Applied Mechanics and Materials Vols. 300-301

Abstract: In the present study, we demonstrate that silver colloid can serve as additive and induced the γ-form polymorph of glycine crystals in the netural solution. The silver colloid could quickly affect the packing arrangements of glycine molecules in aqueous solution leading to the competitive nucleation of the two polymorphs.

Abstract: Obtained a new material named foamed bamboo fiber cushion packaging materials for the express packaging . The producing technics processes as follows, bamboo fiber firstly be dug into the NaOH solutions for N hours, and then wash them into the neutrality. Then, combine them with the gelatinized starches and propane triol. Next add the foamed agents, cross linking agents and nucleator agents. Finally deliver the composites into the reaction container and the composites will be foamed under a high temperature. By adding different contents of photo starches and contrasting the results of the experiments, it could conclude that 20g photo starches could bond the bamboo fibers and adhesives more efficiently without to be excessive. By selecting different kinds of foamed reagents and researching the suitable ratio of them, Finally cut the foamed productions into small grains. Test the static buffer characteristics of the small grains, and then σ -ε、C-ε curves could be recorded.

Abstract: In this work, a PPy actuator was fabricated by galvanostatic electropolymerization. The electrochemical deformation behaviors of the PPy actuator were investigated in aqueous solutions of an electrolyte, lithium bis(trifluoromethanesulphonyl)imide (LiTFSI), containing different concentrations of methanol. Marked improvement of the actuating strain of approximately 9% was achieved when the actuator was driven by a potential between –1 and 1 V in the LiTFSI electrolyte containing 40 to 50% of methanol under a load stress of 0. 3 MPa. On the other hand, the actuator functioned in the electrolyte solutions containing more than 60% of methanol showed rapid decrease of the actuating strain and the electrochemical creep after repeated actuations. Possible mechanisms for these behaviors were discussed.

Abstract: Improved fabrication processes of an all-polyimide micro electroosmotic flow pump using hot embossing are described. Microchannels in the micropump were fabricated by hot embossing on a transparent polyimide substrate. A silicon micromachined mold was pressed into the transparent polyimide substrate at a temperature of 300 oC to form microchannel patterns on the substrate. The depth and width of the microchannels were 25 μm and 50 μm, respectively. A UV ozone treatment was performed to improve adhesion between the transparent polyimide substrate and film capping layer. This UV ozone treatment enhanced adhesion and resulted in the reduction of the adhesion temperature as low as 100 oC, and nearly no deformation of the microchannels was observed. As a result, the electroosmotic flow pump exhibited the flow rate of 0.7 μl/min when a voltage of 50 V was given between the electrodes separated 20 mm each other.

Abstract: Flexible micropumps are important components for advanced microfluidic systems. Here, polyimide (PI) for flexible micropumps was focused on. This is because PI has many advantageous properties such as good biocompatibility, high thermal stability, and superior mechanical strength. However, the difficulty in realizing an all-PI micropump lies in fabricating microstructures on PI film surfaces. In this paper, we present improved performances of a flexible all-PI micropump fabricated using high-temperature hot embossing above 320 oC that is considerably higher than its glass transition temperature of 275 oC. The fabricated micropump had diffuser/nozzle valves and a chamber with 5 mm diameter, and it was functioned by vibrating a 2-µm-thick PI diaphragm with alternating air pressures outside of the diaphragm. The flow rate of deionized water in the micropump reached to 110 μl/min at 3 Hz.

Abstract: Air-actuated valveless micropumps with dual polyimide (PI) diaphragms have been fabricated and characterized. A 5-μm-thick PI membrane was spin-coated on Si wafer, and released by Si ICP etching. The membrane was actuated by alternating air pressure of 10 kPa. The water flow-rate achieved 80 μl/min at the frequency of 1 Hz and 126 μl/min at 3Hz. Due to nice adhesion between Si and polyimide diaphragms, we could fabricate the double diaphragm micropumps with simplified fabrication processes.

Abstract: Transfer printing of Au micro-electrode patterns onto a polyimide (PI) film was investigated, and the optimum transfer conditions were obtained. Here, the line and space patterns with widths of 25 μm and 100 μm were successfully transfered on polyimide films at a molding temperature of 150 °C for 3 min under the molding pressure of 2.5 MPa. This technique is expected to provide simplified processes to fabricate electrode patterns on microelectro mechanical systems (MEMS).

Abstract: Rolling contact fatigue tests of 20mm-diameter 13Cr-2Ni-2Mo stainless steel bars was carried out using a newly developed single-ball system. The bars were quenched by induction heating method and after that tempered. Sectional observations of the subsurface cracks were made after the surface layer separations. Based on the observations, stress analysis was performed in order to investigate the relation between flaking failures and subsurface crack growth. From these calculations it was found that the shear stress propagated subsurface cracks and finally caused the flaking failures. Furthermore, eight specimens were fatigue tested and Weibull statics distribution of RCF life were calculated using Johnson's statistical method. It was found that the basic life (L10) of the bars under 5.3GPa Hertzian stress was 8.33×106 cycles.

Abstract: The elastic oil sump is commonly used as support parts in large-scale thrust bearing. It often operates under fluctuating load conditions during service. So, fatigue analysis of the material of the elastic oil sump is of great significance. In order to obtain the fatigue design data of the material of the elastic oil sump, the systematic tests on uniaxial tension-compression fatigue at room temperature are made. The fatigue limits and the fatigue life curves of the steel of the elastic oil sump are determined at different cyclic stress ratio. The P-S-N equations are calculated by the probabilistic methods. The test results provide a theoretical basis for the safety of life assessment of the elastic oil sump.

Abstract: Major objectives of this study are to evaluation the enrichment, accumulation, and potential biological effects of copper (Cu) in the surface sediments of Jen-Gen River estuary, Taiwan. Eleven sampling locations were installed near the mouth of Jen-Gen River to collect sediment samples for analyzing Cu. Results of laboratory analyses show that concentrations of Cu in the sediments are between 67 and 278 mg/kg with an average of 181±61 mg/kg. The spatial distribution of Cu reveals that the Cu concentration is relatively high in the boundary of the river estuary. This indicates that upstream industrial and municipal wastewater discharges along the river bank are major sources of pollution. Results from the enrichment factor (EF) analysis imply that the sediments can be characterized as minor to moderately severe degree of Cu enrichment. Results of geo-accumulation index (Igeo) analysis indicate that the sediments can be characterized as none to moderate degree of Cu accumulation. Base on the comparison with sediment quality guidelines (SQGs), the concentrations of Cu in Jen-Gen River mouth sediments may cause acute biological damage.