A Simple Method for Seamless Integration of CMOS Chips with Microfluidics

This paper describes a simple method for seamless integration of a CMOS chip with typical centimeter-scale microfluidics. A simple planar mold is used to cast PDMS around the perimeter of a single die-cut CMOS chip (5 mm x 6 mm) mounted on a standard chip package (DIL-48, 1 cm x 4 cm). The casting results in a contiguous intersection between the exposed chip surface and the co-planar PDMS that extends across the package. A microfluidic channel added to the package extends across the chip boundary, while fluid in the channel is in direct contact with the chip surface. The large platform of this chip package allows fluid connections to be located far from the chip to prevent interference with optical detection, and thin-layer PDMS microfluidics (about 350µm) created by casting are compatible with short-working-distance microscope objectives. This method requires no sophisticated chip post-processing, accommodates individual CMOS chips, and expands the footprint available for microfluidics. Temporary bonding using PDMS as adhesive allows removal of the microfluidics and recovery of the chip and planarized package. This is a simple and reversible method that is well-suited for prototyping devices using large footprint disposable fluidics and small high-value CMOS chips.