This just came out earlier this month (March 2023) in Nature

https://www.nature.com/articles/s41598-023-29182-y

A low-cost smartphone fluorescence microscope for research, life science education, and STEM outreach

Schaefer, M.A., Nelson, H.N., Butrum, J.L. et al. A low-cost smartphone fluorescence microscope for research, life science education, and STEM outreach. Sci Rep 13, 2722 (2023). https://doi.org/10.1038/s41598-023-29182-y