A polarimeter is used to characterize a sample by measuring the rotation of polarized light when it interacts with the sample. They can cost upwards of ~$10,000, but a $350 DIY high-resolution polarimeter has recently been detailed in a paper by Andrew Harvie , Tom Phillips, and John deMello.
The bill of materials for the project can be found in the supplementary materials. The supplementary materials also includes some technical diagrams and pictures. The project uses a Teensy micro-controller which we’ve seen used a few times before. Code for the micro-controller, a python GUI, .STL files for 3D printing, and .BRD files for circuit boards can all be found on the project’s GitHub page.
Even if you aren’t interested in a polarimeter, the introduction to the paper is interesting to read for its discussion on why current scientific equipment is so expensive, and how those prices can be reduced in general.