Fig. 2: Description of the thermal trap used in the experiments.

a, Schematic of the PTFE interspacer. The triangular structures cause the formation of gas bubbles on addition of buffer. b, Fluorescence image of the gas bubble and gas–liquid interface in a thermal trap with temperature gradient (CM-Dex:PDDA 6:1 ratio + 0.1% FITC-labelled CM-Dex, total concentration 2 mM). c,d, Lateral sketch (c) and photograph (d) of the thermal trap. The PTFE sheet with defined geometry was placed between a transparent sapphire and a cold copper back-plate. The sapphire was heated with rod resistors whilst the copper back-plate was cooled using a water bath to generate a temperature gradient. Aqueous solution was loaded and removed from the chamber by inlet and outlet tubings. e, Chemical structures of the components used: PDDA, pLys, CM-Dex, ATP, RNA sequence (51 nucleotides (nt)).