On-chip aqueous two-phase system (ATPS) formation, consequential self-mixing, and their influence on drop-to-drop aqueous two-phase extraction kinetics

Abstract

Aqueous two-phase systems (ATPSs) allow an advantageous aqueous two-phase extraction process (ATPE), a special type of liquid–liquid extraction. Compared with conventional liquid–liquid extraction using aqueous/organic extraction media, ATPE is known to provide relatively easy mass transfer and a gentle environment for biological separation applications. Considering the recent interest in microscale ATPE, we aimed to study (i) the potential of preparing ATPS droplets on a digital microfluidic device, and (ii) the influence of the fluidic dynamics created during the formation of ATPS, with the goal of enhancing on-chip ATPE process. On-chip ATPS formation was evaluated by preparing a series of ATPSs on electrowetting on dielectric digital microfluidic chips and comparing their characteristics with the same ATPSs prepared at macroscale using conventional procedures. An enhanced on-chip drop-to-drop ATPE process was achieved by incorporating a self-mixing condition created during ATPSformation. Results indicate a successful on-chip ATPS preparation as well as enhanced extraction performance by self-mixing in the absence of forced mixing. Findings of this research suggest an alternative, simple, yet adequate technique to provide mixing for on-chip applications, such as sample preparation in portable microfluidics, for which it is unfavorable to implement complicated mixing sequences or complex device geometries.

Evaporation-Driven Water-in-Water Droplet Formation

“…This W/W secondary droplet generation method can also be easily automated with liquid-dispensing systems, to reduce cumbersome manual processing. Another area of potential exploration is ATPS sessile drops in conjunction with digital microfluidics for protein detection applications, to enable manipulation and processing of the ATPS drops to study droplet mixing, splitting, and beyond …”

“…Another area of potential exploration is ATPS sessile drops in conjunction with digital microfluidics for protein detection applications, 47 to enable manipulation and processing of the ATPS drops to study droplet mixing, splitting, and beyond. 48 In applications, we show that microparticles and cells can be encapsulated in W/W secondary droplets formed as the primary droplet is evaporating. Paramagnetic beads and blood cells selectively partition to the primarily Ficoll solution.…”

Microfluidic Droplet-Based Tool To Determine Phase Behavior of a Fluid System with High Composition Resolution

“…To accomplish this, many studies produce droplets upstream and capture them downstream through various geometrical droplet traps. − An alternative approach is to initially fill droplet traps with the dispersed phase solution and then utilize the traps to hydrodynamically produce droplets. − This is the approach taken in the present work. Once droplets are produced, we take advantage of the slight solubility of water in the continuous phase oil and diffusion of water through PDMS to slowly increase the concentration in the droplet. − The ability to dehydrate droplets in microfluidic devices has been used in previous studies to investigate crystallization kinetics, − phase separation, − and particle synthesis. − In addition, ATPS have been widely studied in microfluidic devices both in droplets − and in channels. − …”

Determination of Aqueous Two‐Phase System Binodals and Tie‐Lines by Electrowetting‐on‐Dielectric Droplet Manipulation

“…Such characteristics facilitate various biomedical applications including PCR, immunoassay, cell patterning, and proteomics, and initiated the field of droplet‐based digital microfluidics (DMF) . Recently, an EWOD‐based droplet manipulation method was reported to be useful for on‐chip ATPS formation and mixing to study molecular extraction . We hypothesize that droplet manipulation by EWOD could be further extended to determine ATPS binodals and tie‐lines.…”