This lens could turn your smartphone into a microscope


The chance discovery of the power of a simple silicon polymer droplet could revolutionise remote diagnosis. Phil Dooley reports.


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The droplet lens costs less than a cent and would be perfect for health applications in the developing world, its inventor says.
PM Images/Getty Images

Biomedical engineer Stephen Lee has found a cheap and simple way to turn smartphones into microscopes by attaching a hardened droplet of a clear silicon polymer to the camera lens. The modification might help doctors and farmers in remote regions diagnose human and crop diseases.

“It costs less than a cent and would be perfect for the third world,” says Lee, based at the Australian National University, who published his work recently in Biomedical Optics Express. To make one, “all you need is a fine tipped tool, a microscope cover slip, some polymer and an oven”, he says. The droplet, which is scratchproof and won’t shatter, is made from the same material used in contact lenses and breast implants, polydimethylsiloxane (PDMS).

Conventional microscope lenses are made of glass. They are expensive because they require grinding and polishing to create the correct curved shape. By contrast, Lee’s method simply relies on allowing a drop to form. He deposits a small quantity of the PDMS polymer on a microscope cover slip and then inverts it. “We simply let gravity do the work, pulling it into the perfect curvature.”

A small quantity of the polymer forms into a perfect curvature, with gravity doing the work. – ANU/Stuart Hay

The drops are then baked to set the shape. Lee has perfected a method for adding further, smaller drops to allow higher magnifications. Then the droplet lens can be peeled off and stuck directly onto the camera lens. The lens achieves a maximum magnification of 160x with a resolution of four microns – comparable to that of standard medium magnification pathology microscopes.

Lee made his first droplet lenses by accident when creating moulded lenses for endoscopes. “A couple of drops of PDMS were left on a microscope slide in the oven overnight. I nearly threw them away. I happened to mention them to a friend of mine who is a doctor, and he got very excited. So then I decided to try to find the optimum shape, to see how far I could go. When I saw the first images of yeast cells I was like, ‘Wow!’”

The manufacturing process is easy to reproduce. Lee says he easily taught students how to achieve the maximum magnification and resolution.

Mick Foley, a malaria researcher at La Trobe University, says the invention has enormous medical potential in developing countries. Diagnosing malaria, for instance, requires a well-trained technician and a high-quality microscope to spot the parasite in a patient’s blood sample. Both are in short supply in villages, but many people in developing countries have mobile phones. “They could take a picture and send it to a central laboratory where there are trained technicians to look at it, and then they could text back with advice,” Foley says.

The droplets on a microscope slide are baked to set the shape. Smaller drops allow higher magnifications. – ANU/Stuart Hay

He believes farmers also stand to benefit from the new technology, using it to identify fungal crop infections. “The fungi are a little bit larger than malaria parasites; you could send pictures of them with your phone and quickly get an expert opinion.”

There are other possibilities in developed countries, too. Lee has received overtures from a German company interested in developing the technology for remote diagnosis of skin diseases.

Despite the boundless opportunities, Lee is still captivated by the simplicity of his invention. “The interplay between the forces, gravity and the surface tension, it’s quite beautiful.”

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Phil Dooley is an Australian freelance writer, presenter, musician and videomaker. He has a PhD in laser physics, has been a science communicator for the world's largest fusion experiment JET and has performed in science shows and festivals from Adelaide to Glasgow. Under the banner of Phil Up On Science he runs science pub nights around the country and a YouTube channel.
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