  A commercially available membrane filter paper composed of mixed cellulose
esters bearing typically an interconnected pore structure was transformed into
a stimuli-responsive bilayer actuator by depositing a thin film of poly(ionic
liquid)-modified graphene oxide sheets (GO-PIL) onto the filter paper. In
acetone vapor, the as-synthesized bilayer actuator bent readily into multiple
loops at a fast speed with the GO-PIL top film inwards. Upon pulling back into
air the actuator recovered their original shape. The asymmetric swelling of the
top GO-PIL film and the bottom porous filter paper towards organic vapor offers
a favorably synergetic function to drive the actuation. The PIL polymer chains
in the hybrid film were proven crucial to enhance the adhesion strength between
the GO sheets and the adjacent filter paper to avoid interfacial delamination
and thus improve force transfer. The overall construction allows a prolonged
lifetime of the bilayer actuator under constant operation, especially when
compared to that of the GO/filter paper bilayer actuator without PIL.
