Now, cheap 'baked' microscope lenses

Washington: Researchers have developed a new lens-making method, in which drops of silicone are simply baked in an oven, to create inexpensive high quality lenses that will cost less than a penny each.

The lenses can be used in a variety of applications, including tools to detect diseases in the field, scientific research in the lab and optical lenses and microscopes for education in classrooms, researchers said.

"What I'm really excited about is that it opens up lens fabrication technology," Steve Lee from the Research School of Engineering at Australian National University (ANU) said of the new technique.

Many conventional lenses are made by grinding and polishing a flat disk of glass into a particular curved shape.Others are made with more modern methods, such as pouring gel-like materials molds.

But both approaches can be expensive and complex, Lee said.

Advertisement

With the new method, the researchers harvest solid lenses of varying focal lengths by hanging and curing droplets of a gel-like material - a simple and inexpensive approach that avoids costly or complicated machinery.

"What I did was to systematically fine-tune the curvature that's formed by a simple droplet with the help of gravity, and without any molds," Lee said.

Advertisement

Although people have long recognised that a droplet can act as a lens, no one tried to see how good a lens it could be. Now, researchers have developed a process that pushes this concept to its limits, Lee said.

All that's needed is an oven, a microscope glass slide and a common, gel-like silicone polymer called polydimethylsiloxane (PDMS).

Advertisement

First, a small amount of PDMS is dropped onto the slide. It is baked at 70 degrees Celsius to harden it, creating a base. Then, another dollop of PDMS is dropped onto the base and the slide is flipped over. Gravity pulls the new droplet down into a parabolic shape.

The droplet is baked again to solidify the lens. More drops can then be added to hone the shape of the lens that also greatly increases the imaging quality of the lens.

Advertisement

The researchers made lenses about a few millimetres thick with a magnification power of 160 times and a resolution of about 4 microns (millionths of a metre) - two times lower in optical resolution than many commercial microscopes, but more than three orders of magnitude lower in cost.

The researchers also built a lens attachment that turns a smartphone camera into a dermascope, a tool to diagnose skin diseases like melanoma. While normal dermascopes can cost USD 500 or more, the phone version costs around USD 2.

Advertisement

The new dermascope, which was made using a 3-D printer and is designed for use in rural areas or developing countries, is slated to be commercially available in just a
few months, Lee said.

The study is published in The Optical Society's (OSA) open-access journal Biomedical Optics Express.