Related Experiment Video
Updated: Jun 22, 2026
10:56
Confocal Imaging of Confined Quiescent and Flowing Colloid-polymer Mixtures
Published on: May 20, 2014
Suppression of instabilities in multiphase flow by geometric confinement
Katherine J Humphry1, Armand Ajdari, Alberto Fernández-Nieves
1Department of Physics, School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA.
Summary
Geometric confinement controls drop formation in microfluidic devices. Stable jets form when inner fluid width exceeds channel height, while smaller widths induce drop breakup.
Area of Science:
- Fluid dynamics
- Microfluidics
- Interfacial phenomena
Background:
- Microfluidic devices enable precise control over fluid behavior.
- Understanding drop formation is crucial for applications like drug delivery and materials science.
- The interplay between fluid properties and channel geometry influences flow stability.
Purpose of the Study:
- To investigate how geometric confinement affects drop formation in microfluidic co-flow systems.
- To determine the critical geometric parameters that dictate the transition between stable jetting and drop breakup.
- To develop a predictive model for drop formation based on channel geometry.
Main Methods:
- Experimental study of two immiscible liquids flowing co-currently in a microfluidic channel.
- Systematic variation of channel geometry, specifically the ratio of channel width to height.
- Observation and analysis of fluid thread stability and breakup regimes (dripping/jetting).
- Development of a theoretical model to explain the observed phenomena.
Main Results:
- Drop formation is suppressed when the inner fluid thread's width is comparable to or larger than the channel height.
- Hydrodynamic instabilities leading to breakup are promoted when the inner fluid width is significantly smaller than the channel height.
- The study identified distinct dripping and jetting regimes governed by geometric confinement.
- A model was developed that accurately predicts the onset of drop formation based on geometric parameters.
Conclusions:
- Geometric confinement is a key factor in controlling drop formation in microfluidics.
- The width-to-height ratio of the microchannel dictates the stability of the inner fluid thread.
- This geometric control can be exploited to precisely localize drop breakup in microfluidic devices.
Related Concept Videos
01:17Steady, Laminar Flow Between Parallel Plates
Understanding steady, laminar flow between parallel plates is essential for analyzing and designing flow in narrow rectangular channels, commonly found in various water conveyance and drainage systems. The Navier-Stokes equations govern fluid motion and are generally challenging to solve due to their nonlinearity. However, simplifications are possible in certain cases, like the steady laminar flow between parallel plates. For this scenario, we assume steady, incompressible, laminar flow.
01:23Steady, Laminar Flow in Circular Tubes
Hagen-Poiseuille flow describes a viscous fluid's steady, incompressible flow through a cylindrical tube with a constant radius R. This flow profile is often applied to understand fluid transport in narrow channels, such as capillaries. It serves as a foundational example of laminar flow. In this model, cylindrical coordinates (r,θ,z) are used to describe the radial (r), angular (θ), and axial (z) dimensions within the tube. For Hagen-Poiseuille flow, the velocity profile is purely axial,...
01:24Turbulent Flow
Turbulent flow is characterized by unpredictable fluctuations in velocity and pressure, which result in a chaotic fluid movement distinct from the orderly patterns of laminar flow. While laminar flow is governed by smooth, parallel layers with minimal mixing, turbulent flow exhibits highly irregular, three-dimensional patterns. This behavior arises due to instabilities in the fluid's velocity profile, and amplifies as the flow velocity increases. Minor disturbances, known as turbulent spots,...
01:07Conservation of Mass in Fixed, Nondeforming Control Volume
The principle of conservation of mass is fundamental in fluid dynamics and is crucial for analyzing flow within fixed control volumes, such as pipes or ducts. This principle states that the total mass within a control volume remains constant unless altered by the inflow or outflow of mass through the control surfaces. This results in a vital relationship for steady, incompressible flow where the mass entering a system equals the mass leaving it.
In the case of a sewer pipe, which can be modeled...
In the case of a sewer pipe, which can be modeled...
01:22Couette Flow
Couette flow represents the flow of fluid between two parallel plates, with one plate fixed and the other moving with a constant velocity. This configuration allows for a simplified analysis using the Navier-Stokes equations, which govern fluid motion under conditions of viscosity and incompressibility. For Couette flow, the assumptions include a steady, laminar, incompressible flow with a zero-pressure gradient in the flow direction. This flow type is beneficial for understanding shear-driven...
01:16Conservation of Mass in Finite Cotrol Volume
The principle of conservation of mass is a fundamental law in fluid mechanics and is applied using the continuity equation. We apply the concept to a finite control volume to derive the continuity equation.
A system is defined as a collection of unchanging contents, and the conservation of mass states that a system's mass is constant.
A system is defined as a collection of unchanging contents, and the conservation of mass states that a system's mass is constant.