Jet propulsion: Small 14/2009

The cover image shows strain-engineered microtubes traveling as self-propelled catalytic microjet engines along various trajectories with speeds up to ≈ 2 mm s−1 (approximately 50 body lengths per second). The motion of the microjets is generated by gas bubbles thrust out of one opening of the tube. The trajectories of various geometries can be traced by long microbubble tails. A magnetic layer is integrated into the wall of the microjet engine, which allows easy control over the direction of motion by applying external magnetic fields. For more information, please read the Full Paper “Catalytic Microtubular Jet Engines Self-Propelled by Accumulated Gas Bubbles” by Y. Mei et al., beginning on page 1688.