Digital camera chip turned into lens-free microscope
Paul Marks OPTICAL microscopes used to be bulky instruments. Their basic components - lenses to magnify and focus an image - take up a lot of space, and are fragile and expensive to boot. Not any more. Researchers have squeezed a powerful microscope onto a single image-sensing chip, removing the need for lenses. The cheap, portable device could be just what medics in the developing world need to diagnose diseases such as malaria, its inventors suggest. "The whole microscope could fit into an iPod-sized device," says Changhuei Yang of the California Institute of Technology in Pasadena. Yang says the imaging chip itself could be disposable, reducing the risk of contamination between samples. Chip-based microscopes are not a new idea. If a sample is placed directly on top of a "CCD" image-sensing chip, like those used in digital cameras, the chip will produce a rough image of it. Yet since the pixels in commercial CCDs are usually at least 3 micrometres across, they cannot compete with the sub-micrometre resolutions achievable by optical microscopes. To boost the resolution of a CCD microscope, Yang and his colleagues coated the CCD with an ultra-thin layer of aluminium and etched 1-micrometre-wide holes above each physical pixel, so only the light through these tiny apertures could be picked up. That produces a set of snapshots of parts of the sample (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0804612105). To complete the picture, the team puts the sample in a microfluidic chamber, where it is allowed to move under gravity or via electrical charge. This gently shifts it across the sensor surface at a predetermined rate, so every part is imaged in turn. A computer program then compiles the final composite image. The approach allowed the team to image sub-micrometre features of algae, nematodes and pollen. To unsubscribe send a message to [email protected] with the subject unsubscribe. To change your subscription to digest mode or make any other changes, please visit the list home page at http://accessindia.org.in/mailman/listinfo/accessindia_accessindia.org.in
