Microfluidic detection and analysis by integration of evanescent wave sensing with thermocapillary actuation

An integrated system capable of microfluidic actuation, detection and sensing is described which combines evanescent wave sensing with thermocapillary manipulation. Liquid droplets or streams transported across the beam path of a planar thin film waveguide, which encapsulates the microheater array, induce attenuation of the propagating waveguide modes. The attenuated signal is used to monitor droplet location, dye concentration in aqueous solutions and reaction kinetics for enzymatic hydrolysis of the sugar X-galactose by beta-galactosidase

Microfluidic detection and analysis by integration of thermocapillary actuation with a thin-film optical waveguide

We demonstrate a nonintrusive optical method for microfluidic detection and analysis based on evanescent wave sensing. The device consists of a planar thin-film waveguide integrated with a microfluidic chip for directed surface flow. Microliter droplets are electronically transported and positioned over the waveguide surface by thermocapillary actuation. The attenuated intensity of propagating modes is used to detect droplet location, to monitor dye concentration in aqueous solutions, and to measure reaction rates with increasing surface temperature for a chromogenic biochemical assay. This study illustrates a few of the capabilities possible by direct integration of optical sensing with surface-directed fluidic devices

Two-photon imaging of cell-specific fluorophores in transgenic mice – an exploratory tool to study mechanisms of white matter injury

Relatively little is known about specific pathways leading to structural and functional disruption of axons and glial cells in white matter. Because focal cerebral ischemia in humans damages both gray and white matter, an understanding of white matter injury is important in devising potential therapeutic approaches. We have developed a novel brain slice model from transgenic mice under control of cell-specific promoters to understand interactions between oligodendrocytes and axons under high resolution twophoton microscopy. Our data extends over previous findings the vulnerability of oligodendrocytes and axons both in culture and in slice preparations to glutamate toxicity during stroke and hypoglycemia. Conditions as different as stroke, trauma, perinatal brain injury, and multiple sclerosis may share common mechanisms of white matter injury.N/

The Impact of School Reform Design, English Speakers of Other Languages (ESOL) Instruction and Socioeconomic Status on ESOL Students\u27 Reading Achievement

The purpose of this study was to examine how school reform design, English speakers of other languages (ESOL) instruction, and socioeconomic status (SES) impact the academic achievement of ESOL students in Grade 2. Gains in lexile scores on the Scholastic Reading Inventory were used to measure one aspect of academic achievement, namely, general reading ability. The primary research question was: To what extent can gains in lexile scores on the Scholastic Reading Inventory be explained by the independent variable set of school reform design (America\u27s Choice/Direct Instruction), ESOL instruction (ESOL instruction/no ESOL instruction), and SES (free and reduced lunch/no free lunch). Participants were 204 ESOL students enrolled in Grade 2 in Duval County Public Schools during the 2003-2004 academic year, including 53 in Direct Instruction and 151 in America\u27s Choice school reform designs; 151 receiving free and reduced lunch and 53 paying full fee for lunch; 139 receiving ESOL instruction and 65 receiving no ESOL instruction. Findings indicated that students in the Direct Instruction school reform design had greater gains in lexile scores on the SRI than students in the America\u27s Choice design. SES and ESOL instruction were not statistically significant predictors of academic achievement. Further, there were no statistically significant interactions among any of the predictor variables (between school reform design and ESOL instruction; between school reform design and SES; between SES and ESOL instruction; or among school reform design, SES, and ESOL instruction)

Thermocapillary actuation of droplets on chemically patterned surfaces by programmable microheater arrays

We have designed a microfluidic device for the actuation of liquid droplets or continuous streams on a solid surface by means of integrated microheater arrays. The microheaters provide control of the surface temperature distribution with high spatial resolution. These temperature gradients locally alter the surface tension along droplets and thin films thus propelling the liquid toward the colder regions. In combination with liquophilic and liquophobic chemical surface patterning, this device can be used as a logistic platform for the parallel and automated routing, mixing and reacting of a multitude of liquid samples, including alkanes, poly(ethylene glycol) and water

Glutamate and purine catabolites in relation to free radical production during focal ischemia-reperfusion : an in vivo study in cats

The in-vivo interrelation between excitotoxicity and oxidative stress following cerebral ischemia in cats was investigated. To elucidate the role of this mechanism in cerebral ischemia, the study presented herein sought to investigate the spatial and temporal features of the free radical response to elevations of glutamate and purine catabolites in a reproducible model of in vivo focal ischemia/reperfusion. The time course of neurochemical and Reactive Oxygen Species (ROS) were simultaneously conducted in ischemic focus and perifocal region of the brain.peer-reviewe

Microfluidic actuation by modulation of surface stresses

We demonstrate the active manipulation of nanoliter liquid samples on the surface of a glass or silicon substrate by combining chemical surface patterning with electronically addressable microheater arrays. Hydrophilic lanes designate the possible routes for liquid migration while activation of specific heater elements determine the trajectories. The induced temperature fields spatially modulate the liquid surface tension thereby providing electronic control over the direction, timing, and flow rate of continuous streams or discrete drops. Temperature maps can be programed to move, split, trap, and mix ultrasmall volumes without mechanically moving parts and with low operating voltages of 2–3 V. This method of fluidic actuation allows direct accessibility to liquid samples for handling and diagnostic purposes and provides an attractive platform for palm-sized and battery-powered analysis and synthesis