Development of self-vibration/detection AFM probe using quartz tuning fork

We present a novel type of quartz tuning-fork probe, which oscillates and detects its own probe deformation, for atomic force microscopy (AFM) systems. The quartz tuning-fork structure was fabricated using anisotropic wet etching, and a sharp tip was formed on a beam using a focused ion beam (FIB) system. We evaluated the vibration properties of the fabricated tuning fork with the tip structure in an anti-phase vibration mode and obtained a Q-factor value of 2.5 to 2.8 × 10³. This value was one order larger than that of a conventional Si probe. We experimentally clarified that the tuning-fork probe measured a 100-nm step of the Si surface, as well as the debris with a thickness of a few tens of nanometers on the surface by self-vibration and self-detection in cyclic-contact mode AFM. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Development and experimental validation of automatic conversion procedure from mechanical to electrical connection for MEMS equivalent circuit

This paper describes equivalent circuit for micro electromechanical system (MEMS) using a type of behavior model for expressing mechanical and electromechanical element within circuit simulation, in order to simulate their dynamic behaviors easily. To fully treat the equivalent circuit as the behavior model, the equivalent interconnection expression for mechanical splice is required. In this work, a new approach has been proposed for converting the system composed of mechanical and electromechanical elements to equivalent circuit expression. This approach consists of substitution of unit equivalent elements and conversion of each equivalent interconnection for mechanical splices. We applied graph theory for equivalent interconnection. With this approach, complex MEMS consisting of a number of transducers and mechanical elements can be easily converted into equivalent circuits. In order to validate this approach, the resonant property of electrostatic comb-drive actuator was simulated using the equivalent circuit generated and measured experimentally. The simulated resonant frequency was in good agreement with the measurement and the admittance characteristics were well described using this circuit with a consideration of coupling capacitances at the comb electrodes. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Combined effects of antenatal corticosteroids and surfactant supplementation on the outcome of very low birth weight infants

Antenatal corticosteroids in preterm pregnancy may result in the reduction of the incidence of respiratory distress syndrome (RDS) and neonatal mortality. It is well known that postnatal use of surfactant in very low birth weight (VLBW) infants with RDS results in decreased neonatal morbidity and mortality. To evaluate the additive beneficial effects of combined antenatal corticosteroids and postnatal use of rescue surfactant on the outcome of VLBW infants, we retrospectively reviewed 286 maternal/infant charts of preterm infants with gestational ages 23 to 32 weeks and birth weights 501 to 1500 gm who were born at our institution from 1991 through 1994. Of the 87 (30%) infants who were treated with corticosteroids before birth, 41 (47%) had RDS, and of the 199 (70%) infants who were not treated with corticosteroids before birth, 162 (81%) had RDS (p < 0.001). The infants who had RDS and who were treated with corticosteroids before birth had a decreased incidence of pulmonary air leaks and a decreased need for diuretic therapy. In addition, they had a significant reduction in O2 requirement and ventilator settings as reflected by FIO2, mean airway pressure, ventilator rate, O2 index, and A-aDO2 before they received the first dose of rescue surfactant (p < 0.05 to p < 0.01) in contrast to other VLBW infants who had RDS and who were not treated with corticosteroids before birth. We conclude that antenatal corticosteroid therapy in threatened premature labor combined with the use of postnatal rescue surfactant is associated with a decreased incidence of RDS and may be beneficial for reducing the severity of RDS and improving the eventual outcome of VLBW infants.