Encapsulation of Integrated Circuits for Microfluidic Interface in Biosensors
Amy Wu and Bernhard Boser
Compared to traditional bio-detection systems that require bulky and expensive equipment and a lab-quality environment, portable biosensors with combined microfluidic systems and integrated circuits are not only more cost effective and convenient, but also more sensitive in electrical sensing for a variety of detection schemes such as magnetic detection, since this integrated system minimizes the distance between the sample and detection circuitry. The integrated biosensor also has advantages of small sample size and fast detection speed, reducing the overall cost of disease diagnostics.
Stacking layers of independently fabricated detection chips and microfluidic systems allows flexibility in detection schemes and target analyte. However, since microfluidic systems are orders of magnitude larger than ICs and using large silicon area is expensive , ICs can be embedded in a substrate on which metal interconnects and microfluidic channels will be built.
Figure 1: IC is embedded in an etched recessed region in the glass substrate, with the signal sent to the edge of the device through bond wires and patterned metal. A planarizing agent such as spray-on SU8 or PDMS can smooth out wire-bond topography and also create microfluidic channels. Pneumatic and PDMS layers control microfluidic valves for sample preparation, mixing, and separation .
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