Alternate spotting of water and rhodamine 6G.

<p>(a) Bright-field image of four sequentially spotted droplets within 100 min (pos. 1 and 3: glycerol-water; pos. 2 and 4: 50 μM rhodamine 6G); the silhouette of the micropipette can be seen in the background; scale bar = 50 μm; time periods between the delivery of the individual droplets: 1 to 2 in 27 min, 1 to 3 in 74 min, 1 to 4 in 100 min. (b) Corresponding fluorescence image; λ_ex = 485 nm ± 15 nm, λ_em = 535 nm ± 25 nm. (c) Fluorescence intensity profile plot along the red line indicated in (b).