Optical detection for droplet size control in microfluidic droplet-based analysis systems

This paper reports on a hybrid polymeric microfluidic device with optical detection for droplet-based systems. The optical part of the device is integrated by a hybrid concept. The microfluidic structures were fabricated using CO2 laser on poly methylmethacrylate (PMMA) substrate. The microfluidic network consists of two microchannels for forming droplets of an aqueous liquid in an immiscible carrier liquid. The optical component consists of two optical fibers for guiding laser light from the source, through the detection point, to a photo diode. The formed droplets pass the detection point and diffract the incoming laser light. The detected signal at the photo diode can be used for evaluating droplet size, droplet shape, and droplet formation frequency. The device can detect very high formation frequencies, which are not detectable using a conventional CCD camera/microscope setup.