The marching velocity of the capillary meniscus in a microchannel

In this paper we describe an experimental method and an analytical model for characterizing the surface energy inside a microchannel of micrometer size by measuring the marching velocity or position of a capillary meniscus. This method is based on the fact that the force summation of the meniscus surface tension and the filling reservoir gravitation might produce a pressure to pull liquid into the channel, and the marching velocity or the instantaneous position of the meniscus is related to the surface energy. Both parylene and silicon-nitride microchannels with different surface conditions were fabricated to perform the fill-in experiments subject to different liquids. It is shown that our model agrees well with the experimental data and is a valid method

Dielectric charging effects on Parylene electrostatic actuators

We report here the first characterization of dielectric charging effects on Parylene electrostatic actuators. High-resistivity Parylene in-between air gaps can cause undesirable charging effects due to air ionization when operating as electrostatic sensors/actuators at voltages as low as tens of volts. This undesirable effect can either lower the sensitivity of the sensor or increase the pull-in voltage of the actuator. It is further observed that Parylene actuators operating at high voltage could even show "bounce-back" and "pull-in voltage drift" problems. It is concluded that even for MEMS, attention must be paid to the operating voltages and the resistivity of the dielectrics

Photo-patternable gelatin as protection layers in surface micromachinings

This paper describes a newly developed low-temperature photo-patternable Gelatin technology that is useful to produce a thick (greater than 10 microns) Gelatin protecting and strengthening layer for weak MEMS micro-structures. Example demonstrated here is the Gelatin process integrated with the Parylene MEMS technology. What is reported here is the complete processing details and formulae that allow anyone to use Gelatin like photo-resist. We find that it is a chemical-resistant and mechanical-robust material for MEMS applications

Marching velocity of capillary meniscuses in microchannels

[[abstract]]This paper describes a new method and an analytical model for characterizing the surface energy inside a microchannel using the measurement of the marching velocity of a capillary meniscus. This method is based on the fact that surface tension of a liquid meniscus in a hydrophilic case produces pressure to pull liquid into the channel and the velocity of the meniscus is related to the surface energy. Both Parylene and silicon nitride microchannels with different surface conditions were fabricated to perform the liquid-filling experiments. It is shown that our model agrees well with the data and this is a valid method.[[conferencetype]]國際[[conferencedate]]20020120~20020124[[iscallforpapers]]Y[[conferencelocation]]Las Vegas, NV, US

Effect of Opening Size on Wind-Driven Cross Ventilation

The opening size on indoor airflow is important to the ventilation of building because various size openings change the ventilation performance for building. Therefore, the objective of this study is to investigate the effect of opening size on indoor airflow characteristics of naturally ventilated building model. The numerical simulation with steady RANS equations was used. A total of six different opening ratios, namely 4:1, 2:1, 1:1, 1:2, 4:9 and 1:4 were considered in this study. The results of mesh independence study and model validation were also in good agreement with previous study. The simulation results show that velocity and pressure of the indoor air, ventilation rate, and pressure coefficient are highly dependent on the opening ratio. The velocity and pressure contour indicate that the lower the opening ratio, the higher the velocity and subsequently lower pressure inside the building. In addition, the pressure coefficient and ventilation rate are also increased as the opening ratio decreases. Besides, the results indicate that percentage increase in ventilation rate of opening ratio 4:1 and 2:1, 2:1 and 1:1, and 1:1 and 1:2 is higher than those of opening ratio for 1:2 and 4:9, 4:9 and 1:4. The study concluded that pairing a large outlet and small inlet leads to increase in better ventilation rate for building

Dielectric charging effects on Parylene electrostatic actuators

We report here the first characterization of dielectric charging effects on Parylene electrostatic actuators. High-resistivity Parylene in-between air gaps can cause undesirable charging effects due to air ionization when operating as electrostatic sensors/actuators at voltages as low as tens of volts. This undesirable effect can either lower the sensitivity of the sensor or increase the pull-in voltage of the actuator. It is further observed that Parylene actuators operating at high voltage could even show "bounce-back" and "pull-in voltage drift" problems. It is concluded that even for MEMS, attention must be paid to the operating voltages and the resistivity of the dielectrics

Micromachined rubber O-ring micro-fluidic couplers

In this paper, we present a novel type of a "quick-connect" for micro-fluidic devices realized by a simple silicone-rubber O-ring MEMS coupler. As shown in this work, the proposed O-ring couplers are easy to fabricate and utilize, reusable, can withstand high pressure (>60 psi), and provide good seals. In the paper, results from both the leak rate test and pull-out test are presented, demonstrating the functionality of the O-ring couplers

The origin of cultivated mangosteen (Garcinia mangostana L. var. mangostana): Critical assessments and an evolutionary-ecological perspective

Mangosteen (Garcinia mangostana var. mangostana) is a popular tropical fruit, yet many aspects of its biology and evolutionary history are little known. Its origin remains contentious, although recent findings suggest G. mangostana L. var. malaccensis (Hook. f.) Nazre (synonym: G. malaccensis Hook. f.) as the sole progenitor. We review hypotheses on the origin of mangosteen and clarify points that have been affected by errors of fact and interpretation. The narrow focus and lack of detail in published results make their interpretation difficult. When possible, we support our interpretations with field observations and examination of herbarium specimens. We outline the main biological traits (e.g., dioecy, facultative apomixis, and polyploidy) of mangosteen and its wild relatives to infer traits that might have evolved during domestication of mangosteen. We find no clear indication that apomixis and polyploidy evolved during domestication. Polyploidy is known in the wild relatives, but apomixis has not yet been demonstrated. Also, we propose a testable new evolutionary-ecological framework that we call “Forest-Dusun Interface” to infer processes in the origin of mangosteen. Dusun (Malay) refers to subsistence orchards in this context. Lastly, we propose future studies to address identified knowledge gaps