Motion Control of Polymeric Nanomotors Based on Host-Guest Interactions.

Controlling the motion of artificial self-propelled micro- and nanomotors independent of the fuel concentration is still a great challenge. Here we describe the first report of speed manipulation of supramolecular nanomotors via blue light-responsive valves, which can regulate the access of hydrogen peroxide fuel into the motors. Light-sensitive polymeric nanomotors are built up via the self-assembly of functional block copolymers, followed by bowl-shaped stomatocyte formation and incorporation of platinum nanoparticles. Subsequent addition of β-cyclodextrin (β-CD) leads to the formation of inclusion complexes with the trans-isomers of the azobenzene derivatives grafted from the surfaces of the stomatocytes. β-CDs attachment decreases the diffusion rate of hydrogen peroxide into the cavities of the motors because of partly blocking of the openings of the stomatocyte. This results in a lowering of the speed of the nanomotors. Upon blue light irradiation, the trans-azobenzene moieties isomerize to the cis-form, which lead to the detachment of the β-CDs due to their inability to form complexes with the cis-isomer. As a result, the speed of the nanomotors increases accordingly. Such a conformational change provides us with the unique possibility to control the speed of the supramolecular nanomotor via light-responsive host-guest complexation. We envision that such artificial responsive nano-systems with controlled motion could have potential applications in drug delivery.