Bubble-Free Propulsion of Ultrasmall Tubular Nanojets Powered by Biocatalytic Reactions

The motion of self-propelled tubular micro- and nano­jets has so far been achieved by bubble propulsion, e.g., O₂ bubbles formed by catalytic decomposition of H₂O₂, which renders future bio­medical applications inviable. An alternative self-propulsion mechanism for tubular engines on the nano­meter scale is still missing. Here, we report the fabrication and characterization of bubble-free propelled tubular nano­jets (as small as 220 nm diameter), powered by an enzyme-triggered bio­catalytic reaction using urea as fuel. We studied the translational and rotational dynamics of the nano­jets as functions of the length and location of the enzymes. Introducing tracer nano­particles into the system, we demonstrated the presence of an internal flow that extends into the external fluid via the cavity opening, leading to the self-propulsion. One-dimensional nano­size, longitudinal self-propulsion, and bio­compatibility make the tubular nano­jets promising for future bio­medical applications