How to turn your smartphone into a microscope for 1 cent

May 5, 2015

Top row: human skin with hair follicle. (a) through (c) were imaged with an Olympus IX-70 microscope at a magnification of 40, 100 and 200. (d) was imaged with a Nokia Lumia 520 smartphone with a special plastic lens. Bottom row shows magnified regions. Scale bars are 200 and 30 micrometers (credit: University of Houston)

University of Houston (UH) scientists have created an optical lens that  you can directly attach over an inexpensive smartphone camera lens to amplify images 120 times with an imaging resolution of 1 micrometer for just one cent (to create the lens in a lab), according to Wei-Chuan Shih, assistant professor of electrical and computer engineering at UH.

The new lens could also have clinical applications, allowing small or isolated clinics to share images with specialists located elsewhere, he said.

In an open-access paper published in the Journal of Biomedical Optics, Shih and three graduate students describe how they produced the lenses and examine the image quality.

(a) Changing the temperature of the preheated surface modifies the shape of a cured lens. (b) The inkjet print head printing droplet lenses on a heated surface, and (c) The lens can be attached to a smartphone for microscopy applications. (credit: University of Houston)

The lens is made of polydimethylsiloxane (PDMS), a polymer (plastic) with the consistency of honey, dropped precisely on a preheated surface to cure. Lens curvature — and therefore, magnification — depends on how long and at what temperature the PDMS is heated, Sung said.

Attaching to a smartphone

The resulting lenses are flexible, similar to a soft contact lens but thicker and slightly smaller, and the strong yet non-permanent adhesion between PDMS and glass allows the lens to be easily detached after use.

Lens on iPhone 4S (credit: Yulu Sung)

Conventional lenses are produced by mechanical polishing or injection molding of materials such as glass or plastics. Liquid lenses are available, too, but those that aren’t cured require special housing to remain stable.

Other types of liquid lenses require an additional device to adhere to the smartphone, he said. This lens attaches directly to the phone’s camera lens and remains attached, Sung said, so it’s reusable.

For the study, researchers captured images of a human skin-hair follicle histological slide with both the smartphone-PDMS system and an Olympus IX-70 microscope. At a magnification of 120, the smartphone lens was comparable to the Olympus microscope at a magnification of 100, they said, and software-based digital magnification could enhance it further.

A conventional research-quality microscope can cost $10,000. “A microscope is much more versatile, but of course, much more expensive,” Sung said.

The lens would be a cheap and convenient way for younger students to do field studies or classroom work. Because the lens attaches to a smartphone, it’s easy to share images by email or text, he said. And because the lenses are so inexpensive, it wouldn’t be a disaster if a lens was lost or broken.

For now, researchers are producing the lenses by hand, using a hand-built device similar to an inkjet printer. Producing the lenses in bulk will require funding for manufacturing equipment, so the graduate students launched a crowdfunding campaign last year on Indiegogo, hoping to raise $12,000 for the equipment. They’ve raised $3,000 so far.

KurzweilAI has covered three other low-cost microscope projects: a similar 160x droplet lens from The Australian National University, the 150x Micro Phone Lens, and the 800x Microbescope.

Abstract of Fabricating optical lenses by inkjet printing and heat-assisted in situ curing of polydimethylsiloxane for smartphone microscopy

We present a highly repeatable, lithography-free and mold-free method for fabricating flexible optical lenses by in situ curing liquid polydimethylsiloxane droplets on a preheated smooth surface with an inkjet printing process. This method enables us to fabricate lenses with a focal length as short as 5.6 mm, which can be controlled by varying the droplet volume and the temperature of the preheated surface. Furthermore, the lens can be attached to a smartphone camera without any accessories and can produce high-resolution (1  μm) images for microscopy applications.