Engineers at the California Institute of Technology (Caltech) have made a lens-less microscope from a CCD, aiming to make low cost device for health work.
"This microscope has the magnifying power of a top-quality optical microscope, can be used in the field to analyse blood samples for malaria or check water supplies for giardia and other pathogens, and can be mass-produced for around $10," said Caltech.
The microscope uses the contact principle, where the sample is placed directly on a light-sensitive surface and illuminated with parallel light.
If the pixels of CCDs were a micron across, one could be used as a contact microscope. However, the pixel pitch is five to 10 times too coarse.
Instead, Dr Changhuei Yang plates gold over the CCD and etches a 1[micro]m hole above the centre each pixel in a line.
He then places the line of pixels under a narrow microfluidic channel.
The holes are positioned along the channel, but at a slight angle so that an object passing down the channel passes over the holes one at a time, encountering the first one on the extreme left of the channel and the last one on the extreme right.
The angle is such that holes can scan adjacent 1µm strips of the sample.
So long as the sample flows straight down the channel at constant velocity - driven by an electric field or gravity - "all of the images [line scans] are then pieced together to create a surprisingly precise two-dimensional picture of the object," said Caltech.
Yang is now in discussion with biotech companies to mass-produce the chip. He said health workers in rural areas could carry cheap, compact models to test individuals for malaria, and disposable versions could be carried into the battlefield.
"We could build hundreds or thousands of optofluidic microscopes onto a single chip, which would allow many organisms to be imaged and analysed at once," said graduate student Xiquan Cui.
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