Towards a continuous microfluidic rheometer

Abstract

In a previous paper we presented a way to measure the rheological properties of complex fluids on a microfluidic chip (Guillot et al., Langmuir 22:6438, 2006). The principle of our method is to use parallel flows between two immiscible fluids as a pressure sensor. In fact, in a such flow, both fluids flow side by side and the size occupied by each fluid stream depends only on both flow rates and on both viscosities. We use this property to measure the viscosity of one fluid knowing the viscosity of the other one, both flow rates and the relative size of both streams in a cross-section. We showed that using a less viscous fluid as a reference fluid allows to define a mean shear rate with a low standard deviation in the other fluid. This method allows us to measure the flow curve of a fluid with less than 250 lL of fluid. In this paper we implement this principle in a fully automated set up which controls the flow rate, analyzes the picture and calculates the mean shear rate and the viscosity of the studied fluid. We present results obtained for Newtonian fluids and complex fluids using this set up and we compare our data with cone and plate rheometer measurements. By adding a mixing stage in the fluidic network we show how this set up can be used to characterize in a continuous way the evolution of the rheological properties as a function of the formulation composition. We illustrate this by measuring the rheological curve of four formulations of polyethylene oxide solution with only 1.3 mL of concentrated polyethylene oxide solution. This method could be very useful in screening processes where the viscosity range and the behavior of the fluid to an applied stress must be evaluated.

Phase separation of parallel laminar flow for aqueous two phase systems in branched microchannel

“…It was not absolute flow rates but the phase ratio determining the interface location in a certain microchannel, as shown in Fig. 3, which is accordant with the conclusion drawn by Guillot et al (2008). In Fig.…”

Electroviscous effects in steady fully developed flow of a power-law liquid through a cylindrical microchannel

“…The significantly reduced quantity of sample consumption and increased rate of heat/mass transfer and chemical reactions are the key advantages of microfluidic devices. Applications range from pH and temperature sensors to fluid actuators, such as micronozzels, micropumps (Laser and Santiago, 2004;Woias, 2005), micromixers (Hessel et al, 2005;Nguyen and Wu, 2005), microvalves (Kwong and Chong, 2006), micro-rheometers (Guillot et al, 2008), biotechnology areas such as the analysis of DNA and proteins, and biodefence (Whitsides and Stroock, 2001), as well as LOC systems for drug delivery, chemical analysis, and biomedical diagnosis (Bousse et al, 2000). A blood analyzer MEMS requires taking a sample by means of generating blood flow through a microneedle of the microfluidic system.…”

Parallel flow of immiscible liquids in a microreactor: modeling and experimental study

“…Simulations at higher length scales clearly showed that particular movement. The position of the interface between two Newtonian fluids was the same with various flow rates, as long as the ratio between then remained constant, which was also noted by Guillot et al (2008).…”

“…Lu et al (2011) acknowledged parallel laminar flow for being an effective platform for enhanced mass transfer, for simultaneous preservation of separate phases, for fast phase equilibrium or diffusivity determination with trace chemical consumption, and for continuous, efficient and even multi-stage industrial extraction techniques. Münchow et al (2007) utilized parallel flow for electrophoretic partitioning of proteins and Guillot et al (2008) developed a method to perform automated rheological measurements on a microfluidic chip. They also numerically calculated the steady-state developed velocity profiles for two-phase parallel flow and Galambos and Forster (1998) used an analytical solution of simplified Navier-Stokes equations to obtain the velocity profile at steady-state and to predict the position of the interface of developed flow.…”