When characterizing cells or any other microscopic objects it’s sometimes useful to guide them through tiny channels when observing or counting them under the microscope. The term is sometimes called as microfluidics. Therefore many different methods exist to create these devices. One method etches channels in glass or plastic, another additively procedure – sometimes called photolithography – cures a photoresist/resin to get a 3D-like structure after washing the uncured parts away. This usually costs lots of money. Further details here: http://pubs.rsc.org/en/content/articlehtml/2016/lc/c6lc00284f
One part of my research was to improve phase-contrast using a brightfield microscope without adding any special optics like the DIC-prism or phasering in Zernike phase-contrast. Defined phase objects are hard to get. Thinking about a light guide embedded in immersion oil could be one chance to have a phase object, but this extends the field of view (FOV) of a 20x/63x objective which was used in my setup.
Cells are usually amorphous and won’t have defined phase retardation. Therefore I was thinking about a way how I can get a defined phase on the cheap with off the shelf components.