This is a lot of fluff for making a static picture from DNA fluorescence. There is nothing being rendered here in the tubes, it's just adding varying amounts of DNA to tubes arranged in a grid.
That's not how this works. The computation is done in tubes via chemical reactions. The inputs (column and row) are specified by providing a variable concentration of two input solutions to the same base solution which encodes the ray marching algorithm. The scene is static, but you can theoretically sample it at arbitrary points and resolutions by varying the inputs.
Each tube renders/computes a "pixel". The concentrations are not proportional to brightness, but instead linearly correspond to x / y position of the pipettes.