I spent most of the day fiddling with the imaging set-up and water-bead suspension. I came across a few problems which will probably prevent me from getting any real results from this experiment.
- The working distance of the objective is 0.17mm therefore it can only focus on the upper surface of the glass slide and I cannot resolve the water, beads or fibre below. I removed the upper glass slide acting as a cover slip, and...
- I used water as the "index-matching" substance rather than the low-viscosity oil. I was able to obtain very clear images of the fibre in water.
- The beads are therefore going directly into the same water which the objective is moving around in. The beads do not sink (or maybe they do, but my water sample evaporates before I can see this), they just rest on top of the water blob. So, when I put the objective lens into the water for imaging, the beads are pushed away. Only the ones 'stuck' to the fibre stay put. This explains why I could not focus on the beads perfectly - they were pushed away. The first image below shows an unfocused bead in the bottom right corner - I have a video of this undergoing Brownian motion. When I tried to focus on this bead, I just pushed it away with the microscope.
- The lifetime of my sample is not very long because the halogen lamp strongly encourages evaporation!
A simple solution to the bead problem is maybe placing them on the glass slide first and then dropping the water sample over them. I will have to minimise objective movement tomorrow by finding a nice area of the taper with a good bead selection and just staying at that point.
Another option to try and stabilise the beads is to use a water-glycerol solution (glycerol is soluble in water). I will ask around tomorrow to see if I can get some.
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