Electrically active microfluidic fibers

In recent years, novel materials processing techniques involving PDMS and paper materials have enabled revolutionary progress in performance and capability of chip-scale microfluidics. However, microfluidic systems remain largely single-chip constructs, and are far from the level of sophistication that is typically seen in multi-chip multi-board electronic systems. A major limitation lies in the fluidic chip-to-chip interconnects, where the simple tubing materials and structures lack the pumping and monitoring functionalities that are needed in reliable microfluidic systems.

In this dissertation, we address these challenges with the new structures and materials made available by multimaterial fiber processes, which have recently emerged as a materials platform for a variety of sensing modalities. Various functionalities, such as flow actuators or sensors, are integrated into multimaterial fibers for functional chip feedlines.

Integrated fiber pumps are enabled by electrowetting-on-dielectric (EWOD) actuation to precisely manipulate liquid flow. Fiber drawing process allows creating an ultra-thin and uniform dielectric layer, and hence achieving rapid flow response and predictable flow behaviors. Fiber thermal flow sensors, on the other hand, take the advantage of ultra-fast heat transfer at microscale to break the fundamental trade-off between sensitivity, pressure drop, measurement range, and temperature rise in conventional thermal flow sensors. Record-setting flowrate sensitivity was demonstrated over a wide measurement range and unprecedentedly low pressure drop. As a natural extension to the project of fiber flow sensors, we also present the theoretic optimization of geometric and segmentation design of fiber flow sensors to further boost sensitivity and extend measurement range. A new two-segment structure was demonstrated in simulation with greatly extended measurement range and much simpler post-drawing process. At last, we proposed a general strategy for distributed sensing, which was later applied to present distributed flow sensors. Sub-cm spatial resolution was demonstrated in simulations.

Taken as a whole, electrically active microfluidic fibers take advantage of novel materials and new device structures that deliver new functionality and significant improvements in performance. This unconventional form of devices paves the way towards a complete functional overhaul of microfluidics feed lines needed in large-scale multi-chip integration in microfluidics and opens new possibilities in lab-on-fiber technologies.