Extracting the hydrodynamic resistance of droplets from their behavior in microchannel networks.
The overall traffic of droplets in a network of microfluidic channels is strongly influenced by the liquid properties of the moving droplets. In particular, the effective hydrodynamic resistance of individual droplets plays a key role in their global behavior. Here we propose two simple and low-cost experimental methods for measuring this parameter by analyzing the dynamics of a regular sequence of droplets injected into an "asymmetric loop" network. The choice of a droplet taking either route through the loop is influenced by the presence of previous droplets that modulate the hydrodynamic resistance of the branches they are sitting in. We propose to extract the effective resistance of a droplet from easily observable time series, namely, from the choices the droplets make at junctions and from the interdroplet distances. This becomes possible when utilizing a recently proposed theoretical model based on a number of simplifying assumptions. Here we present several sets of measurements of the hydrodynamic resistance of droplets, expressed in terms of a "resistance length." The aim is twofold: (1) to reveal its dependence on a number of parameters, such as the viscosity, the volume of droplets, their velocity as well as the spacing between them. At the same time (2), by using a standard measurement technique, we compare the limitations of the proposed methods. As an important result of this comparison, we obtain the range of validity of the simplifying assumptions made in the theoretical model.
Labrot
Vincent
V
Schindler
Michael
M
Guillot
Pierre
P
Colin
Annie
A
Joanicot
Mathieu
M
Langmuir. 2005 Mar 15;21(6):2113-6
15751995
Science. 2007 Feb 9;315(5813):832-5
17289994
Phys Rev Lett. 2004 Feb 6;92(5):054503
14995311
Phys Rev E Stat Nonlin Soft Matter Phys. 2005 May;71(5 Pt 2):057301
16089701
Anal Chem. 1998 Dec 1;70(23):4974-84
21644679
Phys Rev Lett. 2008 Feb 1;100(4):044501
18352282
J Am Chem Soc. 2003 Sep 17;125(37):11170-1
16220918
Lab Chip. 2006 Sep;6(9):1140-6
16929392
Angew Chem Int Ed Engl. 2003 Feb 17;42(7):768-72
12596195
Phys Rev Lett. 2006 Feb 10;96(5):054501
16486936
Phys Rev Lett. 2005 Jun 17;94(23):234502
16090475
Phys Rev Lett. 2005 Nov 11;95(20):208304
16384111
Phys Rev Lett. 2001 Apr 30;86(18):4163-6
11328121
Science. 2005 Aug 5;309(5736):887-8
16081724
Lab Chip. 2007 Nov;7(11):1479-89
17960275