Microfluidics in pressures lower than one atmosphere

In summary, the experiment is trying to determine why the liquid flows out of the tube when the pressure is below 200mbar. The liquid consists of a few types of tubing with a volumetric plunger pump and a chamber valve. The pump is set to work at a speed of 10µl/s and needs to pump out volumes between 2 and 130µl.
  • #1
cedric goossens
4
0
Hi everyone

I am trying to build an experiment with microfluidics. I have a reservoir containing a bellow. This bellow is a compensation mechanism and makes sure that the liquid (in this case water) can be pushed out of the reservoir. Before storing the fluid in the reservoir, the reservoir is evacuated up to 10^-2bar and the fluid is degassed. Right after the reservoir I have a first valve followed by stainless steel tubing with a diameter of 0.35mm. THis tubing also contains a pump. After the tubing I have a second valve which connects the tubing to a controlled (pressure and temperature) and closed chamber. My experiment is as follows:
- reservoir valve is closed
- chamber valve is opened
- chamber and tubing are evacuated
- pressure is set in chamber and tubing
- reservoir valve is opened
- reservoir valve is closed when liquid reaches chamber
- chamber valve is closed
- chamber is evacuated
- pressure is reset (same value as before)
- chamber valve is opened
- pump is used to inject liquid

Now this works perfectly fine when the set pressure is 1bar, 400mbar,...
But when the pressure is below 200mbar the liquid keeps on flowing out of the tubing. I was wondering what the cause is of this. Is this due to the capillary effect or is it something else that I am missing?
 
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  • #2
cedric goossens said:
10^-2bar and the fluid is degassed.
Through a capillary? Of what length? Containing a pump? And what other impediments to flow? For how long? And what percentage of saturation is 10-2 bar?
 
  • #3
Well the liquid lines consist of a few types of tubing. First of all there is a 1.6mm diameter tubing approximately 20cm in length, as a sidebranch of this tubing there is a volumetric plunger pump to push the liquid out. Behind the final valve there is a tube of 0.35mm diameter tubing of approximately 2cm. The pump is set to work at a speed of 10µl/s and needs to pump out volumes between 2 and 130µl.
The last question I don't quite get. Before filling the reservoir with degassed liquid, it is set to 10^-2 bar. After that the reservoir is filled.
 
  • #4
cedric goossens said:
The last question I don't quite get.
What's vapor pressure of water?
 
  • #5
Considering it's at room temperature this should be about 31mbar
 
  • #6
Bystander said:
What's vapor pressure of water?

Sorry to bother you but do you have any insights?
 

1. What is microfluidics in pressures lower than one atmosphere?

Microfluidics in pressures lower than one atmosphere is the study and manipulation of small volumes of fluids under low pressure conditions, typically less than atmospheric pressure. This field is often used in research and development of microscale technologies, such as lab-on-a-chip devices, which require precise control and manipulation of fluids at low pressures.

2. What are the advantages of using microfluidics in pressures lower than one atmosphere?

Some of the advantages of using microfluidics in pressures lower than one atmosphere include better control and manipulation of fluids, reduced risk of air bubbles and contamination, and the ability to work with a wider range of fluids and materials. Additionally, microfluidic devices operating at low pressures can be more compact and cost-effective compared to traditional methods.

3. How is microfluidics in pressures lower than one atmosphere different from traditional microfluidics?

The main difference between microfluidics in pressures lower than one atmosphere and traditional microfluidics is the operating pressure. Traditional microfluidic devices typically operate at atmospheric pressure, while microfluidic devices in lower pressures require specialized designs and materials to maintain fluid flow and control. Low-pressure microfluidics also offers more flexibility in the use of different fluids and materials.

4. What are some applications of microfluidics in pressures lower than one atmosphere?

Microfluidics in pressures lower than one atmosphere has a wide range of applications, including medical diagnostics, drug delivery systems, environmental monitoring, and chemical analysis. It is also used in research areas such as biotechnology, microbiology, and nanotechnology.

5. What are the challenges in working with microfluidics in pressures lower than one atmosphere?

Some challenges in working with microfluidics in pressures lower than one atmosphere include the need for specialized equipment and materials, difficulty in maintaining consistent fluid flow and pressure, and the potential for air bubbles and contamination. Additionally, the small scale of microfluidic devices can make them more susceptible to external influences, such as temperature changes and vibrations, which can affect their performance.

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