Release Time:2020-08-29  Hits:

Indexed by: Journal Papers

Date of Publication: 2020-04-01

Journal: MICROMACHINES

Included Journals: EI、SCIE、PubMed

Volume: 11

Issue: 4

Key Words: droplet microfluidics; breakup dynamics; filament thinning; non-Newtonian fluids; flow-focusing device; extensional flow; semi-dilute polymer solutions

Abstract: Droplet microfluidics involving non-Newtonian fluids is of great importance in both fundamental mechanisms and practical applications. In the present study, breakup dynamics in droplet generation of semi-dilute polymer solutions in a microfluidic flow-focusing device were experimentally investigated. We found that the filament thinning experiences a transition from a flow-driven to a capillary-driven regime, analogous to that of purely elastic fluids, while the highly elevated viscosity and complex network structures in the semi-dilute polymer solutions induce the breakup stages with a smaller power-law exponent and extensional relaxation time. It is elucidated that the elevated viscosity of the semi-dilute solution decelerates filament thinning in the flow-driven regime and the incomplete stretch of polymer molecules results in the smaller extensional relaxation time in the capillary-driven regime. These results extend the understanding of breakup dynamics in droplet generation of non-Newtonian fluids and provide guidance for microfluidic synthesis applications involving dense polymeric fluids.