A microflow cytometer for optical analysis of phytoplankton

Analysis of the intrinsic scatter and fluorescence profiles of marine algae can be used for general classification of organisms based on cell size and fluorescence properties. We describe the design and fabrication of a Microflow Cytometer on a chip for characterization of phytoplankton. The Microflow Cytometer measured distinct side-scatter and fluorescence properties of Synechococcus sp., Nitzschia d., and Thalassiosira p. Measurements were confirmed using the benchtop Accuri C6 flow cytometer. The Microflow Cytometer proved sensitive enough to detect and characterize picoplankton with diameter approximately 1 mm and larger phytoplankton of up to 80 mm in length. The wide range in size discrimination coupled with detection of intrinsic fluorescent pigments suggests that this Microflow Cytometer will be able to distinguish different populations of phytoplankton on unmanned underwater vehicles. Reversing the orientation of the grooves in the channel walls returns the sample stream to its original unsheathed position allowing separation of the sample stream from the sheath streams and the recycling of the sheath fluid.