For microfluidic devices where off-chip processes such as microdialysis sampling and flow injection analysis need to be coupled with the chip for analytical purposes, a major drawback is making fluidic interconnections in addition to integrating the detector. In this work we show that fluidic tubing such as fused silica capillary, perfluoroalkoxyalkane and fluorinated ethylene propylene can be encapsulated into epoxy and polystyrene devices in a manner in which they can be polished and integrated with microfluidic chips. Similarly, electrodes can also be encapsulated for integrated detection. To evaluate this approach, we looked at the transfer of off-chip droplets, integrating microdialysis sampling to a microchip, and integrating microchip-based flow injection analysis with integrated detection electrodes.  For all methods a comparison was made between the new encapsulating approach and the more traditional insertion of fluidic tubing into the device. For the transfer of off-chip droplets to the microchip, the encapsulated tubing on average showed only 1.2 droplet coalescence after the transfer; however for the inserted method on average 14.6 droplets combined during the transfer. Flow desegmentation of the droplets can also be achieved on chip by corona treating microchannels via an air/water interface. With microdialysis sampling of a concentration change, the encapsulation approach led to a 9 second improvement in lag time and a 35 second smaller peak width (10% height) as compared to the inserted method. Finally, integration of microchip-based flow injection analysis and integrated detection electrodes showed the most dramatic effect (in terms of the analytical performance) when using a small volume on-capillary injection technique (~40nL). In contrast with inserting the capillary into the chip, the embedded approach led to improvement in peak width, peak height and sensitivity. Implications of the new approach for future work with biological systems will also be discussed.

Encapsulation of fluidic tubing and microelectrodes in microfluidic devices for improved analytical performance

246th National Meeting (2013)

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