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

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

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

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

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

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

Infusing Sodium Bicarbonate Suppresses Hydrogen Peroxide Accumulation and Superoxide Dismutase Activity in Hypoxic-Reoxygenated Newborn Piglets

The effectiveness of sodium bicarbonate (SB) has recently been questioned although it is often used to correct metabolic acidosis of neonates. The aim of the present study was to examine its effect on hemodynamic changes and hydrogen peroxide (H(2)O(2)) generation in the resuscitation of hypoxic newborn animals with severe acidosis.Newborn piglets were block-randomized into a sham-operated control group without hypoxia (n = 6) and two hypoxia-reoxygenation groups (2 h normocapnic alveolar hypoxia followed by 4 h room-air reoxygenation, n = 8/group). At 10 min after reoxygenation, piglets were given either i.v. SB (2 mEq/kg), or saline (hypoxia-reoxygenation controls) in a blinded, randomized fashion. Hemodynamic data and blood gas were collected at specific time points and cerebral cortical H(2)O(2) production was continuously monitored throughout experimental period. Plasma superoxide dismutase and catalase and brain tissue glutathione, superoxide dismutase, catalase, nitrotyrosine and lactate levels were assayed.Two hours of normocapnic alveolar hypoxia caused cardiogenic shock with metabolic acidosis (PH: 6.99 ± 0.07, HCO(3)(-): 8.5 ± 1.6 mmol/L). Upon resuscitation, systemic hemodynamics immediately recovered and then gradually deteriorated with normalization of acid-base imbalance over 4 h of reoxygenation. SB administration significantly enhanced the recovery of both pH and HCO(3-) recovery within the first hour of reoxygenation but did not cause any significant effect in the acid-base at 4 h of reoxygenation and the temporal hemodynamic changes. SB administration significantly suppressed the increase in H(2)O(2) accumulation in the brain with inhibition of superoxide dismutase, but not catalase, activity during hypoxia-reoxygenation as compared to those of saline-treated controls.Despite enhancing the normalization of acid-base imbalance, SB administration during resuscitation did not provide any beneficial effects on hemodynamic recovery in asphyxiated newborn piglets. SB treatment also reduced the H(2)O(2) accumulation in the cerebral cortex without significant effects on oxidative stress markers presumably by suppressing superoxide dismutase but not catalase activity