By Colin Jeffrey
Microscopes can be expensive pieces of gear, making access difficult – or non-existent – for students and medical staff in isolated and poorer locales. To help address this, researchers at the University of Houston (UH) have fashioned a lens designed to fit on almost any smartphone. It has the ability to magnify images up to 120 times their original size, and at an estimated production cost of just three cents per lens.
Standard lenses are generally made by polishing glass or molding plastics to create a particular focal length and magnification. The UH lenses, however, are composed of a polymer known as polydimethylsiloxane (PDMS), and are made by dropping this liquid onto a pre-warmed surface to cure. Unlike conventional lens construction, the lens curvature is not then formed or created mechnically, but is dependent upon the length of time the lens is cured and at what temperature. The lenses produced in this way are said to be supple, somewhat like a soft contact lens.
Like many discoveries, Wei-Chuan Shih, assistant professor of electrical and computer engineering at UH, realized the optical properties of PDMS largely by accident. When, in his work in an interdisciplinary team working on nanobiophotonics and nanofluidics, he dropped some of the material on a lab hotplate, he noticed that it solidified on contact with the hot surface. This piqued his interest in the resultant properties of the material and so he decided to attempt making a lens.
“I put it on my phone, and it turns out it works,” says Yu-Lung Sung, a doctoral candidate and one of the research team at UH, using the lens on his Nokia Lumia 520.”
To prove the efficacy of their lens, the researchers took images of epithelial tissue – in this case a skin-hair follicle mounted on a histological slide – using both the PDMS lens mounted on a smartphone and an Olympus IX-70 microscope. According to the researchers, at a 120-times magnification, the performance of the new smartphone lens was comparable to that of the Olympus microscope operating at 100-times magnification. The researchers believe that the capabilities of the PDMS lens could be further improved by utilizing software to digitally magnify and enhance the images.
“Our lens can transform a smartphone camera into a microscope by simply attaching the lens without any supporting attachments or mechanism,” say the researchers. “The strong, yet non-permanent adhesion between PDMS and glass allows the lens to be easily detached after use. An imaging resolution of 1 (micrometer) with an optical magnification of 120X has been achieved.”
The UH lens is not the first stick-on smartphone microscope lens, with a low-magnification polymer lens known as the “Micro Phone Lens” launching via Kickstarter in 2013. In fact, the UH lens is not even the first to use PDMS – a similar lens was developed by researchers at the Australian National University (ANU), but the technique incorporated in the UH unit differs from both of these and may offer manufacturing advantages.
In the ANU lens, for example, the polymer is manipulated in a two-step combination process, whereas the UH system is performed in just one application of the polymer. This may be a significant point of economic viability, especially if units are to be manufactured on a large scale.
“A microscope is much more versatile, but of course, much more expensive,” says Sung. “Nearly everyone has a smartphone. Instead of using a $30 or $50 attachment that students might use only once or twice, they could use this.”
The results of the team’s research were recently published in the Journal of Biomedical Optics.
The short video below shows the lens in real world use.
Source: University of Houston