Using a $1.50 digital camera sensor, scientists at Caltech have created the simplest and cheapest lens-free microscope yet. Such a device could have many applications, including helping diagnose disease in the developing world, and enabling rapid screening of new drugs.
The best current way to diagnose malaria is for a skilled technician to examine blood samples using a conventional optical microscope. But this is impractical in parts of the world where malaria is common. A simple lens-free imaging device connected to a smart phone or a PDA could automatically diagnose disease. A lensless microscope could also be used for rapid cancer or drug screening, with dozens or hundreds of microscopes working simultaneously.
The Caltech device is remarkably simple. A system of microscopic channels called microfluidics lead a sample across the light-sensing chip, which snaps images in rapid succession as the sample passes across. Unlike previous iterations, there are no other parts. Earlier versions featured pinhole apertures and an electrokinetic drive for moving cells in a fixed orientation with an electric field. In the new device, this complexity is eliminated thanks to a clever design and more sophisticated software algorithms. Samples flow through the channel because of a tiny difference in pressure from one end of the chip to the other. The device’s makers call it a subpixel resolving optofluidic microscope, or SROFM.
“The advantage here is that it’s simpler than their previous approaches,” says David Erickson, a microfluidics expert at Cornell University.
Cells tend to roll end over end as they pass through a microfluidic channel. The new device uses this behavior to its advantage by capturing images and producing a video. By imaging a cell from every angle, a clinician can determine its volume, which can be useful when looking for cancer cells, for example. Changhuei Yang, who leads the lab where the microscope was developed, says this means samples, such as blood, do not have to be prepared on slides beforehand.