Biomimetic two-stage micro@nanomotor with weak acid-triggered release of nanomotors

Bionic micro/nanomotor systems, which combine biomimetic design with the motion performance, have shown great potential in many fields. However, so far, it remains a challenge to design and fabricate biomimetic micro/nanomotors with high flexibility to perform complex tasks in complicated and changeable environments. In this work, inspired by the suckerfishes (guest)–shark (host) motion behavior, we designed and prepared a kind of intelligent two-stage micro@nanomotor with weak acid-triggered release of nanomotor. When the suckerfishes, who clinged to the surface of large fish or the bottom of boat and marched with them, reached bait-rich waters, they detached from the host to engage in foraging behavior. Inspired by the suckerfishes–shark system and the coordinated bond interaction, a large amount of Janus Au-Pt nanomotors with hydrogen peroxide (H₂O₂)-driven capacity, analogous to suckerfishes, were attached onto immovable yolk–shell structured polydopamine-mesoporous silica (PDA-MS) micromotor as the host to create two-stage PDA-MS@Au-Pt micro@nanomotor. PDA-MS@Au-Pt micro@nanomotor moved directionally by self-thermophoresis under the propulsion of near infrared ray (NIR) light with low power density. When the PDA-MS@Au-Pt entered into the weak acidic environment formed by a low concentration of H₂O₂, most small Au-Pt nanomotors were detached from the surface of PDA-MS due to the weak acidic sensitivity of the coordinated bond, and then performed self-diffusiophoresis in the environment containing a low concentration of H₂O₂ as a chemical fuel. This bionic intelligent system, which consists of a large-sized micromotor and lots of small-sized nanomotors, should provide a new insight for active two-stage cargo delivery.