Lens-Free Microscope Produces Images on a Chip

Scientists at the University of California Los Angeles California Nanosystems Institute (UCLA; USA), have redefined the concept of a microscope by removing the lens to create a system that is small enough to fit in the palm of a hand, but powerful enough to create three-dimensional tomographic images of miniscule samples. The system takes advantage of the fact that organic structures, such as cells, are partially transparent. Consequently, by shining a light on a sample of cells, the shadows created reveal not only the cells' outlines, but details about their subcellular structures as well.

A partially coherent light source placed approximately 70 mm away from the sensor was employed to record lens-free in-line holograms of the sample from different viewing angles. At each illumination angle, multiple subpixel-shifted holograms were also recorded, which were digitally processed using a pixel super-resolution technique to create a single high-resolution hologram of each angular projection of the object. Tomographic imaging performance was quantified using microbeads of different dimensions, as well as by imaging the free-living nematode Caenorhabditis elegans.

Aydogan Ozcan, PhD, senior author of the study, said, "Wonderful progress has been made in recent years to miniaturize life-sciences tools with microfluidic and lab-on-a-chip technologies, but until now optical microscopy has not kept pace with the miniaturization trend." Prof. Ozcan envisions this lens-free imaging system as one component in a lab-on-a-chip platform. It could potentially fit beneath a microfluidic chip, a tool for the precise control and manipulation of sub-millimeter biological samples and fluids, and the two tools would operate in tandem, with the microfluidic chip depositing and subsequently removing a sample from the lens-free imager in an automated, or high-throughput, process. The study was published on April 19, 2011, in the Proceedings of the National Academy of Sciences of the Unites States of America (PNAS).

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