Mussel inspired locomotive: The moisture induced actuation in a poly(vinyl alcohol) film containing melanin-like dopamine nano spheres

Smart responsive materials are gaining scientific interest, especially those driven by green sources. Moisture induced locomotion is a process of energy conversion that has applications in areas capable of converting chemical potential energy in water gradients to mechanical work. Here we describe for the first time the development of a moisture-responsive polymeric film of polydopamine nanospheres (PDNs) embedded in a polyvinyl alcohol (PVA) matrix. PVA film is a hydroxyl rich polymer known for its high water absorption property. However, after adding PDNs to this matrix, the desorption property increases due to the intramolecular hydrogen bonding between the functional groups of PDNs and the hydroxyl groups of PVA chains. Therefore, anisotropic adsorption and desorption of water vapor, which is responsible for the fast locomotion of PVA@PDNs, were observed.