IPhone becomes multipurpose imaging tool
DAVIS, Calif. — Using materials that cost about as much as a typical app, scientists have transformed the everyday iPhone into a medical-quality imaging and chemical-detection device that performs detailed microscopy and spectroscopy.
The enhanced device could help doctors and nurses diagnose blood diseases in developing nations, where many hospitals and rural clinics have limited or no access to laboratory equipment. Field workers can use the iPhone to take a photo of a blood sample on a slide, then send the photo to specialists around the globe to analyze, said Sebastian Wachsmann-Hogiu of the department of pathology and laboratory medicine at the University of California.
An iPhone microscope consists of a 1-mm-diameter ball lens embedded in a rubber sheet and taped over the smartphone's camera. Images courtesy of Z.J. Smith, K. Chu, A.R. Espenson, M. Rahimzadeh, A. Gryshuk, M. Molinaro, D.M. Dwyre, S. Lane, D. Matthews, S. Wachsmann-Hogiu, University of California at Davis.
Although not the first to build a smartphone microscope, Wachsmann-Hogiu said that he and his team thought they could make something simpler and less expensive than previous versions. "We were inspired by the need for small, simple and inexpensive devices that can perform diagnoses in the field. Cell phones are ideal for this because they are ubiquitous, their cameras contain high-quality detectors, and they have the capability to transmit data."
Before turning to ball lenses, the investigators experimented with drops of water on a camera lens. Although the water formed a meniscus to create a magnifying lens, it evaporated too quickly to use. So they made a prototype with a 1-mm-diameter ball lens that cost $30 to $40, a price they believe could be reduced if mass-produced lenses are substituted. To assemble the microscope's lens, Kaiqin Chu, a postdoctoral researcher in optics, inserted a ball lens into a hole in a rubber sheet, then taped the sheet over the smartphone's camera.
Images of a sugar crystal taken through polarized light filters. At left, traditional microscope; at right, cell phone microscope.
The ball lens, at 5x magnification, could resolve features on the order of 1.5 µm — small enough to identify different types of blood cells — when combined with the smartphone camera. Ball lenses excel at gathering light, which determines resolution. And the camera's semiconductor sensor consists of millions of light-capturing cells. Each cell measures ~1.7 µm across — small enough to capture precisely the tiny image that comes through the lens.
The researchers used digital image processing software to correct for distortion from the ball lens and to stitch together overlapping photos of the tiny in-focus areas into a single image large enough for analysis.
Stained samples of pollen (left images) and plant stems (right two images). Top row, commercial microscope; bottom row, cell phone microscope.
Alhough the smartphone micrographs are not as sharp as those from laboratory microscopes, they do reveal important medical information, such as the reduced number and increased variation of cells in iron-deficiency anemia, and the banana-shaped red blood cells characteristic of sickle-cell anemia.
Wachsmann-Hogiu's team is working with the university's medical center to validate the device and determine how to use it in the field. They also may add features such as larger lenses to diagnose skin diseases, and software to count and classify blood cells automatically to provide instant feedback and to recognize a wider range of diseases.
The upper row shows images of blood samples taken with a traditional microscope. From left, normal iron deficiency anemia and sickle-cell anemia. The bottom row shows the same samples imaged on a smartphone.
When researchers need additional diagnostic tools, the microscope could be swapped for a simple spectrometer that also uses light collected by the iPhone's camera. The researchers' spectrometer is easy to build: Cover both ends of a short plastic tube with black electrical tape, then cut narrow slits in the tape to allow only roughly parallel beams of light from the sample to enter and exit the tube. This grating spreads the light into a spectrum that can be used to identify various molecules.
Although the spectrometer is still in its early stages, the researchers believe it could measure the amount of oxygen in the blood and help diagnose chemical markers of disease.
Wachsmann-Hogiu and his team presented their findings at the Optical Society's annual meeting, Frontiers in Optics, Oct. 16-20, in San Jose.
MORE FROM PHOTONICS MEDIA