Viscosity Measurements Using Microfluidic Droplet Length

Abstract

Viscosity measurements have a wide range of applications from industrial chemical production to medical diagnosis. In this work, we have developed a simple droplet-based, water-in-oil continuous viscometer capable of measuring viscosity changes in 10 s or less and consuming a total sample volume of less than 1 μL/h. The viscometer employs a flow-focusing geometry and generates droplets under constant pressure. The length of the droplets (L) is highly correlated to the aqueous-phase viscosity (μ) at high ratios of aqueous-inlet to oil-inlet pressure (AIP/OIP), yielding a linear relationship between μ and 1/(L - L) where L is the minimal obtainable droplet length and approximately equals to the width of the droplet-generating channel. Theoretical analysis verifies this linear relationship, and the resulting equations can be used to optimize the design of the device such as the channel width, depth, and length. The viscometer can be used for Newtonian fluids and, by accurately calculating the shear rate, for non-Newtonian fluids such as Boger fluids and shear thinning fluids. In these latter cases, the shear rates depend on the velocity of the aqueous phase and can be adjusted by varying the input pressures. The applicable range of viscosity measurements depends on the oil-phase viscosity (μ), and viscosities within the range of 0.01-10 μ can be measured reliably with less than 5% error.

Microfluidic-Based Biosensor for Blood Viscosity and Erythrocyte Sedimentation Rate Using Disposable Fluid Delivery System

“…Second, various devices such as a microelectromechanical system (MEMS)-based microfluidic device, a 3D-printed microfluidic device [13,24], and a paper-based device [25] have been suggested for inducing blood flow in a specifically constrained direction. Third, quantification techniques such as advancing meniscus (i.e., variations of a blood column over time) [15,22,26,27], the falling time of a metal sphere in a tube [28], electric impedances (i.e., resistance, capacitance) [29,30], droplet length [31], digital flow compartment with a microfluidic channel array [11,12], interface detection in co-flowing streams [32,33], and reversal flow switching in a Wheatstone bridge analog of a fluidic circuit [14] have been suggested to measure blood viscosity.…”

Precise measurement and control of the pressure‐driven flows for microfluidic systems

“…Based on the pressure‐driven device, even though the flow‐rate fluctuations coming from the pump source can be drastically reduced, according to the literature, it is still very important and difficult to precisely control the flow rates of the fluids for the pressure‐driven flows. Especially for the droplet microfluidics , as the droplet size is quite sensitive to the variation of the flow rates supplied by the pressure‐driven device, how to accurately control the flow rates of the fluids is of great importance for improving the stability and uniformity of droplet production . In addition to droplet formation, there are various applications of droplet microfluidcs which require high stability and accuracy of the microfluidic flows, especially some flow regulator and stabilizer are designed to improve the stablility of the flow‐rate supply .…”

Simultaneous Measurement of Viscosity and Optical Density of Bacterial Growth and Death in a Microdroplet

“…In turn, Livak-Dahl et al [ 20 ] has calculated the droplet viscosity using an abrupt channel constriction, which has been characterised by a high hydrodynamic resistance, compared to the whole microfluidic system. A different solution has been proposed by Li et al [ 21 ]. The authors took advantage of a relationship between the viscosity and the length of the generated droplets in a flow-focusing microfluidic junction.…”