37 research outputs found

    Microfluidics-based acoustic microbubble biosensor

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    This paper proposes a chip-scale microbubble-based biosensing platform. An encapsulated microbubble oscillates acoustically in liquid when exposed to an ultrasound field with its resonant frequency set by shell parameters. Changes in the resonant frequency of the microbubble can be used to monitor analyte-binding events on the shell. A device concept is proposed where ultrasonic transducers are integrated within a microfluidic channel, inside which electrodes are patterned for differential measurements of microbubble impedance. This device enables simultaneous measurements of the acoustic and electrical response of the microbubble, from which both mechanical and electrical parameters can be extracted. These parameters are used to provide a signature of the analyte. This paper presents acoustic and electrical models of the microbubbles, with the effect of shell parameters being thoroughly discussed. © 2013 IEEE

    Capacitive touchscreen sensing - A measure of electrolyte conductivity

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    Mobile technologies such as smartphones and tablets combine computational power with inbuilt sensors and networking capabilities, making them ideal measurement instruments. There is already a rich history of research and commercially manufactured accessories taking advantage of their sensing and data visualisation capabilities. However, to-date the touchscreen component has not yet been translated to the widely established fields of capacitance-based bio- and environmental sensing. Here, we demonstrate the concept of contactless conductivity sensing of fluid samples placed directly on top of a projected mutual capacitive touchscreen with the measurement of a variety of electrolytes, leveraging the touchscreen's multi-touch capabilities. Electrolyte ions are particularly susceptible to the electric fringe field induced by capacitive touchscreens, and we report here a near-linear response to the ionic concentration of metal cations interesting for drinking water quality and soil health monitoring across a range of 0–500 ÎŒM (up to 100 ÎŒS). Simulation results are compared with experimental findings to reveal both the working principles and the key parameters that will be important for future sensing applications. This sensor demonstration is a starting point for broader exploration of the use of projected touchscreen sensing in mobile technologies and the creation of tools that are accessible to everyone, allowing rapid measurements and communication of data
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