Light focuses into bright spots through two drops of polymer
Steve Lee demonstrates how drops of polymer focus light from the Sun. These lentil-sized lenses each fit over a camera on a smartphone, turning it into a microscope.
Image: Sarah Kellett/CSIRO

Written by Sarah Kellett

You can now turn your phone camera into a microscope with a rubbery lens the size of a lentil. Costing only a cent, it could help track skin diseases and farming pests.

Accidental discovery

It was found by accident. “I was actually trying to use a mould [casting] process to make a really nice flat lens,” says Steve Lee, a physicist and engineer at the Australian National University. “It didn’t work very well, I was very disappointed. At the same time I left a drop in the oven overnight and it formed a really nice curvature.”

Tough and rubbery, the drop had some interesting properties, but Steve didn’t think much of it until he talked to Tri Phan, a doctor working in the microscopy division at Sydney’s Garvan Institute of Medical Research. “He got excited,” says Steve.

The lens simply sticks onto a smartphone camera to provide instant magnification. Steve is now talking to dermatologists who think this tiny lens could track suspicious moles in case they change shape. Farmers could use it to identify pests, perhaps uploading photos to biosecurity agencies.

There are several ways to make a lens. Steve’s process uses only an oven and a polymer called polydimethylsiloxane, the strong, scratch-resistant material found in soft contact lenses. A drop is placed on a glass microscope slide and flipped upside down. Gravity and surface tension pull the droplet into the shape of a lens.

Making a powerful lens

After the accidental discovery, Steve wanted to make the lens better. “I thought maybe I could try layering. I did it again and again until I had refined the time, the sequence steps, how much to drop … Each drop reduces the focal length and increases the magnifying power,” says Steve. “The highest magnification strength we can get is 160 times, resolving four micron [four thousandths of a millimetre] structures.”

The lenses might find use in developing countries as they cost only a cent in material and all you need to make them is an oven. Steve says they are so easy to make you could do it at home. He suggested you could make one with gelatine by experimenting with different viscosities, and it works! You can even make your own jelly lenses and try sticking them on a smartphone.

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