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Sensors 2012, 12(11), 14327-14343; doi:10.3390/s121114327

Mass Transport Effects in Suspended Waveguide Biosensors Integrated in Microfluidic Channels

Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, 3651 Watt Way, Los Angeles, CA 90089, USA
* Author to whom correspondence should be addressed.
Received: 23 August 2012 / Revised: 20 September 2012 / Accepted: 17 October 2012 / Published: 25 October 2012
(This article belongs to the Special Issue Microfluidic Devices)
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Label-free optical biosensors based on integrated photonic devices have demonstrated sensitive and selective detection of biological analytes. Integrating these sensor platforms into microfluidic devices reduces the required sample volume and enables rapid delivery of sample to the sensor surface, thereby improving response times. Conventionally, these devices are embedded in or adjacent to the substrate; therefore, the effective sensing area lies within the slow-flow region at the floor of the channel, reducing the efficiency of sample delivery. Recently, a suspended waveguide sensor was developed in which the device is elevated off of the substrate and the sensing region does not rest on the substrate. This geometry places the sensing region in the middle of the parabolic velocity profile, reduces the distance that a particle must travel by diffusion to be detected, and allows binding to both surfaces of the sensor. We use a finite element model to simulate advection, diffusion, and specific binding of interleukin 6, a signaling protein, to this waveguide-based biosensor at a range of elevations within a microfluidic channel. We compare the transient performance of these suspended waveguide sensors with that of traditional planar devices, studying both the detection threshold response time and the time to reach equilibrium. We also develop a theoretical framework for predicting the behavior of these suspended sensors. These simulation and theoretical results provide a roadmap for improving sensor performance and minimizing the amount of sample required to make measurements.
Keywords: integrated biosensor; finite element simulations; sample delivery; microfluidics integrated biosensor; finite element simulations; sample delivery; microfluidics
This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).

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Murthy, C.R.; Armani, A.M. Mass Transport Effects in Suspended Waveguide Biosensors Integrated in Microfluidic Channels. Sensors 2012, 12, 14327-14343.

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