Polypyrrole actuators with inverse opal structures

Polypyrrole (PPy) films with inverse opal structures were synthesized by electrochemical polymerization of pyrrole using colloidal crystals as the template. The actuators based on these films exhibited higher actuation rates than those of the actuators made from flat PPy films at a given actuation potential. The nanosized caves of the inverse opal can trap particles with diameters smaller than their orifices, whereas the particles with diameters larger than those of cave orifices only can be adhered on the surfaces of actuators. The particles can be seized and released through electrochemical actuation. Furthermore, the particles with diameters smaller or larger than those of cave orifices can be separated from their mixtures.