Emccd ixonem du 897 camera

Microdroplets containing cyanobacteria were generated by the protocol described above. A piece of fine bore polyethylene tubing (5 cm) was used to connect the outlet of the droplet generation chip to a microdroplet reservoir, which was the incubation platform. When the reservoir was filled with microdroplets, it was sealed with two small pieces of closed tubing. The reservoir was placed in a Petri dish containing water to reduce droplet shrinkage, taking advantage of the water permeability of PDMS. The stability of the microdroplets in the reservoir was monitored using a Phantom V72 fast camera every 24 h. Growth kinetics were measured by counting the number of chlorophyll fluorescent cells in droplets at each growth step. The chlorophyll in the cells was detected using an IX71 inverted microscope (Olympus) operated in epifluorescence mode. The fluorescence emission was collected by an objective, filtered (600 nm long-pass edge filter) and finally captured with an EMCCD iXonEM + DU 897 camera (Andor Technology).

A microfluidic device was used for encapsulation of microalgal cells into microdroplets. A suspension of cells in f/2 growth medium was injected as an aqueous phase in a flow-focusing microfluidic device of dimensions 25 μm × 50 μm (width × depth). The aqueous cell suspension flowed perpendicularly to two streams of fluorinated carrier oil Fluorinert™ FC-40 (3 M, United States) containing 2.5 wt% surfactant PicoSurf 1 (Sphere Fluidics, United Kingdom) (SI Fig. 1A). The oil streams enveloped microdroplets that budded off from the aqueous stream and flowed away from the flow-focusing junction. The size of the microdroplets was tuned by changing the flow rate of the aqueous cell suspension or fluorinated carrier oil. The microdroplets were collected and stored in a 1 mL plastic syringe over a period of ~7 days to investigate their growth (SI Fig. 1B). To monitor the growth of P. tricornutum and N. gaditana in microdroplets, microscope images were captured with an EMCCD iXonEM+ DU 897 camera (Andor Technology, United Kingdom) coupled with an IX 81 inverted microscope (Olympus, Japan). The number of cells in microdroplets was determined by counting cells using images taken in technical triplicate. The statistical analyses were performed with Origin 8.0 (OriginLab Co., USA), and the data were expressed as mean ± SD (standard deviation) of three replicates of counting.