To obtain data shown in Figs. & For other experiments, spin coating was used to prepare seeds-coated surface: 50 µL of moved from the chamber and the chamber was rinsed gently with methanol to remove unimer residues, followed by the addition of PCL 45 solution. This alternating sequence was repeated until the desired number of annuli was achieved. Recording started immediately after each unimer addition. A laser power density of 4 µW µm -2 at 637 nm, a camera exposure time of 400 µs, and an overall time-lapsed frame rate of 1 s -1 were selected. For the experiment in Fig. , PCL 45 :PCL 45 -b-PDMA 348 mixtures with sequentially increasing unimer concentration were added at each annulus. A laser power density of 4 µW µm -2 at 637 nm, a camera exposure time of 400 µs, and an overall time-lapsed frame rate 0.5 s -1 were selected.