Polypyrrole microtubule actuators for seizing and transferring microparticles

Bilayer actuators consisting of a layer of aligned PPy microtubules with the length of 15 μm and a layer of compact PPy film with the thickness of 15 μm have been fabricated. The actuators can bend to an angle much larger than 90° at an actuation rate of -100° s^-1 under a driving potential of 0.8 V versus Ag/AgCl. The microtubule layers of both type actuators are "sticky", and can capture or trap polystyrene microparticles from their dilute dispersions. Moreover, the captured particles can be extensively released by sonication or partly released by electrochemically reducing the actuators in the aqueous electrolytes. On the basis of extensive investigations including controlling the conditions of electrochemical actuation and the redox states of PPy microtubules, adjusting the particle size and composition, possible mechanisms for capturing and releasing microparticles were proposed.