Remotely Photocontrolled Microrobots based on Photomechanical Molecular Crystals

Creating
nano-to-macroscopic-sized artificial actuators in response to light
has been a challenging issue. Herein, we describe the design, synthesis,
and operation of a photomechanical molecular crystal (PMMC) that exhibits
well-controlled multiple photo-driven motions, including translation,
rotation, and jumping, by adjusting the irradiation sites. Theoretical
calculation discloses that conversion of light energy into macroscopic
motion occurs through a molecular conformation change between the
excited and ground states mediated by ultrafast conical internal conversion,
making the photomechanical/recovery responses a rapid cycle. Therefore,
our PMMCs can complete the directional and continuous motions using
only one laser beam. We also demonstrated the actuated rotation of
a cross-shaped sample by rotating the polarization of the laser beam
at a rate of >2 Hz, like a dancer under a spotlight. This finding
could lead to remote-controlled micrometer-sized vehicles and valves
on solid substrates.