Hybrid integration of an active pixel sensor and microfluidics for cytometry on a chip

Reported are motivations and approaches for the integration of custom sensors with microfluidic devices for cytometry on a chip and related fluid metering applications. To demonstrate, details of a digital 16-element mixed-signal CMOS active pixel optical sensor with adaptive spatial filtering is first described. The 0.18-μm CMOS fabricated sensor is then shown coupled to a microfluidic channel via a polymer encapsulated chip-on-board approach as well as a preferred flip-chip-on-glass hybrid integration approach. However, both approaches discussed possess attributes that are well suited for reliable high-volume production. Utilizing these two disparate assembly topologies, the intelligent sensor's general behavior, optical input dynamic range, and near-field sensitivity to polymer beads being transported in a microfluidic channel is explored. The findings suggest that discrete near-field sensor integration with microfluidics is a well-positioned integration approach for helping to obviate the need for precision analog-to-digital conversion, optical fiber microchannel coupling, and conventional microscopy for a set of relevant micro total analysis system applications. By opting instead for a hybrid multichip module approach to system integration, this study marks a slight departure in strategy relative to many common monolithic system-on-chip integration efforts.