Mg-Based Micromotors with Motion Responsive to Dual Stimuli.

Mg-based micromotors have emerged as an extremely attractive artificial micro/nanodevice, but suffered from uncontrollable propulsion and limited motion lifetime, restricting the fulfillment of complex tasks. Here, we have demonstrated Mg-based micromotors composed of Mg microspheres asymmetrically coated with Pt and temperature-sensitive poly(N-isopropylacrylamide) (PNIPAM) hydrogel layers in sequence. They can implement different motion behaviors stemming from the driving mechanism transformation when encountering catalyzed substrates such as H2O2 and respond to both H2O2 concentration and temperature in aqueous environment. The as-constructed Mg-based micromotors are self-propelled by Pt-catalyzed H2O2 decomposition following the self-consuming Mg-H2O reaction. In this case, they could further generate bilateral bubbles and thus demonstrate unique self-limitation motion like hovering when the phase transformation of PNIPAM is triggered by decreasing temperature or when the H2O2 concentration after permeating across the PNIPAM hydrogel layer is high enough to facilitate bubble nucleation. Our work for the first time provides a stimuli-induced "hovering" strategy for self-propelled micromotors, which endows Mg-based micromotors with an intelligent response to the surroundings besides the significant extension of their motion lifetime.