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Questions tagged [microfluidics]

For questions which are in the context of microfluidics. Microfluidics is a multidisciplinary field intersecting engineering, physics, chemistry, biochemistry, nanotechnology, and biotechnology, with practical applications to the design of systems in which small volumes of fluids will be handled. This is typically the sub-milimeter scale.

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Can you use the Hagen-Poiseuille equation for a pipe which radius is in the sub-millimeter region?

As this will depend on Pressure drop $\Delta p$, assume that it does not leave the range from 0 to 100 bar. The Hagen-Poiseuille equation for an incompressible fluid is defined as: $$ \dot{V} = \frac{\pi R^4 \Delta p}{8\eta L}$$ I realize that it…
JHK
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Precision measurement of liquid levels

How can I measure changes in liquid level of the order of 50 μm? The tank is cylindrical with a radius of about 12.5 mm and a total volume of about 45 ml. The fluid is water-based. The technique needs to be optical or similar because no external…
Worldsheep
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What's the smallest pin-like hole I can machine into a piece of tungsten using a metal lathe and common carbide tools?

I am going to machine something out of a small 40mm long x 8mm diam tungsten rod. The majority will be hollowed out using a larger bit, but at the very tip, I need a small hole, the smaller the better between .05mm and .6mm. I understand an L/D…
Daniel Donnelly
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Weight Sensing Problem: Need to detect 10kg load down to milligram accuracy

I need to build some type of scale where one can place four 600mL beakers on it and measure out its weight down to a milligram level of accuracy. I'm doing this so I can dose a very small amount of liquid (2 microliters) into the beakers at a time.…
AndrewP
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Shear rate of a fluid in a container with a sliding PTFE top plate. Will the liquid move with the plate?

I am trying to work out how a liquid inside a container will be affected by the back and forth sliding of a Teflon coated plate such as the one in the picture. I know how to work out the shear rate of a fluid between two plates moving at different…
user88720
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Ensuring even flow in liquid pumping in distribution circuit under suction

I have a liquid circuit which looks a bit like that: The system is under suction, and the flow rate through each unit should be about 10ml/min. However, we noticed that unit n and the ones the furthest away from the pump and bottle were not getting…
am304
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Are there basic rules to properly design vein channels?

I am trying to model a prototype resembling a section of vein channels. I am wondering if there are some basic rules for such fluid channels, for instance when a vein splits in two capillaries, is there some quantity conserved (area of the section…
blackdragone
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CFD simulation of an Air and Oxygen gas gradient in a microfluidics device

I am in the process of manufacturing a microfluidic device for use in research, and would like to do a CFD simulation of the interior of the device to see if an oxygen gradient is formed. The idea is to run a CFD (computational fluid dynamics)…
mangoTango
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Why is electroosmotic flow plug-like?

Hey, I am studying for a microfluidic exam and can't wrap my head around electro osmotic flow: why is the velocity profile plug-like? The fluid motion in the bulk phase away from the double layer is driven by the viscous interaction with the double…
frgoe
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PMMA-water contact angle in microchannel

I am using comsol to model a capillary behavior of water in an unmodified PMMA microchannel. In literature, I have seen untreated PMMA called hydrophobic. This makes no sense to me because, since its reported contact angle is 68deg, by definition it…
EBird
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Optimized water droplet formation

What is the best way to "shatter" a water drop falling purely under gravity if the objective is to break it into as many droplets and as fine (smallest diameter) as possible? Should the surface be perpendicular to the direction of the falling drop?…
Francois Grobler
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How do you imagine momentum?

If you want to explain it to a layman (who belongs to the science stream ofc!!) how do you explain it? Also, what is momentum transfer when it comes to fluid mechanics?
Unnati Rotliwala
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How can I confirm nL Volume Measurement for Pump and Sensor Calibration

I'm dispensing around 1uL of volume with 1% accuracy. Although I'm confident in my pump, I'd like to be able to routinely confirm that I'm getting the exact volume I'm requesting every time. How can I reliably measure volume at this small scale?…
GrantG
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Pushing fluid through microfluidics

my team is working on a project where fluid (mostly water) need to be pushed through small channels (like small pipes) in order to reach larger reservoir. We were considering using air to push the water but we fear that the water will simply bubble…
Peter Connors
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How to calculate flow rate of viscous fluids through a funnel-shaped needle?

How would you determine the flow rate of a liquid that flows through a narrow microneedle channel and then through the opening of a funnel, i.e. pouring liquid through the other end of a funnel? I've chosen arbitrary diameters but the pressures are…
AnkilP
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