Characterization of Chlorella vulgaris and Chlorella protothecoides using multi-pixel photon counters in a 3D focusing optofluidic system

Abstract

Analysis of microparticle size and fluorescence intensity can be used to classify microparticles. We designed and fabricated an optofluidic system that characterizes microparticles, including fluorescent microparticles and microalgae. A new type of multi-pixel photon counter (MPPC) was employed to miniaturize the device, lower its power consumption, and make it insensitive to magnetic fields. The system uses a 635 nm laser for excitation of the microparticles' fluorescence. The scattered light from the fluorescent microparticles, as well as Chlorella vulgaris and Chlorella protothecoides, were measured. Additionally, we analyzed the width and height of the measured signals generated as a result of microparticles and microalgae passing through the interrogation region. Using this device, we distinguished fluorescent microparticles of sizes of 3.2 μm and 10.2 μm. Additionally, different types of microalgae were distinguished using this high-throughput 3D focusing system. The analysis of the experimental results also confirms the capability of the device for monitoring of algae growth over time. The unique properties of MPPC as optical detector for both laboratory and field applications are demonstrated.