This work reports a reversible braking system for micromotors that can be controlled by small temperature changes (≈5 °C). To achieve this, gated‐mesoporous organosilica microparticles are internally loaded with metal catalysts (to form the motor) and the exterior (partially) grafted with thermosensitive bottle‐brush polyphosphazenes to form Janus particles. When placed in an aqueous solution of H2O2 (the fuel), rapid forward propulsion of the motors ensues due to decomposition of the fuel. Conformational changes of the polymers at defined temperatures regulate the bubble formation rate and thus act as brakes with considerable deceleration/acceleration observed. As the components can be easily varied, this represents a versatile, modular platform for the exogenous velocity control of micromotors.

No abstract

Self‐propelled micromotors with a reversible braking system are shown. Manganese ions are embedded in microporous silica nanoparticles to catalyse the degradation of the H2O2 “fuel” to water and gaseous oxygen. The bubbles formation propels the microparticles in a rapid forward‐thrusting motion. The micromotors are decorated with thermoresponsive polyphosphazenes which expand/collapse in a temperature‐driven response to regulate the flow of fuel to the motor and thus control their velocity. More information can be found in the Communication by I. Teasdale, Y. Salinas, et al. on page 3262.

Invited for the cover of this issue is the group of Ian Teasdale and Yolanda Salinas at the Johannes Kepler University Linz. The image depicts the self‐propelled Janus micromotors reported in this work. Read the full text of the article at 10.1002/chem.202004792.