High-throughput flow alignment of barcoded hydrogel microparticles

Abstract

Suspension (particle-based) arrays offer several advantages over conventional planar arrays in the detection and quantification of biomolecules, including the use of smaller sample volumes, more favorable probe-target binding kinetics, and rapid probe-set modification. We present a microfluidic system for the rapid alignment of multifunctional hydrogel microparticles designed to bear one or several biomolecule probe regions, as well as a graphical code to identify the embedded probes. Using high-speed imaging, we have developed and optimized a flow-through system that (1) allows for a high particle throughput, (2) ensures proper particle alignment for decoding and target quantification, and (3) can be reliably operated continuously without clogging. A tapered channel flanked by side focusing streams is used to orient the flexible, tablet-shaped particles into a wellordered flow in the center of the channel. The effects of channel geometry, particle geometry, particle composition, particle loading density, and barcode design are explored to determine the best combination for eventual use in biological assays. Particles in the optimized system move at velocities of ~50 cm s −1 and with throughputs of ~40 particles s −1 . Simple physical models and CFD simulations have been used to investigate flow behavior in the device.

Continuous Inertial Focusing and Separation of Particles by Shape

“…Barcoded particles, which are fabricated using approaches such as stop-flow lithography, are used for multiplexed and high-throughput biochemical assays. These particles are usually aligned by sheath flow [7,56], which can lead to unstable focusing, or by active guiding rails [57], which complicate their integration into microsystems. Inertial effects may enable precise control of the alignment and focusing of barcoded particles for the optical reading of their patterns.…”

Engineering particle trajectories in microfluidic flows using particle shape

“…Both practical and theoretical considerations motivate interest in hydrodynamic 'self-steering' (of a single particle) and self-organization (of multiple interacting particles). In microfluidic devices, control over particle position allows the high throughput performance of operations on individual flowing objects, for example, in on-chip cytometry 5 and multiplexed assays with functionalized particles 6 . Although particles can be directly positioned with external fields or sheath flows 6,7 , these methods can require cumbersome apparatus or complex channel structure.…”

“…In microfluidic devices, control over particle position allows the high throughput performance of operations on individual flowing objects, for example, in on-chip cytometry 5 and multiplexed assays with functionalized particles 6 . Although particles can be directly positioned with external fields or sheath flows 6,7 , these methods can require cumbersome apparatus or complex channel structure. An elegant alternative is to tailor particle and channel design for self-steering or self-organization.…”

Self-organizing microfluidic crystals

“…Orderly ow eases recognition and interrogation of suspended objects in cytometry 7 and bioassays. 8 Flowing crystals could be used as dynamically programmable metamaterials, assembled with high throughput in continuously operating microdevices, or as tunable diffraction gratings. 9 Researchers have achieved selforganizing owing crystals with acoustically excited bubbles 10 and weakly inertial spheres.…”