Scientists crack the code for making gel droplets in microfluidic devices
Researchers have mapped out how to reliably control gel droplet formation in microfluidic systems, a finding that could accelerate development of lab-on-a-chip diagnostics and cell engineering tools. The work pinpoints which variables matter most—and which don't—cutting design complexity for companies building next-generation biotech devices.
Originaltitel: Dynamics of non-Newtonian agarose gel droplet formation in two-phase microfluidic systems
<p>Droplet-based microfluidics is a valuable tool in interdisciplinary research fields like cell biology and diagnostics. Newtonian fluids, like aqueous-based solutions, are commonly used for droplet generation. However, non-Newtonian fluids, e.g., hydrogels, are becoming increasingly popular as the dispersed phase. In this study, we investigate the dynamics of non-Newtonian ultra-low-gelling agarose droplet formation under different conditions to evaluate stability, with an aim to better understand the underlying physics of droplet formation. We varied the agarose gel concentration, temperature (40, 50, and 60 degrees C), and the flow rate ratio (phi) between the continuous and dispersed phase and observed droplet formation dynamics in the squeezing regime (capillary number, Ca-c < 0.015) in a T-junction under different flow conditions. We experimentally investigated the droplet size ( L (D) / w ) as a function of those four parameters and found that L- D / w depends strongly on phi, the agarose concentration, and temperature (which affects the viscosity ratio, lambda), but is only weakly dependent on Ca-c . We then confirmed our experimental findings with numerical simulations, which showed good agreement across all conditions. We numerically showed that the agarose droplet formation process consists of five stages, namely, filling, necking, pinching, threading, and breakup, where threading is an additional stage with a non-Newtonian dispersed phase. Finally, with numerical simulation, we concluded that threading length (l(thread )) is directly proportional to phi and has a complex relation with agarose concentration, and temperature.</p>