  A composite porous polymer membrane with aligned CNTs in its matrix is
developed which exhibits programmable, anisotropic actuation towards organic
vapors. The alignment of CNTs in multiple directions and the gradient porous
structure of the membrane are critical for the actuation, and the actuating
direction can be well controlled at a direction perpendicular to the
longitudinal orientation of CNTs. The reversible actuation may be repeated for
300 cycles without obvious fatigue. These polymer composites are promising
building blocks for a wide variety of applications such as sensors and
actuators. The concept of programmable actuation succeeded here in a porous
polymer mateial via complex orientation of CNTs reflects a new high level of
control over physical motions that is applicable to a broad range of soft
actuators.
