title: K-Channel: A Multifunctional Architecture for Dynamically Reconfigurable Sample Processing in Droplet Microfluidics.
abstract: By rapidly creating libraries of thousands of unique, miniaturized reactors, droplet microfluidics provides a powerful method for automating high-throughput chemical analysis. In order to engineer in-droplet assays, microfluidic devices must add reagents into droplets, remove fluid from droplets, and perform other necessary operations, each typically provided by a unique, specialized geometry. Unfortunately, modifying device performance or changing operations usually requires re-engineering the device among these specialized geometries, a time-consuming and costly process when optimizing in-droplet assays. To address this challenge in implementing droplet chemistry, we have developed the "K-channel," which couples a cross-channel flow to the segmented droplet flow to enable a range of operations on passing droplets. K-channels perform reagent injection (0-100% of droplet volume), fluid extraction (0-50% of droplet volume), and droplet splitting (1:1-1:5 daughter droplet ratio). Instead of modifying device dimensions or channel configuration, adjusting external conditions, such as applied pressure and electric field, selects the K-channel process and tunes its magnitude. Finally, interfacing a device-embedded magnet allows selective capture of 96% of droplet-encapsulated superparamagnetic beads during 1:1 droplet splitting events at ∼400 Hz. Addition of a second K-channel for injection (after the droplet splitting K-channel) enables integrated washing of magnetic beads within rapidly moving droplets. Ultimately, the K-channel provides an exciting opportunity to perform many useful droplet operations across a range of magnitudes without requiring architectural modifications. Therefore, we envision the K-channel as a versatile, easy to use microfluidic component enabling diverse, in-droplet (bio)chemical manipulations.
authors.affiliation: Department of Chemistry, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States.|Department of Chemistry, University of Michigan , Ann Arbor, Michigan 48109, United States.
authors.forename: Steven R
authors.initials: SR
authors.lastname: Doonan
authors.affiliation: Department of Chemistry, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States.|Department of Chemistry, University of Michigan , Ann Arbor, Michigan 48109, United States.
authors.forename: Ryan C
authors.identifier: 0000-0003-1021-4267
authors.initials: RC
authors.lastname: Bailey
mesh_terms: D060526:Magnetic Fields; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation*; D010316:Particle Size