The device works by creating a focused excitation spot inside each channel in the array and then collects the resulting fluorescence emission from water drops traveling through the channels, literally taking stop-motion pictures of the drops as they pass.
"Water drops flow through each channel of the device at a rate of several thousand per second," explains lead author Ethan Schonbrun, a graduate student at SEAS. "Each channel is monitored by a single zone plate that both excites and collects fluorescence from the high speed drops. By using large arrays of microfluidic channels and zone plate lenses, we can speed up microfluidic measurements."
The series of images are then recorded by a digital semiconductor (CMOS) camera, allowing high speed observation of all the channels simultaneously. Moreover, the array is designed so that each zone plate collects fluorescence from a well-defined region of the channel, thereby avoiding cross talk between adjacent channels. The end result is a movie of the droplets dancing through the channels.
"Our approach allows us to make measurements over a comparatively large area over the chip. Most microscopes have a relatively limited view and cannot see how the whole system is working. With our device, we can place lenses wherever we want to make a measurement," adds Crozier.
The system can detect nearly 200,000 drops per second, or about four times the existing state-of-the-art detection systems. Further, the lens array is scalable, without any loss in efficiency, and can be peeled on-and-off like a reusable sticker. Ultimately, the integrated design offers the sensitivity of a larger confocal microscope and the ability to measure over a larger area, all in a much smaller, cheaper package.
"Because we have this massively paralle
|Contact: Michael Patrick Rutter|