Micropipette-Based Fabrication of Free-Standing, Conducting Polymer Bilayer Actuators

Electrically driven actuators have found widespread applications in biomimetics and soft robotics. Among different actuation materials, conducting polymers (CPs) have stood out due to their unique doping-based actuation mechanism. Fabricating actuators at the microscale is particularly important, not only in the manufacturing of delicate biomimetic/robotic devices but also in advanced microphysiological studies. However, the choice for microfabrication techniques is limited, with the reported CP microactuators being mainly planar. To overcome this issue, a new micropipette-based method is developed for the fabrication of free-standing 3D CP actuators. The two-layer actuator consists of a layer of PPy:CF3SO3, fabricated by localized electropolymerization, and a layer of PEDOT:PSS, fabricated by a "direct writing" technique. Due to the opposite contraction and expansion behavior of these two CPs, determined by the size of dopants, the electrically driven bending actuators have been demonstrated. This fabrication approach provides unprecedented capability for fabricating high aspect ratio microactuators: the 360 degrees bending orientation of the actuators can be controlled by the relative position of the two layers. As a proof-of-principle, we demonstrate CP "micro-tweezers" and the manipulation of a PDMS microsphere. The technique developed in this work opens exciting opportunities to manufacture advanced artificial muscles and sophisticated soft microrobotics.