Tag Archives: A. Upadhya

From Australia: a recipe for baking lenses

Here’s the recipe from an April 24, 2014 Optical Society news release on EurekAlert,

All that’s needed is an oven, a microscope glass slide and a common, gel-like silicone polymer called polydimethylsiloxane (PDMS). First, drop a small amount of PDMS onto the slide. Then bake it at 70 degrees Celsius to harden it, creating a base. Then, drop another dollop of PDMS onto the base and flip the slide over. Gravity pulls the new droplet down into a parabolic shape. Bake the droplet 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. “It’s a low cost and easy lens-making recipe,” Lee [ Steve Lee from the Research School of Engineering at Australian National University] says.

I’m still marveling over this image,

Caption: This photo shows a single droplet lens suspended on a fingertip. Credit: Stuart Hay. Courtesy: The Optical Society

Caption: This photo shows a single droplet lens suspended on a fingertip. Credit: Stuart Hay. Courtesy: The Optical Society

For anyone who doesn’t know much about producing lenses and why these baked droplets could improve lives, the Optical Society news release provides some insight,

A droplet of clear liquid can bend light, acting as a lens. Now, by exploiting this well-known phenomenon, researchers have developed a new process to create inexpensive high quality lenses that will cost less than a penny apiece.

Because they’re so inexpensive, 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.

“What I’m really excited about is that it opens up lens fabrication technology,” says Steve Lee from the Research School of Engineering at Australian National University (ANU) …

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, Lee says. 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,” he explains.

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

The researchers made 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. “We’re quite surprised at the magnification enhancement using such a simple process,” he notes.

An April 24, 2014 Australian National University (ANU) news release on EurekAlert adds more details to the story,

The lenses are made by using the natural shape of liquid droplets.

“We put a droplet of polymer onto a microscope cover slip and then invert it. Then we let gravity do the work, to pull it into the perfect curvature,” Dr Lee said.

“By successively adding small amounts of fluid to the droplet, we discovered that we can reach a magnifying power of up to 160 times with an imaging resolution of four micrometers.”

The polymer, polydimethylsiloxane (PDMS), is the same as that used for contact lenses, and it won’t break or scratch.

“It would be perfect for the third world. All you need is a fine tipped tool, a cover slip, some polymer and an oven,” Dr Lee said.

The first droplet lens was made by accident. [emphasis mine]

I nearly threw them away. [emphasis mine] I happened to mention them to my colleague Tri Phan, and he got very excited,” Dr Lee said.

“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!'”

Dr Lee and his team worked with Dr Phan to design a lightweight 3D-printable frame to hold the lens, along with a couple of miniature LED lights for illumination, and a coin battery.

The technology taps into the current citizen science revolution [emphasis mine], which is rapidly transforming owners of smart phones into potential scientists. There are also exciting possibilities for remote medical diagnosis.

Dr Phan said the tiny microscope has a wide range of potential uses, particularly if coupled with the right smartphone apps.

“This is a whole new era of miniaturisation and portability – image analysis software could instantly transform most smartphones into sophisticated mobile laboratories,” Dr Phan said.

“I am most able to see the potential for this device in the practice of medicine, although I am sure specialists in other fields will immediately see its value for them.”

Dr Lee said the low-cost lens had already attracted interest from a German group interested in using disposable lenses for tele-dermatology.

“There are also possibilities for farmers,” he said. “They can photograph fungus or insects on their crops, upload the pictures to the internet where a specialist can identify if they are a problem or not.”

That Lee created his first droplet by accident and almost threw it away echoes many, many other science stories. In addition to that age old science story, I love the simplicity of the idea, the reference to Isaac Newton, and the inclusion of citizen science.

Here’s a link to and a citation for the paper,

Fabricating low cost and high performance elastomer lenses using hanging droplets by W. M. Lee, A. Upadhya, P. J. Reece, and Tri Giang Phan. Biomedical Optics Express, Vol. 5, Issue 5, pp. 1626-1635 (2014) http://dx.doi.org/10.1364/BOE.5.001626

This paper is open access.

I wish Lee and his team great success in making this technology available, assuming that it lives up to its promise.