Microfluidic rheology of methylcellulose solutions in hyperbolic contractions and the effect of salt in shear and extensional flows

Soft Matter ◽  
2020 ◽  
Vol 16 (22) ◽  
pp. 5273-5281
Author(s):  
Benjamin L. Micklavzina ◽  
Athena E. Metaxas ◽  
Cari S. Dutcher
Keyword(s):  
Extensional Viscosity ◽  
Extensional Flows

The addition of NaCl to methylcellulose solutions increases the extensional viscosity, which can be measured quantitatively using hyperbolic microfluidic contractions. Fluid stresses during flow can be visualized via birefringence.

scholarly journals Motility induced changes in viscosity of suspensions of swimming microbes in extensional flows

Soft Matter ◽  
2015 ◽  
Vol 11 (23) ◽  
pp. 4658-4668 ◽  
Author(s):  
Amarin G. McDonnell ◽  
Tilvawala C. Gopesh ◽  
Jennifer Lo ◽  
Moira O'Bryan ◽  
Leslie Y. Yeo ◽  
...  
Keyword(s):  
Cell Suspensions ◽  
Extensional Viscosity ◽  
Model Systems ◽  
Extensional Flows ◽  
Induced Changes ◽  
Living Materials

Cell suspensions are model systems for studying properties of living materials. A comparison of theory against microfluidic experiments confirms that particle motility causes extensional viscosity to decrease in “pushers” and increase in “pushers”.

scholarly journals Interfacial Tension Measurements in Microfluidic Quasi-Static Extensional Flows

Micromachines ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 272
Author(s):  
Doojin Lee ◽  
Amy Q. Shen
Keyword(s):  
Interfacial Tension ◽  
Microfluidic Device ◽  
Extensional Flow ◽  
Immiscible Fluids ◽  
Droplet Microfluidics ◽  
Channel Height ◽  
Deformation Model ◽  
Droplet Deformation ◽  
Extensional Flows ◽  
2D Model

Droplet microfluidics provides a versatile tool for measuring interfacial tensions between two immiscible fluids owing to its abilities of fast response, enhanced throughput, portability and easy manipulations of fluid compositions, comparing to conventional techniques. Purely homogeneous extension in the microfluidic device is desirable to measure the interfacial tension because the flow field enables symmetric droplet deformation along the outflow direction. To do so, we designed a microfluidic device consisting of a droplet production region to first generate emulsion droplets at a flow-focusing area. The droplets are then trapped at a stagnation point in the cross junction area, subsequently being stretched along the outflow direction under the extensional flow. These droplets in the device are either confined or unconfined in the channel walls depending on the channel height, which yields different droplet deformations. To calculate the interfacial tension for confined and unconfined droplet cases, quasi-static 2D Darcy approximation model and quasi-static 3D small deformation model are used. For the confined droplet case under the extensional flow, an effective viscosity of the two immiscible fluids, accounting for the viscosity ratio of continuous and dispersed phases, captures the droplet deformation well. However, the 2D model is limited to the case where the droplet is confined in the channel walls and deforms two-dimensionally. For the unconfined droplet case, the 3D model provides more robust estimates than the 2D model. We demonstrate that both 2D and 3D models provide good interfacial tension measurements under quasi-static extensional flows in comparison with the conventional pendant drop method.

Extensional flows with viscous heating

2007 ◽  
Vol 571 ◽  
pp. 359-370 ◽  
Author(s):  
JONATHAN J. WYLIE ◽  
HUAXIONG HUANG
Keyword(s):  
Critical Value ◽  
The Other ◽  
Viscous Heating ◽  
Constant Force ◽  
Temperature Dependent ◽  
Downstream Location ◽  
Temperature Dependent Viscosity ◽  
Pulling Forces ◽  
Extensional Flows ◽  
Dependent Viscosity

In this paper we investigate the role played by viscous heating in extensional flows of viscous threads with temperature-dependent viscosity. We show that there exists an interesting interplay between the effects of viscous heating, which accelerates thinning, and inertia, which prevents pinch-off. We first consider steady drawing of a thread that is fed through a fixed aperture at given speed and pulled with a constant force at a fixed downstream location. For pulling forces above a critical value, we show that inertialess solutions cannot exist and inertia is crucial in controlling the dynamics. We also consider the unsteady stretching of a thread that is fixed at one end and pulled with a constant force at the other end. In contrast to the case in which inertia is neglected, the thread will always pinch at the end where the force is applied. Our results show that viscous heating can have a profound effect on the final shape and total extension at pinching.

A comparison of extensional viscosity measurements from various RME rheometers

2001 ◽  
Vol 40 (5) ◽  
pp. 457-466 ◽  
Author(s):  
Jonathan S. Schulze ◽  
Timothy P. Lodge ◽  
Christopher W. Macosko ◽  
Jens Hepperle ◽  
Helmut M�nstedt ◽  
...  
Keyword(s):  
Extensional Viscosity ◽  
Viscosity Measurements

Local versus integral measurements of the extensional viscosity of polymer melts

2009 ◽  
Vol 53 (6) ◽  
pp. 1363-1377 ◽  
Author(s):  
Teodor I. Burghelea ◽  
Zdeněk Starý ◽  
Helmut Münstedt
Keyword(s):  
Polymer Melts ◽  
Extensional Viscosity

The interpretation of transient extensional viscosity data

1997 ◽  
Vol 68 (2-3) ◽  
pp. 241-257 ◽  
Author(s):  
J Ferguson ◽  
N.E Hudson ◽  
M.A Odriozola
Keyword(s):  
Extensional Viscosity ◽  
Viscosity Data
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