April 27, 2014

Australian National University (ANU) researchers have developed a new process to create inexpensive lenses that will cost less than a penny for each piece. This new method has allowed the team to build a 3D printed lens attachment that turns a smartphone into a microscope to detect skin diseases.

Many conventional lenses are made the same way lenses have been made since the days of Isaac Newton - 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.

A droplet of clear liquid can bend light, acting as a lens. The researchers decided to exploit this phenomenon to try to analyse how effective of a lens it can be.

Drop, Bake, Repeat

'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 moulds,' said Dr Lee.

The process requires an oven, a microscope glass slide and a common, gel-like silicone polymer called polydimethylsiloxane (PDMS). First they droped a small amount of PDMS onto the slide and then baked the drops in the oven at 70 degrees Celsius to harden it, creating a base.

Then they added another dollop of PDMS onto the base and flipped the slide over. Gravity pulls the new droplet down into a parabolic shape, and then it is baked again to solidify the lens in that shape. More drops can then be added to hone the shape of the lens that also greatly increases the imaging quality of the lens.

With the new method, the researchers were able to produce solid lenses about a few millimeters thick with a magnification power of 160 times and a resolution of about 4 microns (millionths of a meter)—two times lower in optical resolution than many commercial microscopes, but more than three orders of magnitude lower in cost.

A 3D Printed Microscope for $2

In particular, the researchers have built a lens attachment using 3D printing that turns a smartphone camera into a dermascope, a tool to diagnose skin diseases like melanoma. While normal dermascopes can cost $500 or more, the phone version costs around $2.

Prototype of 3D printed dermascope on a Smartphone (Nexus 4, Google) that consists of two LEDs (angled at 20o), a watch battery and a droplet lens. The attachment costs $2USD to make. Credit: Stuart Hay

Comparison of a human tissue histological sample between the 1-cent PDMS lens (left) and a $300 microscope lens (right). Credit: Biomedical Optics Express.

The new dermascope, which was made using a 3D printer and is designed for use in rural areas or developing countries, is expected to be commercially available in just a few months, Lee says. A similar smartphone-based tool can also help farmers identify pests out in their fields.

The lenses could be used in the lab as implantable lenses that biologists can use to study cells in vivo. And they would also be ideal for hobbyists or as part of low cost mobile microscopes that can be distributed to kids. "Simple optics can be very powerful." Lee says.

The new technique is decribed in a paper published in The Optical Society's (OSA) open-access journal Biomedical Optics Express.

Posted in 3D Printing Applications

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