A prototype submersible sheathless flow cytometer designed for autonomous platforms

Abstract Development of submersible flow cytometers has allowed for continuous, in situ measurements of natural assemblages of phytoplankton cells. Here we introduce DeepCyte, a sensitive prototype submersible flow cytometer developed for deployment on autonomous platforms. DeepCyte continuously collects multidimensional characteristics of individual phytoplankton cells (~0.5–10 μ m in diameter), including Prochlorococcus , and transmits this data in real‐time to remote observatories via a network connection. DeepCyte utilizes a virtual sample core technology and an open flow system, enabling direct measures from the surrounding environment without the use of a clean carrier fluid. The primary surfaces of excitation and collection optics are exposed to the outside of the instrument, and the only fluid path is a 6 mm diameter length of silicon tubing. These design features allow for simple maintenance of optical surfaces and minimize sampling downtime due to clogs or air bubbles. An innovative arrangement of the optical system means the instrument fits within a volume of 0.017 m 3 , and our selection and design of low power electronics yield power consumption of 36 watts when operated as a standalone instrument with integrated pump. The DeepCyte is characterized by high optical sensitivity, low power consumption, compact size, and low maintenance. This technology will provide a continuous view of the dynamics and structure of the smallest phytoplankton populations, aligning with and expanding upon other continuous measurements such as chlorophyll‐ a fluorescence, temperature, and salinity.