I've been fabricating traction force microscopy devices in glass bottom dishes, using a method that first spins a 100 micron PDMS layer, then a ~1 micron PDMS + fluorescent beads mixture layer. After curing, they look evenly dispersed and flat, but after a night with seeded cells and media, they look warped. Removing the cells and media and drying the devices back in the oven reverts it to being flat. What is causing this? Is there any way to fix this issue such that I can use my previously made devices? Any feedback is appreciated. Thanks.
Hi,
This is not my expertise. I was just curious and wanted to join the discussion.
I am curious about a couple of ideas.
1) Do you think it is possible that the cells (if adhered properly) apply force on the beads and move them around?
2) do you think it might be due to the changing refractive index of the medium with cells in it that warp the image? However, I think this wouldn't be an issue if the microscope is inverted.
3) I am not sure what chemical reaction you use on your PDMS, or what is the properties of the beads, but do you think that it might swell? Technically, if i remember correctly PDMS do not swell in water-based solvent. However, it swells in IPA.
I would love to know what is the reason when you find it.
Minh-Tam Tran Le
There might be a few issues, first, the stiffness of PDMS, can you please share what is the ratio of PDMS you are using? What is the curing temperature and time? The issue of wrapping happens when the top layer is too soft. When you are making the top player of PDMS with beads, the ratio of PDMS and solution that uses fluorescent beads might lead to a reduced concentration of PDMS. Let me know if these could help and let me know if you want to discuss it more. Thanks
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