The effect of H2O2 concentration on motion behaviors of the Mg-based micromotor. (a) The average speed of the Mg-based micromotor in a solution with different concentrations of H2O2 at 38°C. The black line represents the trend line. (b) The H2O2 concentration of the aqueous solution containing the Mg-based micromotor versus time. The insets show typical states of the micromotor in each period, and the dotted line represents a transitional period after which a constant local H2O2 concentration is available in the system. Scale bar: 100 μm. In the aqueous solution without H2O2 (0~250 s), bubbles generate from the open end of the Mg-based micromotor, while adding H2O2 to raise the concentration to 0.8 wt% results in bilateral bubble production (250~480 s). Further reducing H2O2 concentration to 0.67 wt% via diluting makes the reaction occur in a unilateral side (480~820 s), and the reaction again occurs in bilateral sides when the concentration reaches 1.23 wt% by adding H2O2 again (820~1100 s).