Discrete-state Photomechanical Actuators

Directly transducing light into work is attractive for remotely powering soft mechanisms designed from photoresponsive polymers, but presents challenges for achieving reliable actuation within a control framework. Here, we utilize azobenzene-functionalized polyimides to fabricate actuators characterized by mechanically discrete states. Irradiation initiates the photochemically induced, quasistatic deformation to advance the actuator to the edge of instability. Following this latency, ultrafast snap through actuation (∼10 ms-scale) ensues. Restricting the role of control to the attainment of the edge of instability, strategies for achieving repetitive actuation via multiplexed irradiation are demonstrated. Approaches are examined for modulating the latency of the actuator using an all-optical strategy as well as mechanical design of the actuator. Prototypical assemblies of these actuators in arrays are used to fabricate morphable surfaces and structures, which is aided by the realization that the ultrafast actuation is characterized by a high power-density on the order of ∼kW/m3.