Fig. 2.

Permanent, instantaneous switching of a solid to a fluid. a A general formulation that gives a material which can be switched from a solid to a fluid with UV light. b As is, the solid sample does not adopt a new shape when twisted; however, after irradiation (5 min, 365 nm, 75 mW/cm²), the now fluid sample permanently adopted the twisted shape. c Rheometry shows that this material acts as a solid (immediately after polymerization: G′ = grey filled square; G″ = grey open square; 1.5 h after polymerization: G′ = red filled circle; G″ = red open circle) until exposure to UV light, which switches it to a fluid (immediately after UV light: G′ = black filled triangle; G″ = black open triangle; 1.5 h after UV light: G′ = blue filled diamond; G″ = blue open diamond). d The nearly instantaneous fluidization of the network upon exposure to UV light, shown here by the relaxation of stress at a constant strain (10% strain, light on at 5 (blue), 10 (red), and 15 (green) minutes, continuously irradiated, 365 nm, 75 mW/cm²). Grey line—not irradiated