Measuring Very Small Forces in the Lab

In summary, the conversation discusses methods for measuring very small forces in the lab, such as using laser interferometry on a weak deflector or an electrostatic balance. These methods involve measuring tiny displacements and calibrating for force versus displacement, with potential applications in mechanics and material science. The conversation also mentions using a micromachined cantilever board as a deflecting element and notes that the sensitivity of these methods may vary.
  • #1
zoobyshoe
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I'm curious about how very small forces are actually measured in the lab. I read somewhere that a dyne, for instance, exerts about the same force as a mosquito landing. What kind of set ups and instruments are needed to accurately measure a force that small, and smaller?
 
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  • #2
Maybe laser interferometry on a weak deflector? I'd be interested in hearing about actual lab setups too.
 
  • #3
berkeman said:
Maybe laser interferometry on a weak deflector?
What's the principle behind this?
 
  • #4
Laser interferometry is just a way to measure very small displacements, on the order of the wavelength of the laser light. You combine a reflected version of the light (off of whatever is deflecting from the force) with some of the original beam, and count the number of fringes that the combination passes through as the deflecting element moves.

Laser interferometry is relative, though, so you need to start with the deflecting element stationary in a rest position first. Then apply the mosquito force, and count the number of fringes that the combined beam goes through until the deflection is stationary again. You'd need to calibrate for the force versus displacement of the deflecting element, of course, but hopefully that would just me a mechanics/material science exercise.

I'm not sure what the best deflecting element would be -- depends on the force magnitude, direction, stability, etc. You could even use a micromachined cantilever board on silicon if the thing you want to measure could be interfaced to the end of the lever...
 
  • #5
That method would take care of the very tiny forces for sure. Pretty fascinating.

I wonder about in- between situations for which that would be too sensitive.
 
  • #6
One could use an electrostatic balance. This is a balance that uses electrostatic forces rather than counter weights.
 
  • #7

1. What is the purpose of measuring very small forces in the lab?

The purpose of measuring very small forces in the lab is to understand and study the behavior of materials and systems at a microscopic level. This can provide valuable insights into various physical phenomena and help in the development of new technologies.

2. How are very small forces measured in the lab?

There are various techniques used to measure very small forces in the lab, such as atomic force microscopy, laser interferometry, and optical tweezers. These techniques involve using sensitive instruments and equipment to detect and measure minute forces.

3. What are some applications of measuring very small forces in the lab?

Measuring very small forces in the lab has numerous applications in fields such as materials science, biophysics, and nanotechnology. It can be used to study the mechanical properties of materials, investigate biological processes at the cellular level, and manipulate and control nanoparticles.

4. What are some challenges in measuring very small forces in the lab?

One of the main challenges in measuring very small forces in the lab is the presence of noise and interference from various sources. This can make it difficult to accurately detect and measure the forces. Another challenge is the fragility of some materials, which may be easily affected by the instruments used for measurement.

5. How can the accuracy of measuring very small forces in the lab be improved?

To improve the accuracy of measuring very small forces in the lab, it is important to use high-quality instruments and carefully calibrate them. Reducing sources of noise and interference, such as vibrations and electrical signals, can also increase the accuracy. Additionally, performing multiple measurements and averaging the results can help to minimize errors.

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