Cell phone digital microscopy using an oil droplet

We introduce an accessible imaging method using droplets of microscope immersion and consumer-grade oils and a cell phone camera. We found that oil droplets were more resistant to evaporation than water droplets. We characterized the transverse magnification of oil and water droplets using cell phone screens and a resolution target. We further harnessed the close refractive index of cooking oils to that of the immersion oil and demonstrated their use as lenses for cell phone microscopy. Our method enables stable droplet-based optical imaging without specialized setups or manufacturing processes.