Turn a $40 needle into a 3D microscope

Researchers from the University of Utah have discovered a method for turning a small, $40 needle into a 3D microscope capable of taking images up to 70 times smaller than the width of a human hair.

Designed by Associate Professor Rajesh Menon and graduate student Ganghun Kim, the technique works when an LED light is illuminated and guided through a fibre-optic needle or cannula. Writing in the journal Applied Physics Letters, the researchers explained, “Since the cannula is only 14.7 mm long and 200 μm in diameter, this allows for highly miniaturised microscopes that utilise no optics and no scanning.”

“Light rays propagate from one end of the cannula to the other, resulting in a complex intensity distribution,” the authors added. “This distribution is unique to the position of the source of the rays.

Ganghun Kim holds a needle or cannula that is a key component of the new 3D microscopy method. Photo credit: Rajesh Menon.

Returned pictures are reconstructed into 3D images using algorithms developed by Menon and Kim. Menon said that, as the approach does not use optics and is primarily computational, it will allow researchers to take images far smaller than those taken by current miniature microscopes - at a fraction of the cost.

“We can get approximately 1 μm-resolution images that only $250,000 and higher microscopes are capable of generating,” Menon said. “Miniature microscopes are limited to the few tens of microns.”

The University of Utah engineers hope their new microscope technology, shown here, can be implanted into the brains of mice to show images of cells. Photo credit: Ganghun Kim.

The microscope was originally designed for the lab of Professor Mario R Capecchi, whose team will use it to observe the brains of living mice to gain insight into how certain proteins in the brain react to various stimuli. Because the microscope can be assembled inexpensively and easily go into hard-to-reach places, Menon and Kim expect many other uses for the device.

“Its low-cost, small-size, large field-of-view and implantable features will allow researchers to use this in fields ranging from biochemistry to mining,” Menon said. In future, he hopes to extend the technology so it can see details down to submicron resolutions.

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