Figure 4 Illustration of the actuation of (A)the homochiral and (B) the heterochiral artificial muscles in response to solvents. Photographs of (C) the homochiral and(D) the heterochiral artificial muscles before and after actuation in water and ethanol. (E) Tensile stroke of the homochiral artificial muscles with the twist density of 2500 turns m-1 and the diameters of 1.6 mm, 3.0 mm, 5.0 mm, 7.0 mm, and 8.0 mm. (F) Tensile stroke of the heterochiral artificial muscles with the twist density of 2650 turns m-1 and the diameters of 1.6 mm, 3.0 mm, 5.0 mm, 7.0 mm, and 8.0 mm. (G) Tensile stroke of the homochiral artificial muscles with the diameter of 7.0 mm and the twist densities of 1000 turns m-1, 1500 turns m-1, 2000 turns m-1, 2500 turns m-1, and 2650 turns m-1. (H) Tensile stroke of the heterochiral artificial muscles with the diameter of 8.0 mm and the twist densities of 1000 turns m-1, 1500 turns m-1, 2000 turns m-1, 2500 turns m-1, and 2650 turns m-1.