleic acid) nanoparticles. The results showed that the smallest cutoff aerodynamic diameters achieved for OA and NaCl nanoparticles were 21.7 nm (cyclone inlet pressure: 4.3 Torr, flow rate: 0.351 slpm) and 21.2 nm (5.4 Torr, 0.454 slpm), respectively. The collection efficiencies for NaCl and OA particles were close to each other for the aerodynamic diameter ranging from 25 to 180 nm indicating there was almost no solid particle bounce in the cyclone. The 3-D numerical simulation was conducted to calculate the flow field in the cyclone and the flow was found to be nearly paraboloid. Numerical simulation of the particle collection efficiency based on the paraboloid flow assumption showed that the collection efficiency was in good agreement with the experimental data with less than 15% of error. A semi-empirical equation for predicting the cutoff aerodynamic diameter at different inlet pressures and flow rates was also obtained. The semi-empirical equation is able to predict the cutoff aerodynamic diameter accurately within 9% of error. From the empirical cutoff aerodynamic diameter, a semi-empirical square root of the cutoff Stokes number, root St*(50), was calculated and found to be a constant value of 0.241. This value is useful to the design of the cyclone operating in vacuum to remove nanoparticles.
An Efficient Single-Stage Wet Electrostatic Precipitator for Fine and Nanosized Particle Control
(2010)
Lin, Guan-Yu
;
Tsai, Chuen-Jinn
;
Chen, Sheng-Chieh
;
Chen, Tzu-Ming
;
Li, Shou-Nan
In this study, an efficient parallel-plate single-stage wet electrostatic precipitator (wet ESP) with a width of 75 mm, effective precipitation length of 48 mm and gap of 9.0 mm was designed and tested to control fine and nanosized particles without the need of rapping. The collection plates are made of sand-blasted copper plates coated with TiO(2) nanopowder instead of hydrophilic membranes. Three gold wires (diameter: 100 mu m) were used as the discharge electrodes and a pulse jet valve was used to regularly purge the wires. The design of the present wet ESP is aimed at solving the problems of traditional dry ESPs: reduction of the collection efficiency due to particle deposition on the discharge electrodes and collection electrodes, back corona, and particle re-entrainment. The collection efficiency at initially clean and heavy particle loading conditions was tested and compared to a similar dry ESP. Experimental results showed that when the wet ESP was initially clean, the particle collection efficiency ranged from 96.9-99.7% for particles ranging from 16.8 to 615 nm in electrical mobility diameter at an aerosol flow rate of 5 L/min (residence time of 0.39 s) and an applied voltage of 4.3 kV. After heavy loading with TiO(2) nanopowder about 1.2 +/- 0.06 g/plate, the collection efficiency of the present wet ESP for corn oil particles was shown to reduce only slightly to 94.7-99.0% for particles from 16.8 to 615 nm in diameter.
Chemical Mass Closure and Chemical Characteristics of Ambient Ultrafine Particles and other PM Fractions
(2010)
Chen, Sheng-Chieh
;
Tsai, Chuen-Jinn
;
Huang, Cheng-Yu
;
Chen, Hong-Dar
;
Chen, Shui-Jen
Ambient ultrafine particles (UPs or PM(0.1)), PM(2.5) and PM(10) were investigated at the roadside of Syuefu road in Hsinchu city and in the Syueshan highway tunnel in Taipei, Taiwan. A SMPS (TSI Model 3936), three Dichotomous samplers (Andersen Model SA-241), and three MOUDIs (MSP Model 110) were collocated to determine the PM number and mass concentrations simultaneously. The filter samples were further analyzed for organic carbon (OC), element carbon (EC), water-soluble ions, and trace elements. The OC artifact was studied and quantified using the quartz behind quartz (QBQ) method for all PM fractions. Taking into account the OC artifact, chemical mass closure (ratio of the reconstructed chemical mass to the gravimetrical mass) of PM(0.1), PM(2.5), and PM(10) was then calculated and found to be good. The chemical analysis results of UPs at both sites showed that UPs in the present tunnel was mostly contributed from the vehicle emissions while UPs at the roadside was mainly influenced by urban sources.
Cholesteric liquid crystal devices with nanoparticle aggregation
(2010-10-11)
Jeng, Shie-Chang
;
Hwang, Shug-June
;
Hung, Yu-Hsiang
;
Chen, Sheng-Chieh
;
影像與生醫光電研究所
A broadband cholesteric liquid crystal (CLC) device with a multi-domain structure is demonstrated by using an aggregation of polyhedral oligomeric silsesquioxane (POSS) nanoparticles in the CLC layer. The aggregation pattern of the self-assembled POSS nanoparticles depends on the concentration of POSS doped in the mixture of POSS/CLC and the cooling rate of the mixture from a temperature higher than the clear point. POSS-induced changes in the bulk and surface properties of the cholesteric cells, such as a promotion of homeotropic alignment, help to form a cholesteric structure with a broadband reflection of light; the latter can be used for improvement of bistable CLC devices. A higher POSS concentration and a higher cooling rate both improve the appearance of the black-white CLC device. (C) 2010 Optical Society of America
Cholesteric liquid crystal devices with nanoparticle aggregation
(2010-10-11)
Jeng, Shie-Chang
;
Hwang, Shug-June
;
Hung, Yu-Hsiang
;
Chen, Sheng-Chieh
;
影像與生醫光電研究所
A broadband cholesteric liquid crystal (CLC) device with a multi-domain structure is demonstrated by using an aggregation of polyhedral oligomeric silsesquioxane (POSS) nanoparticles in the CLC layer. The aggregation pattern of the self-assembled POSS nanoparticles depends on the concentration of POSS doped in the mixture of POSS/CLC and the cooling rate of the mixture from a temperature higher than the clear point. POSS-induced changes in the bulk and surface properties of the cholesteric cells, such as a promotion of homeotropic alignment, help to form a cholesteric structure with a broadband reflection of light; the latter can be used for improvement of bistable CLC devices. A higher POSS concentration and a higher cooling rate both improve the appearance of the black-white CLC device. (C) 2010 Optical Society of America
Development of composite filters with high efficiency, low pressure drop, and high holding capacity PM2.5 filtration
(2019-04-01)
Chang, De-Qiang
;
Tien, Chi-Yu
;
Peng, Chien-Yuan
;
Tang, Min
;
Chen, Sheng-Chieh
Many efforts are being made to develop filters with high efficiency and high holding capacity but remaining a low pressure drop. A two-layer composite filter to achieve the goal was developed, in which the first layer was a charged coarse fibers to provide large void space for particle loading and the second was a thin layer of charged melt-blown with finer fibers to enhance the overall efficiency. Experimental results showed that although the new composite media had a lower initial efficiency than the other two HEPA filters (PTFE and glass fiber filter), its figure of merit (FOM) was the highest. Besides, the composite media had a better holding capacity for PM2.5 than the other two. At a fixed mass load, i.e., 2 g m(-2), the PTFE (Delta P = 380 Pa) and glass fiber (Delta P = 165 Pa) required around 7.6 and 3.3 times more power, respectively, than the composite media (Delta P = 50 Pa). Due to the low charge level of the coarse fiber layer and the fine fiber diameter of the melt-blown layer, resulted in no efficiency reduction along the loading process. Theoretical analysis showed that the charge shielding and the loss of efficiency in the successive top-down layers were timely compensated by the efficiency enhancement caused by the loading effects, which made the composite media a much uniform deposition of PM2.5 in layers. This was the main reason resulting in the high holding capacity and low pressure drop of the current composite media which acted like a perfect depth filtration media.
Dielectric and phase behaviors of blue-phase liquid crystals
(2014-11-01)
Chen, Sheng-Chieh
;
Wu, Po-Chang
;
Lee, Wei
;
影像與生醫光電研究所
;
Institute of Imaging and Biomedical Photonics
Dielectric spectra of two pristine blue-phase liquid crystals and a polymer-stabilized counterpart were acquired at various temperatures in conjunction with simultaneous observations of their optical transmission spectra and birefringent textures. The temperature-dependent dielectric data at 5.5 kHz were specifically retrieved for further examination of the feasibility of the dielectric technique as a means to identify phase transitions. With complementary identification by optical images at specific temperatures, it is suggested that investigations of the second derivative of the real-part permittivity with respect to the temperature can be considered as one of the applicable ways to depict the phase sequence of the blue-phase liquid crystals on the cooling process from the isotropic phase through the chiral nematic phase. (C) 2014 Optical Society of America
Dispersion of gas pollutant in a fan-filter-unit (FFU) cleanroom
(2007-05-01)
Chen, Sheng-Chieh
;
Tsai, Chuen-Jinn
;
Li, Shou-Nan
;
Shih, Hui-Ya
;
環境工程研究所
. Numerical simulation and. experimental measurement of flow and concentration fields in a working fan-filter-unit (FFU) cleanroom have been conaucted in this study. The purpose,of the study is to find out the unsteady concentration distribution of a leaking gas pollutant. The standard K-e model was used for the simulation of the flow field. To obtain the gas concentration field, SF6 gas with a certain concentration was released as a simulated leaking source from a valve manifold box (VMB) for 5 or 10 min, respectively. Three Fourier transform infrared spectrometers (FTIRs) were simultaneously used to measure the spatial and temporal distributions of SF6 concentrations. The measured data were then compared with the numerical results and the agreement is seen to be quite good. From the numerical results, the pollutant hot spots, peak pollutant concentration at the end of leaking, and time taken for the concentration to reduce to near background level are obtained. (c) 2006 Elsevier Ltd. All rights reserved.
Drag Coefficient of a Spherical Particle Attached on the Flat Surface
(2011-10-01)
Liu, Chun-Nan
;
Chien, Chih-Liang
;
Lo, Chu-Chun
;
Lin, Guan-Yu
;
Chen, Sheng-Chieh
The previous analytical solution for the drag coefficient (C(d)) for a spherical particle attached on the flat surface, which was derived by O'Neill (1968), is only valid in the creeping flow conditions. It is important to extend O'Neill's formula to cover a wide range of particle Reynolds number (Re(p)). In this study, the drag coefficient was calculated numerically to cover Re(p) from 0.1 to 250. For a particle suspended in the air, an empirical drag coefficient exists, which is defined as C(d) = f x 24/Re(p), where f is a correction factor depending on Re(p). The applicability of the correction factor f for O'Neill's analytical equation for the spherical particle attached on the flat surface for Re(p) = 0.1 to 250 was examined in this study.
Dustiness test of nanopowders using a standard rotating drum with a modified sampling train
(2009-01-01)
Tsai, Chuen-Jinn
;
Wu, Chien-Hsien
;
Leu, Ming-Long
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Chen, Sheng-Chieh
;
Huang, Cheng-Yu
The standard rotating drum tester was used to determine the dustiness of two nanopowders, nano-TiO(2) and fine ZnO, in standard 1-min tests. Then, the sampling train was modified to determine the number and mass distributions of the generated particles in the respirable size range using a Scanning Mobility Particle Sizer (SMPS), an Aerodynamic Particle Sizer (APS) and a Multi-orifice Uniform Deposit Impactor (MOUDI) in the 30-min tests. It was found that very few particles below 100 nm were generated and the released rate of particles decreased with increasing rotation time for both nanopowders in the 30-min tests. Due to the fluffy structure of the released TiO(2) agglomerated particles, the mass distributions measured by the MOUDI showed large differences with those determined by the APS assuming the apparent bulk densities of the powders. The differences were small for the ZnO agglomerates, which were more compact than the TiO(2) agglomerates.
Dynamic variations of ultrafine, fine and coarse particles at the Lu-Lin background site in East Asia
(2013-10-01)
Chen, Sheng-Chieh
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Hsu, Shih-Chieh
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Tsai, Chuen-Jinn
;
Chou, Charles C. -K.
;
Lin, Neng-Huei
The characteristics of atmospheric ultrafine particles (i.e. <100 nm, nanoparticles or PM0.1), PM2.5 and PM10 were studied at the Lulin Atmospheric Background Station (LABS, 2862 m a.s.l., Taiwan) as part of the 7SEAS/Dongsha campaign. Sampling was conducted in July and August of 2009 and September to November of 2010, during which two 96-h and four 72-h PM samples were taken. Real-time particle size distributions were measured continuously from July to August of 2009 and July to November of 2010. PM0.1, PM2.5 and PM10 were collected by using two MOUDIs (micro-orifice uniform deposit impactor, MSP 110) and a Dichotomous PM10 sampler (Andersen SA-241) while real-time size distributions of particles of 5.5-350 nm in diameter were measured by an SMPS (scanning mobility particle sizer, TSI 3936). Filter samples were analyzed for gravimetric mass and chemical compositions, including organic carbon (OC), element carbon (EC), water-soluble ions and trace elements. Meteorology parameters and gaseous O-3 and CO concentrations were also monitored along with the SMPS data for studying particle nucleation, condensation, SOA (secondary organic aerosol) formation and long-range air pollutant transport at the LABS. SMPS data showed that nanoparticle concentrations at the LABS remained relatively stable at low level (similar to 300-500 #/cm(3)) during the nighttime (22:00-04:00), increased during daytime, and reached a maximum (similar to 2000-4000 #/cm(3)) in the afternoon (12:00-16:00). The NMD (number median diameter) showed an opposite trend with the peak number concentrations observed in the afternoon corresponding to the smallest NMD (20-40 nm). These results indicate the dominance of local sources rather than the transport from other atmospheric air because that the lifetime of nanoparticles was only few minutes. Chemical analysis of filter samples showed that the concentrations of trace elements K and Mn, which serve as biomass burning markers, were elevated in the fine particle fractions during November 9-12th when the air mass passed through South and Southeast Asia prior to reaching the LABS. The concentrations of K and Mn would have been low if the aerosols had local origins The biomass burning derived K was found in all fine particle samples at the LABS suggesting that the free troposphere around Taiwan is frequently impacted by the long-range transport of biomass burning plumes via the westerly winds. (c) 2012 Elsevier Ltd. All rights reserved.
Experimental and theoretical analysis of loading characteristics of different electret media with various properties toward the design of ideal depth filtration for nanoparticles and fine particles
(2020-02-15)
Tien, Chi-Yu
;
Chen, Jiang-Ping
;
Li, Shihang
;
Li, Ziyi
;
Zheng, Yu-Ming
Loading experiments of four electret fibrous media having various properties, including fiber diameter, porosity, thickness, charging density and fibrous structure, with fine and nanosized particles were conducted for finding out the influencing factors on efficiency decline and particle holding capacity. The four media include a commercial HVAC media rated with the minimum efficiency reporting value of 13 (MERV13), and three home-made media, including a coarse fiber (CF) layer, a melt-blown (MB) layer, and a bead-on-string (BS) layer. A theoretical model for predicting the pressure drop growth along the loading was applied and compared with that of experiments. The experimental results revealed that the charges of electret media did enhance the holding capacity. The decline of efficiency was found to closely relate to the holding capacity of each media. Higher capacity resulted in a higher decline of efficiency. The theoretical calculation illustrated that the ideal holding capacity was significantly higher than the current electret media had achieved, which indicates that it leaves much improvement of media design more desirable. Comparing the theoretical and experimental results of pressure drop growth with respect to mass load, it was found the current electret layers performed different levels of ideal depth filtration, with an order of CF > MERV13 > BS > MB. Beyond the ideal filtration, pressure drop growth raised exponentially. By utilizing their individual ideal filtration stage, three composite media consisting of 3-4 layers of these electrets with a total thickness less than 1 mm were combined and tested. At 1 in-H2O of pressure drop, the composite electret CF + MERV13 + BS achieved the highest holding capacity with 14.1 g m(-2) which was at least 5-10 times higher than the existing commercial HEPA filters. The bead-onstring fibrous structure of BS enhanced the holding capacity of the composite media significantly. The newly developed electret-based composite filters performed an energy efficient filtration for fine and nanosized particles.
Exposure assessment of nano-sized and respirable particles at different workplaces
(2011-09-01)
Tsai, Chuen-Jinn
;
Huang, Cheng-Yu
;
Chen, Sheng-Chieh
;
Ho, Chi-En
;
Huang, Cheng-Hsiung
In this study, nanoparticle (NP, diameter < 100 nm) and respirable particles measurements were conducted at three different nanopowder workplaces, including the mixing area of a nano-SiO(2)-epoxy molding compound plant (primary diameter: 15 nm), bagging areas of a nano-carbon black (nano-CB) (primary diameter: 32 nm) and a nano-CaCO(3) (primary diameter: 94 nm) manufacturing plant. Chemical analysis of respirable particle mass (RPM) and NPs was performed to quantify the content of manufactured nanoparticles in the collected samples. Nanopowder products obtained from the plants were used in the laboratory dustiness testing using a rotating drum tester to obtain particle mass and number distributions. The obtained laboratory data were then used to elucidate the field data. Both field and laboratory data showed that NP number and mass concentrations of manufactured materials were close to the background level. Number concentration was elevated only for particles with the electrical mobility diameter > 100 nm during bagging or feeding processes, unless there were combustion-related incidental sources existed. Large fraction of nanomaterials was found in the RPM due to agglomeration of nanomaterials or attachment of nanomaterials to the larger particles. From this study, it is concluded that RPM concentration measurements are necessary for the exposure assessment of nanoparticles in workplaces.
Laboratory and field tests of a novel three-stage personal dust sampler for sampling three dust fractions simultaneously
(2008-01-01)
Tsai, Chuen-Jinn
;
Chang, Cheng-Sheng
;
Chen, Sheng-Chieh
;
Chen, Penny
;
Shih, Tung-Sheng
This study designed and calibrated a novel three-stage personal dust sampler for sampling inhalable, thoracic, and respirable dust fractions simultaneously. The sampler has an annular inlet as the first stage for inhalable dust sampling, two impactors in the second and third stages to classify thoracic and respirable dusts, respectively, and a final filter. Laboratory calibration tests using monodisperse liquid and solid particles showed that with 100 ppi (pores per inch) PUF (porous polyurethane foam) substrates and at the flow rate of 3.2 L/min, the sampling efficiency curves of both impactor stages matched with the ISO/CEN/ACGIH thoracic and respirable sampling criteria, respectively. The sampler also agreed with the inhalable criterion for particles smaller than 17 mu m while the deviation increases with increasing particle diameter with a maximum of 28% for 27 mu m particles. It was also found that collection efficiency curve for solid particles was similar to that of liquid particles, indicating that there was no solid particle bounce from the PUF substrates for both impactors. This study also compared inhalable, thoracic, and respirable dust concentrations measured by the present three-stage personal dust samplers with those of the Respicon samplers at three different workplaces. Without using a correction factor of 1.5 for the extrathoracic dusts of the Respicon, field results showed that the present three-stage sampler measured three dust fractions comparable to those of the Respicon samplers. The inhalable dust concentrations of the two samplers differed within 5% while the thoracic and respirable concentration differed by less than 22%.
Multi-wavelength laser tuning based on cholesteric liquid crystals with nanoparticles
(2016-04-27)
Chen, Sheng-Chieh
;
Lin, Jia-De
;
Lee, Chia-Rong
;
Hwang, Shug-June
;
影像與生醫光電研究所
A controllable multi-wavelength laser from a dye-doped cholesteric liquid crystal (DDCLC) cell is demonstrated by incorporating self-assembled polyhedral oligomeric silsesquioxane (POSS) nanoparticles (NPs). Multi-wavelength lasing emission is achieved by formation of multiple planar domains; this formation is dominantly influenced by the vertical alignment of NP clusters adsorbed on the substrate surface through a rapid thermal annealing process. The multi-wavelength lasing peaks are generated through the resultant effect of multiple longitudinal resonant modes of a Fabry-Perot etalon between the cell substrates and the amplification of fluorescence photons with the resonant wavelengths within the broadening long-wavelength edge of the reflection band of the multi-domain CLC. The amount of multi-wavelength lasing peaks can be controlled by changing the POSS NP concentration and the cooling rate of the cell. Furthermore, thermo-reversible control of the multi-wavelength lasing emission can be attained by controlling the thermally induced phase separation process of the POSS/DDCLC cell via a heating/cooling cyclic process.
Nanoparticle-mediated Polyimide for Pretilt Angle Control of Liquid Crystals Devices
(2010)
Jeng, Shie-Chang
;
Hwang, Shug-June
;
Shieh, Yi-Ming
;
Chen, Sheng-Chieh
;
影像與生醫光電研究所
The pretilt angles theta(p) of liquid crystal molecules can be controlled by using conventional polyimide alignment (PI) material doped with different concentrations of Polyhedral Oligomeric Silsequioxanes (POSS) nanoparticle. The addition of POSS in the homogenous PI changes the surface energy of the PI and generates the variable Op. Experimental results demonstrate that Op is a function of the POSS concentration, and it can be controlled over the range of 0 degrees < theta(p) < 90 degrees.
Novel Active Personal Nanoparticle Sampler for the Exposure Assessment of Nanoparticles in Workplaces
(2012-04-17)
Tsai, Chuen-Jinn
;
Liu, Chun-Nan
;
Hung, Shao-Ming
;
Chen, Sheng-Chieh
;
Uang, Shi-Nian
A novel active personal nanoparticle sampler (PENS), which enables the collection of both respirable particulate mass (RPM) and nanoparticles (NPs) simultaneously, was developed to meet the critical demand for personal sampling of engineered nanomaterials (ENMs) in workplaces. The PENS consists of a respirable cyclone and a micro-orifice impactor with the cutoff aerodynamic diameter (d(pa50)) of 4 mu m and 100 nm, respectively. The micro-orifice impactor has a fixed micro-orifice plate (137 nozzles of 55 mu m in the inner diameter) and a rotating, silicone oil-coated Teflon filter substrate at 1 rpm to achieve a uniform particle deposition and avoid solid particle bounce. A final filter is used after the impactor to collect the NPs. Calibration results show that the d(pa50) of the respirable cyclone and the micro-orifice impactor are 3.92 +/- 0.22 mu m and 101.4 +/- 0.1 nm, respectively. The d(pa50) at the loaded micro-Al2O3 mass of 0.36-3.18 mg is shifted to 102.9-101.2 nm, respectively, while it is shifted to 98.9-97.8 nm at the loaded nano-TiO2 mass of 0.92-1.78 mg, respectively. That is, the shift of d(pa50) due to solid particle loading is small if the PENS is not overloaded. Both NPs and RPM concentrations were found to agree well with those of the IOSH respirable cyclone and MOUDI. By using the present PENS, the collected samples can be further analyzed for chemical species concentrations besides gravimetric analysis to determine the actual exposure concentrations of ENMs in both RPM and NPs fractions in workplaces, which are often influenced by the background or incident pollution sources.