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Related Concept Videos

Steady, Laminar Flow Between Parallel Plates01:17

Steady, 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.
Design Example: Forces in Sluice Gate01:11

Design Example: Forces in Sluice Gate

In hydraulic engineering, sluice gates are essential for managing water flow through channels, reservoirs, and irrigation systems. Sluice gates, acting as vertical barriers, regulate water by adjusting the gate's opening height, which changes the velocity and pressure of water flowing beneath the gate. Understanding the forces involved is crucial to designing sluice gates that can withstand dynamic pressure differences, especially when the gate is closed or partially open.
Key variables in...
Steady, Laminar Flow in Circular Tubes01:23

Steady, 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,...
Laminar Flow01:27

Laminar Flow

Laminar flow represents a smooth, orderly fluid motion where particles move along parallel paths, resulting in minimal mixing between layers. Streamlined particle paths characterize this flow regime and occur under conditions where viscous forces dominate over inertial forces. The distinction between laminar, transitional, and turbulent flow is primarily determined by the Reynolds number, a dimensionless quantity calculated as:
Steady Flow of a Fluid Stream01:27

Steady Flow of a Fluid Stream

Consider a control volume, such as a pipe with solid boundaries, through which fluid flows and changes direction due to the impulse exerted by the resulting force from the pipe walls. In steady flow, the mass of fluid entering the control volume at a given time, t, with velocity v1, is equal to the mass leaving after infinitesimal time dt, with velocity v2.
During this process, the momentum of the fluid within the control volume remains constant over the time interval dt. By applying the...
Gradually Varying Flow01:29

Gradually Varying Flow

Gradually varying flow (GVF) in open channels describes situations where water depth changes slowly along the channel due to factors like non-uniform bed slope, channel shape variations, or obstructions. This flow type occurs when the depth adjusts gradually to balance gravitational forces, shear forces, and energy requirements, resulting in a low rate of depth change.Characteristics of Gradually Varying FlowGVF is commonly observed in natural streams, rivers, and canals, where flow depth...

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Related Experiment Video

Updated: Jul 12, 2026

Multi-step Variable Height Photolithography for Valved Multilayer Microfluidic Devices
10:18

Multi-step Variable Height Photolithography for Valved Multilayer Microfluidic Devices

Published on: January 27, 2017

A virtual valve for smooth contamination-free flow switching.

Thomas Braschler1, Joel Theytaz, Ronit Zvitov-Marabi

  • 1EPFL, LMIS 4, Station 17, BM3125, Lausanne, VD 1015, Switzerland. thomas.braschler@epfl.ch

Lab on a Chip
|August 24, 2007
PubMed
Summary

This study introduces a novel microchip channel geometry for contamination-free fluid switching. The pneumatic virtual valve system ensures stable downstream flow, enabling applications like hydrogel construction and cell culture perfusion.

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Multi-step Variable Height Photolithography for Valved Multilayer Microfluidic Devices
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Published on: January 27, 2017

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Area of Science:

  • Microfluidics
  • Biotechnology
  • Chemical Engineering

Background:

  • Microfluidic devices often face challenges with cross-contamination during fluidic switching.
  • Maintaining stable downstream flow during inlet switching is critical for reproducible experiments.

Purpose of the Study:

  • To develop a novel channel geometry for microfluidic systems enabling clean and efficient switching between multiple inlets.
  • To demonstrate a pneumatic pressure-driven virtual valve that minimizes downstream flow disturbance.
  • To validate the practical utility of the system in microfabrication and explore potential applications.

Main Methods:

  • Design and fabrication of a microchip with a unique channel geometry for virtual valving.
  • Implementation of a pneumatic pressure control system for simultaneous variation of inlet pressures.
  • Spectroscopic measurement of downstream dye concentrations to assess switching efficiency.
  • Sequential construction of alginate hydrogel layers to demonstrate practical application.

Main Results:

  • The developed channel geometry successfully prevented contamination between inlets and maintained downstream flow integrity.
  • The pneumatic virtual valve system demonstrated minimal disturbance during fluid switching.
  • Spectroscopic analysis confirmed efficient and clean fluid transfer.
  • Successful sequential layering of alginate hydrogel was achieved, showcasing the system's utility.

Conclusions:

  • The presented microfluidic channel geometry and pneumatic virtual valve offer a robust solution for contamination-free fluid switching.
  • The system's ability to maintain flow stability and its demonstrated utility in hydrogel fabrication highlight its potential for diverse microfluidic applications.
  • This technology is applicable to cell culture, chemical reactions, chromatography, and precise fluid metering.