Fig. 4. Chemical and simulated medical applications using the robot.

(A) Demonstration of stepwise chemical reactions. The robot split a daughter drop of 1.5 μl from a NaOH droplet and transport it to an indicator droplet (phenolphthalein). In the second step, the robot leaves the indicator droplet, splits a daughter drop from a HCl droplet, and then moves back to the indicator droplet. The volumes of the NaOH droplet, the indicator droplet, and the HCl droplet are all 250 μl. (B) Simulation of the calculi removal. The robot transports a droplet of drug to calculi placed on the substrate. The calculi are collected and taken away from the substrate. (C) Simulation of the vascular clearance. The drug droplet and the plaque placed inside a tube filled with water. The drug droplet is transported to the plaque by the robot. After 1 min, the plaque is dissolved and taken away. The black arrow indicates the movement of the droplet. The moving speed is 2 mm/s. Scale bars, 10 mm.