Fig. 4

Photocurrent of GR-GFP in E. coli BL21 (DE3). Phases of alternating light and dark persisted in every 2 min, as the induction of proton by illumination in GR-host droplet could be observed with the start of illumination at the 120th second to 240 s. Drastic upload of photocurrent was detected at the very start of the illumination and followed with constant plateau of photocurrent, meaning that GR-GFP at first were excited by illumination. The electrodes on the chip directly measured the current in the droplet under constant voltage potential (0.1 v). The measurement was done in biological triplicates and proved to be of the same pattern as the graph showed