  It is highly desirable to discover an electromechanical coupling that allows
a dielectric material to generate curvature in response to a uniform electric
field, which would add a new degree of freedom for designing actuators.
Flexoelectricity, a two-way coupling between polarization and strain gradient,
is a good candidate. But its applications are usually limited to the nanoscale
due to its inherent size dependence. Here, an inverse flexoelectret effect in
silicone elastomers is introduced to overcome this limitation. Based on this
idea, a flexing actuator which can generate large curvature at the millimeter
length scale is fabricated and shown to have excellent actuation performance
comparable with current nanoscale flexoelectric actuators. Theoretical analysis
indicates that the new phenomenon originates from the interplay of electrets
and Maxwell stress. This work opens an avenue for applying macroscopic
flexoelectricity in actuators and flexible electronics.
