  In this work, we propose novel designs of cellular structures exhibiting
unconventional in-plane actuation responses to external stimuli. We
strategically introduce stimuli-responsive bilayer bridge films within
conventional honeycombs to achieve the desired actuation. The films are
incorporated such that, in response to an external field (thermal, electric,
chemical, etc.), the bridge film bends out-of-plane, activating the honeycomb
in the plane. The conventional out-of-plane deformation of the bridge film can
lead to interesting and unconventional actuation in the plane. An analytical
model of this coupled unit cell behaviour is developed using curved beam
theory, and the model is validated against finite element simulations. Several
applications of such designs are presented. Unit cell architectures exhibiting
both positive and negative macroscopic actuation are proposed, and the
criterion for achieving such actuation is derived analytically. Furthermore, we
demonstrate that by altering the topology, unidirectional and bidirectional
negative actuation can be achieved. We also propose designs that result in the
negative actuation of the structure with both monotonically increasing and
monotonically decreasing stimuli. Finally, by combining two macroscopic
structures with positive and negative actuation, we design efficient
actuators/sensors that bend in the plane in response to a stimulus.
